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@@ -0,0 +1,17 @@
|
||||
compat/zlib/contrib/dotzlib/DotZLib/UnitTests.cs
|
||||
compat/zlib/contrib/vstudio/readme.txt
|
||||
compat/zlib/contrib/vstudio/*/zlib.rc
|
||||
compat/zlib/win32/*.txt
|
||||
compat/zlib/win64/*.txt
|
||||
libtommath/*.dsp
|
||||
libtommath/*.sln
|
||||
libtommath/*.vcproj
|
||||
tools/tcl.hpj.in
|
||||
tools/tcl.wse.in
|
||||
win/buildall.vc.bat
|
||||
win/coffbase.txt
|
||||
win/makefile.vc
|
||||
win/rules.vc
|
||||
win/tcl.dsp
|
||||
win/tcl.dsw
|
||||
win/tcl.hpj.in
|
||||
@@ -3,11 +3,13 @@ compat/zlib/contrib/vstudio/readme.txt
|
||||
compat/zlib/contrib/vstudio/*/zlib.rc
|
||||
compat/zlib/win32/*.txt
|
||||
compat/zlib/win64/*.txt
|
||||
libtommath/*.dsp
|
||||
libtommath/*.sln
|
||||
libtommath/*.vcproj
|
||||
tools/tcl.hpj.in
|
||||
tools/tcl.wse.in
|
||||
win/buildall.vc.bat
|
||||
win/coffbase.txt
|
||||
win/makefile.bc
|
||||
win/makefile.vc
|
||||
win/rules.vc
|
||||
win/tcl.dsp
|
||||
|
||||
@@ -2,7 +2,6 @@ tools/tcl.hpj.in
|
||||
tools/tcl.wse.in
|
||||
win/buildall.vc.bat
|
||||
win/coffbase.txt
|
||||
win/makefile.bc
|
||||
win/makefile.vc
|
||||
win/rules.vc
|
||||
win/tcl.dsp
|
||||
|
||||
@@ -18,6 +18,7 @@
|
||||
*/tclsh*
|
||||
*/tcltest*
|
||||
*/versions.vc
|
||||
*/version.vc
|
||||
html
|
||||
libtommath/bn.ilg
|
||||
libtommath/bn.ind
|
||||
@@ -40,7 +41,8 @@ unix/dltest.marker
|
||||
unix/tcl.pc
|
||||
unix/tclIndex
|
||||
unix/pkgs/*
|
||||
win/Debug_VC*
|
||||
win/Release_VC*
|
||||
win/Debug*
|
||||
win/Release*
|
||||
win/pkgs/*
|
||||
win/tcl.hpj
|
||||
win/tcl.hpj
|
||||
win/nmhlp-out.txt
|
||||
|
||||
@@ -1,6 +1,6 @@
|
||||
<?xml version="1.0" encoding="UTF-8"?>
|
||||
<projectDescription>
|
||||
<name>tcl8.7</name>
|
||||
<name>tcl8.6</name>
|
||||
<comment></comment>
|
||||
<projects>
|
||||
</projects>
|
||||
|
||||
@@ -1,5 +1,5 @@
|
||||
README: Tcl
|
||||
This is the Tcl 8.7a0 source distribution.
|
||||
This is the Tcl 8.6.7 source distribution.
|
||||
http://sourceforge.net/projects/tcl/files/Tcl/
|
||||
You can get any source release of Tcl from the URL above.
|
||||
|
||||
@@ -49,7 +49,7 @@ and selling it either in whole or in part. See the file
|
||||
|
||||
Extensive documentation is available at our website.
|
||||
The home page for this release, including new features, is
|
||||
http://www.tcl.tk/software/tcltk/8.7.html
|
||||
http://www.tcl.tk/software/tcltk/8.6.html
|
||||
|
||||
Detailed release notes can be found at the file distributions page
|
||||
by clicking on the relevant version.
|
||||
@@ -61,9 +61,9 @@ Information about Tcl itself can be found at
|
||||
There have been many Tcl books on the market. Many are mentioned in the Wiki:
|
||||
http://wiki.tcl.tk/_/ref?N=25206
|
||||
|
||||
To view the complete set of reference manual entries for Tcl 8.7 online,
|
||||
To view the complete set of reference manual entries for Tcl 8.6 online,
|
||||
visit the URL:
|
||||
http://www.tcl.tk/man/tcl8.7/
|
||||
http://www.tcl.tk/man/tcl8.6/
|
||||
|
||||
2a. Unix Documentation
|
||||
----------------------
|
||||
|
||||
@@ -8624,3 +8624,177 @@ improvements to regexp engine from Postgres (lane,porter,fellows,seltenreich)
|
||||
2016-02-22 (bug)[9b4702] [info exists env(missing)] kills trace (nijtmans)
|
||||
|
||||
--- Released 8.6.5, February 29, 2016 --- http://core.tcl.tk/tcl/ for details
|
||||
|
||||
2016-03-01 (bug)[803042] mem leak due to reference cycle (porter)
|
||||
|
||||
2016-03-08 (bug)[bbc304] reflected watch race condition (porter)
|
||||
|
||||
2016-03-17 (bug)[fadc99] compile-5.3 (rodriguez,porter)
|
||||
|
||||
2016-03-17 (enhancement)[1a25fd] compile [variable ${ns}::v] (porter)
|
||||
|
||||
2016-03-20 (bug)[1af8de] crash in compiled [string replace] (harder,fellows)
|
||||
|
||||
2016-03-21 (bug)[d30718] segv in notifier finalize (hirofumi,nijtmans)
|
||||
|
||||
2016-03-23 (enhancement)[7d0db7] parallel make (yarda,nijtmans)
|
||||
|
||||
2016-03-23 [f12535] enable test bindings customization (vogel,nijtmans)
|
||||
|
||||
2016-04-04 (bug)[47ac84] compiled [lreplace] fixes (aspect,ferrieux,fellows)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-04-08 (bug)[866368] RE \w includes 'Punctuation Connector' (nijtmans)
|
||||
|
||||
2016-04-08 (bug)[2538f3] Win crash Tcl_OpenTcpServer() (griffin)
|
||||
|
||||
2016-04-10 [07d13d] Restore TclBlend support lost in 8.6.1 (buratti)
|
||||
|
||||
2016-05-13 (bug)[3154ea] Mem corruption in assembler exceptions (tkob,kenny)
|
||||
|
||||
2016-05-13 (bug) registry package support any Unicode env (nijtmans)
|
||||
=> registry 1.3.2
|
||||
|
||||
2016-05-21 (bug)[f7d4e] [namespace delete] performance (fellows)
|
||||
|
||||
2016-06-02 (TIP 447) execution time verbosity option (cerutti)
|
||||
=> tcltest 2.4.0
|
||||
|
||||
2016-06-16 (bug)[16828b] crash due to [vwait] trace undo fail (dah,porter)
|
||||
|
||||
2016-06-16 (enhancement)[4b61af] good [info frame] from more cases (beric)
|
||||
|
||||
2016-06-21 (bug)[c383eb] crash in [glob -path a] (oehlmann,porter)
|
||||
|
||||
2016-06-21 (update) Update Unicode data to 9.0 (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-06-22 (bug)[16896d] Tcl_DString tolerate append to self. (dah,porter)
|
||||
|
||||
2016-06-23 (bug)[d55322] crash in [dict update] (yorick,fellows)
|
||||
|
||||
2016-06-27 (bug)[dd260a] crash in [chan configure -dictionary] (madden,aspect)
|
||||
|
||||
2016-07-02 (bug)[f961d7] usage message with parameters with spaces (porter)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-07-02 (enhancement)[09fabc] Sort order of -relateddir (lanam)
|
||||
|
||||
2016-07-07 (bug)[5d7ca0] Win: [file executable] for .cmd and .ps1 (nadkarni)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-07-08 (bug)[a47641] [file normalize] & Windows junctions (nadkarni)
|
||||
|
||||
2016-07-09 [ae61a6] [file] handling of Win hardcoded names (CON) (nadkarni)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-07-09 [3613671] [file owned] (more) useful on Win (nadkarni)
|
||||
|
||||
2016-07-09 (bug)[1493a4] [namespace upvar] use of resolvers (beric,fellows)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-07-10 (bug)[da340d] integer division in clock math (nadkarni)
|
||||
|
||||
2016-07-20 tzdata updated to Olson's tzdata2016f (venkat)
|
||||
|
||||
--- Released 8.6.6, July 27, 2016 --- http://core.tcl.tk/tcl/ for details
|
||||
|
||||
2016-09-07 (bug)[c09edf] Bad caching with custom resolver (neumann,nijtmans)
|
||||
|
||||
2016-09-07 (bug)[4dbdd9] Memleak in test var-8.3 (mr_calvin,porter)
|
||||
|
||||
2016-10-03 (bug)[2bf561] Allow empty command as alias target (yorick,nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-10-04 (bug)[4d5ae7] Crash in async connects host no address (gahr,fellows)
|
||||
|
||||
2016-10-08 (bug)[838e99] treat application/xml as text (gahr,fellows)
|
||||
=> http 2.8.10
|
||||
|
||||
2016-10-11 (bug)[3cc1d9] Thread finalization crash in zippy (neumann)
|
||||
|
||||
2016-10-12 (bug)[be003d] Fix [scan 0x1 %b], [scan 0x1 %o] (porter)
|
||||
|
||||
2016-10-14 (bug)[eb6b68] Fix stringComp-14.5 (porter)
|
||||
|
||||
2016-10-30 (bug)[b26e38] Fix zlib-7.8 (fellows)
|
||||
|
||||
2016-10-30 (bug)[1ae129] Fix memleak in [history] destruction (fellows)
|
||||
|
||||
2016-11-04 (feature) Provisional Tcl 9 support in msgcat and tcltest (nijtmans)
|
||||
=> msgcat 1.6.1
|
||||
=> tcltest 2.4.1
|
||||
|
||||
2016-11-04 (bug)[824752] Crash in Tcl_ListObjReplace() (gahr,porter)
|
||||
|
||||
2016-11-11 (bug)[79614f] invalidate VFS mounts on sytem encoding change (yorick)
|
||||
|
||||
2016-11-14 OSX: End panic() as legacy support macro; system conflicts (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2016-11-15 (bug) TclOO fix stops crash mixing Itcl and snit (fellows)
|
||||
|
||||
2016-11-17 (update) Reconcile libtommath updates; purge unused files (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2017-01-09 (bug)[b87ad7] Repair drifts in timer clock (sebres)
|
||||
|
||||
2017-01-17 (update) => zlib 1.2.11 (nijtmans)
|
||||
|
||||
2017-01-31 (bug)[39f630] Revise Tcl_LinkVar to tolerate some prefixes (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2017-02-01 (bug)[d0f7ba] Improper NAN optimization. expr-22.1[01] (aspect)
|
||||
|
||||
2017-02-26 (bug)[25842c] zlib stream finalization (aspect)
|
||||
|
||||
2017-03-07 (deprecate) Remove unmaintained makefile.bc file (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2017-03-14 (enhancement) [clock] and [encoding] are now ensembles (kenny)
|
||||
|
||||
2017-03-15 (enhancement) several [clock] subcommands bytecoded (kenny)
|
||||
|
||||
2017-03-23 tzdata updated to Olson's tzdata2017b (jima)
|
||||
|
||||
2017-03-29 (bug)[900cb0] Fix OO unexport introspection (napier)
|
||||
|
||||
2017-04-12 (bug)[42202b] Nesting imbalance in coro injection (nadkarni,sebres)
|
||||
|
||||
2017-04-18 (bug)[bc4322] http package support for safe interps (nash,nijtmans)
|
||||
|
||||
2017-04-28 (bug)[f34cf8] [file join a //b] => /b (neumann,porter)
|
||||
|
||||
2017-05-01 (bug)[8bd13f] Windows threads and pipes (sebres,nijtmans)
|
||||
|
||||
2017-05-01 (bug)[f9fe90] [file join //a b] EIAS violation (aspect,porter)
|
||||
|
||||
2017-05-04 (bug) Make test filesystem-1.52 pass on Windows (nijtmans)
|
||||
|
||||
2017-05-05 (bug)[601522] [binary] field spec overflow -> segfault (porter)
|
||||
|
||||
2017-05-08 (bug)[6ca52a] http memleak handling keep-alive (aspect,nijtmans)
|
||||
=> http 2.8.11
|
||||
|
||||
2017-05-29 (bug)[a3fb33] crash in [lsort] on long lists (sebres)
|
||||
|
||||
2017-06-05 (bug)[67aa9a] Tcl_UtfToUniChar() revised handling invalid UTF-8 (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2017-06-08 (bug)[2738427] Tcl_NumUtfChars() corner case utf-4.9 (nijtmans)
|
||||
|
||||
2017-06-22 (update) Update Unicode data to 10.0 (nijtmans)
|
||||
*** POTENTIAL INCOMPATIBILITY ***
|
||||
|
||||
2017-06-22 (TIP 473) Let [oo::copy] specify target namespace (fellows)
|
||||
|
||||
2017-06-26 (bug)[46f801] Repair autoloader fragility (porter)
|
||||
|
||||
2017-07-06 (bug)[adb198] Plug memleak in TclJoinPath (sebres,porter)
|
||||
|
||||
2017-07-17 (bug)[fb2208] Repeatable tclIndex generation (wiedemann,nijtmans)
|
||||
|
||||
--- Released 8.6.7, August 9, 2017 --- http://core.tcl.tk/tcl/ for details
|
||||
|
||||
2017-08-31 (bug)[2a9465] http state 100 continue handling broken (oehlmann)
|
||||
=> http 2.8.12
|
||||
|
||||
+1
-1
@@ -106,5 +106,5 @@ closedir(
|
||||
close(dirp->dd_fd);
|
||||
dirp->dd_fd = -1;
|
||||
dirp->dd_loc = 0;
|
||||
ckfree(dirp);
|
||||
ckfree((char *) dirp);
|
||||
}
|
||||
|
||||
+1
-1
@@ -100,7 +100,7 @@ waitpid(
|
||||
} else {
|
||||
prevPtr->nextPtr = waitPtr->nextPtr;
|
||||
}
|
||||
ckfree(waitPtr);
|
||||
ckfree((char *) waitPtr);
|
||||
return result;
|
||||
}
|
||||
|
||||
|
||||
@@ -1,209 +0,0 @@
|
||||
1. Compression algorithm (deflate)
|
||||
|
||||
The deflation algorithm used by gzip (also zip and zlib) is a variation of
|
||||
LZ77 (Lempel-Ziv 1977, see reference below). It finds duplicated strings in
|
||||
the input data. The second occurrence of a string is replaced by a
|
||||
pointer to the previous string, in the form of a pair (distance,
|
||||
length). Distances are limited to 32K bytes, and lengths are limited
|
||||
to 258 bytes. When a string does not occur anywhere in the previous
|
||||
32K bytes, it is emitted as a sequence of literal bytes. (In this
|
||||
description, `string' must be taken as an arbitrary sequence of bytes,
|
||||
and is not restricted to printable characters.)
|
||||
|
||||
Literals or match lengths are compressed with one Huffman tree, and
|
||||
match distances are compressed with another tree. The trees are stored
|
||||
in a compact form at the start of each block. The blocks can have any
|
||||
size (except that the compressed data for one block must fit in
|
||||
available memory). A block is terminated when deflate() determines that
|
||||
it would be useful to start another block with fresh trees. (This is
|
||||
somewhat similar to the behavior of LZW-based _compress_.)
|
||||
|
||||
Duplicated strings are found using a hash table. All input strings of
|
||||
length 3 are inserted in the hash table. A hash index is computed for
|
||||
the next 3 bytes. If the hash chain for this index is not empty, all
|
||||
strings in the chain are compared with the current input string, and
|
||||
the longest match is selected.
|
||||
|
||||
The hash chains are searched starting with the most recent strings, to
|
||||
favor small distances and thus take advantage of the Huffman encoding.
|
||||
The hash chains are singly linked. There are no deletions from the
|
||||
hash chains, the algorithm simply discards matches that are too old.
|
||||
|
||||
To avoid a worst-case situation, very long hash chains are arbitrarily
|
||||
truncated at a certain length, determined by a runtime option (level
|
||||
parameter of deflateInit). So deflate() does not always find the longest
|
||||
possible match but generally finds a match which is long enough.
|
||||
|
||||
deflate() also defers the selection of matches with a lazy evaluation
|
||||
mechanism. After a match of length N has been found, deflate() searches for
|
||||
a longer match at the next input byte. If a longer match is found, the
|
||||
previous match is truncated to a length of one (thus producing a single
|
||||
literal byte) and the process of lazy evaluation begins again. Otherwise,
|
||||
the original match is kept, and the next match search is attempted only N
|
||||
steps later.
|
||||
|
||||
The lazy match evaluation is also subject to a runtime parameter. If
|
||||
the current match is long enough, deflate() reduces the search for a longer
|
||||
match, thus speeding up the whole process. If compression ratio is more
|
||||
important than speed, deflate() attempts a complete second search even if
|
||||
the first match is already long enough.
|
||||
|
||||
The lazy match evaluation is not performed for the fastest compression
|
||||
modes (level parameter 1 to 3). For these fast modes, new strings
|
||||
are inserted in the hash table only when no match was found, or
|
||||
when the match is not too long. This degrades the compression ratio
|
||||
but saves time since there are both fewer insertions and fewer searches.
|
||||
|
||||
|
||||
2. Decompression algorithm (inflate)
|
||||
|
||||
2.1 Introduction
|
||||
|
||||
The key question is how to represent a Huffman code (or any prefix code) so
|
||||
that you can decode fast. The most important characteristic is that shorter
|
||||
codes are much more common than longer codes, so pay attention to decoding the
|
||||
short codes fast, and let the long codes take longer to decode.
|
||||
|
||||
inflate() sets up a first level table that covers some number of bits of
|
||||
input less than the length of longest code. It gets that many bits from the
|
||||
stream, and looks it up in the table. The table will tell if the next
|
||||
code is that many bits or less and how many, and if it is, it will tell
|
||||
the value, else it will point to the next level table for which inflate()
|
||||
grabs more bits and tries to decode a longer code.
|
||||
|
||||
How many bits to make the first lookup is a tradeoff between the time it
|
||||
takes to decode and the time it takes to build the table. If building the
|
||||
table took no time (and if you had infinite memory), then there would only
|
||||
be a first level table to cover all the way to the longest code. However,
|
||||
building the table ends up taking a lot longer for more bits since short
|
||||
codes are replicated many times in such a table. What inflate() does is
|
||||
simply to make the number of bits in the first table a variable, and then
|
||||
to set that variable for the maximum speed.
|
||||
|
||||
For inflate, which has 286 possible codes for the literal/length tree, the size
|
||||
of the first table is nine bits. Also the distance trees have 30 possible
|
||||
values, and the size of the first table is six bits. Note that for each of
|
||||
those cases, the table ended up one bit longer than the ``average'' code
|
||||
length, i.e. the code length of an approximately flat code which would be a
|
||||
little more than eight bits for 286 symbols and a little less than five bits
|
||||
for 30 symbols.
|
||||
|
||||
|
||||
2.2 More details on the inflate table lookup
|
||||
|
||||
Ok, you want to know what this cleverly obfuscated inflate tree actually
|
||||
looks like. You are correct that it's not a Huffman tree. It is simply a
|
||||
lookup table for the first, let's say, nine bits of a Huffman symbol. The
|
||||
symbol could be as short as one bit or as long as 15 bits. If a particular
|
||||
symbol is shorter than nine bits, then that symbol's translation is duplicated
|
||||
in all those entries that start with that symbol's bits. For example, if the
|
||||
symbol is four bits, then it's duplicated 32 times in a nine-bit table. If a
|
||||
symbol is nine bits long, it appears in the table once.
