1 /* zlib.h -- interface of the 'zlib' general purpose compression library

     2   version 1.2.5, April 19th, 2010

     3 

     4   Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler

     5 

     6   This software is provided 'as-is', without any express or implied

     7   warranty.  In no event will the authors be held liable for any damages

     8   arising from the use of this software.

     9 

    10   Permission is granted to anyone to use this software for any purpose,

    11   including commercial applications, and to alter it and redistribute it

    12   freely, subject to the following restrictions:

    13 

    14   1. The origin of this software must not be misrepresented; you must not

    15      claim that you wrote the original software. If you use this software

    16      in a product, an acknowledgment in the product documentation would be

    17      appreciated but is not required.

    18   2. Altered source versions must be plainly marked as such, and must not be

    19      misrepresented as being the original software.

    20   3. This notice may not be removed or altered from any source distribution.

    21 

    22   Jean-loup Gailly        Mark Adler

    23   jloup@gzip.org          madler@alumni.caltech.edu

    24 

    25 

    26   The data format used by the zlib library is described by RFCs (Request for

    27   Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt

    28   (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).

    29 */

    30 

    31 #ifndef ZLIB_H

    32 #define ZLIB_H

    33 

    34 #include "zconf.h"

    35 

    36 #ifdef __cplusplus

    37 extern "C" {

    38 #endif

    39 

    40 #define ZLIB_VERSION "1.2.5"

    41 #define ZLIB_VERNUM 0x1250

    42 #define ZLIB_VER_MAJOR 1

    43 #define ZLIB_VER_MINOR 2

    44 #define ZLIB_VER_REVISION 5

    45 #define ZLIB_VER_SUBREVISION 0

    46 

    47 /*

    48     The 'zlib' compression library provides in-memory compression and

    49   decompression functions, including integrity checks of the uncompressed data.

    50   This version of the library supports only one compression method (deflation)

    51   but other algorithms will be added later and will have the same stream

    52   interface.

    53 

    54     Compression can be done in a single step if the buffers are large enough,

    55   or can be done by repeated calls of the compression function.  In the latter

    56   case, the application must provide more input and/or consume the output

    57   (providing more output space) before each call.

    58 

    59     The compressed data format used by default by the in-memory functions is

    60   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped

    61   around a deflate stream, which is itself documented in RFC 1951.

    62 

    63     The library also supports reading and writing files in gzip (.gz) format

    64   with an interface similar to that of stdio using the functions that start

    65   with "gz".  The gzip format is different from the zlib format.  gzip is a

    66   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.

    67 

    68     This library can optionally read and write gzip streams in memory as well.

    69 

    70     The zlib format was designed to be compact and fast for use in memory

    71   and on communications channels.  The gzip format was designed for single-

    72   file compression on file systems, has a larger header than zlib to maintain

    73   directory information, and uses a different, slower check method than zlib.

    74 

    75     The library does not install any signal handler.  The decoder checks

    76   the consistency of the compressed data, so the library should never crash

    77   even in case of corrupted input.

    78 */

    79 

    80 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));

    81 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));

    82 

    83 struct internal_state;

    84 

    85 typedef struct z_stream_s {

    86     Bytef    *next_in;  /* next input byte */

    87     uInt     avail_in;  /* number of bytes available at next_in */

    88     uLong    total_in;  /* total nb of input bytes read so far */

    89 

    90     Bytef    *next_out; /* next output byte should be put there */

    91     uInt     avail_out; /* remaining free space at next_out */

    92     uLong    total_out; /* total nb of bytes output so far */

    93 

    94     char     *msg;      /* last error message, NULL if no error */

    95     struct internal_state FAR *state; /* not visible by applications */

    96 

    97     alloc_func zalloc;  /* used to allocate the internal state */

    98     free_func  zfree;   /* used to free the internal state */

    99     voidpf     opaque;  /* private data object passed to zalloc and zfree */

   100 

   101     int     data_type;  /* best guess about the data type: binary or text */

   102     uLong   adler;      /* adler32 value of the uncompressed data */

   103     uLong   reserved;   /* reserved for future use */

   104 } z_stream;

   105 

   106 typedef z_stream FAR *z_streamp;

   107 

   108 /*

   109      gzip header information passed to and from zlib routines.  See RFC 1952

   110   for more details on the meanings of these fields.

