- ChangeLog file for zlib
+ ChangeLog file for zlib
+
+Changes in 1.2.1 (17 November 2003)
+- Remove a tab in contrib/gzappend/gzappend.c
+- Update some interfaces in contrib for new zlib functions
+- Update zlib version number in some contrib entries
+- Add Windows CE definition for ptrdiff_t in zutil.h [Mai, Truta]
+- Support shared libraries on Hurd and KFreeBSD [Brown]
+- Fix error in NO_DIVIDE option of adler32.c
+
+Changes in 1.2.0.8 (4 November 2003)
+- Update version in contrib/delphi/ZLib.pas and contrib/pascal/zlibpas.pas
+- Add experimental NO_DIVIDE #define in adler32.c
+ - Possibly faster on some processors (let me know if it is)
+- Correct Z_BLOCK to not return on first inflate call if no wrap
+- Fix strm->data_type on inflate() return to correctly indicate EOB
+- Add deflatePrime() function for appending in the middle of a byte
+- Add contrib/gzappend for an example of appending to a stream
+- Update win32/DLL_FAQ.txt [Truta]
+- Delete Turbo C comment in README [Truta]
+- Improve some indentation in zconf.h [Truta]
+- Fix infinite loop on bad input in configure script [Church]
+- Fix gzeof() for concatenated gzip files [Johnson]
+- Add example to contrib/visual-basic.txt [Michael B.]
+- Add -p to mkdir's in Makefile.in [vda]
+- Fix configure to properly detect presence or lack of printf functions
+- Add AS400 support [Monnerat]
+- Add a little Cygwin support [Wilson]
+
+Changes in 1.2.0.7 (21 September 2003)
+- Correct some debug formats in contrib/infback9
+- Cast a type in a debug statement in trees.c
+- Change search and replace delimiter in configure from % to # [Beebe]
+- Update contrib/untgz to 0.2 with various fixes [Truta]
+- Add build support for Amiga [Nikl]
+- Remove some directories in old that have been updated to 1.2
+- Add dylib building for Mac OS X in configure and Makefile.in
+- Remove old distribution stuff from Makefile
+- Update README to point to DLL_FAQ.txt, and add comment on Mac OS X
+- Update links in README
+
+Changes in 1.2.0.6 (13 September 2003)
+- Minor FAQ updates
+- Update contrib/minizip to 1.00 [Vollant]
+- Remove test of gz functions in example.c when GZ_COMPRESS defined [Truta]
+- Update POSTINC comment for 68060 [Nikl]
+- Add contrib/infback9 with deflate64 decoding (unsupported)
+- For MVS define NO_vsnprintf and undefine FAR [van Burik]
+- Add pragma for fdopen on MVS [van Burik]
+
+Changes in 1.2.0.5 (8 September 2003)
+- Add OF to inflateBackEnd() declaration in zlib.h
+- Remember start when using gzdopen in the middle of a file
+- Use internal off_t counters in gz* functions to properly handle seeks
+- Perform more rigorous check for distance-too-far in inffast.c
+- Add Z_BLOCK flush option to return from inflate at block boundary
+- Set strm->data_type on return from inflate
+ - Indicate bits unused, if at block boundary, and if in last block
+- Replace size_t with ptrdiff_t in crc32.c, and check for correct size
+- Add condition so old NO_DEFLATE define still works for compatibility
+- FAQ update regarding the Windows DLL [Truta]
+- INDEX update: add qnx entry, remove aix entry [Truta]
+- Install zlib.3 into mandir [Wilson]
+- Move contrib/zlib_dll_FAQ.txt to win32/DLL_FAQ.txt; update [Truta]
+- Adapt the zlib interface to the new DLL convention guidelines [Truta]
+- Introduce ZLIB_WINAPI macro to allow the export of functions using
+ the WINAPI calling convention, for Visual Basic [Vollant, Truta]
+- Update msdos and win32 scripts and makefiles [Truta]
+- Export symbols by name, not by ordinal, in win32/zlib.def [Truta]
+- Add contrib/ada [Anisimkov]
+- Move asm files from contrib/vstudio/vc70_32 to contrib/asm386 [Truta]
+- Rename contrib/asm386 to contrib/masmx86 [Truta, Vollant]
+- Add contrib/masm686 [Truta]
+- Fix offsets in contrib/inflate86 and contrib/masmx86/inffas32.asm
+ [Truta, Vollant]
+- Update contrib/delphi; rename to contrib/pascal; add example [Truta]
+- Remove contrib/delphi2; add a new contrib/delphi [Truta]
+- Avoid inclusion of the nonstandard <memory.h> in contrib/iostream,
+ and fix some method prototypes [Truta]
