cpython-lru_cache-weakref: Modules/zlib/FAQ annotate

annotate Modules/zlib/FAQ @ 58765:2ba7677bfa95 legacy-trunk

testCopysign was defined twice in test_math; combine the definitions

author	Mark Dickinson <dickinsm@gmail.com>
date	Sat, 06 Feb 2010 23:11:25 +0000
parents	81fa47d2d477
children	467019588fcc

rev	line source
36186 81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	1
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	2 Frequently Asked Questions about zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	3
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	4
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	5 If your question is not there, please check the zlib home page
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	6 http://www.zlib.org which may have more recent information.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	7 The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	8
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	9
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	10 1. Is zlib Y2K-compliant?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	11
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	12 Yes. zlib doesn't handle dates.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	13
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	14 2. Where can I get a Windows DLL version?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	15
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	16 The zlib sources can be compiled without change to produce a DLL.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	17 See the file win32/DLL_FAQ.txt in the zlib distribution.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	18 Pointers to the precompiled DLL are found in the zlib web site at
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	19 http://www.zlib.org.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	20
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	21 3. Where can I get a Visual Basic interface to zlib?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	22
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	23 See
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	24 * http://www.dogma.net/markn/articles/zlibtool/zlibtool.htm
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	25 * contrib/visual-basic.txt in the zlib distribution
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	26 * win32/DLL_FAQ.txt in the zlib distribution
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	27
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	28 4. compress() returns Z_BUF_ERROR.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	29
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	30 Make sure that before the call of compress, the length of the compressed
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	31 buffer is equal to the total size of the compressed buffer and not
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	32 zero. For Visual Basic, check that this parameter is passed by reference
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	33 ("as any"), not by value ("as long").
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	34
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	35 5. deflate() or inflate() returns Z_BUF_ERROR.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	36
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	37 Before making the call, make sure that avail_in and avail_out are not
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	38 zero. When setting the parameter flush equal to Z_FINISH, also make sure
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	39 that avail_out is big enough to allow processing all pending input.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	40 Note that a Z_BUF_ERROR is not fatal--another call to deflate() or
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	41 inflate() can be made with more input or output space. A Z_BUF_ERROR
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	42 may in fact be unavoidable depending on how the functions are used, since
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	43 it is not possible to tell whether or not there is more output pending
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	44 when strm.avail_out returns with zero.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	45
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	46 6. Where's the zlib documentation (man pages, etc.)?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	47
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	48 It's in zlib.h for the moment, and Francis S. Lin has converted it to a
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	49 web page zlib.html. Volunteers to transform this to Unix-style man pages,
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	50 please contact us (zlib@gzip.org). Examples of zlib usage are in the files
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	51 example.c and minigzip.c.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	52
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	53 7. Why don't you use GNU autoconf or libtool or ...?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	54
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	55 Because we would like to keep zlib as a very small and simple
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	56 package. zlib is rather portable and doesn't need much configuration.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	57
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	58 8. I found a bug in zlib.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	59
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	60 Most of the time, such problems are due to an incorrect usage of
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	61 zlib. Please try to reproduce the problem with a small program and send
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	62 the corresponding source to us at zlib@gzip.org . Do not send
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	63 multi-megabyte data files without prior agreement.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	64
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	65 9. Why do I get "undefined reference to gzputc"?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	66
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	67 If "make test" produces something like
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	68
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	69 example.o(.text+0x154): undefined reference to `gzputc'
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	70
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	71 check that you don't have old files libz.* in /usr/lib, /usr/local/lib or
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	72 /usr/X11R6/lib. Remove any old versions, then do "make install".
