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diff --git a/zlib/FAQ b/zlib/FAQ deleted file mode 100644 index 1a22750..0000000 --- a/zlib/FAQ +++ /dev/null @@ -1,366 +0,0 @@ - - Frequently Asked Questions about zlib - - -If your question is not there, please check the zlib home page -http://zlib.net/ which may have more recent information. -The lastest zlib FAQ is at http://zlib.net/zlib_faq.html - - - 1. Is zlib Y2K-compliant? - - Yes. zlib doesn't handle dates. - - 2. Where can I get a Windows DLL version? - - The zlib sources can be compiled without change to produce a DLL. See the - file win32/DLL_FAQ.txt in the zlib distribution. Pointers to the - precompiled DLL are found in the zlib web site at http://zlib.net/ . - - 3. Where can I get a Visual Basic interface to zlib? - - See - * http://marknelson.us/1997/01/01/zlib-engine/ - * win32/DLL_FAQ.txt in the zlib distribution - - 4. compress() returns Z_BUF_ERROR. - - Make sure that before the call of compress(), the length of the compressed - buffer is equal to the available size of the compressed buffer and not - zero. For Visual Basic, check that this parameter is passed by reference - ("as any"), not by value ("as long"). - - 5. deflate() or inflate() returns Z_BUF_ERROR. - - Before making the call, make sure that avail_in and avail_out are not zero. - When setting the parameter flush equal to Z_FINISH, also make sure that - avail_out is big enough to allow processing all pending input. Note that a - Z_BUF_ERROR is not fatal--another call to deflate() or inflate() can be - made with more input or output space. A Z_BUF_ERROR may in fact be - unavoidable depending on how the functions are used, since it is not - possible to tell whether or not there is more output pending when - strm.avail_out returns with zero. See http://zlib.net/zlib_how.html for a - heavily annotated example. - - 6. Where's the zlib documentation (man pages, etc.)? - - It's in zlib.h . Examples of zlib usage are in the files example.c and - minigzip.c, with more in examples/ . - - 7. Why don't you use GNU autoconf or libtool or ...? - - Because we would like to keep zlib as a very small and simple package. - zlib is rather portable and doesn't need much configuration. - - 8. I found a bug in zlib. - - Most of the time, such problems are due to an incorrect usage of zlib. - Please try to reproduce the problem with a small program and send the - corresponding source to us at zlib@gzip.org . Do not send multi-megabyte - data files without prior agreement. - - 9. Why do I get "undefined reference to gzputc"? - - If "make test" produces something like - - example.o(.text+0x154): undefined reference to `gzputc' - - check that you don't have old files libz.* in /usr/lib, /usr/local/lib or - /usr/X11R6/lib. Remove any old versions, then do "make install". - -10. I need a Delphi interface to zlib. - - See the contrib/delphi directory in the zlib distribution. - -11. Can zlib handle .zip archives? - - Not by itself, no. See the directory contrib/minizip in the zlib - distribution. - -12. Can zlib handle .Z files? - - No, sorry. You have to spawn an uncompress or gunzip subprocess, or adapt - the code of uncompress on your own. - -13. How can I make a Unix shared library? - - make clean - ./configure -s - make - -14. How do I install a shared zlib library on Unix? - - After the above, then: - - make install - - However, many flavors of Unix come with a shared zlib already installed. - Before going to the trouble of compiling a shared version of zlib and - trying to install it, you may want to check if it's already there! If you - can #include <zlib.h>, it's there. The -lz option will probably link to - it. You can check the version at the top of zlib.h or with the - ZLIB_VERSION symbol defined in zlib.h . - -15. I have a question about OttoPDF. - - We are not the authors of OttoPDF. The real author is on the OttoPDF web - site: Joel Hainley, jhainley@myndkryme.com. - -16. Can zlib decode Flate data in an Adobe PDF file? - - Yes. See http://www.pdflib.com/ . To modify PDF forms, see - http://sourceforge.net/projects/acroformtool/ . - -17. Why am I getting this "register_frame_info not found" error on Solaris? - - After installing zlib 1.1.4 on Solaris 2.6, running applications using zlib - generates an error such as: - - ld.so.1: rpm: fatal: relocation error: file /usr/local/lib/libz.so: - symbol __register_frame_info: referenced symbol not found - - The symbol __register_frame_info is not part of zlib, it is generated by - the C compiler (cc or gcc). You must recompile applications using zlib - which have this problem. This problem is specific to Solaris. See - http://www.sunfreeware.com for Solaris versions of zlib and applications - using zlib. - -18. Why does gzip give an error on a file I make with compress/deflate? - - The compress and deflate functions produce data in the zlib format, which - is different and incompatible with the gzip format. The gz* functions in - zlib on the other hand use the gzip format. Both the zlib and gzip formats - use the same compressed data format internally, but have different headers - and trailers around the compressed data. - -19. Ok, so why are there two different formats? - - The gzip format was designed to retain the directory information about a - single file, such as the name and last modification date. The zlib format - on the other hand was designed for in-memory