+- Fix the ZCR_SEED2 constant to avoid warnings in contrib/minizip
+ [Truta]
+- Avoid the use of backslash (\) in contrib/minizip [Vollant]
+- Fix file time handling in contrib/untgz; update makefiles [Truta]
+- Update contrib/vstudio/vc70_32 to comply with the new DLL guidelines
+ [Vollant]
+- Remove contrib/vstudio/vc15_16 [Vollant]
+- Rename contrib/vstudio/vc70_32 to contrib/vstudio/vc7 [Truta]
+- Update README.contrib [Truta]
+- Invert the assignment order of match_head and s->prev[...] in
+ INSERT_STRING [Truta]
+- Compare TOO_FAR with 32767 instead of 32768, to avoid 16-bit warnings
+ [Truta]
+- Compare function pointers with 0, not with NULL or Z_NULL [Truta]
+- Fix prototype of syncsearch in inflate.c [Truta]
+- Introduce ASMINF macro to be enabled when using an ASM implementation
+ of inflate_fast [Truta]
+- Change NO_DEFLATE to NO_GZCOMPRESS [Truta]
+- Modify test_gzio in example.c to take a single file name as a
+ parameter [Truta]
+- Exit the example.c program if gzopen fails [Truta]
+- Add type casts around strlen in example.c [Truta]
+- Remove casting to sizeof in minigzip.c; give a proper type
+ to the variable compared with SUFFIX_LEN [Truta]
+- Update definitions of STDC and STDC99 in zconf.h [Truta]
+- Synchronize zconf.h with the new Windows DLL interface [Truta]
+- Use SYS16BIT instead of __32BIT__ to distinguish between
+ 16- and 32-bit platforms [Truta]
+- Use far memory allocators in small 16-bit memory models for
+ Turbo C [Truta]
+- Add info about the use of ASMV, ASMINF and ZLIB_WINAPI in
+ zlibCompileFlags [Truta]
+- Cygwin has vsnprintf [Wilson]
+- In Windows16, OS_CODE is 0, as in MSDOS [Truta]
+- In Cygwin, OS_CODE is 3 (Unix), not 11 (Windows32) [Wilson]
+
+Changes in 1.2.0.4 (10 August 2003)
+- Minor FAQ updates
+- Be more strict when checking inflateInit2's windowBits parameter
+- Change NO_GUNZIP compile option to NO_GZIP to cover deflate as well
+- Add gzip wrapper option to deflateInit2 using windowBits
+- Add updated QNX rule in configure and qnx directory [Bonnefoy]
+- Make inflate distance-too-far checks more rigorous
+- Clean up FAR usage in inflate
+- Add casting to sizeof() in gzio.c and minigzip.c
+
+Changes in 1.2.0.3 (19 July 2003)
+- Fix silly error in gzungetc() implementation [Vollant]
+- Update contrib/minizip and contrib/vstudio [Vollant]
+- Fix printf format in example.c
+- Correct cdecl support in zconf.in.h [Anisimkov]
+- Minor FAQ updates
+
+Changes in 1.2.0.2 (13 July 2003)
+- Add ZLIB_VERNUM in zlib.h for numerical preprocessor comparisons
+- Attempt to avoid warnings in crc32.c for pointer-int conversion
+- Add AIX to configure, remove aix directory [Bakker]
+- Add some casts to minigzip.c
+- Improve checking after insecure sprintf() or vsprintf() calls
+- Remove #elif's from crc32.c
+- Change leave label to inf_leave in inflate.c and infback.c to avoid
+ library conflicts
+- Remove inflate gzip decoding by default--only enable gzip decoding by
+ special request for stricter backward compatibility
+- Add zlibCompileFlags() function to return compilation information
+- More typecasting in deflate.c to avoid warnings
+- Remove leading underscore from _Capital #defines [Truta]
+- Fix configure to link shared library when testing
+- Add some Windows CE target adjustments [Mai]
+- Remove #define ZLIB_DLL in zconf.h [Vollant]
+- Add zlib.3 [Rodgers]
+- Update RFC URL in deflate.c and algorithm.txt [Mai]
+- Add zlib_dll_FAQ.txt to contrib [Truta]
+- Add UL to some constants [Truta]
+- Update minizip and vstudio [Vollant]
+- Remove vestigial NEED_DUMMY_RETURN from zconf.in.h
+- Expand use of NO_DUMMY_DECL to avoid all dummy structures
+- Added iostream3 to contrib [Schwardt]
+- Replace rewind() with fseek() for WinCE [Truta]
+- Improve setting of zlib format compression level flags
+ - Report 0 for huffman and rle strategies and for level == 0 or 1
+ - Report 2 only for level == 6
+- Only deal with 64K limit when necessary at compile time [Truta]
+- Allow TOO_FAR check to be turned off at compile time [Truta]
+- Add gzclearerr() function [Souza]