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	73
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	74 10. I need a Delphi interface to zlib.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	75
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	76 See the contrib/delphi directory in the zlib distribution.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	77
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	78 11. Can zlib handle .zip archives?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	79
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	80 Not by itself, no. See the directory contrib/minizip in the zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	81 distribution.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	82
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	83 12. Can zlib handle .Z files?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	84
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	85 No, sorry. You have to spawn an uncompress or gunzip subprocess, or adapt
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	86 the code of uncompress on your own.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	87
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	88 13. How can I make a Unix shared library?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	89
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	90 make clean
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	91 ./configure -s
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	92 make
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	93
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	94 14. How do I install a shared zlib library on Unix?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	95
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	96 After the above, then:
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	97
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	98 make install
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	99
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	100 However, many flavors of Unix come with a shared zlib already installed.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	101 Before going to the trouble of compiling a shared version of zlib and
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	102 trying to install it, you may want to check if it's already there! If you
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	103 can #include <zlib.h>, it's there. The -lz option will probably link to it.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	104
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	105 15. I have a question about OttoPDF.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	106
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	107 We are not the authors of OttoPDF. The real author is on the OttoPDF web
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	108 site: Joel Hainley, jhainley@myndkryme.com.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	109
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	110 16. Can zlib decode Flate data in an Adobe PDF file?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	111
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	112 Yes. See http://www.fastio.com/ (ClibPDF), or http://www.pdflib.com/ .
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	113 To modify PDF forms, see http://sourceforge.net/projects/acroformtool/ .
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	114
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	115 17. Why am I getting this "register_frame_info not found" error on Solaris?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	116
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	117 After installing zlib 1.1.4 on Solaris 2.6, running applications using zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	118 generates an error such as:
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	119
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	120 ld.so.1: rpm: fatal: relocation error: file /usr/local/lib/libz.so:
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	121 symbol __register_frame_info: referenced symbol not found
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	122
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	123 The symbol __register_frame_info is not part of zlib, it is generated by
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	124 the C compiler (cc or gcc). You must recompile applications using zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	125 which have this problem. This problem is specific to Solaris. See
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	126 http://www.sunfreeware.com for Solaris versions of zlib and applications
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	127 using zlib.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	128
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	129 18. Why does gzip give an error on a file I make with compress/deflate?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	130
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	131 The compress and deflate functions produce data in the zlib format, which
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	132 is different and incompatible with the gzip format. The gz* functions in
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	133 zlib on the other hand use the gzip format. Both the zlib and gzip
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	134 formats use the same compressed data format internally, but have different
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	135 headers and trailers around the compressed data.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	136
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	137 19. Ok, so why are there two different formats?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	138
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	139 The gzip format was designed to retain the directory information about
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	140 a single file, such as the name and last modification date. The zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	141 format on the other hand was designed for in-memory and communication
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	142 channel applications, and has a much more compact header and trailer and
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	143 uses a faster integrity check than gzip.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	144
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	145 20. Well that's nice, but how do I make a gzip file in memory?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	146
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	147 You can request that deflate write the gzip format instead of the zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	148 format using deflateInit2(). You can also request that inflate decode
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	149 the gzip format using inflateInit2(). Read zlib.h for more details.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	150
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	151 21. Is zlib thread-safe?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	152
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	153 Yes. However any library routines that zlib uses and any application-
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	154 provided memory allocation routines must also be thread-safe. zlib's gz*
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	155 functions use stdio library routines, and most of zlib's functions use the
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	156 library memory allocation routines by default. zlib's Init functions allow
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	157 for the application to provide custom memory allocation routines.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	158
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	159 Of course, you should only operate on any given zlib or gzip stream from a
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	160 single thread at a time.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	161
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	162 22. Can I use zlib in my commercial application?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	163
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	164 Yes. Please read the license in zlib.h.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	165
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	166 23. Is zlib under the GNU license?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	167
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	168 No. Please read the license in zlib.h.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	169
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	170 24. The license says that altered source versions must be "plainly marked". So
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	171 what exactly do I need to do to meet that requirement?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	172
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	173 You need to change the ZLIB_VERSION and ZLIB_VERNUM #defines in zlib.h. In
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	174 particular, the final version number needs to be changed to "f", and an
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	175 identification string should be appended to ZLIB_VERSION. Version numbers