and communication channel - applications, and has a much more compact header and trailer and uses a - faster integrity check than gzip. - -20. Well that's nice, but how do I make a gzip file in memory? - - You can request that deflate write the gzip format instead of the zlib - format using deflateInit2(). You can also request that inflate decode the - gzip format using inflateInit2(). Read zlib.h for more details. - -21. Is zlib thread-safe? - - Yes. However any library routines that zlib uses and any application- - provided memory allocation routines must also be thread-safe. zlib's gz* - functions use stdio library routines, and most of zlib's functions use the - library memory allocation routines by default. zlib's *Init* functions - allow for the application to provide custom memory allocation routines. - - Of course, you should only operate on any given zlib or gzip stream from a - single thread at a time. - -22. Can I use zlib in my commercial application? - - Yes. Please read the license in zlib.h. - -23. Is zlib under the GNU license? - - No. Please read the license in zlib.h. - -24. The license says that altered source versions must be "plainly marked". So - what exactly do I need to do to meet that requirement? - - You need to change the ZLIB_VERSION and ZLIB_VERNUM #defines in zlib.h. In - particular, the final version number needs to be changed to "f", and an - identification string should be appended to ZLIB_VERSION. Version numbers - x.x.x.f are reserved for modifications to zlib by others than the zlib - maintainers. For example, if the version of the base zlib you are altering - is "1.2.3.4", then in zlib.h you should change ZLIB_VERNUM to 0x123f, and - ZLIB_VERSION to something like "1.2.3.f-zachary-mods-v3". You can also - update the version strings in deflate.c and inftrees.c. - - For altered source distributions, you should also note the origin and - nature of the changes in zlib.h, as well as in ChangeLog and README, along - with the dates of the alterations. The origin should include at least your - name (or your company's name), and an email address to contact for help or - issues with the library. - - Note that distributing a compiled zlib library along with zlib.h and - zconf.h is also a source distribution, and so you should change - ZLIB_VERSION and ZLIB_VERNUM and note the origin and nature of the changes - in zlib.h as you would for a full source distribution. - -25. Will zlib work on a big-endian or little-endian architecture, and can I - exchange compressed data between them? - - Yes and yes. - -26. Will zlib work on a 64-bit machine? - - Yes. It has been tested on 64-bit machines, and has no dependence on any - data types being limited to 32-bits in length. If you have any - difficulties, please provide a complete problem report to zlib@gzip.org - -27. Will zlib decompress data from the PKWare Data Compression Library? - - No. The PKWare DCL uses a completely different compressed data format than - does PKZIP and zlib. However, you can look in zlib's contrib/blast - directory for a possible solution to your problem. - -28. Can I access data randomly in a compressed stream? - - No, not without some preparation. If when compressing you periodically use - Z_FULL_FLUSH, carefully write all the pending data at those points, and - keep an index of those locations, then you can start decompression at those - points. You have to be careful to not use Z_FULL_FLUSH too often, since it - can significantly degrade compression. Alternatively, you can scan a - deflate stream once to generate an index, and then use that index for - random access. See examples/zran.c . - -29. Does zlib work on MVS, OS/390, CICS, etc.? - - It has in the past, but we have not heard of any recent evidence. There - were working ports of zlib 1.1.4 to MVS, but those links no longer work. - If you know of recent, successful applications of zlib on these operating - systems, please let us know. Thanks. - -30. Is there some simpler, easier to read version of inflate I can look at to - understand the deflate format? - - First off, you should read RFC 1951. Second, yes. Look in zlib's - contrib/puff directory. - -31. Does zlib infringe on any patents? - - As far as we know, no. In fact, that was originally the whole point behind - zlib. Look here for some more information: - - http://www.gzip.org/#faq11 - -32. Can zlib work with greater than 4 GB of data? - - Yes. inflate() and deflate() will process any amount of data correctly. - Each call of inflate() or deflate() is limited to input and output chunks - of the maximum value that can be stored in the compiler's "unsigned int" - type, but there is no limit to the number of chunks. Note however that the - strm.total_in and strm_total_out counters may be limited to 4 GB. These - counters are provided as a convenience and are not used internally by - inflate() or deflate(). The application can easily set up its own counters - updated after each call of inflate() or deflate() to count beyond 4 GB. - compress() and uncompress() may be limited to 4 GB, since they operate in a - single call. gzseek() and gztell() may be limited to 4 GB depending on how - zlib is compiled. See the zlibCompileFlags() function in zlib.h. - - The word "may" appears several times above since there is a 4 GB limit only - if the compiler's "long" type is 32 bits. If the compiler's "long" type is - 64 bits, then the