+- Add gzungetc() function
+
+Changes in 1.2.0.1 (17 March 2003)
+- Add Z_RLE strategy for run-length encoding [Truta]
+ - When Z_RLE requested, restrict matches to distance one
+ - Update zlib.h, minigzip.c, gzopen(), gzdopen() for Z_RLE
+- Correct FASTEST compilation to allow level == 0
+- Clean up what gets compiled for FASTEST
+- Incorporate changes to zconf.in.h [Vollant]
+ - Refine detection of Turbo C need for dummy returns
+ - Refine ZLIB_DLL compilation
+ - Include additional header file on VMS for off_t typedef
+- Try to use _vsnprintf where it supplants vsprintf [Vollant]
+- Add some casts in inffast.c
+- Enchance comments in zlib.h on what happens if gzprintf() tries to
+ write more than 4095 bytes before compression
+- Remove unused state from inflateBackEnd()
+- Remove exit(0) from minigzip.c, example.c
+- Get rid of all those darn tabs
+- Add "check" target to Makefile.in that does the same thing as "test"
+- Add "mostlyclean" and "maintainer-clean" targets to Makefile.in
+- Update contrib/inflate86 [Anderson]
+- Update contrib/testzlib, contrib/vstudio, contrib/minizip [Vollant]
+- Add msdos and win32 directories with makefiles [Truta]
+- More additions and improvements to the FAQ
+
+Changes in 1.2.0 (9 March 2003)
+- New and improved inflate code
+ - About 20% faster
+ - Does not allocate 32K window unless and until needed
+ - Automatically detects and decompresses gzip streams
+ - Raw inflate no longer needs an extra dummy byte at end
+ - Added inflateBack functions using a callback interface--even faster
+ than inflate, useful for file utilities (gzip, zip)
+ - Added inflateCopy() function to record state for random access on
+ externally generated deflate streams (e.g. in gzip files)
+ - More readable code (I hope)
+- New and improved crc32()
+ - About 50% faster, thanks to suggestions from Rodney Brown
+- Add deflateBound() and compressBound() functions
+- Fix memory leak in deflateInit2()
+- Permit setting dictionary for raw deflate (for parallel deflate)
+- Fix const declaration for gzwrite()
+- Check for some malloc() failures in gzio.c
+- Fix bug in gzopen() on single-byte file 0x1f
+- Fix bug in gzread() on concatenated file with 0x1f at end of buffer
+ and next buffer doesn't start with 0x8b
+- Fix uncompress() to return Z_DATA_ERROR on truncated input
+- Free memory at end of example.c
+- Remove MAX #define in trees.c (conflicted with some libraries)
+- Fix static const's in deflate.c, gzio.c, and zutil.[ch]
+- Declare malloc() and free() in gzio.c if STDC not defined
+- Use malloc() instead of calloc() in zutil.c if int big enough
+- Define STDC for AIX
+- Add aix/ with approach for compiling shared library on AIX
+- Add HP-UX support for shared libraries in configure
+- Add OpenUNIX support for shared libraries in configure
+- Use $cc instead of gcc to build shared library
+- Make prefix directory if needed when installing
+- Correct Macintosh avoidance of typedef Byte in zconf.h
+- Correct Turbo C memory allocation when under Linux
+- Use libz.a instead of -lz in Makefile (assure use of compiled library)
+- Update configure to check for snprintf or vsnprintf functions and their
+ return value, warn during make if using an insecure function
+- Fix configure problem with compile-time knowledge of HAVE_UNISTD_H that
+ is lost when library is used--resolution is to build new zconf.h
+- Documentation improvements (in zlib.h):
+ - Document raw deflate and inflate
+ - Update RFCs URL
+ - Point out that zlib and gzip formats are different
+ - Note that Z_BUF_ERROR is not fatal
+ - Document string limit for gzprintf() and possible buffer overflow
+ - Note requirement on avail_out when flushing
+ - Note permitted values of flush parameter of inflate()
+- Add some FAQs (and even answers) to the FAQ
+- Add contrib/inflate86/ for x86 faster inflate
+- Add contrib/blast/ for PKWare Data Compression Library decompression
+- Add contrib/puff/ simple inflate for deflate format description
Changes in 1.1.4 (11 March 2002)
- ZFREE was repeated on same allocation on some error conditions.