|
||||
|
||||
If the symbol is longer than nine bits, then that entry in the table points
|
||||
to another similar table for the remaining bits. Again, there are duplicated
|
||||
entries as needed. The idea is that most of the time the symbol will be short
|
||||
and there will only be one table look up. (That's whole idea behind data
|
||||
compression in the first place.) For the less frequent long symbols, there
|
||||
will be two lookups. If you had a compression method with really long
|
||||
symbols, you could have as many levels of lookups as is efficient. For
|
||||
inflate, two is enough.
|
||||
|
||||
So a table entry either points to another table (in which case nine bits in
|
||||
the above example are gobbled), or it contains the translation for the symbol
|
||||
and the number of bits to gobble. Then you start again with the next
|
||||
ungobbled bit.
|
||||
|
||||
You may wonder: why not just have one lookup table for how ever many bits the
|
||||
longest symbol is? The reason is that if you do that, you end up spending
|
||||
more time filling in duplicate symbol entries than you do actually decoding.
|
||||
At least for deflate's output that generates new trees every several 10's of
|
||||
kbytes. You can imagine that filling in a 2^15 entry table for a 15-bit code
|
||||
would take too long if you're only decoding several thousand symbols. At the
|
||||
other extreme, you could make a new table for every bit in the code. In fact,
|
||||
that's essentially a Huffman tree. But then you spend too much time
|
||||
traversing the tree while decoding, even for short symbols.
|
||||
|
||||
So the number of bits for the first lookup table is a trade of the time to
|
||||
fill out the table vs. the time spent looking at the second level and above of
|
||||
the table.
|
||||
|
||||
Here is an example, scaled down:
|
||||
|
||||
The code being decoded, with 10 symbols, from 1 to 6 bits long:
|
||||
|
||||
A: 0
|
||||
B: 10
|
||||
C: 1100
|
||||
D: 11010
|
||||
E: 11011
|
||||
F: 11100
|
||||
G: 11101
|
||||
H: 11110
|
||||
I: 111110
|
||||
J: 111111
|
||||
|
||||
Let's make the first table three bits long (eight entries):
|
||||
|
||||
000: A,1
|
||||
001: A,1
|
||||
010: A,1
|
||||
011: A,1
|
||||
100: B,2
|
||||
101: B,2
|
||||
110: -> table X (gobble 3 bits)
|
||||
111: -> table Y (gobble 3 bits)
|
||||
|
||||
Each entry is what the bits decode as and how many bits that is, i.e. how
|
||||
many bits to gobble. Or the entry points to another table, with the number of
|
||||
bits to gobble implicit in the size of the table.
|
||||
|
||||
Table X is two bits long since the longest code starting with 110 is five bits
|
||||
long:
|
||||
|
||||
00: C,1
|
||||
01: C,1
|
||||
10: D,2
|
||||
11: E,2
|
||||
|
||||
Table Y is three bits long since the longest code starting with 111 is six
|
||||
bits long:
|
||||
|
||||
000: F,2
|
||||
001: F,2
|
||||
010: G,2
|
||||
011: G,2
|
||||
100: H,2
|
||||
101: H,2
|
||||
110: I,3
|
||||
111: J,3
|
||||
|
||||
So what we have here are three tables with a total of 20 entries that had to
|
||||
be constructed. That's compared to 64 entries for a single table. Or
|
||||
compared to 16 entries for a Huffman tree (six two entry tables and one four
|
||||
entry table). Assuming that the code ideally represents the probability of
|
||||
the symbols, it takes on the average 1.25 lookups per symbol. That's compared
|
||||
to one lookup for the single table, or 1.66 lookups per symbol for the
|
||||
Huffman tree.
|
||||
|
||||
There, I think that gives you a picture of what's going on. For inflate, the
|
||||
meaning of a particular symbol is often more than just a letter. It can be a
|
||||
byte (a "literal"), or it can be either a length or a distance which
|
||||
indicates a base value and a number of bits to fetch after the code that is
|
||||
added to the base value. Or it might be the special end-of-block code. The
|
||||
data structures created in inftrees.c try to encode all that information
|
||||
compactly in the tables.
|
||||
|
||||
|
||||
Jean-loup Gailly Mark Adler
|
||||
jloup@gzip.org madler@alumni.caltech.edu
|
||||
|
||||
|
||||
References:
|
||||
|
||||
[LZ77] Ziv J., Lempel A., ``A Universal Algorithm for Sequential Data
|
||||
Compression,'' IEEE Transactions on Information Theory, Vol. 23, No. 3,
|
||||
pp. 337-343.
|
||||
|
||||
``DEFLATE Compressed Data Format Specification'' available in
|
||||
http://tools.ietf.org/html/rfc1951
|
||||
@@ -1,619 +0,0 @@
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Network Working Group P. Deutsch
|
||||
Request for Comments: 1950 Aladdin Enterprises
|
||||
Category: Informational J-L. Gailly
|
||||
Info-ZIP
|
||||
May 1996
|
||||
|
||||
|
||||
ZLIB Compressed Data Format Specification version 3.3
|
||||
|
||||
Status of This Memo
|
||||
|
||||
This memo provides information for the Internet community. This memo
|
||||
does not specify an Internet standard of any kind. Distribution of
|
||||
this memo is unlimited.
|
||||
|
||||
IESG Note:
|
||||
|
||||
The IESG takes no position on the validity of any Intellectual
|
||||
Property Rights statements contained in this document.
|
||||
|
||||
Notices
|
||||
|
||||
Copyright (c) 1996 L. Peter Deutsch and Jean-Loup Gailly
|
||||
|
||||
Permission is granted to copy and distribute this document for any
|
||||
purpose and without charge, including translations into other
|
||||
languages and incorporation into compilations, provided that the
|
||||
copyright notice and this notice are preserved, and that any
|
||||
substantive changes or deletions from the original are clearly
|
||||
marked.
|
||||
|
||||
A pointer to the latest version of this and related documentation in
|
||||
HTML format can be found at the URL
|
||||
<ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>.
|
||||
|
||||
Abstract
|
||||
|
||||
This specification defines a lossless compressed data format. The
|
||||
data can be produced or consumed, even for an arbitrarily long
|
||||
sequentially presented input data stream, using only an a priori
|
||||
bounded amount of intermediate storage. The format presently uses
|
||||
the DEFLATE compression method but can be easily extended to use
|
||||
other compression methods. It can be implemented readily in a manner
|
||||
not covered by patents. This specification also defines the ADLER-32
|
||||
checksum (an extension and improvement of the Fletcher checksum),
|
||||
used for detection of data corruption, and provides an algorithm for
|
||||
computing it.
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 1]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
Table of Contents
|
||||
|
||||
1. Introduction ................................................... 2
|
||||
1.1. Purpose ................................................... 2
|
||||
1.2. Intended audience ......................................... 3
|
||||
1.3. Scope ..................................................... 3
|
||||
1.4. Compliance ................................................ 3
|
||||
1.5. Definitions of terms and conventions used ................ 3
|
||||
1.6. Changes from previous versions ............................ 3
|
||||
2. Detailed specification ......................................... 3
|
||||
2.1. Overall conventions ....................................... 3
|
||||
2.2. Data format ............................................... 4
|
||||
2.3. Compliance ................................................ 7
|
||||
3. References ..................................................... 7
|
||||
4. Source code .................................................... 8
|
||||
5. Security Considerations ........................................ 8
|
||||
6. Acknowledgements ............................................... 8
|
||||
7. Authors' Addresses ............................................. 8
|
||||
8. Appendix: Rationale ............................................ 9
|
||||
9. Appendix: Sample code ..........................................10
|
||||
|
||||
1. Introduction
|
||||
|
||||
1.1. Purpose
|
||||
|
||||
The purpose of this specification is to define a lossless
|
||||
compressed data format that:
|
||||
|
||||
* Is independent of CPU type, operating system, file system,
|
||||
and character set, and hence can be used for interchange;
|
||||
|
||||
* Can be produced or consumed, even for an arbitrarily long
|
||||
sequentially presented input data stream, using only an a
|
||||
priori bounded amount of intermediate storage, and hence can
|
||||
be used in data communications or similar structures such as
|
||||
Unix filters;
|
||||
|
||||
* Can use a number of different compression methods;
|
||||
|
||||
* Can be implemented readily in a manner not covered by
|
||||
patents, and hence can be practiced freely.
|
||||
|
||||
The data format defined by this specification does not attempt to
|
||||
allow random access to compressed data.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 2]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
1.2. Intended audience
|
||||
|
||||
This specification is intended for use by implementors of software
|
||||
to compress data into zlib format and/or decompress data from zlib
|
||||
format.
|
||||
|
||||
The text of the specification assumes a basic background in
|
||||
programming at the level of bits and other primitive data
|
||||
representations.
|
||||
|
||||
1.3. Scope
|
||||
|
||||
The specification specifies a compressed data format that can be
|
||||
used for in-memory compression of a sequence of arbitrary bytes.
|
||||
|
||||
1.4. Compliance
|
||||
|
||||
Unless otherwise indicated below, a compliant decompressor must be
|
||||
able to accept and decompress any data set that conforms to all
|
||||
the specifications presented here; a compliant compressor must
|
||||
produce data sets that conform to all the specifications presented
|
||||
here.
|
||||
|
||||
1.5. Definitions of terms and conventions used
|
||||
|
||||
byte: 8 bits stored or transmitted as a unit (same as an octet).
|
||||
(For this specification, a byte is exactly 8 bits, even on
|
||||
machines which store a character on a number of bits different
|
||||
from 8.) See below, for the numbering of bits within a byte.
|
||||
|
||||
1.6. Changes from previous versions
|
||||
|
||||
Version 3.1 was the first public release of this specification.
|
||||
In version 3.2, some terminology was changed and the Adler-32
|
||||
sample code was rewritten for clarity. In version 3.3, the
|
||||
support for a preset dictionary was introduced, and the
|
||||
specification was converted to RFC style.
|
||||
|
||||
2. Detailed specification
|
||||
|
||||
2.1. Overall conventions
|
||||
|
||||
In the diagrams below, a box like this:
|
||||
|
||||
+---+
|
||||
| | <-- the vertical bars might be missing
|
||||
+---+
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 3]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
represents one byte; a box like this:
|
||||
|
||||
+==============+
|
||||
| |
|
||||
+==============+
|
||||
|
||||
represents a variable number of bytes.
|
||||
|
||||
Bytes stored within a computer do not have a "bit order", since
|
||||
they are always treated as a unit. However, a byte considered as
|
||||
an integer between 0 and 255 does have a most- and least-
|
||||
significant bit, and since we write numbers with the most-
|
||||
significant digit on the left, we also write bytes with the most-
|
||||
significant bit on the left. In the diagrams below, we number the
|
||||
bits of a byte so that bit 0 is the least-significant bit, i.e.,
|
||||
the bits are numbered:
|
||||
|
||||
+--------+
|
||||
|76543210|
|
||||
+--------+
|
||||
|
||||
Within a computer, a number may occupy multiple bytes. All
|
||||
multi-byte numbers in the format described here are stored with
|
||||
the MOST-significant byte first (at the lower memory address).
|
||||
For example, the decimal number 520 is stored as:
|
||||
|
||||
0 1
|
||||
+--------+--------+
|
||||
|00000010|00001000|
|
||||
+--------+--------+
|
||||
^ ^
|
||||
| |
|
||||
| + less significant byte = 8
|
||||
+ more significant byte = 2 x 256
|
||||
|
||||
2.2. Data format
|
||||
|
||||
A zlib stream has the following structure:
|
||||
|
||||
0 1
|
||||
+---+---+
|
||||
|CMF|FLG| (more-->)
|
||||
+---+---+
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 4]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
(if FLG.FDICT set)
|
||||
|
||||
0 1 2 3
|
||||
+---+---+---+---+
|
||||
| DICTID | (more-->)
|
||||
+---+---+---+---+
|
||||
|
||||
+=====================+---+---+---+---+
|
||||
|...compressed data...| ADLER32 |
|
||||
+=====================+---+---+---+---+
|
||||
|
||||
Any data which may appear after ADLER32 are not part of the zlib
|
||||
stream.
|
||||
|
||||
CMF (Compression Method and flags)
|
||||
This byte is divided into a 4-bit compression method and a 4-
|
||||
bit information field depending on the compression method.
|
||||
|
||||
bits 0 to 3 CM Compression method
|
||||
bits 4 to 7 CINFO Compression info
|
||||
|
||||
CM (Compression method)
|
||||
This identifies the compression method used in the file. CM = 8
|
||||
denotes the "deflate" compression method with a window size up
|
||||
to 32K. This is the method used by gzip and PNG (see
|
||||
references [1] and [2] in Chapter 3, below, for the reference
|
||||
documents). CM = 15 is reserved. It might be used in a future
|
||||
version of this specification to indicate the presence of an
|
||||
extra field before the compressed data.
|
||||
|
||||
CINFO (Compression info)
|
||||
For CM = 8, CINFO is the base-2 logarithm of the LZ77 window
|
||||
size, minus eight (CINFO=7 indicates a 32K window size). Values
|
||||
of CINFO above 7 are not allowed in this version of the
|
||||
specification. CINFO is not defined in this specification for
|
||||
CM not equal to 8.
|
||||
|
||||
FLG (FLaGs)
|
||||
This flag byte is divided as follows:
|
||||
|
||||
bits 0 to 4 FCHECK (check bits for CMF and FLG)
|
||||
bit 5 FDICT (preset dictionary)
|
||||
bits 6 to 7 FLEVEL (compression level)
|
||||
|
||||
The FCHECK value must be such that CMF and FLG, when viewed as
|
||||
a 16-bit unsigned integer stored in MSB order (CMF*256 + FLG),
|
||||
is a multiple of 31.
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 5]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
FDICT (Preset dictionary)
|
||||
If FDICT is set, a DICT dictionary identifier is present
|
||||
immediately after the FLG byte. The dictionary is a sequence of
|
||||
bytes which are initially fed to the compressor without
|
||||
producing any compressed output. DICT is the Adler-32 checksum
|
||||
of this sequence of bytes (see the definition of ADLER32
|
||||
below). The decompressor can use this identifier to determine
|
||||
which dictionary has been used by the compressor.
|
||||
|
||||
FLEVEL (Compression level)
|
||||
These flags are available for use by specific compression
|
||||
methods. The "deflate" method (CM = 8) sets these flags as
|
||||
follows:
|
||||
|
||||
0 - compressor used fastest algorithm
|
||||
1 - compressor used fast algorithm
|
||||
2 - compressor used default algorithm
|
||||
3 - compressor used maximum compression, slowest algorithm
|
||||
|
||||
The information in FLEVEL is not needed for decompression; it
|
||||
is there to indicate if recompression might be worthwhile.
|
||||
|
||||
compressed data
|
||||
For compression method 8, the compressed data is stored in the
|
||||
deflate compressed data format as described in the document
|
||||
"DEFLATE Compressed Data Format Specification" by L. Peter
|
||||
Deutsch. (See reference [3] in Chapter 3, below)
|
||||
|
||||
Other compressed data formats are not specified in this version
|
||||
of the zlib specification.
|
||||
|
||||
ADLER32 (Adler-32 checksum)
|
||||
This contains a checksum value of the uncompressed data
|
||||
(excluding any dictionary data) computed according to Adler-32
|
||||
algorithm. This algorithm is a 32-bit extension and improvement
|
||||
of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073
|
||||
standard. See references [4] and [5] in Chapter 3, below)
|
||||
|
||||
Adler-32 is composed of two sums accumulated per byte: s1 is
|
||||
the sum of all bytes, s2 is the sum of all s1 values. Both sums
|
||||
are done modulo 65521. s1 is initialized to 1, s2 to zero. The
|
||||
Adler-32 checksum is stored as s2*65536 + s1 in most-
|
||||
significant-byte first (network) order.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 6]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
2.3. Compliance
|
||||
|
||||
A compliant compressor must produce streams with correct CMF, FLG
|
||||
and ADLER32, but need not support preset dictionaries. When the
|
||||
zlib data format is used as part of another standard data format,
|
||||
the compressor may use only preset dictionaries that are specified
|
||||
by this other data format. If this other format does not use the
|
||||
preset dictionary feature, the compressor must not set the FDICT
|
||||
flag.
|
||||
|
||||
A compliant decompressor must check CMF, FLG, and ADLER32, and
|
||||
provide an error indication if any of these have incorrect values.
|
||||
A compliant decompressor must give an error indication if CM is
|
||||
not one of the values defined in this specification (only the
|
||||
value 8 is permitted in this version), since another value could
|
||||
indicate the presence of new features that would cause subsequent
|
||||
data to be interpreted incorrectly. A compliant decompressor must
|
||||
give an error indication if FDICT is set and DICTID is not the
|
||||
identifier of a known preset dictionary. A decompressor may
|
||||
ignore FLEVEL and still be compliant. When the zlib data format
|
||||
is being used as a part of another standard format, a compliant
|
||||
decompressor must support all the preset dictionaries specified by
|
||||
the other format. When the other format does not use the preset
|
||||
dictionary feature, a compliant decompressor must reject any
|
||||
stream in which the FDICT flag is set.
|
||||
|
||||
3. References
|
||||
|
||||
[1] Deutsch, L.P.,"GZIP Compressed Data Format Specification",
|
||||
available in ftp://ftp.uu.net/pub/archiving/zip/doc/
|
||||
|
||||
[2] Thomas Boutell, "PNG (Portable Network Graphics) specification",
|
||||
available in ftp://ftp.uu.net/graphics/png/documents/
|
||||
|
||||
[3] Deutsch, L.P.,"DEFLATE Compressed Data Format Specification",
|
||||
available in ftp://ftp.uu.net/pub/archiving/zip/doc/
|
||||
|
||||
[4] Fletcher, J. G., "An Arithmetic Checksum for Serial
|
||||
Transmissions," IEEE Transactions on Communications, Vol. COM-30,
|
||||
No. 1, January 1982, pp. 247-252.
|
||||
|
||||
[5] ITU-T Recommendation X.224, Annex D, "Checksum Algorithms,"
|
||||
November, 1993, pp. 144, 145. (Available from
|
||||
gopher://info.itu.ch). ITU-T X.244 is also the same as ISO 8073.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 7]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
4. Source code
|
||||
|
||||
Source code for a C language implementation of a "zlib" compliant
|
||||
library is available at ftp://ftp.uu.net/pub/archiving/zip/zlib/.
|
||||
|
||||
5. Security Considerations
|
||||
|
||||
A decoder that fails to check the ADLER32 checksum value may be
|
||||
subject to undetected data corruption.
|
||||
|
||||
6. Acknowledgements
|
||||
|
||||
Trademarks cited in this document are the property of their
|
||||
respective owners.
|
||||
|
||||
Jean-Loup Gailly and Mark Adler designed the zlib format and wrote
|
||||
the related software described in this specification. Glenn
|
||||
Randers-Pehrson converted this document to RFC and HTML format.
|
||||
|
||||
7. Authors' Addresses
|
||||
|
||||
L. Peter Deutsch
|
||||
Aladdin Enterprises
|
||||
203 Santa Margarita Ave.
|
||||
Menlo Park, CA 94025
|
||||
|
||||
Phone: (415) 322-0103 (AM only)
|
||||
FAX: (415) 322-1734
|
||||
EMail: <ghost@aladdin.com>
|
||||
|
||||
|
||||
Jean-Loup Gailly
|
||||
|
||||
EMail: <gzip@prep.ai.mit.edu>
|
||||
|
||||
Questions about the technical content of this specification can be
|
||||
sent by email to
|
||||
|
||||
Jean-Loup Gailly <gzip@prep.ai.mit.edu> and
|
||||
Mark Adler <madler@alumni.caltech.edu>
|
||||
|
||||
Editorial comments on this specification can be sent by email to
|
||||
|
||||
L. Peter Deutsch <ghost@aladdin.com> and
|
||||
Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 8]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
8. Appendix: Rationale
|
||||
|
||||
8.1. Preset dictionaries
|
||||
|
||||
A preset dictionary is specially useful to compress short input
|
||||
sequences. The compressor can take advantage of the dictionary
|
||||
context to encode the input in a more compact manner. The
|
||||
decompressor can be initialized with the appropriate context by
|
||||
virtually decompressing a compressed version of the dictionary
|
||||
without producing any output. However for certain compression
|
||||
algorithms such as the deflate algorithm this operation can be
|
||||
achieved without actually performing any decompression.
|
||||
|
||||
The compressor and the decompressor must use exactly the same
|
||||
dictionary. The dictionary may be fixed or may be chosen among a
|
||||
certain number of predefined dictionaries, according to the kind
|
||||
of input data. The decompressor can determine which dictionary has
|
||||
been chosen by the compressor by checking the dictionary
|
||||
identifier. This document does not specify the contents of
|
||||
predefined dictionaries, since the optimal dictionaries are
|
||||
application specific. Standard data formats using this feature of
|
||||
the zlib specification must precisely define the allowed
|
||||
dictionaries.
|
||||
|
||||
8.2. The Adler-32 algorithm
|
||||
|
||||
The Adler-32 algorithm is much faster than the CRC32 algorithm yet
|
||||
still provides an extremely low probability of undetected errors.
|
||||
|
||||
The modulo on unsigned long accumulators can be delayed for 5552
|
||||
bytes, so the modulo operation time is negligible. If the bytes
|
||||
are a, b, c, the second sum is 3a + 2b + c + 3, and so is position
|
||||
and order sensitive, unlike the first sum, which is just a
|
||||
checksum. That 65521 is prime is important to avoid a possible
|
||||
large class of two-byte errors that leave the check unchanged.
|
||||
(The Fletcher checksum uses 255, which is not prime and which also
|
||||
makes the Fletcher check insensitive to single byte changes 0 <->
|
||||
255.)
|
||||
|
||||
The sum s1 is initialized to 1 instead of zero to make the length
|
||||
of the sequence part of s2, so that the length does not have to be
|
||||
checked separately. (Any sequence of zeroes has a Fletcher
|
||||
checksum of zero.)