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	176 x.x.x.f are reserved for modifications to zlib by others than the zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	177 maintainers. For example, if the version of the base zlib you are altering
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	178 is "1.2.3.4", then in zlib.h you should change ZLIB_VERNUM to 0x123f, and
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	179 ZLIB_VERSION to something like "1.2.3.f-zachary-mods-v3". You can also
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	180 update the version strings in deflate.c and inftrees.c.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	181
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	182 For altered source distributions, you should also note the origin and
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	183 nature of the changes in zlib.h, as well as in ChangeLog and README, along
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	184 with the dates of the alterations. The origin should include at least your
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	185 name (or your company's name), and an email address to contact for help or
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	186 issues with the library.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	187
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	188 Note that distributing a compiled zlib library along with zlib.h and
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	189 zconf.h is also a source distribution, and so you should change
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	190 ZLIB_VERSION and ZLIB_VERNUM and note the origin and nature of the changes
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	191 in zlib.h as you would for a full source distribution.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	192
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	193 25. Will zlib work on a big-endian or little-endian architecture, and can I
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	194 exchange compressed data between them?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	195
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	196 Yes and yes.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	197
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	198 26. Will zlib work on a 64-bit machine?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	199
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	200 It should. It has been tested on 64-bit machines, and has no dependence
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	201 on any data types being limited to 32-bits in length. If you have any
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	202 difficulties, please provide a complete problem report to zlib@gzip.org
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	203
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	204 27. Will zlib decompress data from the PKWare Data Compression Library?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	205
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	206 No. The PKWare DCL uses a completely different compressed data format
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	207 than does PKZIP and zlib. However, you can look in zlib's contrib/blast
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	208 directory for a possible solution to your problem.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	209
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	210 28. Can I access data randomly in a compressed stream?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	211
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	212 No, not without some preparation. If when compressing you periodically
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	213 use Z_FULL_FLUSH, carefully write all the pending data at those points,
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	214 and keep an index of those locations, then you can start decompression
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	215 at those points. You have to be careful to not use Z_FULL_FLUSH too
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	216 often, since it can significantly degrade compression.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	217
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	218 29. Does zlib work on MVS, OS/390, CICS, etc.?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	219
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	220 We don't know for sure. We have heard occasional reports of success on
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	221 these systems. If you do use it on one of these, please provide us with
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	222 a report, instructions, and patches that we can reference when we get
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	223 these questions. Thanks.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	224
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	225 30. Is there some simpler, easier to read version of inflate I can look at
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	226 to understand the deflate format?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	227
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	228 First off, you should read RFC 1951. Second, yes. Look in zlib's
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	229 contrib/puff directory.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	230
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	231 31. Does zlib infringe on any patents?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	232
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	233 As far as we know, no. In fact, that was originally the whole point behind
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	234 zlib. Look here for some more information:
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	235
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	236 http://www.gzip.org/#faq11
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	237
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	238 32. Can zlib work with greater than 4 GB of data?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	239
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	240 Yes. inflate() and deflate() will process any amount of data correctly.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	241 Each call of inflate() or deflate() is limited to input and output chunks
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	242 of the maximum value that can be stored in the compiler's "unsigned int"
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	243 type, but there is no limit to the number of chunks. Note however that the
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	244 strm.total_in and strm_total_out counters may be limited to 4 GB. These
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	245 counters are provided as a convenience and are not used internally by
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	246 inflate() or deflate(). The application can easily set up its own counters
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	247 updated after each call of inflate() or deflate() to count beyond 4 GB.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	248 compress() and uncompress() may be limited to 4 GB, since they operate in a
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	249 single call. gzseek() and gztell() may be limited to 4 GB depending on how
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	250 zlib is compiled. See the zlibCompileFlags() function in zlib.h.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	251
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	252 The word "may" appears several times above since there is a 4 GB limit
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	253 only if the compiler's "long" type is 32 bits. If the compiler's "long"
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	254 type is 64 bits, then the limit is 16 exabytes.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	255
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	256 33. Does zlib have any security vulnerabilities?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	257
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	258 The only one that we are aware of is potentially in gzprintf(). If zlib
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	259 is compiled to use sprintf() or vsprintf(), then there is no protection
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	260 against a buffer overflow of a 4K string space, other than the caller of
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	261 gzprintf() assuring that the output will not exceed 4K. On the other
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	262 hand, if zlib is compiled to use snprintf() or vsnprintf(), which should
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	263 normally be the case, then there is no vulnerability. The ./configure
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	264 script will display warnings if an insecure variation of sprintf() will
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	265 be used by gzprintf(). Also the zlibCompileFlags() function will return
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	266 information on what variant of sprintf() is used by gzprintf().