less than 32K.
- force windowBits > 8 to avoid a bug in the encoder for a window size
of 256 bytes. (A complete fix will be available in 1.1.5).
-
+
Changes in 1.1.3 (9 July 1998)
- fix "an inflate input buffer bug that shows up on rare but persistent
occasions" (Mark)
- added Makefile.nt (thanks to Stephen Williams)
- added the unsupported "contrib" directory:
contrib/asm386/ by Gilles Vollant <info@winimage.com>
- 386 asm code replacing longest_match().
+ 386 asm code replacing longest_match().
contrib/iostream/ by Kevin Ruland <kevin@rodin.wustl.edu>
A C++ I/O streams interface to the zlib gz* functions
contrib/iostream2/ by Tyge Løvset <Tyge.Lovset@cmr.no>
- Another C++ I/O streams interface
+ Another C++ I/O streams interface
contrib/untgz/ by "Pedro A. Aranda Guti\irrez" <paag@tid.es>
- A very simple tar.gz file extractor using zlib
+ A very simple tar.gz file extractor using zlib
contrib/visual-basic.txt by Carlos Rios <c_rios@sonda.cl>
How to use compress(), uncompress() and the gz* functions from VB.
- pass params -f (filtered data), -h (huffman only), -1 to -9 (compression
- add NEED_DUMMY_RETURN for Borland
- use variable z_verbose for tracing in debug mode (L. Peter Deutsch).
- allow compilation with CC
-- defined STDC for OS/2 (David Charlap)
+- defined STDC for OS/2 (David Charlap)
- limit external names to 8 chars for MVS (Thomas Lund)
- in minigzip.c, use static buffers only for 16-bit systems
- fix suffix check for "minigzip -d foo.gz"
- Eliminate memory leaks on error conditions in inflate
- Removed some vestigial code in inflate
- Update web address in README
-
+
Changes in 1.0.4 (24 Jul 96)
- In very rare conditions, deflate(s, Z_FINISH) could fail to produce an EOF
bit, so the decompressor could decompress all the correct data but went
-ChangeLog history of changes
-INDEX this file
-FAQ Frequently Asked Questions about zlib
-Make_vms.com script for Vax/VMS
-Makefile makefile for Unix (generated by configure)
-Makefile.in makefile for Unix (template for configure)
-Makefile.riscos makefile for RISCOS
-README guess what
-algorithm.txt description of the (de)compression algorithm
-configure configure script for Unix
-descrip.mms makefile for Vax/VMS
-zlib.3 mini man page for zlib (volunteers to write full
- man pages from zlib.h welcome. write to jloup@gzip.org)
-
-amiga/Makefile.sas makefile for Amiga SAS/C
-amiga/Makefile.pup makefile for Amiga powerUP SAS/C PPC
-
-msdos/Makefile.w32 makefile for Microsoft Visual C++ 32-bit
-msdos/Makefile.b32 makefile for Borland C++ 32-bit
-msdos/Makefile.bor makefile for Borland C/C++ 16-bit
-msdos/Makefile.dj2 makefile for DJGPP 2.x
-msdos/Makefile.emx makefile for EMX 0.9c (32-bit DOS/OS2)
-msdos/Makefile.msc makefile for Microsoft C 16-bit
-msdos/Makefile.tc makefile for Turbo C
-msdos/Makefile.wat makefile for Watcom C
-msdos/zlib.def definition file for Windows DLL
-msdos/zlib.rc definition file for Windows DLL
-
-nt/Makefile.nt makefile for Windows NT
-nt/zlib.dnt definition file for Windows NT DLL
-nt/Makefile.emx makefile for EMX 0.9c/RSXNT 1.41 (Win32 Intel)
-nt/Makefile.gcc makefile for Windows NT using GCC (mingw32)
-
-
- zlib public header files (must be kept):
+ChangeLog history of changes
+FAQ Frequently Asked Questions about zlib
+INDEX this file
+Makefile makefile for Unix (generated by configure)
+Makefile.in makefile for Unix (template for configure)