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 9]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
9. Appendix: Sample code
|
||||
|
||||
The following C code computes the Adler-32 checksum of a data buffer.
|
||||
It is written for clarity, not for speed. The sample code is in the
|
||||
ANSI C programming language. Non C users may find it easier to read
|
||||
with these hints:
|
||||
|
||||
& Bitwise AND operator.
|
||||
>> Bitwise right shift operator. When applied to an
|
||||
unsigned quantity, as here, right shift inserts zero bit(s)
|
||||
at the left.
|
||||
<< Bitwise left shift operator. Left shift inserts zero
|
||||
bit(s) at the right.
|
||||
++ "n++" increments the variable n.
|
||||
% modulo operator: a % b is the remainder of a divided by b.
|
||||
|
||||
#define BASE 65521 /* largest prime smaller than 65536 */
|
||||
|
||||
/*
|
||||
Update a running Adler-32 checksum with the bytes buf[0..len-1]
|
||||
and return the updated checksum. The Adler-32 checksum should be
|
||||
initialized to 1.
|
||||
|
||||
Usage example:
|
||||
|
||||
unsigned long adler = 1L;
|
||||
|
||||
while (read_buffer(buffer, length) != EOF) {
|
||||
adler = update_adler32(adler, buffer, length);
|
||||
}
|
||||
if (adler != original_adler) error();
|
||||
*/
|
||||
unsigned long update_adler32(unsigned long adler,
|
||||
unsigned char *buf, int len)
|
||||
{
|
||||
unsigned long s1 = adler & 0xffff;
|
||||
unsigned long s2 = (adler >> 16) & 0xffff;
|
||||
int n;
|
||||
|
||||
for (n = 0; n < len; n++) {
|
||||
s1 = (s1 + buf[n]) % BASE;
|
||||
s2 = (s2 + s1) % BASE;
|
||||
}
|
||||
return (s2 << 16) + s1;
|
||||
}
|
||||
|
||||
/* Return the adler32 of the bytes buf[0..len-1] */
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 10]
|
||||
|
||||
RFC 1950 ZLIB Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
unsigned long adler32(unsigned char *buf, int len)
|
||||
{
|
||||
return update_adler32(1L, buf, len);
|
||||
}
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch & Gailly Informational [Page 11]
|
||||
|
||||
@@ -1,955 +0,0 @@
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Network Working Group P. Deutsch
|
||||
Request for Comments: 1951 Aladdin Enterprises
|
||||
Category: Informational May 1996
|
||||
|
||||
|
||||
DEFLATE Compressed Data Format Specification version 1.3
|
||||
|
||||
Status of This Memo
|
||||
|
||||
This memo provides information for the Internet community. This memo
|
||||
does not specify an Internet standard of any kind. Distribution of
|
||||
this memo is unlimited.
|
||||
|
||||
IESG Note:
|
||||
|
||||
The IESG takes no position on the validity of any Intellectual
|
||||
Property Rights statements contained in this document.
|
||||
|
||||
Notices
|
||||
|
||||
Copyright (c) 1996 L. Peter Deutsch
|
||||
|
||||
Permission is granted to copy and distribute this document for any
|
||||
purpose and without charge, including translations into other
|
||||
languages and incorporation into compilations, provided that the
|
||||
copyright notice and this notice are preserved, and that any
|
||||
substantive changes or deletions from the original are clearly
|
||||
marked.
|
||||
|
||||
A pointer to the latest version of this and related documentation in
|
||||
HTML format can be found at the URL
|
||||
<ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>.
|
||||
|
||||
Abstract
|
||||
|
||||
This specification defines a lossless compressed data format that
|
||||
compresses data using a combination of the LZ77 algorithm and Huffman
|
||||
coding, with efficiency comparable to the best currently available
|
||||
general-purpose compression methods. The data can be produced or
|
||||
consumed, even for an arbitrarily long sequentially presented input
|
||||
data stream, using only an a priori bounded amount of intermediate
|
||||
storage. The format can be implemented readily in a manner not
|
||||
covered by patents.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 1]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
Table of Contents
|
||||
|
||||
1. Introduction ................................................... 2
|
||||
1.1. Purpose ................................................... 2
|
||||
1.2. Intended audience ......................................... 3
|
||||
1.3. Scope ..................................................... 3
|
||||
1.4. Compliance ................................................ 3
|
||||
1.5. Definitions of terms and conventions used ................ 3
|
||||
1.6. Changes from previous versions ............................ 4
|
||||
2. Compressed representation overview ............................. 4
|
||||
3. Detailed specification ......................................... 5
|
||||
3.1. Overall conventions ....................................... 5
|
||||
3.1.1. Packing into bytes .................................. 5
|
||||
3.2. Compressed block format ................................... 6
|
||||
3.2.1. Synopsis of prefix and Huffman coding ............... 6
|
||||
3.2.2. Use of Huffman coding in the "deflate" format ....... 7
|
||||
3.2.3. Details of block format ............................. 9
|
||||
3.2.4. Non-compressed blocks (BTYPE=00) ................... 11
|
||||
3.2.5. Compressed blocks (length and distance codes) ...... 11
|
||||
3.2.6. Compression with fixed Huffman codes (BTYPE=01) .... 12
|
||||
3.2.7. Compression with dynamic Huffman codes (BTYPE=10) .. 13
|
||||
3.3. Compliance ............................................... 14
|
||||
4. Compression algorithm details ................................. 14
|
||||
5. References .................................................... 16
|
||||
6. Security Considerations ....................................... 16
|
||||
7. Source code ................................................... 16
|
||||
8. Acknowledgements .............................................. 16
|
||||
9. Author's Address .............................................. 17
|
||||
|
||||
1. Introduction
|
||||
|
||||
1.1. Purpose
|
||||
|
||||
The purpose of this specification is to define a lossless
|
||||
compressed data format that:
|
||||
* Is independent of CPU type, operating system, file system,
|
||||
and character set, and hence can be used for interchange;
|
||||
* Can be produced or consumed, even for an arbitrarily long
|
||||
sequentially presented input data stream, using only an a
|
||||
priori bounded amount of intermediate storage, and hence
|
||||
can be used in data communications or similar structures
|
||||
such as Unix filters;
|
||||
* Compresses data with efficiency comparable to the best
|
||||
currently available general-purpose compression methods,
|
||||
and in particular considerably better than the "compress"
|
||||
program;
|
||||
* Can be implemented readily in a manner not covered by
|
||||
patents, and hence can be practiced freely;
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 2]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
* Is compatible with the file format produced by the current
|
||||
widely used gzip utility, in that conforming decompressors
|
||||
will be able to read data produced by the existing gzip
|
||||
compressor.
|
||||
|
||||
The data format defined by this specification does not attempt to:
|
||||
|
||||
* Allow random access to compressed data;
|
||||
* Compress specialized data (e.g., raster graphics) as well
|
||||
as the best currently available specialized algorithms.
|
||||
|
||||
A simple counting argument shows that no lossless compression
|
||||
algorithm can compress every possible input data set. For the
|
||||
format defined here, the worst case expansion is 5 bytes per 32K-
|
||||
byte block, i.e., a size increase of 0.015% for large data sets.
|
||||
English text usually compresses by a factor of 2.5 to 3;
|
||||
executable files usually compress somewhat less; graphical data
|
||||
such as raster images may compress much more.
|
||||
|
||||
1.2. Intended audience
|
||||
|
||||
This specification is intended for use by implementors of software
|
||||
to compress data into "deflate" format and/or decompress data from
|
||||
"deflate" format.
|
||||
|
||||
The text of the specification assumes a basic background in
|
||||
programming at the level of bits and other primitive data
|
||||
representations. Familiarity with the technique of Huffman coding
|
||||
is helpful but not required.
|
||||
|
||||
1.3. Scope
|
||||
|
||||
The specification specifies a method for representing a sequence
|
||||
of bytes as a (usually shorter) sequence of bits, and a method for
|
||||
packing the latter bit sequence into bytes.
|
||||
|
||||
1.4. Compliance
|
||||
|
||||
Unless otherwise indicated below, a compliant decompressor must be
|
||||
able to accept and decompress any data set that conforms to all
|
||||
the specifications presented here; a compliant compressor must
|
||||
produce data sets that conform to all the specifications presented
|
||||
here.
|
||||
|
||||
1.5. Definitions of terms and conventions used
|
||||
|
||||
Byte: 8 bits stored or transmitted as a unit (same as an octet).
|
||||
For this specification, a byte is exactly 8 bits, even on machines
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 3]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
which store a character on a number of bits different from eight.
|
||||
See below, for the numbering of bits within a byte.
|
||||
|
||||
String: a sequence of arbitrary bytes.
|
||||
|
||||
1.6. Changes from previous versions
|
||||
|
||||
There have been no technical changes to the deflate format since
|
||||
version 1.1 of this specification. In version 1.2, some
|
||||
terminology was changed. Version 1.3 is a conversion of the
|
||||
specification to RFC style.
|
||||
|
||||
2. Compressed representation overview
|
||||
|
||||
A compressed data set consists of a series of blocks, corresponding
|
||||
to successive blocks of input data. The block sizes are arbitrary,
|
||||
except that non-compressible blocks are limited to 65,535 bytes.
|
||||
|
||||
Each block is compressed using a combination of the LZ77 algorithm
|
||||
and Huffman coding. The Huffman trees for each block are independent
|
||||
of those for previous or subsequent blocks; the LZ77 algorithm may
|
||||
use a reference to a duplicated string occurring in a previous block,
|
||||
up to 32K input bytes before.
|
||||
|
||||
Each block consists of two parts: a pair of Huffman code trees that
|
||||
describe the representation of the compressed data part, and a
|
||||
compressed data part. (The Huffman trees themselves are compressed
|
||||
using Huffman encoding.) The compressed data consists of a series of
|
||||
elements of two types: literal bytes (of strings that have not been
|
||||
detected as duplicated within the previous 32K input bytes), and
|
||||
pointers to duplicated strings, where a pointer is represented as a
|
||||
pair <length, backward distance>. The representation used in the
|
||||
"deflate" format limits distances to 32K bytes and lengths to 258
|
||||
bytes, but does not limit the size of a block, except for
|
||||
uncompressible blocks, which are limited as noted above.
|
||||
|
||||
Each type of value (literals, distances, and lengths) in the
|
||||
compressed data is represented using a Huffman code, using one code
|
||||
tree for literals and lengths and a separate code tree for distances.
|
||||
The code trees for each block appear in a compact form just before
|
||||
the compressed data for that block.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 4]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
3. Detailed specification
|
||||
|
||||
3.1. Overall conventions In the diagrams below, a box like this:
|
||||
|
||||
+---+
|
||||
| | <-- the vertical bars might be missing
|
||||
+---+
|
||||
|
||||
represents one byte; a box like this:
|
||||
|
||||
+==============+
|
||||
| |
|
||||
+==============+
|
||||
|
||||
represents a variable number of bytes.
|
||||
|
||||
Bytes stored within a computer do not have a "bit order", since
|
||||
they are always treated as a unit. However, a byte considered as
|
||||
an integer between 0 and 255 does have a most- and least-
|
||||
significant bit, and since we write numbers with the most-
|
||||
significant digit on the left, we also write bytes with the most-
|
||||
significant bit on the left. In the diagrams below, we number the
|
||||
bits of a byte so that bit 0 is the least-significant bit, i.e.,
|
||||
the bits are numbered:
|
||||
|
||||
+--------+
|
||||
|76543210|
|
||||
+--------+
|
||||
|
||||
Within a computer, a number may occupy multiple bytes. All
|
||||
multi-byte numbers in the format described here are stored with
|
||||
the least-significant byte first (at the lower memory address).
|
||||
For example, the decimal number 520 is stored as:
|
||||
|
||||
0 1
|
||||
+--------+--------+
|
||||
|00001000|00000010|
|
||||
+--------+--------+
|
||||
^ ^
|
||||
| |
|
||||
| + more significant byte = 2 x 256
|
||||
+ less significant byte = 8
|
||||
|
||||
3.1.1. Packing into bytes
|
||||
|
||||
This document does not address the issue of the order in which
|
||||
bits of a byte are transmitted on a bit-sequential medium,
|
||||
since the final data format described here is byte- rather than
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 5]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
bit-oriented. However, we describe the compressed block format
|
||||
in below, as a sequence of data elements of various bit
|
||||
lengths, not a sequence of bytes. We must therefore specify
|
||||
how to pack these data elements into bytes to form the final
|
||||
compressed byte sequence:
|
||||
|
||||
* Data elements are packed into bytes in order of
|
||||
increasing bit number within the byte, i.e., starting
|
||||
with the least-significant bit of the byte.
|
||||
* Data elements other than Huffman codes are packed
|
||||
starting with the least-significant bit of the data
|
||||
element.
|
||||
* Huffman codes are packed starting with the most-
|
||||
significant bit of the code.
|
||||
|
||||
In other words, if one were to print out the compressed data as
|
||||
a sequence of bytes, starting with the first byte at the
|
||||
*right* margin and proceeding to the *left*, with the most-
|
||||
significant bit of each byte on the left as usual, one would be
|
||||
able to parse the result from right to left, with fixed-width
|
||||
elements in the correct MSB-to-LSB order and Huffman codes in
|
||||
bit-reversed order (i.e., with the first bit of the code in the
|
||||
relative LSB position).
|
||||
|
||||
3.2. Compressed block format
|
||||
|
||||
3.2.1. Synopsis of prefix and Huffman coding
|
||||
|
||||
Prefix coding represents symbols from an a priori known
|
||||
alphabet by bit sequences (codes), one code for each symbol, in
|
||||
a manner such that different symbols may be represented by bit
|
||||
sequences of different lengths, but a parser can always parse
|
||||
an encoded string unambiguously symbol-by-symbol.
|
||||
|
||||
We define a prefix code in terms of a binary tree in which the
|
||||
two edges descending from each non-leaf node are labeled 0 and
|
||||
1 and in which the leaf nodes correspond one-for-one with (are
|
||||
labeled with) the symbols of the alphabet; then the code for a
|
||||
symbol is the sequence of 0's and 1's on the edges leading from
|
||||
the root to the leaf labeled with that symbol. For example:
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 6]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
/\ Symbol Code
|
||||
0 1 ------ ----
|
||||
/ \ A 00
|
||||
/\ B B 1
|
||||
0 1 C 011
|
||||
/ \ D 010
|
||||
A /\
|
||||
0 1
|
||||
/ \
|
||||
D C
|
||||
|
||||
A parser can decode the next symbol from an encoded input
|
||||
stream by walking down the tree from the root, at each step
|
||||
choosing the edge corresponding to the next input bit.
|
||||
|
||||
Given an alphabet with known symbol frequencies, the Huffman
|
||||
algorithm allows the construction of an optimal prefix code
|
||||
(one which represents strings with those symbol frequencies
|
||||
using the fewest bits of any possible prefix codes for that
|
||||
alphabet). Such a code is called a Huffman code. (See
|
||||
reference [1] in Chapter 5, references for additional
|
||||
information on Huffman codes.)
|
||||
|
||||
Note that in the "deflate" format, the Huffman codes for the
|
||||
various alphabets must not exceed certain maximum code lengths.
|
||||
This constraint complicates the algorithm for computing code
|
||||
lengths from symbol frequencies. Again, see Chapter 5,
|
||||
references for details.
|
||||
|
||||
3.2.2. Use of Huffman coding in the "deflate" format
|
||||
|
||||
The Huffman codes used for each alphabet in the "deflate"
|
||||
format have two additional rules:
|
||||
|
||||
* All codes of a given bit length have lexicographically
|
||||
consecutive values, in the same order as the symbols
|
||||
they represent;
|
||||
|
||||
* Shorter codes lexicographically precede longer codes.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 7]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
We could recode the example above to follow this rule as
|
||||
follows, assuming that the order of the alphabet is ABCD:
|
||||
|
||||
Symbol Code
|
||||
------ ----
|
||||
A 10
|
||||
B 0
|
||||
C 110
|
||||
D 111
|
||||
|
||||
I.e., 0 precedes 10 which precedes 11x, and 110 and 111 are
|
||||
lexicographically consecutive.
|
||||
|
||||
Given this rule, we can define the Huffman code for an alphabet
|
||||
just by giving the bit lengths of the codes for each symbol of
|
||||
the alphabet in order; this is sufficient to determine the
|
||||
actual codes. In our example, the code is completely defined
|
||||
by the sequence of bit lengths (2, 1, 3, 3). The following
|
||||
algorithm generates the codes as integers, intended to be read
|
||||
from most- to least-significant bit. The code lengths are
|
||||
initially in tree[I].Len; the codes are produced in
|
||||
tree[I].Code.
|
||||
|
||||
1) Count the number of codes for each code length. Let
|
||||
bl_count[N] be the number of codes of length N, N >= 1.
