zlib 1.2.0v1.2.0

1 files changed, 168 insertions, 5 deletions

diff --git a/FAQ b/FAQ
index 47a7d60..abf680c 100644
--- a/FAQ
+++ b/FAQ
@@ -36,6 +36,11 @@ The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html
     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.
 
  6. Where's the zlib documentation (man pages, etc.)?
 
@@ -88,13 +93,171 @@ The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html
 14. Why does "make test" fail on Mac OS X?
 
     Mac OS X already includes zlib as a shared library, and so -lz links the
-    shared library instead of the one that the "make" compiled. For zlib
-    1.1.3, the two are incompatible due to different compile-time
-    options. Simply change the -lz in the Makefile to libz.a, and it will use
-    the compiled library instead of the shared one and the "make test" will
-    succeed.
+    shared library instead of the one that the "make" compiled. The two are
+    incompatible due to different compile-time options. Simply change the -lz
+    in the Makefile to libz.a, and it will use the compiled library instead
+    of the shared one and the "make test" will succeed.
 
 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. 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, but have different headers
+    and trailers.
+
+17. 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.
+
+18. Well that's nice, but how do I make a gzip file in memory?
+
+    Read RFC 1952 for the gzip header and trailer format, and roll your own
+    gzip formatted data using raw deflate and crc32().
+
+19. Is zlib thread-safe?
+
+    Yes. However any library routines that zlib uses and any application-
+    provided memory allocation routines must also be thread-safe. Of course,
+    you should only operate on any given zlib or gzip stream from a single
+    thread. 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.
+
+20. Can I use zlib in my commercial application?
+
+    Yes. Please read the license in zlib.h.
+
+21. Is zlib under the GNU license?
+
+    No. Please read the license in zlib.h.
+
+22. Will zlib work on a big-endian or little-endian architecture, and can I
+    exchange compressed data between them?
+
+    Yes and yes.
+
+23. Will zlib work on a 64-bit machine?
+
+    It should. 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
+
+24. 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.
+
+25. 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.
+
+26. Does zlib work on MVS, OS/390, CICS, etc.?
+
+    We don't know for sure. We have heard occasional reports of success on
+    these systems. If you do use it on one of these, please provide us with
+    a report, instructions, and patches that we can reference when we get
+    these questions. Thanks.
+
+27. 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.
+
+28. 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
+
+29. Can zlib work with greater than 4 GB of data?
+
+    Yes. inflate() and deflate() will process any amount of data correctly.
+    However the strm.total_in and strm_total_out counters may be limited to
+    4 GB. The user can easily set up their 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 using unsigned long lengths. gzseek() may be limited to 4 GB
+    depending on how zlib is compiled.
+
+30. 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 a 4K string space, other than the caller of
+    gzprintf() assuring that the output will not exceed 4K. On the other
+    hand, if zlib is compiled to use snprintf() or vsnprintf(), then there is
+    no vulnerability.
+
+    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.
+
+31. 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 class. If you really want
+    a version of zlib written in the Java language, look on the zlib home
+    page for links: http://www.zlib.org/
+
+32. I get this or that compiler or source-code scanner warning. 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. So now, we simply make sure that the code always
+    works.
+
+33. 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.
+
+34. How can I encrypt/decrypt zip files with zlib?
+
+    zlib doesn't support encryption. PKZIP encryption is very weak and can be
+    broken with freely available programs. To get strong encryption, use gpg
+    which already includes zlib compression.
+
+35. 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.
+
+36. 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.
+
+37. 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.