+README guess what
+algorithm.txt description of the (de)compression algorithm
+configure configure script for Unix
+zconf.in.h template for zconf.h (used by configure)
+
+msdos/ makefiles for MSDOS
+old/ makefiles for various architectures and zlib documentation
+ files that have not yet been updated for zlib 1.2.x
+qnx/ makefiles for QNX
+win32/ makefiles for Windows
+
+ zlib public header files (must be kept):
zconf.h
zlib.h
- private source files used to build the zlib library:
+ private source files used to build the zlib library:
adler32.c
compress.c
crc32.c
+crc32.h
deflate.c
deflate.h
gzio.c
-infblock.c
-infblock.h
-infcodes.c
-infcodes.h
+infback.c
inffast.c
inffast.h
+inffixed.h
inflate.c
+inflate.h
inftrees.c
inftrees.h
-infutil.c
-infutil.h
-maketree.c
trees.c
+trees.h
uncompr.c
zutil.c
zutil.h
- source files for sample programs:
+ source files for sample programs:
example.c
minigzip.c
- unsupported contribution by third parties
-
-contrib/asm386/ by Gilles Vollant <info@winimage.com>
- 386 asm code replacing longest_match().
-
-contrib/minizip/ by Gilles Vollant <info@winimage.com>
- Mini zip and unzip based on zlib
- See http://www.winimage.com/zLibDll/unzip.html
-
-contrib/iostream/ by Kevin Ruland <kevin@rodin.wustl.edu>
- A C++ I/O streams interface to the zlib gz* functions
-
-contrib/iostream2/ by Tyge Løvset <Tyge.Lovset@cmr.no>
- Another C++ I/O streams interface
-
-contrib/untgz/ by "Pedro A. Aranda Guti\irrez" <paag@tid.es>
- A very simple tar.gz extractor using zlib
-
-contrib/visual-basic.txt by Carlos Rios <c_rios@sonda.cl>
- How to use compress(), uncompress() and the gz* functions from VB.
+ unsupported contribution by third parties
+See contrib/README.contrib
-zlib 1.1.4 is a general purpose data compression library. All the code
-is thread safe. The data format used by the zlib library
-is described by RFCs (Request for Comments) 1950 to 1952 in the files
-http://www.ietf.org/rfc/rfc1950.txt (zlib format), rfc1951.txt (deflate
-format) and rfc1952.txt (gzip format). These documents are also available in
-other formats from ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html
+ZLIB DATA COMPRESSION LIBRARY
+
+zlib 1.2.1 is a general purpose data compression library. All the code is
+thread safe. The data format used by the zlib library is described by RFCs
+(Request for Comments) 1950 to 1952 in the files
+http://www.ietf.org/rfc/rfc1950.txt (zlib format), rfc1951.txt (deflate format)
+and rfc1952.txt (gzip format). These documents are also available in other
+formats from ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html
All functions of the compression library are documented in the file zlib.h
-(volunteer to write man pages welcome, contact jloup@gzip.org). A usage
-example of the library is given in the file example.c which also tests that
-the library is working correctly. Another example is given in the file
-minigzip.c. The compression library itself is composed of all source files
-except example.c and minigzip.c.
-
-To compile all files and run the test program, follow the instructions
-given at the top of Makefile. In short "make test; make install"
-should work for most machines. For Unix: "./configure; make test; make install"
-For MSDOS, use one of the special makefiles such as Makefile.msc.
-For VMS, use Make_vms.com or descrip.mms.