|
||||
|
||||
2) Find the numerical value of the smallest code for each
|
||||
code length:
|
||||
|
||||
code = 0;
|
||||
bl_count[0] = 0;
|
||||
for (bits = 1; bits <= MAX_BITS; bits++) {
|
||||
code = (code + bl_count[bits-1]) << 1;
|
||||
next_code[bits] = code;
|
||||
}
|
||||
|
||||
3) Assign numerical values to all codes, using consecutive
|
||||
values for all codes of the same length with the base
|
||||
values determined at step 2. Codes that are never used
|
||||
(which have a bit length of zero) must not be assigned a
|
||||
value.
|
||||
|
||||
for (n = 0; n <= max_code; n++) {
|
||||
len = tree[n].Len;
|
||||
if (len != 0) {
|
||||
tree[n].Code = next_code[len];
|
||||
next_code[len]++;
|
||||
}
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 8]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
}
|
||||
|
||||
Example:
|
||||
|
||||
Consider the alphabet ABCDEFGH, with bit lengths (3, 3, 3, 3,
|
||||
3, 2, 4, 4). After step 1, we have:
|
||||
|
||||
N bl_count[N]
|
||||
- -----------
|
||||
2 1
|
||||
3 5
|
||||
4 2
|
||||
|
||||
Step 2 computes the following next_code values:
|
||||
|
||||
N next_code[N]
|
||||
- ------------
|
||||
1 0
|
||||
2 0
|
||||
3 2
|
||||
4 14
|
||||
|
||||
Step 3 produces the following code values:
|
||||
|
||||
Symbol Length Code
|
||||
------ ------ ----
|
||||
A 3 010
|
||||
B 3 011
|
||||
C 3 100
|
||||
D 3 101
|
||||
E 3 110
|
||||
F 2 00
|
||||
G 4 1110
|
||||
H 4 1111
|
||||
|
||||
3.2.3. Details of block format
|
||||
|
||||
Each block of compressed data begins with 3 header bits
|
||||
containing the following data:
|
||||
|
||||
first bit BFINAL
|
||||
next 2 bits BTYPE
|
||||
|
||||
Note that the header bits do not necessarily begin on a byte
|
||||
boundary, since a block does not necessarily occupy an integral
|
||||
number of bytes.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 9]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
BFINAL is set if and only if this is the last block of the data
|
||||
set.
|
||||
|
||||
BTYPE specifies how the data are compressed, as follows:
|
||||
|
||||
00 - no compression
|
||||
01 - compressed with fixed Huffman codes
|
||||
10 - compressed with dynamic Huffman codes
|
||||
11 - reserved (error)
|
||||
|
||||
The only difference between the two compressed cases is how the
|
||||
Huffman codes for the literal/length and distance alphabets are
|
||||
defined.
|
||||
|
||||
In all cases, the decoding algorithm for the actual data is as
|
||||
follows:
|
||||
|
||||
do
|
||||
read block header from input stream.
|
||||
if stored with no compression
|
||||
skip any remaining bits in current partially
|
||||
processed byte
|
||||
read LEN and NLEN (see next section)
|
||||
copy LEN bytes of data to output
|
||||
otherwise
|
||||
if compressed with dynamic Huffman codes
|
||||
read representation of code trees (see
|
||||
subsection below)
|
||||
loop (until end of block code recognized)
|
||||
decode literal/length value from input stream
|
||||
if value < 256
|
||||
copy value (literal byte) to output stream
|
||||
otherwise
|
||||
if value = end of block (256)
|
||||
break from loop
|
||||
otherwise (value = 257..285)
|
||||
decode distance from input stream
|
||||
|
||||
move backwards distance bytes in the output
|
||||
stream, and copy length bytes from this
|
||||
position to the output stream.
|
||||
end loop
|
||||
while not last block
|
||||
|
||||
Note that a duplicated string reference may refer to a string
|
||||
in a previous block; i.e., the backward distance may cross one
|
||||
or more block boundaries. However a distance cannot refer past
|
||||
the beginning of the output stream. (An application using a
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 10]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
preset dictionary might discard part of the output stream; a
|
||||
distance can refer to that part of the output stream anyway)
|
||||
Note also that the referenced string may overlap the current
|
||||
position; for example, if the last 2 bytes decoded have values
|
||||
X and Y, a string reference with <length = 5, distance = 2>
|
||||
adds X,Y,X,Y,X to the output stream.
|
||||
|
||||
We now specify each compression method in turn.
|
||||
|
||||
3.2.4. Non-compressed blocks (BTYPE=00)
|
||||
|
||||
Any bits of input up to the next byte boundary are ignored.
|
||||
The rest of the block consists of the following information:
|
||||
|
||||
0 1 2 3 4...
|
||||
+---+---+---+---+================================+
|
||||
| LEN | NLEN |... LEN bytes of literal data...|
|
||||
+---+---+---+---+================================+
|
||||
|
||||
LEN is the number of data bytes in the block. NLEN is the
|
||||
one's complement of LEN.
|
||||
|
||||
3.2.5. Compressed blocks (length and distance codes)
|
||||
|
||||
As noted above, encoded data blocks in the "deflate" format
|
||||
consist of sequences of symbols drawn from three conceptually
|
||||
distinct alphabets: either literal bytes, from the alphabet of
|
||||
byte values (0..255), or <length, backward distance> pairs,
|
||||
where the length is drawn from (3..258) and the distance is
|
||||
drawn from (1..32,768). In fact, the literal and length
|
||||
alphabets are merged into a single alphabet (0..285), where
|
||||
values 0..255 represent literal bytes, the value 256 indicates
|
||||
end-of-block, and values 257..285 represent length codes
|
||||
(possibly in conjunction with extra bits following the symbol
|
||||
code) as follows:
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 11]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
Extra Extra Extra
|
||||
Code Bits Length(s) Code Bits Lengths Code Bits Length(s)
|
||||
---- ---- ------ ---- ---- ------- ---- ---- -------
|
||||
257 0 3 267 1 15,16 277 4 67-82
|
||||
258 0 4 268 1 17,18 278 4 83-98
|
||||
259 0 5 269 2 19-22 279 4 99-114
|
||||
260 0 6 270 2 23-26 280 4 115-130
|
||||
261 0 7 271 2 27-30 281 5 131-162
|
||||
262 0 8 272 2 31-34 282 5 163-194
|
||||
263 0 9 273 3 35-42 283 5 195-226
|
||||
264 0 10 274 3 43-50 284 5 227-257
|
||||
265 1 11,12 275 3 51-58 285 0 258
|
||||
266 1 13,14 276 3 59-66
|
||||
|
||||
The extra bits should be interpreted as a machine integer
|
||||
stored with the most-significant bit first, e.g., bits 1110
|
||||
represent the value 14.
|
||||
|
||||
Extra Extra Extra
|
||||
Code Bits Dist Code Bits Dist Code Bits Distance
|
||||
---- ---- ---- ---- ---- ------ ---- ---- --------
|
||||
0 0 1 10 4 33-48 20 9 1025-1536
|
||||
1 0 2 11 4 49-64 21 9 1537-2048
|
||||
2 0 3 12 5 65-96 22 10 2049-3072
|
||||
3 0 4 13 5 97-128 23 10 3073-4096
|
||||
4 1 5,6 14 6 129-192 24 11 4097-6144
|
||||
5 1 7,8 15 6 193-256 25 11 6145-8192
|
||||
6 2 9-12 16 7 257-384 26 12 8193-12288
|
||||
7 2 13-16 17 7 385-512 27 12 12289-16384
|
||||
8 3 17-24 18 8 513-768 28 13 16385-24576
|
||||
9 3 25-32 19 8 769-1024 29 13 24577-32768
|
||||
|
||||
3.2.6. Compression with fixed Huffman codes (BTYPE=01)
|
||||
|
||||
The Huffman codes for the two alphabets are fixed, and are not
|
||||
represented explicitly in the data. The Huffman code lengths
|
||||
for the literal/length alphabet are:
|
||||
|
||||
Lit Value Bits Codes
|
||||
--------- ---- -----
|
||||
0 - 143 8 00110000 through
|
||||
10111111
|
||||
144 - 255 9 110010000 through
|
||||
111111111
|
||||
256 - 279 7 0000000 through
|
||||
0010111
|
||||
280 - 287 8 11000000 through
|
||||
11000111
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 12]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
The code lengths are sufficient to generate the actual codes,
|
||||
as described above; we show the codes in the table for added
|
||||
clarity. Literal/length values 286-287 will never actually
|
||||
occur in the compressed data, but participate in the code
|
||||
construction.
|
||||
|
||||
Distance codes 0-31 are represented by (fixed-length) 5-bit
|
||||
codes, with possible additional bits as shown in the table
|
||||
shown in Paragraph 3.2.5, above. Note that distance codes 30-
|
||||
31 will never actually occur in the compressed data.
|
||||
|
||||
3.2.7. Compression with dynamic Huffman codes (BTYPE=10)
|
||||
|
||||
The Huffman codes for the two alphabets appear in the block
|
||||
immediately after the header bits and before the actual
|
||||
compressed data, first the literal/length code and then the
|
||||
distance code. Each code is defined by a sequence of code
|
||||
lengths, as discussed in Paragraph 3.2.2, above. For even
|
||||
greater compactness, the code length sequences themselves are
|
||||
compressed using a Huffman code. The alphabet for code lengths
|
||||
is as follows:
|
||||
|
||||
0 - 15: Represent code lengths of 0 - 15
|
||||
16: Copy the previous code length 3 - 6 times.
|
||||
The next 2 bits indicate repeat length
|
||||
(0 = 3, ... , 3 = 6)
|
||||
Example: Codes 8, 16 (+2 bits 11),
|
||||
16 (+2 bits 10) will expand to
|
||||
12 code lengths of 8 (1 + 6 + 5)
|
||||
17: Repeat a code length of 0 for 3 - 10 times.
|
||||
(3 bits of length)
|
||||
18: Repeat a code length of 0 for 11 - 138 times
|
||||
(7 bits of length)
|
||||
|
||||
A code length of 0 indicates that the corresponding symbol in
|
||||
the literal/length or distance alphabet will not occur in the
|
||||
block, and should not participate in the Huffman code
|
||||
construction algorithm given earlier. If only one distance
|
||||
code is used, it is encoded using one bit, not zero bits; in
|
||||
this case there is a single code length of one, with one unused
|
||||
code. One distance code of zero bits means that there are no
|
||||
distance codes used at all (the data is all literals).
|
||||
|
||||
We can now define the format of the block:
|
||||
|
||||
5 Bits: HLIT, # of Literal/Length codes - 257 (257 - 286)
|
||||
5 Bits: HDIST, # of Distance codes - 1 (1 - 32)
|
||||
4 Bits: HCLEN, # of Code Length codes - 4 (4 - 19)
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 13]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
(HCLEN + 4) x 3 bits: code lengths for the code length
|
||||
alphabet given just above, in the order: 16, 17, 18,
|
||||
0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
|
||||
|
||||
These code lengths are interpreted as 3-bit integers
|
||||
(0-7); as above, a code length of 0 means the
|
||||
corresponding symbol (literal/length or distance code
|
||||
length) is not used.
|
||||
|
||||
HLIT + 257 code lengths for the literal/length alphabet,
|
||||
encoded using the code length Huffman code
|
||||
|
||||
HDIST + 1 code lengths for the distance alphabet,
|
||||
encoded using the code length Huffman code
|
||||
|
||||
The actual compressed data of the block,
|
||||
encoded using the literal/length and distance Huffman
|
||||
codes
|
||||
|
||||
The literal/length symbol 256 (end of data),
|
||||
encoded using the literal/length Huffman code
|
||||
|
||||
The code length repeat codes can cross from HLIT + 257 to the
|
||||
HDIST + 1 code lengths. In other words, all code lengths form
|
||||
a single sequence of HLIT + HDIST + 258 values.
|
||||
|
||||
3.3. Compliance
|
||||
|
||||
A compressor may limit further the ranges of values specified in
|
||||
the previous section and still be compliant; for example, it may
|
||||
limit the range of backward pointers to some value smaller than
|
||||
32K. Similarly, a compressor may limit the size of blocks so that
|
||||
a compressible block fits in memory.
|
||||
|
||||
A compliant decompressor must accept the full range of possible
|
||||
values defined in the previous section, and must accept blocks of
|
||||
arbitrary size.
|
||||
|
||||
4. Compression algorithm details
|
||||
|
||||
While it is the intent of this document to define the "deflate"
|
||||
compressed data format without reference to any particular
|
||||
compression algorithm, the format is related to the compressed
|
||||
formats produced by LZ77 (Lempel-Ziv 1977, see reference [2] below);
|
||||
since many variations of LZ77 are patented, it is strongly
|
||||
recommended that the implementor of a compressor follow the general
|
||||
algorithm presented here, which is known not to be patented per se.
|
||||
The material in this section is not part of the definition of the
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 14]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
specification per se, and a compressor need not follow it in order to
|
||||
be compliant.
|
||||
|
||||
The compressor terminates a block when it determines that starting a
|
||||
new block with fresh trees would be useful, or when the block size
|
||||
fills up the compressor's block buffer.
|
||||
|
||||
The compressor uses a chained hash table to find duplicated strings,
|
||||
using a hash function that operates on 3-byte sequences. At any
|
||||
given point during compression, let XYZ be the next 3 input bytes to
|
||||
be examined (not necessarily all different, of course). First, the
|
||||
compressor examines the hash chain for XYZ. If the chain is empty,
|
||||
the compressor simply writes out X as a literal byte and advances one
|
||||
byte in the input. If the hash chain is not empty, indicating that
|
||||
the sequence XYZ (or, if we are unlucky, some other 3 bytes with the
|
||||
same hash function value) has occurred recently, the compressor
|
||||
compares all strings on the XYZ hash chain with the actual input data
|
||||
sequence starting at the current point, and selects the longest
|
||||
match.
|
||||
|
||||
The compressor searches the hash chains starting with the most recent
|
||||
strings, to favor small distances and thus take advantage of the
|
||||
Huffman encoding. The hash chains are singly linked. There are no
|
||||
deletions from the hash chains; the algorithm simply discards matches
|
||||
that are too old. To avoid a worst-case situation, very long hash
|
||||
chains are arbitrarily truncated at a certain length, determined by a
|
||||
run-time parameter.
|
||||
|
||||
To improve overall compression, the compressor optionally defers the
|
||||
selection of matches ("lazy matching"): after a match of length N has
|
||||
been found, the compressor searches for a longer match starting at
|
||||
the next input byte. If it finds a longer match, it truncates the
|
||||
previous match to a length of one (thus producing a single literal
|
||||
byte) and then emits the longer match. Otherwise, it emits the
|
||||
original match, and, as described above, advances N bytes before
|
||||
continuing.
|
||||
|
||||
Run-time parameters also control this "lazy match" procedure. If
|
||||
compression ratio is most important, the compressor attempts a
|
||||
complete second search regardless of the length of the first match.
|
||||
In the normal case, if the current match is "long enough", the
|
||||
compressor reduces the search for a longer match, thus speeding up
|
||||
the process. If speed is most important, the compressor inserts new
|
||||
strings in the hash table only when no match was found, or when the
|
||||
match is not "too long". This degrades the compression ratio but
|
||||
saves time since there are both fewer insertions and fewer searches.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 15]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
5. References
|
||||
|
||||
[1] Huffman, D. A., "A Method for the Construction of Minimum
|
||||
Redundancy Codes", Proceedings of the Institute of Radio
|
||||
Engineers, September 1952, Volume 40, Number 9, pp. 1098-1101.
|
||||
|
||||
[2] Ziv J., Lempel A., "A Universal Algorithm for Sequential Data
|
||||
Compression", IEEE Transactions on Information Theory, Vol. 23,
|
||||
No. 3, pp. 337-343.
|
||||
|
||||
[3] Gailly, J.-L., and Adler, M., ZLIB documentation and sources,
|
||||
available in ftp://ftp.uu.net/pub/archiving/zip/doc/
|
||||
|
||||
[4] Gailly, J.-L., and Adler, M., GZIP documentation and sources,
|
||||
available as gzip-*.tar in ftp://prep.ai.mit.edu/pub/gnu/
|
||||
|
||||
[5] Schwartz, E. S., and Kallick, B. "Generating a canonical prefix
|
||||
encoding." Comm. ACM, 7,3 (Mar. 1964), pp. 166-169.
|
||||
|
||||
[6] Hirschberg and Lelewer, "Efficient decoding of prefix codes,"
|
||||
Comm. ACM, 33,4, April 1990, pp. 449-459.
|
||||
|
||||
6. Security Considerations
|
||||
|
||||
Any data compression method involves the reduction of redundancy in
|
||||
the data. Consequently, any corruption of the data is likely to have
|
||||
severe effects and be difficult to correct. Uncompressed text, on
|
||||
the other hand, will probably still be readable despite the presence
|
||||
of some corrupted bytes.
|
||||
|
||||
It is recommended that systems using this data format provide some
|
||||
means of validating the integrity of the compressed data. See
|
||||
reference [3], for example.
|
||||
|
||||
7. Source code
|
||||
|
||||
Source code for a C language implementation of a "deflate" compliant
|
||||
compressor and decompressor is available within the zlib package at
|
||||
ftp://ftp.uu.net/pub/archiving/zip/zlib/.
|
||||
|
||||
8. Acknowledgements
|
||||
|
||||
Trademarks cited in this document are the property of their
|
||||
respective owners.
|
||||
|
||||
Phil Katz designed the deflate format. Jean-Loup Gailly and Mark
|
||||
Adler wrote the related software described in this specification.
|
||||
Glenn Randers-Pehrson converted this document to RFC and HTML format.
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 16]
|
||||
|
||||
RFC 1951 DEFLATE Compressed Data Format Specification May 1996
|
||||
|
||||
|
||||
9. Author's Address
|
||||
|
||||
L. Peter Deutsch
|
||||
Aladdin Enterprises
|
||||
203 Santa Margarita Ave.
|
||||
Menlo Park, CA 94025
|
||||
|
||||
Phone: (415) 322-0103 (AM only)
|
||||
FAX: (415) 322-1734
|
||||
EMail: <ghost@aladdin.com>
|
||||
|
||||
Questions about the technical content of this specification can be
|
||||
sent by email to:
|
||||
|
||||
Jean-Loup Gailly <gzip@prep.ai.mit.edu> and
|
||||
Mark Adler <madler@alumni.caltech.edu>
|
||||
|
||||
Editorial comments on this specification can be sent by email to:
|
||||
|
||||
L. Peter Deutsch <ghost@aladdin.com> and
|
||||
Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 17]
|
||||
|
||||
@@ -1,675 +0,0 @@
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Network Working Group P. Deutsch
|
||||
Request for Comments: 1952 Aladdin Enterprises
|
||||
Category: Informational May 1996
|
||||
|
||||
|
||||
GZIP file format specification version 4.3
|
||||
|
||||
Status of This Memo
|
||||
|
||||
This memo provides information for the Internet community. This memo
|
||||
does not specify an Internet standard of any kind. Distribution of
|
||||
this memo is unlimited.
|
||||
|
||||
IESG Note:
|
||||
|
||||
The IESG takes no position on the validity of any Intellectual
|
||||
Property Rights statements contained in this document.
|
||||
|
||||
Notices
|
||||
|
||||
Copyright (c) 1996 L. Peter Deutsch
|
||||
|
||||
Permission is granted to copy and distribute this document for any
|
||||
purpose and without charge, including translations into other
|
||||
languages and incorporation into compilations, provided that the
|
||||
copyright notice and this notice are preserved, and that any
|
||||
substantive changes or deletions from the original are clearly
|
||||
marked.
|
||||
|
||||
A pointer to the latest version of this and related documentation in
|
||||
HTML format can be found at the URL
|
||||
<ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>.
|
||||
|
||||
Abstract
|
||||
|
||||
This specification defines a lossless compressed data format that is
|
||||
compatible with the widely used GZIP utility. The format includes a
|
||||
cyclic redundancy check value for detecting data corruption. The
|
||||
format presently uses the DEFLATE method of compression but can be
|
||||
easily extended to use other compression methods. The format can be
|
||||
implemented readily in a manner not covered by patents.