limit is 16 exabytes. - -33. Does zlib have any security vulnerabilities? - - The only one that we are aware of is potentially in gzprintf(). If zlib is - compiled to use sprintf() or vsprintf(), then there is no protection - against a buffer overflow of an 8K string space (or other value as set by - gzbuffer()), other than the caller of gzprintf() assuring that the output - will not exceed 8K. On the other hand, if zlib is compiled to use - snprintf() or vsnprintf(), which should normally be the case, then there is - no vulnerability. The ./configure script will display warnings if an - insecure variation of sprintf() will be used by gzprintf(). Also the - zlibCompileFlags() function will return information on what variant of - sprintf() is used by gzprintf(). - - If you don't have snprintf() or vsnprintf() and would like one, you can - find a portable implementation here: - - http://www.ijs.si/software/snprintf/ - - Note that you should be using the most recent version of zlib. Versions - 1.1.3 and before were subject to a double-free vulnerability, and versions - 1.2.1 and 1.2.2 were subject to an access exception when decompressing - invalid compressed data. - -34. Is there a Java version of zlib? - - Probably what you want is to use zlib in Java. zlib is already included - as part of the Java SDK in the java.util.zip package. If you really want - a version of zlib written in the Java language, look on the zlib home - page for links: http://zlib.net/ . - -35. I get this or that compiler or source-code scanner warning when I crank it - up to maximally-pedantic. Can't you guys write proper code? - - Many years ago, we gave up attempting to avoid warnings on every compiler - in the universe. It just got to be a waste of time, and some compilers - were downright silly as well as contradicted each other. So now, we simply - make sure that the code always works. - -36. Valgrind (or some similar memory access checker) says that deflate is - performing a conditional jump that depends on an uninitialized value. - Isn't that a bug? - - No. That is intentional for performance reasons, and the output of deflate - is not affected. This only started showing up recently since zlib 1.2.x - uses malloc() by default for allocations, whereas earlier versions used - calloc(), which zeros out the allocated memory. Even though the code was - correct, versions 1.2.4 and later was changed to not stimulate these - checkers. - -37. Will zlib read the (insert any ancient or arcane format here) compressed - data format? - - Probably not. Look in the comp.compression FAQ for pointers to various - formats and associated software. - -38. How can I encrypt/decrypt zip files with zlib? - - zlib doesn't support encryption. The original PKZIP encryption is very - weak and can be broken with freely available programs. To get strong - encryption, use GnuPG, http://www.gnupg.org/ , which already includes zlib - compression. For PKZIP compatible "encryption", look at - http://www.info-zip.org/ - -39. What's the difference between the "gzip" and "deflate" HTTP 1.1 encodings? - - "gzip" is the gzip format, and "deflate" is the zlib format. They should - probably have called the second one "zlib" instead to avoid confusion with - the raw deflate compressed data format. While the HTTP 1.1 RFC 2616 - correctly points to the zlib specification in RFC 1950 for the "deflate" - transfer encoding, there have been reports of servers and browsers that - incorrectly produce or expect raw deflate data per the deflate - specficiation in RFC 1951, most notably Microsoft. So even though the - "deflate" transfer encoding using the zlib format would be the more - efficient approach (and in fact exactly what the zlib format was designed - for), using the "gzip" transfer encoding is probably more reliable due to - an unfortunate choice of name on the part of the HTTP 1.1 authors. - - Bottom line: use the gzip format for HTTP 1.1 encoding. - -40. Does zlib support the new "Deflate64" format introduced by PKWare? - - No. PKWare has apparently decided to keep that format proprietary, since - they have not documented it as they have previous compression formats. In - any case, the compression improvements are so modest compared to other more - modern approaches, that it's not worth the effort to implement. - -41. I'm having a problem with the zip functions in zlib, can you help? - - There are no zip functions in zlib. You are probably using minizip by - Giles Vollant, which is found in the contrib directory of zlib. It is not - part of zlib. In fact none of the stuff in contrib is part of zlib. The - files in there are not supported by the zlib authors. You need to contact - the authors of the respective contribution for help. - -42. The match.asm code in contrib is under the GNU General Public License. - Since it's part of zlib, doesn't that mean that all of zlib falls under the - GNU GPL? - - No. The files in contrib are not part of zlib. They were contributed by - other authors and are provided as a convenience to the user within the zlib - distribution. Each item in contrib has its own license. - -43. Is zlib subject to export controls? What is its ECCN? - - zlib is not subject to export controls, and so is classified as EAR99. - -44. Can you please sign these lengthy legal documents and fax them back to us - so that we can use your software in our product? - - No. Go away. Shoo. |