-
-Questions about zlib should be sent to <zlib@gzip.org>, or to
-Gilles Vollant <info@winimage.com> for the Windows DLL version.
-The zlib home page is http://www.zlib.org or http://www.gzip.org/zlib/
-Before reporting a problem, please check this site to verify that
-you have the latest version of zlib; otherwise get the latest version and
-check whether the problem still exists or not.
-
-PLEASE read the zlib FAQ http://www.gzip.org/zlib/zlib_faq.html
-before asking for help.
+(volunteer to write man pages welcome, contact zlib@gzip.org). A usage example
+of the library is given in the file example.c which also tests that the library
+is working correctly. Another example is given in the file minigzip.c. The
+compression library itself is composed of all source files except example.c and
+minigzip.c.
+
+To compile all files and run the test program, follow the instructions given at
+the top of Makefile. In short "make test; make install" should work for most
+machines. For Unix: "./configure; make test; make install" For MSDOS, use one
+of the special makefiles such as Makefile.msc. For VMS, use Make_vms.com or
+descrip.mms.
+
+Questions about zlib should be sent to <zlib@gzip.org>, or to Gilles Vollant
+<info@winimage.com> for the Windows DLL version. The zlib home page is
+http://www.zlib.org or http://www.gzip.org/zlib/ Before reporting a problem,
+please check this site to verify that you have the latest version of zlib;
+otherwise get the latest version and check whether the problem still exists or
+not.
+
+PLEASE read the zlib FAQ http://www.gzip.org/zlib/zlib_faq.html before asking
+for help.
Mark Nelson <markn@ieee.org> wrote an article about zlib for the Jan. 1997
issue of Dr. Dobb's Journal; a copy of the article is available in
http://dogma.net/markn/articles/zlibtool/zlibtool.htm
-The changes made in version 1.1.4 are documented in the file ChangeLog.
-The only changes made since 1.1.3 are bug corrections:
-
-- ZFREE was repeated on same allocation on some error conditions.
- This creates a security problem described in
- http://www.zlib.org/advisory-2002-03-11.txt
-- Returned incorrect error (Z_MEM_ERROR) on some invalid data
-- Avoid accesses before window for invalid distances with inflate window
- less than 32K.
-- force windowBits > 8 to avoid a bug in the encoder for a window size
- of 256 bytes. (A complete fix will be available in 1.1.5).
-
-The beta version 1.1.5beta includes many more changes. A new official
-version 1.1.5 will be released as soon as extensive testing has been
-completed on it.
-
+The changes made in version 1.2.1 are documented in the file ChangeLog.
Unsupported third party contributions are provided in directory "contrib".
A Java implementation of zlib is available in the Java Development Kit
-http://www.javasoft.com/products/JDK/1.1/docs/api/Package-java.util.zip.html
+http://java.sun.com/j2se/1.4.2/docs/api/java/util/zip/package-summary.html
See the zlib home page http://www.zlib.org for details.
-A Perl interface to zlib written by Paul Marquess <pmarquess@bfsec.bt.co.uk>
-is in the CPAN (Comprehensive Perl Archive Network) sites
+A Perl interface to zlib written by Paul Marquess <pmqs@cpan.org> is in the
+CPAN (Comprehensive Perl Archive Network) sites
http://www.cpan.org/modules/by-module/Compress/
-A Python interface to zlib written by A.M. Kuchling <amk@magnet.com>
-is available in Python 1.5 and later versions, see
+A Python interface to zlib written by A.M. Kuchling <amk@magnet.com> is
+available in Python 1.5 and later versions, see
http://www.python.org/doc/lib/module-zlib.html
-A zlib binding for TCL written by Andreas Kupries <a.kupries@westend.com>
-is availlable at http://www.westend.com/~kupries/doc/trf/man/man.html
+A zlib binding for TCL written by Andreas Kupries <a.kupries@westend.com> is
+availlable at http://www.oche.de/~akupries/soft/trf/trf_zip.html
-An experimental package to read and write files in .zip format,
-written on top of zlib by Gilles Vollant <info@winimage.com>, is
-available at http://www.winimage.com/zLibDll/unzip.html
-and also in the contrib/minizip directory of zlib.
+An experimental package to read and write files in .zip format, written on top
+of zlib by Gilles Vollant <info@winimage.com>, is available in the
+contrib/minizip directory of zlib.