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 1]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
Table of Contents
|
||||
|
||||
1. Introduction ................................................... 2
|
||||
1.1. Purpose ................................................... 2
|
||||
1.2. Intended audience ......................................... 3
|
||||
1.3. Scope ..................................................... 3
|
||||
1.4. Compliance ................................................ 3
|
||||
1.5. Definitions of terms and conventions used ................. 3
|
||||
1.6. Changes from previous versions ............................ 3
|
||||
2. Detailed specification ......................................... 4
|
||||
2.1. Overall conventions ....................................... 4
|
||||
2.2. File format ............................................... 5
|
||||
2.3. Member format ............................................. 5
|
||||
2.3.1. Member header and trailer ........................... 6
|
||||
2.3.1.1. Extra field ................................... 8
|
||||
2.3.1.2. Compliance .................................... 9
|
||||
3. References .................................................. 9
|
||||
4. Security Considerations .................................... 10
|
||||
5. Acknowledgements ........................................... 10
|
||||
6. Author's Address ........................................... 10
|
||||
7. Appendix: Jean-Loup Gailly's gzip utility .................. 11
|
||||
8. Appendix: Sample CRC Code .................................. 11
|
||||
|
||||
1. Introduction
|
||||
|
||||
1.1. Purpose
|
||||
|
||||
The purpose of this specification is to define a lossless
|
||||
compressed data format that:
|
||||
|
||||
* Is independent of CPU type, operating system, file system,
|
||||
and character set, and hence can be used for interchange;
|
||||
* Can compress or decompress a data stream (as opposed to a
|
||||
randomly accessible file) to produce another data stream,
|
||||
using only an a priori bounded amount of intermediate
|
||||
storage, and hence can be used in data communications or
|
||||
similar structures such as Unix filters;
|
||||
* Compresses data with efficiency comparable to the best
|
||||
currently available general-purpose compression methods,
|
||||
and in particular considerably better than the "compress"
|
||||
program;
|
||||
* Can be implemented readily in a manner not covered by
|
||||
patents, and hence can be practiced freely;
|
||||
* Is compatible with the file format produced by the current
|
||||
widely used gzip utility, in that conforming decompressors
|
||||
will be able to read data produced by the existing gzip
|
||||
compressor.
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 2]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
The data format defined by this specification does not attempt to:
|
||||
|
||||
* Provide random access to compressed data;
|
||||
* Compress specialized data (e.g., raster graphics) as well as
|
||||
the best currently available specialized algorithms.
|
||||
|
||||
1.2. Intended audience
|
||||
|
||||
This specification is intended for use by implementors of software
|
||||
to compress data into gzip format and/or decompress data from gzip
|
||||
format.
|
||||
|
||||
The text of the specification assumes a basic background in
|
||||
programming at the level of bits and other primitive data
|
||||
representations.
|
||||
|
||||
1.3. Scope
|
||||
|
||||
The specification specifies a compression method and a file format
|
||||
(the latter assuming only that a file can store a sequence of
|
||||
arbitrary bytes). It does not specify any particular interface to
|
||||
a file system or anything about character sets or encodings
|
||||
(except for file names and comments, which are optional).
|
||||
|
||||
1.4. Compliance
|
||||
|
||||
Unless otherwise indicated below, a compliant decompressor must be
|
||||
able to accept and decompress any file that conforms to all the
|
||||
specifications presented here; a compliant compressor must produce
|
||||
files that conform to all the specifications presented here. The
|
||||
material in the appendices is not part of the specification per se
|
||||
and is not relevant to compliance.
|
||||
|
||||
1.5. Definitions of terms and conventions used
|
||||
|
||||
byte: 8 bits stored or transmitted as a unit (same as an octet).
|
||||
(For this specification, a byte is exactly 8 bits, even on
|
||||
machines which store a character on a number of bits different
|
||||
from 8.) See below for the numbering of bits within a byte.
|
||||
|
||||
1.6. Changes from previous versions
|
||||
|
||||
There have been no technical changes to the gzip format since
|
||||
version 4.1 of this specification. In version 4.2, some
|
||||
terminology was changed, and the sample CRC code was rewritten for
|
||||
clarity and to eliminate the requirement for the caller to do pre-
|
||||
and post-conditioning. Version 4.3 is a conversion of the
|
||||
specification to RFC style.
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 3]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
2. Detailed specification
|
||||
|
||||
2.1. Overall conventions
|
||||
|
||||
In the diagrams below, a box like this:
|
||||
|
||||
+---+
|
||||
| | <-- the vertical bars might be missing
|
||||
+---+
|
||||
|
||||
represents one byte; a box like this:
|
||||
|
||||
+==============+
|
||||
| |
|
||||
+==============+
|
||||
|
||||
represents a variable number of bytes.
|
||||
|
||||
Bytes stored within a computer do not have a "bit order", since
|
||||
they are always treated as a unit. However, a byte considered as
|
||||
an integer between 0 and 255 does have a most- and least-
|
||||
significant bit, and since we write numbers with the most-
|
||||
significant digit on the left, we also write bytes with the most-
|
||||
significant bit on the left. In the diagrams below, we number the
|
||||
bits of a byte so that bit 0 is the least-significant bit, i.e.,
|
||||
the bits are numbered:
|
||||
|
||||
+--------+
|
||||
|76543210|
|
||||
+--------+
|
||||
|
||||
This document does not address the issue of the order in which
|
||||
bits of a byte are transmitted on a bit-sequential medium, since
|
||||
the data format described here is byte- rather than bit-oriented.
|
||||
|
||||
Within a computer, a number may occupy multiple bytes. All
|
||||
multi-byte numbers in the format described here are stored with
|
||||
the least-significant byte first (at the lower memory address).
|
||||
For example, the decimal number 520 is stored as:
|
||||
|
||||
0 1
|
||||
+--------+--------+
|
||||
|00001000|00000010|
|
||||
+--------+--------+
|
||||
^ ^
|
||||
| |
|
||||
| + more significant byte = 2 x 256
|
||||
+ less significant byte = 8
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 4]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
2.2. File format
|
||||
|
||||
A gzip file consists of a series of "members" (compressed data
|
||||
sets). The format of each member is specified in the following
|
||||
section. The members simply appear one after another in the file,
|
||||
with no additional information before, between, or after them.
|
||||
|
||||
2.3. Member format
|
||||
|
||||
Each member has the following structure:
|
||||
|
||||
+---+---+---+---+---+---+---+---+---+---+
|
||||
|ID1|ID2|CM |FLG| MTIME |XFL|OS | (more-->)
|
||||
+---+---+---+---+---+---+---+---+---+---+
|
||||
|
||||
(if FLG.FEXTRA set)
|
||||
|
||||
+---+---+=================================+
|
||||
| XLEN |...XLEN bytes of "extra field"...| (more-->)
|
||||
+---+---+=================================+
|
||||
|
||||
(if FLG.FNAME set)
|
||||
|
||||
+=========================================+
|
||||
|...original file name, zero-terminated...| (more-->)
|
||||
+=========================================+
|
||||
|
||||
(if FLG.FCOMMENT set)
|
||||
|
||||
+===================================+
|
||||
|...file comment, zero-terminated...| (more-->)
|
||||
+===================================+
|
||||
|
||||
(if FLG.FHCRC set)
|
||||
|
||||
+---+---+
|
||||
| CRC16 |
|
||||
+---+---+
|
||||
|
||||
+=======================+
|
||||
|...compressed blocks...| (more-->)
|
||||
+=======================+
|
||||
|
||||
0 1 2 3 4 5 6 7
|
||||
+---+---+---+---+---+---+---+---+
|
||||
| CRC32 | ISIZE |
|
||||
+---+---+---+---+---+---+---+---+
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 5]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
2.3.1. Member header and trailer
|
||||
|
||||
ID1 (IDentification 1)
|
||||
ID2 (IDentification 2)
|
||||
These have the fixed values ID1 = 31 (0x1f, \037), ID2 = 139
|
||||
(0x8b, \213), to identify the file as being in gzip format.
|
||||
|
||||
CM (Compression Method)
|
||||
This identifies the compression method used in the file. CM
|
||||
= 0-7 are reserved. CM = 8 denotes the "deflate"
|
||||
compression method, which is the one customarily used by
|
||||
gzip and which is documented elsewhere.
|
||||
|
||||
FLG (FLaGs)
|
||||
This flag byte is divided into individual bits as follows:
|
||||
|
||||
bit 0 FTEXT
|
||||
bit 1 FHCRC
|
||||
bit 2 FEXTRA
|
||||
bit 3 FNAME
|
||||
bit 4 FCOMMENT
|
||||
bit 5 reserved
|
||||
bit 6 reserved
|
||||
bit 7 reserved
|
||||
|
||||
If FTEXT is set, the file is probably ASCII text. This is
|
||||
an optional indication, which the compressor may set by
|
||||
checking a small amount of the input data to see whether any
|
||||
non-ASCII characters are present. In case of doubt, FTEXT
|
||||
is cleared, indicating binary data. For systems which have
|
||||
different file formats for ascii text and binary data, the
|
||||
decompressor can use FTEXT to choose the appropriate format.
|
||||
We deliberately do not specify the algorithm used to set
|
||||
this bit, since a compressor always has the option of
|
||||
leaving it cleared and a decompressor always has the option
|
||||
of ignoring it and letting some other program handle issues
|
||||
of data conversion.
|
||||
|
||||
If FHCRC is set, a CRC16 for the gzip header is present,
|
||||
immediately before the compressed data. The CRC16 consists
|
||||
of the two least significant bytes of the CRC32 for all
|
||||
bytes of the gzip header up to and not including the CRC16.
|
||||
[The FHCRC bit was never set by versions of gzip up to
|
||||
1.2.4, even though it was documented with a different
|
||||
meaning in gzip 1.2.4.]
|
||||
|
||||
If FEXTRA is set, optional extra fields are present, as
|
||||
described in a following section.
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 6]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
If FNAME is set, an original file name is present,
|
||||
terminated by a zero byte. The name must consist of ISO
|
||||
8859-1 (LATIN-1) characters; on operating systems using
|
||||
EBCDIC or any other character set for file names, the name
|
||||
must be translated to the ISO LATIN-1 character set. This
|
||||
is the original name of the file being compressed, with any
|
||||
directory components removed, and, if the file being
|
||||
compressed is on a file system with case insensitive names,
|
||||
forced to lower case. There is no original file name if the
|
||||
data was compressed from a source other than a named file;
|
||||
for example, if the source was stdin on a Unix system, there
|
||||
is no file name.
|
||||
|
||||
If FCOMMENT is set, a zero-terminated file comment is
|
||||
present. This comment is not interpreted; it is only
|
||||
intended for human consumption. The comment must consist of
|
||||
ISO 8859-1 (LATIN-1) characters. Line breaks should be
|
||||
denoted by a single line feed character (10 decimal).
|
||||
|
||||
Reserved FLG bits must be zero.
|
||||
|
||||
MTIME (Modification TIME)
|
||||
This gives the most recent modification time of the original
|
||||
file being compressed. The time is in Unix format, i.e.,
|
||||
seconds since 00:00:00 GMT, Jan. 1, 1970. (Note that this
|
||||
may cause problems for MS-DOS and other systems that use
|
||||
local rather than Universal time.) If the compressed data
|
||||
did not come from a file, MTIME is set to the time at which
|
||||
compression started. MTIME = 0 means no time stamp is
|
||||
available.
|
||||
|
||||
XFL (eXtra FLags)
|
||||
These flags are available for use by specific compression
|
||||
methods. The "deflate" method (CM = 8) sets these flags as
|
||||
follows:
|
||||
|
||||
XFL = 2 - compressor used maximum compression,
|
||||
slowest algorithm
|
||||
XFL = 4 - compressor used fastest algorithm
|
||||
|
||||
OS (Operating System)
|
||||
This identifies the type of file system on which compression
|
||||
took place. This may be useful in determining end-of-line
|
||||
convention for text files. The currently defined values are
|
||||
as follows:
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 7]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
0 - FAT filesystem (MS-DOS, OS/2, NT/Win32)
|
||||
1 - Amiga
|
||||
2 - VMS (or OpenVMS)
|
||||
3 - Unix
|
||||
4 - VM/CMS
|
||||
5 - Atari TOS
|
||||
6 - HPFS filesystem (OS/2, NT)
|
||||
7 - Macintosh
|
||||
8 - Z-System
|
||||
9 - CP/M
|
||||
10 - TOPS-20
|
||||
11 - NTFS filesystem (NT)
|
||||
12 - QDOS
|
||||
13 - Acorn RISCOS
|
||||
255 - unknown
|
||||
|
||||
XLEN (eXtra LENgth)
|
||||
If FLG.FEXTRA is set, this gives the length of the optional
|
||||
extra field. See below for details.
|
||||
|
||||
CRC32 (CRC-32)
|
||||
This contains a Cyclic Redundancy Check value of the
|
||||
uncompressed data computed according to CRC-32 algorithm
|
||||
used in the ISO 3309 standard and in section 8.1.1.6.2 of
|
||||
ITU-T recommendation V.42. (See http://www.iso.ch for
|
||||
ordering ISO documents. See gopher://info.itu.ch for an
|
||||
online version of ITU-T V.42.)
|
||||
|
||||
ISIZE (Input SIZE)
|
||||
This contains the size of the original (uncompressed) input
|
||||
data modulo 2^32.
|
||||
|
||||
2.3.1.1. Extra field
|
||||
|
||||
If the FLG.FEXTRA bit is set, an "extra field" is present in
|
||||
the header, with total length XLEN bytes. It consists of a
|
||||
series of subfields, each of the form:
|
||||
|
||||
+---+---+---+---+==================================+
|
||||
|SI1|SI2| LEN |... LEN bytes of subfield data ...|
|
||||
+---+---+---+---+==================================+
|
||||
|
||||
SI1 and SI2 provide a subfield ID, typically two ASCII letters
|
||||
with some mnemonic value. Jean-Loup Gailly
|
||||
<gzip@prep.ai.mit.edu> is maintaining a registry of subfield
|
||||
IDs; please send him any subfield ID you wish to use. Subfield
|
||||
IDs with SI2 = 0 are reserved for future use. The following
|
||||
IDs are currently defined:
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 8]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
SI1 SI2 Data
|
||||
---------- ---------- ----
|
||||
0x41 ('A') 0x70 ('P') Apollo file type information
|
||||
|
||||
LEN gives the length of the subfield data, excluding the 4
|
||||
initial bytes.
|
||||
|
||||
2.3.1.2. Compliance
|
||||
|
||||
A compliant compressor must produce files with correct ID1,
|
||||
ID2, CM, CRC32, and ISIZE, but may set all the other fields in
|
||||
the fixed-length part of the header to default values (255 for
|
||||
OS, 0 for all others). The compressor must set all reserved
|
||||
bits to zero.
|
||||
|
||||
A compliant decompressor must check ID1, ID2, and CM, and
|
||||
provide an error indication if any of these have incorrect
|
||||
values. It must examine FEXTRA/XLEN, FNAME, FCOMMENT and FHCRC
|
||||
at least so it can skip over the optional fields if they are
|
||||
present. It need not examine any other part of the header or
|
||||
trailer; in particular, a decompressor may ignore FTEXT and OS
|
||||
and always produce binary output, and still be compliant. A
|
||||
compliant decompressor must give an error indication if any
|
||||
reserved bit is non-zero, since such a bit could indicate the
|
||||
presence of a new field that would cause subsequent data to be
|
||||
interpreted incorrectly.
|
||||
|
||||
3. References
|
||||
|
||||
[1] "Information Processing - 8-bit single-byte coded graphic
|
||||
character sets - Part 1: Latin alphabet No.1" (ISO 8859-1:1987).
|
||||
The ISO 8859-1 (Latin-1) character set is a superset of 7-bit
|
||||
ASCII. Files defining this character set are available as
|
||||
iso_8859-1.* in ftp://ftp.uu.net/graphics/png/documents/
|
||||
|
||||
[2] ISO 3309
|
||||
|
||||
[3] ITU-T recommendation V.42
|
||||
|
||||
[4] Deutsch, L.P.,"DEFLATE Compressed Data Format Specification",
|
||||
available in ftp://ftp.uu.net/pub/archiving/zip/doc/
|
||||
|
||||
[5] Gailly, J.-L., GZIP documentation, available as gzip-*.tar in
|
||||
ftp://prep.ai.mit.edu/pub/gnu/
|
||||
|
||||
[6] Sarwate, D.V., "Computation of Cyclic Redundancy Checks via Table
|
||||
Look-Up", Communications of the ACM, 31(8), pp.1008-1013.