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	267
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	268 If you don't have snprintf() or vsnprintf() and would like one, you can
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	269 find a portable implementation here:
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	270
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	271 http://www.ijs.si/software/snprintf/
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	272
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	273 Note that you should be using the most recent version of zlib. Versions
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	274 1.1.3 and before were subject to a double-free vulnerability.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	275
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	276 34. Is there a Java version of zlib?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	277
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	278 Probably what you want is to use zlib in Java. zlib is already included
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	279 as part of the Java SDK in the java.util.zip package. If you really want
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	280 a version of zlib written in the Java language, look on the zlib home
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	281 page for links: http://www.zlib.org/
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	282
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	283 35. I get this or that compiler or source-code scanner warning when I crank it
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	284 up to maximally-pedantic. Can't you guys write proper code?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	285
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	286 Many years ago, we gave up attempting to avoid warnings on every compiler
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	287 in the universe. It just got to be a waste of time, and some compilers
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	288 were downright silly. So now, we simply make sure that the code always
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	289 works.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	290
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	291 36. Valgrind (or some similar memory access checker) says that deflate is
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	292 performing a conditional jump that depends on an uninitialized value.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	293 Isn't that a bug?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	294
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	295 No. That is intentional for performance reasons, and the output of
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	296 deflate is not affected. This only started showing up recently since
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	297 zlib 1.2.x uses malloc() by default for allocations, whereas earlier
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	298 versions used calloc(), which zeros out the allocated memory.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	299
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	300 37. Will zlib read the (insert any ancient or arcane format here) compressed
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	301 data format?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	302
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	303 Probably not. Look in the comp.compression FAQ for pointers to various
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	304 formats and associated software.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	305
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	306 38. How can I encrypt/decrypt zip files with zlib?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	307
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	308 zlib doesn't support encryption. The original PKZIP encryption is very weak
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	309 and can be broken with freely available programs. To get strong encryption,
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	310 use GnuPG, http://www.gnupg.org/ , which already includes zlib compression.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	311 For PKZIP compatible "encryption", look at http://www.info-zip.org/
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	312
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	313 39. What's the difference between the "gzip" and "deflate" HTTP 1.1 encodings?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	314
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	315 "gzip" is the gzip format, and "deflate" is the zlib format. They should
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	316 probably have called the second one "zlib" instead to avoid confusion
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	317 with the raw deflate compressed data format. While the HTTP 1.1 RFC 2616
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	318 correctly points to the zlib specification in RFC 1950 for the "deflate"
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	319 transfer encoding, there have been reports of servers and browsers that
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	320 incorrectly produce or expect raw deflate data per the deflate
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	321 specficiation in RFC 1951, most notably Microsoft. So even though the
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	322 "deflate" transfer encoding using the zlib format would be the more
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	323 efficient approach (and in fact exactly what the zlib format was designed
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	324 for), using the "gzip" transfer encoding is probably more reliable due to
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	325 an unfortunate choice of name on the part of the HTTP 1.1 authors.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	326
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	327 Bottom line: use the gzip format for HTTP 1.1 encoding.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	328
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	329 40. Does zlib support the new "Deflate64" format introduced by PKWare?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	330
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	331 No. PKWare has apparently decided to keep that format proprietary, since
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	332 they have not documented it as they have previous compression formats.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	333 In any case, the compression improvements are so modest compared to other
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	334 more modern approaches, that it's not worth the effort to implement.
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	335
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	336 41. Can you please sign these lengthy legal documents and fax them back to us
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	337 so that we can use your software in our product?
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	338
81fa47d2d477 Import zlib into Python tree. Martin v. Löwis <martin@v.loewis.de> parents: diff changeset	339 No. Go away. Shoo.

Mercurial > cpython-lru_cache-weakref

annotate Modules/zlib/FAQ @ 58765:2ba7677bfa95 legacy-trunk