Notes for some targets:
-- To build a Windows DLL version, include in a DLL project zlib.def, zlib.rc
- and all .c files except example.c and minigzip.c; compile with -DZLIB_DLL
- The zlib DLL support was initially done by Alessandro Iacopetti and is
- now maintained by Gilles Vollant <info@winimage.com>. Check the zlib DLL
- home page at http://www.winimage.com/zLibDll
-
- From Visual Basic, you can call the DLL functions which do not take
- a structure as argument: compress, uncompress and all gz* functions.
- See contrib/visual-basic.txt for more information, or get
- http://www.tcfb.com/dowseware/cmp-z-it.zip
+- For Windows DLL versions, please see win32/DLL_FAQ.txt
-- For 64-bit Irix, deflate.c must be compiled without any optimization.
- With -O, one libpng test fails. The test works in 32 bit mode (with
- the -n32 compiler flag). The compiler bug has been reported to SGI.
+- For 64-bit Irix, deflate.c must be compiled without any optimization. With
+ -O, one libpng test fails. The test works in 32 bit mode (with the -n32
+ compiler flag). The compiler bug has been reported to SGI.
-- zlib doesn't work with gcc 2.6.3 on a DEC 3000/300LX under OSF/1 2.1
- it works when compiled with cc.
+- zlib doesn't work with gcc 2.6.3 on a DEC 3000/300LX under OSF/1 2.1 it works
+ when compiled with cc.
-- on Digital Unix 4.0D (formely OSF/1) on AlphaServer, the cc option -std1
- is necessary to get gzprintf working correctly. This is done by configure.
+- On Digital Unix 4.0D (formely OSF/1) on AlphaServer, the cc option -std1 is
+ necessary to get gzprintf working correctly. This is done by configure.
-- zlib doesn't work on HP-UX 9.05 with some versions of /bin/cc. It works
- with other compilers. Use "make test" to check your compiler.
+- zlib doesn't work on HP-UX 9.05 with some versions of /bin/cc. It works with
+ other compilers. Use "make test" to check your compiler.
- gzdopen is not supported on RISCOS, BEOS and by some Mac compilers.
-- For Turbo C the small model is supported only with reduced performance to
- avoid any far allocation; it was tested with -DMAX_WBITS=11 -DMAX_MEM_LEVEL=3
+- For PalmOs, see http://palmzlib.sourceforge.net/
-- For PalmOs, see http://www.cs.uit.no/~perm/PASTA/pilot/software.html
- Per Harald Myrvang <perm@stud.cs.uit.no>
+- When building a shared, i.e. dynamic library on Mac OS X, the library must be
+ installed before testing (do "make install" before "make test"), since the
+ library location is specified in the library.
Acknowledgments:
Copyright notice:
- (C) 1995-2002 Jean-loup Gailly and Mark Adler
+ (C) 1995-2003 Jean-loup Gailly and Mark Adler
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
include third-party code.
If you redistribute modified sources, we would appreciate that you include
-in the file ChangeLog history information documenting your changes.
+in the file ChangeLog history information documenting your changes. Please
+read the FAQ for more information on the distribution of modified source
+versions.
2.1 Introduction
-The real question is, given a Huffman tree, how to decode fast. The most
-important realization 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.
+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
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 set it
-for the maximum speed.
-
-inflate() sends new trees relatively often, so it is possibly set for a
-smaller first level table than an application that has only one tree for
-all the data. 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. It would be
-interesting to see if optimizing the first level table for other
-applications gave values within a bit or two of the flat code size.
+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
+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
+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
+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
+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
+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
+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 two much time
+that's essentially a Huffman tree. But then you spend two 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
+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.
110: -> table X (gobble 3 bits)
111: -> table Y (gobble 3 bits)
-Each entry is what the bits decode to and how many bits that is, i.e. how
+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.
10: D,2
11: E,2
-Table Y is three bits long since the longest code starting with 111 is six
+Table Y is three bits long since the longest code starting with 111 is six
bits long:
000: F,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
+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
+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
+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.
pp. 337-343.
``DEFLATE Compressed Data Format Specification'' available in
-ftp://ds.internic.net/rfc/rfc1951.txt
+http://www.ietf.org/rfc/rfc1951.txt
projects / wxWidgets.git / commitdiff