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 9]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
[7] Schwaderer, W.D., "CRC Calculation", April 85 PC Tech Journal,
|
||||
pp.118-133.
|
||||
|
||||
[8] ftp://ftp.adelaide.edu.au/pub/rocksoft/papers/crc_v3.txt,
|
||||
describing the CRC concept.
|
||||
|
||||
4. Security Considerations
|
||||
|
||||
Any data compression method involves the reduction of redundancy in
|
||||
the data. Consequently, any corruption of the data is likely to have
|
||||
severe effects and be difficult to correct. Uncompressed text, on
|
||||
the other hand, will probably still be readable despite the presence
|
||||
of some corrupted bytes.
|
||||
|
||||
It is recommended that systems using this data format provide some
|
||||
means of validating the integrity of the compressed data, such as by
|
||||
setting and checking the CRC-32 check value.
|
||||
|
||||
5. Acknowledgements
|
||||
|
||||
Trademarks cited in this document are the property of their
|
||||
respective owners.
|
||||
|
||||
Jean-Loup Gailly designed the gzip format and wrote, with Mark Adler,
|
||||
the related software described in this specification. Glenn
|
||||
Randers-Pehrson converted this document to RFC and HTML format.
|
||||
|
||||
6. Author's Address
|
||||
|
||||
L. Peter Deutsch
|
||||
Aladdin Enterprises
|
||||
203 Santa Margarita Ave.
|
||||
Menlo Park, CA 94025
|
||||
|
||||
Phone: (415) 322-0103 (AM only)
|
||||
FAX: (415) 322-1734
|
||||
EMail: <ghost@aladdin.com>
|
||||
|
||||
Questions about the technical content of this specification can be
|
||||
sent by email to:
|
||||
|
||||
Jean-Loup Gailly <gzip@prep.ai.mit.edu> and
|
||||
Mark Adler <madler@alumni.caltech.edu>
|
||||
|
||||
Editorial comments on this specification can be sent by email to:
|
||||
|
||||
L. Peter Deutsch <ghost@aladdin.com> and
|
||||
Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 10]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
7. Appendix: Jean-Loup Gailly's gzip utility
|
||||
|
||||
The most widely used implementation of gzip compression, and the
|
||||
original documentation on which this specification is based, were
|
||||
created by Jean-Loup Gailly <gzip@prep.ai.mit.edu>. Since this
|
||||
implementation is a de facto standard, we mention some more of its
|
||||
features here. Again, the material in this section is not part of
|
||||
the specification per se, and implementations need not follow it to
|
||||
be compliant.
|
||||
|
||||
When compressing or decompressing a file, gzip preserves the
|
||||
protection, ownership, and modification time attributes on the local
|
||||
file system, since there is no provision for representing protection
|
||||
attributes in the gzip file format itself. Since the file format
|
||||
includes a modification time, the gzip decompressor provides a
|
||||
command line switch that assigns the modification time from the file,
|
||||
rather than the local modification time of the compressed input, to
|
||||
the decompressed output.
|
||||
|
||||
8. Appendix: Sample CRC Code
|
||||
|
||||
The following sample code represents a practical implementation of
|
||||
the CRC (Cyclic Redundancy Check). (See also ISO 3309 and ITU-T V.42
|
||||
for a formal specification.)
|
||||
|
||||
The sample code is in the ANSI C programming language. Non C users
|
||||
may find it easier to read with these hints:
|
||||
|
||||
& Bitwise AND operator.
|
||||
^ Bitwise exclusive-OR operator.
|
||||
>> Bitwise right shift operator. When applied to an
|
||||
unsigned quantity, as here, right shift inserts zero
|
||||
bit(s) at the left.
|
||||
! Logical NOT operator.
|
||||
++ "n++" increments the variable n.
|
||||
0xNNN 0x introduces a hexadecimal (base 16) constant.
|
||||
Suffix L indicates a long value (at least 32 bits).
|
||||
|
||||
/* Table of CRCs of all 8-bit messages. */
|
||||
unsigned long crc_table[256];
|
||||
|
||||
/* Flag: has the table been computed? Initially false. */
|
||||
int crc_table_computed = 0;
|
||||
|
||||
/* Make the table for a fast CRC. */
|
||||
void make_crc_table(void)
|
||||
{
|
||||
unsigned long c;
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 11]
|
||||
|
||||
RFC 1952 GZIP File Format Specification May 1996
|
||||
|
||||
|
||||
int n, k;
|
||||
for (n = 0; n < 256; n++) {
|
||||
c = (unsigned long) n;
|
||||
for (k = 0; k < 8; k++) {
|
||||
if (c & 1) {
|
||||
c = 0xedb88320L ^ (c >> 1);
|
||||
} else {
|
||||
c = c >> 1;
|
||||
}
|
||||
}
|
||||
crc_table[n] = c;
|
||||
}
|
||||
crc_table_computed = 1;
|
||||
}
|
||||
|
||||
/*
|
||||
Update a running crc with the bytes buf[0..len-1] and return
|
||||
the updated crc. The crc should be initialized to zero. Pre- and
|
||||
post-conditioning (one's complement) is performed within this
|
||||
function so it shouldn't be done by the caller. Usage example:
|
||||
|
||||
unsigned long crc = 0L;
|
||||
|
||||
while (read_buffer(buffer, length) != EOF) {
|
||||
crc = update_crc(crc, buffer, length);
|
||||
}
|
||||
if (crc != original_crc) error();
|
||||
*/
|
||||
unsigned long update_crc(unsigned long crc,
|
||||
unsigned char *buf, int len)
|
||||
{
|
||||
unsigned long c = crc ^ 0xffffffffL;
|
||||
int n;
|
||||
|
||||
if (!crc_table_computed)
|
||||
make_crc_table();
|
||||
for (n = 0; n < len; n++) {
|
||||
c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
|
||||
}
|
||||
return c ^ 0xffffffffL;
|
||||
}
|
||||
|
||||
/* Return the CRC of the bytes buf[0..len-1]. */
|
||||
unsigned long crc(unsigned char *buf, int len)
|
||||
{
|
||||
return update_crc(0L, buf, len);
|
||||
}
|
||||
|
||||
|
||||
|
||||
|
||||
Deutsch Informational [Page 12]
|
||||
|
||||
@@ -1,107 +0,0 @@
|
||||
A Fast Method for Identifying Plain Text Files
|
||||
==============================================
|
||||
|
||||
|
||||
Introduction
|
||||
------------
|
||||
|
||||
Given a file coming from an unknown source, it is sometimes desirable
|
||||
to find out whether the format of that file is plain text. Although
|
||||
this may appear like a simple task, a fully accurate detection of the
|
||||
file type requires heavy-duty semantic analysis on the file contents.
|
||||
It is, however, possible to obtain satisfactory results by employing
|
||||
various heuristics.
|
||||
|
||||
Previous versions of PKZip and other zip-compatible compression tools
|
||||
were using a crude detection scheme: if more than 80% (4/5) of the bytes
|
||||
found in a certain buffer are within the range [7..127], the file is
|
||||
labeled as plain text, otherwise it is labeled as binary. A prominent
|
||||
limitation of this scheme is the restriction to Latin-based alphabets.
|
||||
Other alphabets, like Greek, Cyrillic or Asian, make extensive use of
|
||||
the bytes within the range [128..255], and texts using these alphabets
|
||||
are most often misidentified by this scheme; in other words, the rate
|
||||
of false negatives is sometimes too high, which means that the recall
|
||||
is low. Another weakness of this scheme is a reduced precision, due to
|
||||
the false positives that may occur when binary files containing large
|
||||
amounts of textual characters are misidentified as plain text.
|
||||
|
||||
In this article we propose a new, simple detection scheme that features
|
||||
a much increased precision and a near-100% recall. This scheme is
|
||||
designed to work on ASCII, Unicode and other ASCII-derived alphabets,
|
||||
and it handles single-byte encodings (ISO-8859, MacRoman, KOI8, etc.)
|
||||
and variable-sized encodings (ISO-2022, UTF-8, etc.). Wider encodings
|
||||
(UCS-2/UTF-16 and UCS-4/UTF-32) are not handled, however.
|
||||
|
||||
|
||||
The Algorithm
|
||||
-------------
|
||||
|
||||
The algorithm works by dividing the set of bytecodes [0..255] into three
|
||||
categories:
|
||||
- The white list of textual bytecodes:
|
||||
9 (TAB), 10 (LF), 13 (CR), 32 (SPACE) to 255.
|
||||
- The gray list of tolerated bytecodes:
|
||||
7 (BEL), 8 (BS), 11 (VT), 12 (FF), 26 (SUB), 27 (ESC).
|
||||
- The black list of undesired, non-textual bytecodes:
|
||||
0 (NUL) to 6, 14 to 31.
|
||||
|
||||
If a file contains at least one byte that belongs to the white list and
|
||||
no byte that belongs to the black list, then the file is categorized as
|
||||
plain text; otherwise, it is categorized as binary. (The boundary case,
|
||||
when the file is empty, automatically falls into the latter category.)
|
||||
|
||||
|
||||
Rationale
|
||||
---------
|
||||
|
||||
The idea behind this algorithm relies on two observations.
|
||||
|
||||
The first observation is that, although the full range of 7-bit codes
|
||||
[0..127] is properly specified by the ASCII standard, most control
|
||||
characters in the range [0..31] are not used in practice. The only
|
||||
widely-used, almost universally-portable control codes are 9 (TAB),
|
||||
10 (LF) and 13 (CR). There are a few more control codes that are
|
||||
recognized on a reduced range of platforms and text viewers/editors:
|
||||
7 (BEL), 8 (BS), 11 (VT), 12 (FF), 26 (SUB) and 27 (ESC); but these
|
||||
codes are rarely (if ever) used alone, without being accompanied by
|
||||
some printable text. Even the newer, portable text formats such as
|
||||
XML avoid using control characters outside the list mentioned here.
|
||||
|
||||
The second observation is that most of the binary files tend to contain
|
||||
control characters, especially 0 (NUL). Even though the older text
|
||||
detection schemes observe the presence of non-ASCII codes from the range
|
||||
[128..255], the precision rarely has to suffer if this upper range is
|
||||
labeled as textual, because the files that are genuinely binary tend to
|
||||
contain both control characters and codes from the upper range. On the
|
||||
other hand, the upper range needs to be labeled as textual, because it
|
||||
is used by virtually all ASCII extensions. In particular, this range is
|
||||
used for encoding non-Latin scripts.
|
||||
|
||||
Since there is no counting involved, other than simply observing the
|
||||
presence or the absence of some byte values, the algorithm produces
|
||||
consistent results, regardless what alphabet encoding is being used.
|
||||
(If counting were involved, it could be possible to obtain different
|
||||
results on a text encoded, say, using ISO-8859-16 versus UTF-8.)
|
||||
|
||||
There is an extra category of plain text files that are "polluted" with
|
||||
one or more black-listed codes, either by mistake or by peculiar design
|
||||
considerations. In such cases, a scheme that tolerates a small fraction
|
||||
of black-listed codes would provide an increased recall (i.e. more true
|
||||
positives). This, however, incurs a reduced precision overall, since
|
||||
false positives are more likely to appear in binary files that contain
|
||||
large chunks of textual data. Furthermore, "polluted" plain text should
|
||||
be regarded as binary by general-purpose text detection schemes, because
|
||||
general-purpose text processing algorithms might not be applicable.
|
||||
Under this premise, it is safe to say that our detection method provides
|
||||
a near-100% recall.
|
||||
|
||||
Experiments have been run on many files coming from various platforms
|
||||
and applications. We tried plain text files, system logs, source code,
|
||||
formatted office documents, compiled object code, etc. The results
|
||||
confirm the optimistic assumptions about the capabilities of this
|
||||
algorithm.
|
||||
|
||||
|
||||
--
|
||||
Cosmin Truta
|
||||
Last updated: 2006-May-28
|
||||
+1
-1
@@ -119,7 +119,7 @@ retrieve the stack trace when script evaluation returns
|
||||
\fBTCL_ERROR\fR, like so:
|
||||
.PP
|
||||
.CS
|
||||
int code = Tcl_EvalEx(interp, script, -1, 0);
|
||||
int code = Tcl_Eval(interp, script);
|
||||
if (code == TCL_ERROR) {
|
||||
Tcl_Obj *options = \fBTcl_GetReturnOptions\fR(interp, code);
|
||||
Tcl_Obj *key = Tcl_NewStringObj("-errorinfo", -1);
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_CallWhenDeleted 3 7.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_CommandComplete 3 "" Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_Concat 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_CreateFileHandler 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_CreateInterp 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_CreateTimerHandler 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_DetachPids 3 "" Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_DictObj 3 8.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_DoWhenIdle 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_PutEnv 3 "7.5" Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -205,7 +205,7 @@ and sets \fIinterp\fR's result to an error message indicating that
|
||||
the \fBreturn\fR, \fBbreak\fR, or \fBcontinue\fR command was
|
||||
invoked in an inappropriate place.
|
||||
This means that top-level applications should never see a return code
|
||||
from \fBTcl_EvalObjEx\fR other then \fBTCL_OK\fR or \fBTCL_ERROR\fR.
|
||||
from \fBTcl_EvalObjEx\fR other than \fBTCL_OK\fR or \fBTCL_ERROR\fR.
|
||||
|
||||
.SH KEYWORDS
|
||||
execute, file, global, result, script, value
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_ExprLongObj 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_FindExecutable 3 8.1 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_GetCwd 3 8.1 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_GetIndexFromObj 3 8.1 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_GetOpenFile 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_GetTime 3 8.4 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -281,7 +281,7 @@ The \fIhashKeyProc\fR member contains the address of a function called to
|
||||
calculate a hash value for the key.
|
||||
.PP
|
||||
.CS
|
||||
typedef TCL_HASH_TYPE \fBTcl_HashKeyProc\fR(
|
||||
typedef unsigned int \fBTcl_HashKeyProc\fR(
|
||||
Tcl_HashTable *\fItablePtr\fR,
|
||||
void *\fIkeyPtr\fR);
|
||||
.CE
|
||||
|
||||
+1
-1
@@ -1,7 +1,7 @@
|
||||
'\"
|
||||
'\" Copyright (c) 1998-2000 by Scriptics Corporation.
|
||||
'\" All rights reserved.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_Init 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+4
-4
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_InitStubs 3 8.1 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
@@ -23,11 +23,11 @@ Tcl interpreter handle.
|
||||
A version string consisting of one or more decimal numbers
|
||||
separated by dots.
|
||||
.AP int exact in
|
||||
1 means that only the particular version specified by
|
||||
Non-zero means that only the particular version specified by
|
||||
\fIversion\fR is acceptable.
|
||||
0 means that versions newer than \fIversion\fR are also
|
||||
Zero means that versions newer than \fIversion\fR are also
|
||||
acceptable as long as they have the same major version number
|
||||
as \fIversion\fR. Other bits have no effect.
|
||||
as \fIversion\fR.
|
||||
.BE
|
||||
.SH INTRODUCTION
|
||||
.PP
|
||||
|
||||
+1
-1
@@ -97,7 +97,7 @@ are provided by the C language standard. The \fBTcl_WideInt\fR type is a
|
||||
typedef defined to be whatever signed integral type covers at least the
|
||||
64-bit integer range (-9223372036854775808 to 9223372036854775807). Depending
|
||||
on the platform and the C compiler, the actual type might be
|
||||
\fBlong int\fR, \fBlong long int\fR, \fBint64\fR, or something else.
|
||||
\fBlong int\fR, \fBlong long int\fR, \fB__int64\fR, or something else.
|
||||
The \fBmp_int\fR type is a multiple-precision integer type defined
|
||||
by the LibTomMath multiple-precision integer library.
|
||||
.PP
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_LimitCheck 3 8.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Load 3 8.6 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+2
-2
@@ -3,10 +3,10 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
'\" Note that some of these functions do not seem to belong, but they
|
||||
'\" were all introduced with the same TIP (#139)
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_Namespace 3 8.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+3
-17
@@ -4,12 +4,12 @@
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
.TH Tcl_OpenTcpClient 3 8.7 Tcl "Tcl Library Procedures"
|
||||
.TH Tcl_OpenTcpClient 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
'\" Note: do not modify the .SH NAME line immediately below!
|
||||
.SH NAME
|
||||
Tcl_OpenTcpClient, Tcl_MakeTcpClientChannel, Tcl_OpenTcpServer, Tcl_OpenTcpServerEx \- procedures to open channels using TCP sockets
|
||||
Tcl_OpenTcpClient, Tcl_MakeTcpClientChannel, Tcl_OpenTcpServer \- procedures to open channels using TCP sockets
|
||||
.SH SYNOPSIS
|
||||
.nf
|
||||
\fB#include <tcl.h> \fR
|
||||
@@ -23,9 +23,6 @@ Tcl_Channel
|
||||
Tcl_Channel
|
||||
\fBTcl_OpenTcpServer\fR(\fIinterp, port, myaddr, proc, clientData\fR)
|
||||
.sp
|
||||
Tcl_Channel
|
||||
\fBTcl_OpenTcpServerEx\fR(\fIinterp, service, myaddr, flags, proc, clientData\fR)
|
||||
.sp
|
||||
.SH ARGUMENTS
|
||||
.AS Tcl_TcpAcceptProc clientData
|
||||
.AP Tcl_Interp *interp in
|
||||
@@ -33,9 +30,6 @@ Tcl interpreter to use for error reporting. If non-NULL and an
|
||||
error occurs, an error message is left in the interpreter's result.
|
||||
.AP int port in
|
||||
A port number to connect to as a client or to listen on as a server.
|
||||
.AP "const char" *service in
|
||||
A string specifying the port number to connect to as a client or to listen on as
|
||||
a server.
|
||||
.AP "const char" *host in
|
||||
A string specifying a host name or address for the remote end of the connection.
|
||||
.AP int myport in
|
||||
@@ -47,9 +41,6 @@ for the local end of the connection. If NULL, a default interface is
|
||||
chosen.
|
||||
.AP int async in
|
||||
If nonzero, the client socket is connected asynchronously to the server.
|
||||
.AP "unsigned int" flags in
|
||||
ORed combination of \fBTCL_TCPSERVER\fR flags that specify additional
|
||||
informations about the socket being created.
|
||||
.AP ClientData sock in
|
||||
Platform-specific handle for client TCP socket.
|
||||
.AP Tcl_TcpAcceptProc *proc in
|
||||
@@ -139,7 +130,7 @@ for the new channel, \fIhostName\fR points to a string containing
|
||||
the name of the client host making the connection, and \fIport\fR
|
||||
will contain the client's port number.
|
||||
The new channel
|
||||
is opened for both input and output.
|
||||
is opened for both input and output.
|
||||
If \fIproc\fR raises an error, the connection is closed automatically.
|
||||
\fIProc\fR has no return value, but if it wishes to reject the
|
||||
connection it can close \fIchannel\fR.
|
||||
@@ -167,11 +158,6 @@ register it, use \fBTcl_RegisterChannel\fR.
|
||||
If one of the standard channels, \fBstdin\fR, \fBstdout\fR or \fBstderr\fR was
|
||||
previously closed, the act of creating the new channel also assigns it as a
|
||||
replacement for the standard channel.
|
||||
.SS TCL_OPENTCPSERVEREX
|
||||
.PP
|
||||
\fBTcl_OpenTcpServerEx\fR behaviour is identical to \fBTcl_OpenTcpServer\fR but
|
||||
gives more flexibility to the user by providing a mean to further customize some
|
||||
aspects of the socket via the \fIflags\fR parameter.
|
||||
.SH "PLATFORM ISSUES"
|
||||
.PP
|
||||
On Unix platforms, the socket handle is a Unix file descriptor as
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_ParseArgsObjv 3 8.6 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_Preserve 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_PrintDouble 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_RecordAndEvalObj 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_RecordAndEval 3 7.4 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SetErrno 3 8.3 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SetRecursionLimit 3 7.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SignalId 3 8.3 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_Sleep 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SplitList 3 8.0 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SplitPath 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_StaticPackage 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH "Standard Channels" 3 7.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_StringMatch 3 8.5 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH Tcl_SubstObj 3 8.4 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+2
-2
@@ -1,8 +1,8 @@
|
||||
'\"
|
||||
'\"
|
||||
'\" Copyright (c) 1992-1999 Karl Lehenbauer and Mark Diekhans.
|
||||
'\" Copyright (c) 2000 by Scriptics Corporation.
|
||||
'\" All rights reserved.
|
||||
'\"
|
||||
'\"
|
||||
.TH TCL_MEM_DEBUG 3 8.1 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH TclZlib 3 8.6 Tcl "Tcl Library Procedures"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -47,6 +47,13 @@ been the return value from a previous invocation of
|
||||
Returns 1 if \fIarrayName\fR is an array variable, 0 if there
|
||||
is no variable by that name or if it is a scalar variable.
|
||||
.TP
|
||||
\fBarray for {\fIkeyVariable ?valueVariable?\fB} \fIarrayName body\fR
|
||||
The first argument is a one or two element list of variable names for the
|
||||
key and value of each entry in the array. The second argument is the
|
||||
array name to iterate over. The third argument is the body to execute
|
||||
for each key and value returned.
|
||||
The ordering of the returned keys is undefined.
|
||||
.TP
|
||||
\fBarray get \fIarrayName\fR ?\fIpattern\fR?
|
||||
Returns a list containing pairs of elements. The first
|
||||
element in each pair is the name of an element in \fIarrayName\fR
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH break n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH case n 7.0 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH cd n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+7
-6
@@ -89,9 +89,10 @@ have 59 or 61 seconds.
|
||||
.TP
|
||||
\fIunit\fR
|
||||
One of the words, \fBseconds\fR, \fBminutes\fR, \fBhours\fR,
|
||||
\fBdays\fR, \fBweekdays\fR, \fBweeks\fR, \fBmonths\fR, or \fByears\fR.
|
||||
Used in conjunction with \fIcount\fR to identify an interval of time,
|
||||
for example, \fI3 seconds\fR or \fI1 year\fR.
|
||||
\fBdays\fR, \fBweeks\fR, \fBmonths\fR, or \fByears\fR, or
|
||||
any unique prefix of such a word. Used in conjunction with \fIcount\fR
|
||||
to identify an interval of time, for example, \fI3 seconds\fR or
|
||||
\fI1 year\fR.
|
||||
.SS "OPTIONS"
|
||||
.TP
|
||||
\fB\-base\fR time
|
||||
@@ -174,7 +175,8 @@ given as its first argument. The remaining arguments (other than the
|
||||
possible \fB\-timezone\fR, \fB\-locale\fR and \fB\-gmt\fR options)
|
||||
are integers and keywords in alternation, where the keywords are chosen
|
||||
from \fBseconds\fR, \fBminutes\fR, \fBhours\fR,
|
||||
\fBdays\fR, \fBweekdays\fR, \fBweeks\fR, \fBmonths\fR, or \fByears\fR.
|
||||
\fBdays\fR, \fBweeks\fR, \fBmonths\fR, or \fByears\fR, or
|
||||
any unique prefix of such a word.
|
||||
.PP
|
||||
Addition of seconds, minutes and hours is fairly straightforward;
|
||||
the given time increment (times sixty for minutes, or 3600 for hours)
|
||||
@@ -211,8 +213,7 @@ the given time to a calendar day and time of day in the appropriate
|
||||
time zone and locale. The requisite number of days (weeks are converted
|
||||
to days by multiplying by seven) is added to the calendar day, and
|
||||
the date and time are then converted back to a count of seconds from
|
||||
the epoch time. The \fBweekdays\fR keyword is similar to \fBdays\fR,
|
||||
with the only difference that weekends - Saturdays and Sundays - are skipped.
|
||||
the epoch time.
|
||||
.PP
|
||||
Adding and subtracting a given number of days across the point that
|
||||
the time changes at the start or end of summer time (Daylight Saving Time)
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH close n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH concat n 8.3 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH continue n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+16
-6
@@ -14,7 +14,7 @@ oo::copy \- create copies of objects and classes
|
||||
.nf
|
||||
package require TclOO
|
||||
|
||||
\fBoo::copy\fI sourceObject \fR?\fItargetObject\fR?
|
||||
\fBoo::copy\fI sourceObject \fR?\fItargetObject\fR? ?\fItargetNamespace\fR?
|
||||
.fi
|
||||
.BE
|
||||
.SH DESCRIPTION
|
||||
@@ -22,11 +22,21 @@ package require TclOO
|
||||
The \fBoo::copy\fR command creates a copy of an object or class. It takes the
|
||||
name of the object or class to be copied, \fIsourceObject\fR, and optionally
|
||||
the name of the object or class to create, \fItargetObject\fR, which will be
|
||||
resolved relative to the current namespace if not an absolute qualified name.
|
||||
If \fItargetObject\fR is omitted, a new name is chosen. The copied object will
|
||||
be of the same class as the source object, and will have all its per-object
|
||||
methods copied. If it is a class, it will also have all the class methods in
|
||||
the class copied, but it will not have any of its instances copied.
|
||||
resolved relative to the current namespace if not an absolute qualified name
|
||||
and
|
||||
.VS TIP473
|
||||
\fItargetNamespace\fR which is the name of the namespace that will hold the
|
||||
internal state of the object (\fBmy\fR command, etc.); it \fImust not\fR
|
||||
refer to an existing namespace.
|
||||
If either \fItargetObject\fR or \fItargetNamespace\fR is omitted or is given
|
||||
as the empty string, a new name is chosen. Names, unless specified, are
|
||||
chosen with the same algorithm used by the \fBnew\fR method of
|
||||
\fBoo::class\fR.
|
||||
.VE TIP473
|
||||
The copied object will be of the same class as the source object, and will have
|
||||
all its per-object methods copied. If it is a class, it will also have all the
|
||||
class methods in the class copied, but it will not have any of its instances
|
||||
copied.
|
||||
.PP
|
||||
.VS
|
||||
After the \fItargetObject\fR has been created and all definitions of its
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH coroutine n 8.6 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -437,7 +437,7 @@ puts $foo
|
||||
# prints: \fIa b foo {a b} bar 2 baz 3\fR
|
||||
.CE
|
||||
.SH "SEE ALSO"
|
||||
append(n), array(n), foreach(n), mapeach(n), incr(n), list(n), lappend(n), set(n)
|
||||
append(n), array(n), foreach(n), incr(n), list(n), lappend(n), lmap(n), set(n)
|
||||
.SH KEYWORDS
|
||||
dictionary, create, update, lookup, iterate, filter, map
|
||||
'\" Local Variables:
|
||||
|
||||
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH eof n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH eval n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH exit n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+214
-171
@@ -17,14 +17,14 @@ expr \- Evaluate an expression
|
||||
.BE
|
||||
.SH DESCRIPTION
|
||||
.PP
|
||||
Concatenates \fIarg\fRs, separated by a space, into an expression, and evaluates
|
||||
that expression, returning its value.
|
||||
The operators permitted in an expression include a subset of
|
||||
Concatenates \fIarg\fRs (adding separator spaces between them),
|
||||
evaluates the result as a Tcl expression, and returns the value.
|
||||
The operators permitted in Tcl expressions include a subset of
|
||||
the operators permitted in C expressions. For those operators
|
||||
common to both Tcl and C, Tcl applies the same meaning and precedence
|
||||
as the corresponding C operators.
|
||||
The value of an expression is often a numeric result, either an integer or a
|
||||
floating-point value, but may also be a non-numeric value.
|
||||
Expressions almost always yield numeric results
|
||||
(integer or floating-point values).
|
||||
For example, the expression
|
||||
.PP
|
||||
.CS
|
||||
@@ -32,68 +32,78 @@ For example, the expression
|
||||
.CE
|
||||
.PP
|
||||
evaluates to 14.2.
|
||||
Expressions differ from C expressions in the way that
|
||||
operands are specified. Expressions also support
|
||||
non-numeric operands, string comparisons, and some
|
||||
Tcl expressions differ from C expressions in the way that
|
||||
operands are specified. Also, Tcl expressions support
|
||||
non-numeric operands and string comparisons, as well as some
|
||||
additional operators not found in C.
|
||||
.PP
|
||||
When an expression evaluates to an integer, the value is the decimal form of
|
||||
the integer, and when an expression evaluates to a floating-point number, the
|
||||
value is the form produced by the \fB%g\fR format specifier of Tcl's
|
||||
\fBformat\fR command.
|
||||
.SS OPERANDS
|
||||
.PP
|
||||
An expression consists of a combination of operands, operators, parentheses and
|
||||
commas, possibly with whitespace between any of these elements, which is
|
||||
ignored.
|
||||
An integer operand may be specified in decimal, binary
|
||||
(the first two characters are \fB0b\fR), octal
|
||||
(the first two characters are \fB0o\fR), or hexadecimal
|
||||
(the first two characters are \fB0x\fR) form. For
|
||||
compatibility with older Tcl releases, an operand that begins with \fB0\fR is
|
||||
interpreted as an octal integer even if the second character is not \fBo\fR.
|
||||
A floating-point number may be specified in any of several
|
||||
common decimal formats, and may use the decimal point \fB.\fR,
|
||||
\fBe\fR or \fBE\fR for scientific notation, and
|
||||
the sign characters \fB+\fR and \fB\-\fR. The
|
||||
following are all valid floating-point numbers: 2.1, 3., 6e4, 7.91e+16.
|
||||
The strings \fBInf\fR
|
||||
and \fBNaN\fR, in any combination of case, are also recognized as floating point
|
||||
values. An operand that doesn't have a numeric interpretation must be quoted
|
||||
with either braces or with double quotes.
|
||||
A Tcl expression consists of a combination of operands, operators,
|
||||
parentheses and commas.
|
||||
White space may be used between the operands and operators and
|
||||
parentheses (or commas); it is ignored by the expression's instructions.
|
||||
Where possible, operands are interpreted as integer values.
|
||||
Integer values may be specified in decimal (the normal case), in binary
|
||||
(if the first two characters of the operand are \fB0b\fR), in octal
|
||||
(if the first two characters of the operand are \fB0o\fR), or in hexadecimal
|
||||
(if the first two characters of the operand are \fB0x\fR). For
|
||||
compatibility with older Tcl releases, an octal integer value is also
|
||||
indicated simply when the first character of the operand is \fB0\fR,
|
||||
whether or not the second character is also \fBo\fR.
|
||||
If an operand does not have one of the integer formats given
|
||||
above, then it is treated as a floating-point number if that is
|
||||
possible. Floating-point numbers may be specified in any of several
|
||||
common formats making use of the decimal digits, the decimal point \fB.\fR,
|
||||
the characters \fBe\fR or \fBE\fR indicating scientific notation, and
|
||||
the sign characters \fB+\fR or \fB\-\fR. For example, all of the
|
||||
following are valid floating-point numbers: 2.1, 3., 6e4, 7.91e+16.
|
||||
Also recognized as floating point values are the strings \fBInf\fR
|
||||
and \fBNaN\fR making use of any case for each character.
|
||||
If no numeric interpretation is possible (note that all literal
|
||||
operands that are not numeric or boolean must be quoted with either
|
||||
braces or with double quotes), then an operand is left as a string
|
||||
(and only a limited set of operators may be applied to it).
|
||||
.PP
|
||||
An operand may be specified in any of the following ways:
|
||||
Operands may be specified in any of the following ways:
|
||||
.IP [1]
|
||||
As a numeric value, either integer or floating-point.
|
||||
.IP [2]
|
||||
As a boolean value, using any form understood by \fBstring is\fR
|
||||
\fBboolean\fR.
|
||||
.IP [3]
|
||||
As a variable, using standard \fB$\fR notation.
|
||||
The value of the variable is then the value of the operand.
|
||||
As a Tcl variable, using standard \fB$\fR notation.
|
||||
The variable's value will be used as the operand.
|
||||
.IP [4]
|
||||
As a string enclosed in double-quotes.
|
||||
Backslash, variable, and command substitution are performed as described in
|
||||
\fBTcl\fR.
|
||||
The expression parser will perform backslash, variable, and
|
||||
command substitutions on the information between the quotes,
|
||||
and use the resulting value as the operand
|
||||
.IP [5]
|
||||
As a string enclosed in braces.
|
||||
The operand is treated as a braced value as described in \fBTcl\fR.
|
||||
The characters between the open brace and matching close brace
|
||||
will be used as the operand without any substitutions.
|
||||
.IP [6]
|
||||
As a Tcl command enclosed in brackets.
|
||||
Command substitution is performed as described in \fBTcl\fR.
|
||||
The command will be executed and its result will be used as
|
||||
the operand.
|
||||
.IP [7]
|
||||
As a mathematical function such as \fBsin($x)\fR, whose arguments have any of the above
|
||||
forms for operands. See \fBMATH FUNCTIONS\fR below for
|
||||
As a mathematical function whose arguments have any of the above
|
||||
forms for operands, such as \fBsin($x)\fR. See \fBMATH FUNCTIONS\fR below for
|
||||
a discussion of how mathematical functions are handled.
|
||||
.PP
|
||||
Because \fBexpr\fR parses and performs substitutions on values that have
|
||||
already been parsed and substituted by \fBTcl\fR, it is usually best to enclose
|
||||
expressions in braces to avoid the first round of substitutions by
|
||||
\fBTcl\fR.
|
||||
Where the above substitutions occur (e.g. inside quoted strings), they
|
||||
are performed by the expression's instructions.
|
||||
However, the command parser may already have performed one round of
|
||||
substitution before the expression processor was called.
|
||||
As discussed below, it is usually best to enclose expressions
|
||||
in braces to prevent the command parser from performing substitutions
|
||||
on the contents.
|
||||
.PP
|
||||
Below are some examples of simple expressions where the value of \fBa\fR is 3
|
||||
and the value of \fBb\fR is 6. The command on the left side of each line
|
||||
produces the value on the right side.
|
||||
For some examples of simple expressions, suppose the variable
|
||||
\fBa\fR has the value 3 and
|
||||
the variable \fBb\fR has the value 6.
|
||||
Then the command on the left side of each of the lines below
|
||||
will produce the value on the right side of the line:
|
||||
.PP
|
||||
.CS
|
||||
.ta 6c
|
||||
@@ -104,41 +114,34 @@ produces the value on the right side.
|
||||
.CE
|
||||
.SS OPERATORS
|
||||
.PP
|
||||
For operators having both a numeric mode and a string mode, the numeric mode is
|
||||
chosen when all operands have a numeric interpretation. The integer
|
||||
interpretation of an operand is preferred over the floating-point
|
||||
interpretation. To ensure string operations on arbitrary values it is generally a
|
||||
good idea to use \fBeq\fR, \fBne\fR, or the \fBstring\fR command instead of
|
||||
more versatile operators such as \fB==\fR.
|
||||
.PP
|
||||
Unless otherwise specified, operators accept non-numeric operands. The value
|
||||
of a boolean operation is 1 if true, 0 otherwise. See also \fBstring is\fR
|
||||
\fBboolean\fR. The valid operators, most of which are also available as
|
||||
commands in the \fBtcl::mathop\fR namespace (see \fBmathop\fR(n)), are listed
|
||||
below, grouped in decreasing order of precedence:
|
||||
The valid operators (most of which are also available as commands in
|
||||
the \fBtcl::mathop\fR namespace; see the \fBmathop\fR(n) manual page
|
||||
for details) are listed below, grouped in decreasing order of precedence:
|
||||
.TP 20
|
||||
\fB\-\0\0+\0\0~\0\0!\fR
|
||||
.
|
||||
Unary minus, unary plus, bit-wise NOT, logical NOT. These operators
|
||||
may only be applied to numeric operands, and bit-wise NOT may only be
|
||||
applied to integers.
|
||||
Unary minus, unary plus, bit-wise NOT, logical NOT. None of these operators
|
||||
may be applied to string operands, and bit-wise NOT may be
|
||||
applied only to integers.
|
||||
.TP 20
|
||||
\fB**\fR
|
||||
.
|
||||
Exponentiation. Valid for numeric operands.
|
||||
Exponentiation. Valid for any numeric operands.
|
||||
.TP 20
|
||||
\fB*\0\0/\0\0%\fR
|
||||
.
|
||||
Multiply and divide, which are valid for numeric operands, and remainder, which
|
||||
is valid for integers. The remainder, an absolute value smaller than the
|
||||
absolute value of the divisor, has the same sign as the divisor.
|
||||
Multiply, divide, remainder. None of these operators may be
|
||||
applied to string operands, and remainder may be applied only
|
||||
to integers.
|
||||
The remainder will always have the same sign as the divisor and
|
||||
an absolute value smaller than the absolute value of the divisor.
|
||||
.RS
|
||||
.PP
|
||||
When applied to integers, division and remainder can be
|
||||
considered to partition the number line into a sequence of
|
||||
adjacent non-overlapping pieces, where each piece is the size of the divisor;
|
||||
the quotient identifies which piece the dividend lies within, and the
|
||||
remainder identifies where within that piece the dividend lies. A
|
||||
When applied to integers, the division and remainder operators can be
|
||||
considered to partition the number line into a sequence of equal-sized
|
||||
adjacent non-overlapping pieces where each piece is the size of the divisor;
|
||||
the division result identifies which piece the divisor lay within, and the
|
||||
remainder result identifies where within that piece the divisor lay. A
|
||||
consequence of this is that the result of
|
||||
.QW "-57 \fB/\fR 10"
|
||||
is always -6, and the result of
|
||||
@@ -148,157 +151,177 @@ is always 3.
|
||||
.TP 20
|
||||
\fB+\0\0\-\fR
|
||||
.
|
||||
Add and subtract. Valid for numeric operands.
|
||||
Add and subtract. Valid for any numeric operands.
|
||||
.TP 20
|
||||
\fB<<\0\0>>\fR
|
||||
.
|
||||
Left and right shift. Valid for integers.
|
||||
Left and right shift. Valid for integer operands only.
|
||||
A right shift always propagates the sign bit.
|
||||
.TP 20
|
||||
\fB<\0\0>\0\0<=\0\0>=\fR
|
||||
.
|
||||
Boolean less than, greater than, less than or equal, and greater than or equal.
|
||||
Boolean less, greater, less than or equal, and greater than or equal.
|
||||
Each operator produces 1 if the condition is true, 0 otherwise.
|
||||
These operators may be applied to strings as well as numeric operands,
|
||||
in which case string comparison is used.
|
||||
.TP 20
|
||||
\fB==\0\0!=\fR
|
||||
.
|
||||
Boolean equal and not equal.
|
||||
Boolean equal and not equal. Each operator produces a zero/one result.
|
||||
Valid for all operand types.
|
||||
.TP 20
|
||||
\fBeq\0\0ne\fR
|
||||
.
|
||||
Boolean string equal and string not equal.
|
||||
Boolean string equal and string not equal. Each operator produces a
|
||||
zero/one result. The operand types are interpreted only as strings.
|
||||
.TP 20
|
||||
\fBin\0\0ni\fR
|
||||
.
|
||||
List containment and negated list containment. The first argument is
|
||||
interpreted as a string, the second as a list. \fBin\fR tests for membership
|
||||
in the list, and \fBni\fR is the inverse.
|
||||
List containment and negated list containment. Each operator produces
|
||||
a zero/one result and treats its first argument as a string and its
|
||||
second argument as a Tcl list. The \fBin\fR operator indicates
|
||||
whether the first argument is a member of the second argument list;
|
||||
the \fBni\fR operator inverts the sense of the result.
|
||||
.TP 20
|
||||
\fB&\fR
|
||||
.
|
||||
Bit-wise AND. Valid for integer operands.
|
||||
Bit-wise AND. Valid for integer operands only.
|
||||
.TP 20
|
||||
\fB^\fR
|
||||
.
|
||||
Bit-wise exclusive OR. Valid for integer operands.
|
||||
Bit-wise exclusive OR. Valid for integer operands only.
|
||||
.TP 20
|
||||
\fB|\fR
|
||||
.
|
||||
Bit-wise OR. Valid for integer operands.
|
||||
Bit-wise OR. Valid for integer operands only.
|
||||
.TP 20
|
||||
\fB&&\fR
|
||||
.
|
||||
Logical AND. If both operands are true, the result is 1, or 0 otherwise.
|
||||
|
||||
Logical AND. Produces a 1 result if both operands are non-zero,
|
||||
0 otherwise.
|
||||
Valid for boolean and numeric (integers or floating-point) operands only.
|
||||
.TP 20
|
||||
\fB||\fR
|
||||
.
|
||||
Logical OR. If both operands are false, the result is 0, or 1 otherwise.
|
||||
Logical OR. Produces a 0 result if both operands are zero, 1 otherwise.
|
||||
Valid for boolean and numeric (integers or floating-point) operands only.
|
||||
.TP 20
|
||||
\fIx\fB?\fIy\fB:\fIz\fR
|
||||
.
|
||||
If-then-else, as in C. If \fIx\fR is false , the result is the value of
|
||||
\fIy\fR. Otherwise the result is the value of \fIz\fR.
|
||||
If-then-else, as in C. If \fIx\fR
|
||||
evaluates to non-zero, then the result is the value of \fIy\fR.
|
||||
Otherwise the result is the value of \fIz\fR.
|
||||
The \fIx\fR operand must have a boolean or numeric value.
|
||||
.PP
|
||||
The exponentiation operator promotes types in the same way that the multiply
|
||||
and divide operators do, and the result is is the same as the result of
|
||||
\fBpow\fR.
|
||||
Exponentiation groups right-to-left within a precedence level. Other binary
|
||||
operators group left-to-right. For example, the value of
|
||||
See the C manual for more details on the results
|
||||
produced by each operator.
|
||||
The exponentiation operator promotes types like the multiply and
|
||||
divide operators, and produces a result that is the same as the output
|
||||
of the \fBpow\fR function (after any type conversions.)
|
||||
All of the binary operators but exponentiation group left-to-right
|
||||
within the same precedence level; exponentiation groups right-to-left. For example, the command
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {4*2 < 7}
|
||||
.CE
|
||||
.PP
|
||||
is 0, while the value of
|
||||
returns 0, while
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {2**3**2}
|
||||
.CE
|
||||
.PP
|
||||
is 512.
|
||||
returns 512.
|
||||
.PP
|
||||
As in C, \fB&&\fR, \fB||\fR, and \fB?:\fR feature
|
||||
The \fB&&\fR, \fB||\fR, and \fB?:\fR operators have
|
||||
.QW "lazy evaluation" ,
|
||||
which means that operands are not evaluated if they are
|
||||
not needed to determine the outcome. For example, in
|
||||
just as in C, which means that operands are not evaluated if they are
|
||||
not needed to determine the outcome. For example, in the command
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {$v ? [a] : [b]}
|
||||
.CE
|
||||
.PP
|
||||
only one of \fB[a]\fR or \fB[b]\fR is evaluated,
|
||||
depending on the value of \fB$v\fR. This is not true of the normal Tcl parser,
|
||||
so it is normally recommended to enclose the arguments to \fBexpr\fR in braces.
|
||||
Without braces, as in
|
||||
\fBexpr\fR $v ? [a] : [b]
|
||||
both \fB[a]\fR and \fB[b]\fR are evaluated before \fBexpr\fR is even called.
|
||||
.PP
|
||||
For more details on the results
|
||||
produced by each operator, see the documentation for C.
|
||||
only one of
|
||||
.QW \fB[a]\fR
|
||||
or
|
||||
.QW \fB[b]\fR
|
||||
will actually be evaluated,
|
||||
depending on the value of \fB$v\fR. Note, however, that this is
|
||||
only true if the entire expression is enclosed in braces; otherwise
|
||||
the Tcl parser will evaluate both
|
||||
.QW \fB[a]\fR
|
||||
and
|
||||
.QW \fB[b]\fR
|
||||
before invoking the \fBexpr\fR command.
|
||||
.SS "MATH FUNCTIONS"
|
||||
.PP
|
||||
A mathematical function such as \fBsin($x)\fR is replaced with a call to an ordinary
|
||||
Tcl command in the \fBtcl::mathfunc\fR namespace. The evaluation
|
||||
of an expression such as
|
||||
When the expression parser encounters a mathematical function
|
||||
such as \fBsin($x)\fR, it replaces it with a call to an ordinary
|
||||
Tcl function in the \fBtcl::mathfunc\fR namespace. The processing
|
||||
of an expression such as:
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {sin($x+$y)}
|
||||
.CE
|
||||
.PP
|
||||
is the same in every way as the evaluation of
|
||||
is the same in every way as the processing of:
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {[tcl::mathfunc::sin [\fBexpr\fR {$x+$y}]]}
|
||||
.CE
|
||||
.PP
|
||||
which in turn is the same as the evaluation of
|
||||
which in turn is the same as the processing of:
|
||||
.PP
|
||||
.CS
|
||||
tcl::mathfunc::sin [\fBexpr\fR {$x+$y}]
|
||||
.CE
|
||||
.PP
|
||||
\fBtcl::mathfunc::sin\fR is resolved as described in
|
||||
\fBNAMESPACE RESOLUTION\fR in the \fBnamespace\fR(n) documentation. Given the
|
||||
default value of \fBnamespace path\fR, \fB[namespace
|
||||
current]::tcl::mathfunc::sin\fR or \fB::tcl::mathfunc::sin\fR are the typical
|
||||
resolutions.
|
||||
The executor will search for \fBtcl::mathfunc::sin\fR using the usual
|
||||
rules for resolving functions in namespaces. Either
|
||||
\fB::tcl::mathfunc::sin\fR or \fB[namespace
|
||||
current]::tcl::mathfunc::sin\fR will satisfy the request, and others
|
||||
may as well (depending on the current \fBnamespace path\fR setting).
|
||||
.PP
|
||||
As in C, a mathematical function may accept multiple arguments separated by commas. Thus,
|
||||
Some mathematical functions have several arguments, separated by commas like in C. Thus:
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {hypot($x,$y)}
|
||||
.CE
|
||||
.PP
|
||||
becomes
|
||||
ends up as
|
||||
.PP
|
||||
.CS
|
||||
tcl::mathfunc::hypot $x $y
|
||||
.CE
|
||||
.PP
|
||||
See the \fBmathfunc\fR(n) documentation for the math functions that are
|
||||
See the \fBmathfunc\fR(n) manual page for the math functions that are
|
||||
available by default.
|
||||
.SS "TYPES, OVERFLOW, AND PRECISION"
|
||||
.PP
|
||||
When needed to guarantee exact performance, internal computations involving
|
||||
integers use the LibTomMath multiple precision integer library. In Tcl releases
|
||||
prior to 8.5, integer calculations were performed using one of the C types
|
||||
All internal computations involving integers are done calling on the
|
||||
LibTomMath multiple precision integer library as required so that all
|
||||
integer calculations are performed exactly. Note that in Tcl releases
|
||||
prior to 8.5, integer calculations were performed with one of the C types
|
||||
\fIlong int\fR or \fITcl_WideInt\fR, causing implicit range truncation
|
||||
in those calculations where values overflowed the range of those types.
|
||||
Any code that relied on these implicit truncations should instead call
|
||||
\fBint()\fR or \fBwide()\fR, which do truncate.
|
||||
Any code that relied on these implicit truncations will need to explicitly
|
||||
add \fBint()\fR or \fBwide()\fR function calls to expressions at the points
|
||||
where such truncation is required to take place.
|
||||
.PP
|
||||
Internal floating-point computations are
|
||||
performed using the \fIdouble\fR C type.
|
||||
When converting a string to floating-point value, exponent overflow is
|
||||
All internal computations involving floating-point are
|
||||
done with the C type \fIdouble\fR.
|
||||
When converting a string to floating-point, exponent overflow is
|
||||
detected and results in the \fIdouble\fR value of \fBInf\fR or
|
||||
\fB\-Inf\fR as appropriate. Floating-point overflow and underflow
|
||||
are detected to the degree supported by the hardware, which is generally
|
||||
fairly reliable.
|
||||
pretty reliable.
|
||||
.PP
|
||||
Conversion among internal representations for integer, floating-point, and
|
||||
string operands is done automatically as needed. For arithmetic computations,
|
||||
integers are used until some floating-point number is introduced, after which
|
||||
floating-point values are used. For example,
|
||||
Conversion among internal representations for integer, floating-point,
|
||||
and string operands is done automatically as needed.
|
||||
For arithmetic computations, integers are used until some
|
||||
floating-point number is introduced, after which floating-point is used.
|
||||
For example,
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {5 / 4}
|
||||
@@ -312,62 +335,82 @@ returns 1, while
|
||||
.CE
|
||||
.PP
|
||||
both return 1.25.
|
||||
A floating-point result can be distinguished from an integer result by the
|
||||
presence of either
|
||||
Floating-point values are always returned with a
|
||||
.QW \fB.\fR
|
||||
or
|
||||
or an
|
||||
.QW \fBe\fR
|
||||
.PP
|
||||
. For example,
|
||||
so that they will not look like integer values. For example,
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {20.0/5.0}
|
||||
.CE
|
||||
.PP
|
||||
returns \fB4.0\fR, not \fB4\fR.
|
||||
.SS "STRING OPERATIONS"
|
||||
.PP
|
||||
String values may be used as operands of the comparison operators,
|
||||
although the expression evaluator tries to do comparisons as integer
|
||||
or floating-point when it can,
|
||||
i.e., when all arguments to the operator allow numeric interpretations,
|
||||
except in the case of the \fBeq\fR and \fBne\fR operators.
|
||||
If one of the operands of a comparison is a string and the other
|
||||
has a numeric value, a canonical string representation of the numeric
|
||||
operand value is generated to compare with the string operand.
|
||||
Canonical string representation for integer values is a decimal string
|
||||
format. Canonical string representation for floating-point values
|
||||
is that produced by the \fB%g\fR format specifier of Tcl's
|
||||
\fBformat\fR command. For example, the commands
|
||||
.PP
|
||||
.CS
|
||||
\fBexpr\fR {"0x03" > "2"}
|
||||
\fBexpr\fR {"0y" > "0x12"}
|
||||
.CE
|
||||
.PP
|
||||
both return 1. The first comparison is done using integer
|
||||
comparison, and the second is done using string comparison.
|
||||
Because of Tcl's tendency to treat values as numbers whenever
|
||||
possible, it is not generally a good idea to use operators like \fB==\fR
|
||||
when you really want string comparison and the values of the
|
||||
operands could be arbitrary; it is better in these cases to use
|
||||
the \fBeq\fR or \fBne\fR operators, or the \fBstring\fR command instead.
|
||||
.SH "PERFORMANCE CONSIDERATIONS"
|
||||
.PP
|
||||
Where an expression contains syntax that Tcl would otherwise perform
|
||||
substitutions on, enclosing an expression in braces or otherwise quoting it
|
||||
so that it's a static value allows the Tcl compiler to generate bytecode for
|
||||
the expression, resulting in better speed and smaller storage requirements.
|
||||
This also avoids issues that can arise if Tcl is allowed to perform
|
||||
substitution on the value before \fBexpr\fR is called.
|
||||
Enclose expressions in braces for the best speed and the smallest
|
||||
storage requirements.
|
||||
This allows the Tcl bytecode compiler to generate the best code.
|
||||
.PP
|
||||
As mentioned above, expressions are substituted twice:
|
||||
once by the Tcl parser and once by the \fBexpr\fR command.
|
||||
For example, the commands
|
||||
.PP
|
||||
In the following example, the value of the expression is 11 because the Tcl parser first
|
||||
substitutes \fB$b\fR and \fBexpr\fR then substitutes \fB$a\fR. Enclosing the
|
||||
expression in braces would result in a syntax error.
|
||||
.CS
|
||||
set a 3
|
||||
set b {$a + 2}
|
||||
\fBexpr\fR $b*4
|
||||
.CE
|
||||
.PP
|
||||
|
||||
When an expression is generated at runtime, like the one above is, the bytcode
|
||||
compiler must ensure that new code is generated each time the expression
|
||||
is evaluated. This is the most costly kind of expression from a performance
|
||||
perspective. In such cases, consider directly using the commands described in
|
||||
the \fBmathfunc\fR(n) or \fBmathop\fR(n) documentation instead of \fBexpr\fR.
|
||||
|
||||
Most expressions are not formed at runtime, but are literal strings or contain
|
||||
substitutions that don't introduce other substitutions. To allow the bytecode
|
||||
compiler to work with an expression as a string literal at compilation time,
|
||||
ensure that it contains no substitutions or that it is enclosed in braces or
|
||||
otherwise quoted to prevent Tcl from performing substitutions, allowing
|
||||
\fBexpr\fR to perform them instead.
|
||||
return 11, not a multiple of 4.
|
||||
This is because the Tcl parser will first substitute \fB$a + 2\fR for
|
||||
the variable \fBb\fR,
|
||||
then the \fBexpr\fR command will evaluate the expression \fB$a + 2*4\fR.
|
||||
.PP
|
||||
Most expressions do not require a second round of substitutions.
|
||||
Either they are enclosed in braces or, if not,
|
||||
their variable and command substitutions yield numbers or strings
|
||||
that do not themselves require substitutions.
|
||||
However, because a few unbraced expressions
|
||||
need two rounds of substitutions,
|
||||
the bytecode compiler must emit
|
||||
additional instructions to handle this situation.
|
||||
The most expensive code is required for
|
||||
unbraced expressions that contain command substitutions.
|
||||
These expressions must be implemented by generating new code
|
||||
each time the expression is executed.
|
||||
When the expression is unbraced to allow the substitution of a function or
|
||||
operator, consider using the commands documented in the \fBmathfunc\fR(n) or
|
||||
\fBmathop\fR(n) manual pages directly instead.
|
||||
.SH EXAMPLES
|
||||
.PP
|
||||
A numeric comparison whose result is 1:
|
||||
.CS
|
||||
\fBexpr\fR {"0x03" > "2"}
|
||||
.CE
|
||||
.PP
|
||||
A string comparison whose result is 1:
|
||||
.CS
|
||||
\fBexpr\fR {"0y" > "0x12"}
|
||||
.CE
|
||||
.PP
|
||||
Define a procedure that computes an
|
||||
.QW interesting
|
||||
mathematical function:
|
||||
@@ -401,8 +444,8 @@ each other:
|
||||
puts "a and b are [\fBexpr\fR {$a eq $b ? {equal} : {different}}]"
|
||||
.CE
|
||||
.PP
|
||||
Set a variable indicating whether an environment variable is defined and has
|
||||
value of true:
|
||||
Set a variable to whether an environment variable is both defined at
|
||||
all and also set to a true boolean value:
|
||||
.PP
|
||||
.CS
|
||||
set isTrue [\fBexpr\fR {
|
||||
|
||||
+1
-1
@@ -1,4 +1,4 @@
|
||||
'\"
|
||||
'\"
|
||||
'\" Copyright (c) 1996 Sun Microsystems, Inc.
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
|
||||
+1
-1
@@ -390,7 +390,7 @@ that use the third component do not attempt to perform tilde
|
||||
substitution.
|
||||
.RE
|
||||
.TP
|
||||
\fBfile stat \fIname varName\fR
|
||||
\fBfile stat \fIname varName\fR
|
||||
.
|
||||
Invokes the \fBstat\fR kernel call on \fIname\fR, and uses the variable
|
||||
given by \fIvarName\fR to hold information returned from the kernel call.
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH flush n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH foreach n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH gets n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH history n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH if n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH incr n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+4
-5
@@ -7,7 +7,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH info n 8.4 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
@@ -297,11 +297,10 @@ scripts are stored.
|
||||
This is actually the value of the \fBtcl_library\fR
|
||||
variable and may be changed by setting \fBtcl_library\fR.
|
||||
.TP
|
||||
\fBinfo loaded \fR?\fIinterp\fR? \fR?\fIpackage\fR?
|
||||
\fBinfo loaded \fR?\fIinterp\fR?
|
||||
.
|
||||
Returns the filename loaded as part of \fIpackage\fR. If \fIpackage\fR
|
||||
is not specified, returns a list describing all of the packages
|
||||
that have been loaded into \fIinterp\fR with the \fBload\fR command.
|
||||
Returns a list describing all of the packages that have been loaded into
|
||||
\fIinterp\fR with the \fBload\fR command.
|
||||
Each list element is a sub-list with two elements consisting of the
|
||||
name of the file from which the package was loaded and the name of
|
||||
the package.
|
||||
|
||||
+1
-1
@@ -5,7 +5,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH interp n 8.6 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH join n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -5,7 +5,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH lappend n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH lassign n 8.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -5,7 +5,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH list n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH load n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH lrepeat n 8.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH lreverse n 8.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -303,7 +303,7 @@ used for qualified namespace or variable names.
|
||||
Sets or returns the unknown command handler for the current namespace.
|
||||
The handler is invoked when a command called from within the namespace
|
||||
cannot be found in the current namespace, the namespace's path nor in
|
||||
the global namespace.
|
||||
the global namespace.
|
||||
The \fIscript\fR argument, if given, should be a well
|
||||
formed list representing a command name and optional arguments. When
|
||||
the handler is invoked, the full invocation line will be appended to the
|
||||
|
||||
+1
-1
@@ -138,7 +138,7 @@ before chaining from subclass, args = x 1 2 3 y
|
||||
in the superclass, args = a x 1 2 3 y b
|
||||
in the superclass, args = pureSynthesis
|
||||
after chaining from subclass
|
||||
before chaining from subclass, args =
|
||||
before chaining from subclass, args =
|
||||
in the superclass, args = a b
|
||||
in the superclass, args = pureSynthesis
|
||||
after chaining from subclass
|
||||
|
||||
+2
-10
@@ -12,7 +12,6 @@
|
||||
package \- Facilities for package loading and version control
|
||||
.SH SYNOPSIS
|
||||
.nf
|
||||
\fBpackage files\fR \fIpackage\fR
|
||||
\fBpackage forget\fR ?\fIpackage package ...\fR?
|
||||
\fBpackage ifneeded \fIpackage version\fR ?\fIscript\fR?
|
||||
\fBpackage names\fR
|
||||
@@ -44,13 +43,6 @@ primarily by system scripts that maintain the package database.
|
||||
The behavior of the \fBpackage\fR command is determined by its first argument.
|
||||
The following forms are permitted:
|
||||
.TP
|
||||
\fBpackage files\fR \fIpackage\fR
|
||||
.
|
||||
Lists all files forming part of \fIpackage\fR. Auto-loaded files are not
|
||||
included in this list, only files which were directly sourced during package
|
||||
initialization. The list order corresponds with the order in which the
|
||||
files were sourced.
|
||||
.TP
|
||||
\fBpackage forget\fR ?\fIpackage package ...\fR?
|
||||
.
|
||||
Removes all information about each specified package from this interpreter,
|
||||
@@ -291,8 +283,8 @@ error.
|
||||
.PP
|
||||
When an interpreter is created, its initial selection mode value is set to
|
||||
.QW stable
|
||||
unless the environment variable \fBTCL_PKG_PREFER_LATEST\fR is set
|
||||
(to any value) or the Tcl package itself is unstable. Otherwise
|
||||
unless the environment variable \fBTCL_PKG_PREFER_LATEST\fR
|
||||
is set. If that environment variable is defined (with any value) then
|
||||
the initial (and permanent) selection mode value is set to
|
||||
.QW latest .
|
||||
.RE
|
||||
|
||||
+1
-1
@@ -1,7 +1,7 @@
|
||||
'\"
|
||||
'\" Copyright (c) 1998-2000 by Scriptics Corporation.
|
||||
'\" All rights reserved.
|
||||
'\"
|
||||
'\"
|
||||
.TH pkg::create n 8.3 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH pid n 7.0 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH "platform" n 1.0.4 platform "Tcl Bundled Packages"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH "platform::shell" n 1.1.4 platform::shell "Tcl Bundled Packages"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -3,7 +3,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH prefix n 8.6 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH puts n 7.5 Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
@@ -4,7 +4,7 @@
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
||||
'\"
|
||||
'\"
|
||||
.TH pwd n "" Tcl "Tcl Built-In Commands"
|
||||
.so man.macros
|
||||
.BS
|
||||
|
||||
+1
-1
@@ -1,4 +1,4 @@
|
||||
'\"
|
||||
'\"
|
||||
'\" Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>
|
||||
'\"
|
||||
'\" See the file "license.terms" for information on usage and redistribution
|
||||
|
||||
Some files were not shown because too many files have changed in this diff Show More
Reference in New Issue
Block a user