   111 */

   112 typedef struct gz_header_s {

   113     int     text;       /* true if compressed data believed to be text */

   114     uLong   time;       /* modification time */

   115     int     xflags;     /* extra flags (not used when writing a gzip file) */

   116     int     os;         /* operating system */

   117     Bytef   *extra;     /* pointer to extra field or Z_NULL if none */

   118     uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */

   119     uInt    extra_max;  /* space at extra (only when reading header) */

   120     Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */

   121     uInt    name_max;   /* space at name (only when reading header) */

   122     Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */

   123     uInt    comm_max;   /* space at comment (only when reading header) */

   124     int     hcrc;       /* true if there was or will be a header crc */

   125     int     done;       /* true when done reading gzip header (not used

   126                            when writing a gzip file) */

   127 } gz_header;

   128 

   129 typedef gz_header FAR *gz_headerp;

   130 

   131 /*

   132      The application must update next_in and avail_in when avail_in has dropped

   133    to zero.  It must update next_out and avail_out when avail_out has dropped

   134    to zero.  The application must initialize zalloc, zfree and opaque before

   135    calling the init function.  All other fields are set by the compression

   136    library and must not be updated by the application.

   137 

   138      The opaque value provided by the application will be passed as the first

   139    parameter for calls of zalloc and zfree.  This can be useful for custom

   140    memory management.  The compression library attaches no meaning to the

   141    opaque value.

   142 

   143      zalloc must return Z_NULL if there is not enough memory for the object.

   144    If zlib is used in a multi-threaded application, zalloc and zfree must be

   145    thread safe.

   146 

   147      On 16-bit systems, the functions zalloc and zfree must be able to allocate

   148    exactly 65536 bytes, but will not be required to allocate more than this if

   149    the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers

   150    returned by zalloc for objects of exactly 65536 bytes *must* have their

   151    offset normalized to zero.  The default allocation function provided by this

   152    library ensures this (see zutil.c).  To reduce memory requirements and avoid

   153    any allocation of 64K objects, at the expense of compression ratio, compile

   154    the library with -DMAX_WBITS=14 (see zconf.h).

   155 

   156      The fields total_in and total_out can be used for statistics or progress

   157    reports.  After compression, total_in holds the total size of the

   158    uncompressed data and may be saved for use in the decompressor (particularly

   159    if the decompressor wants to decompress everything in a single step).

   160 */

   161 

   162                         /* constants */

   163 

   164 #define Z_NO_FLUSH      0

   165 #define Z_PARTIAL_FLUSH 1

   166 #define Z_SYNC_FLUSH    2

   167 #define Z_FULL_FLUSH    3

   168 #define Z_FINISH        4

   169 #define Z_BLOCK         5

   170 #define Z_TREES         6

   171 /* Allowed flush values; see deflate() and inflate() below for details */

   172 

   173 #define Z_OK            0

   174 #define Z_STREAM_END    1

   175 #define Z_NEED_DICT     2

   176 #define Z_ERRNO        (-1)

   177 #define Z_STREAM_ERROR (-2)

   178 #define Z_DATA_ERROR   (-3)

   179 #define Z_MEM_ERROR    (-4)

   180 #define Z_BUF_ERROR    (-5)

   181 #define Z_VERSION_ERROR (-6)

   182 /* Return codes for the compression/decompression functions. Negative values

   183  * are errors, positive values are used for special but normal events.

   184  */

   185 

   186 #define Z_NO_COMPRESSION         0

   187 #define Z_BEST_SPEED             1

   188 #define Z_BEST_COMPRESSION       9

   189 #define Z_DEFAULT_COMPRESSION  (-1)

   190 /* compression levels */

   191 

   192 #define Z_FILTERED            1

   193 #define Z_HUFFMAN_ONLY        2

   194 #define Z_RLE                 3

   195 #define Z_FIXED               4

   196 #define Z_DEFAULT_STRATEGY    0

   197 /* compression strategy; see deflateInit2() below for details */

   198 

   199 #define Z_BINARY   0

   200 #define Z_TEXT     1

   201 #define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */

   202 #define Z_UNKNOWN  2

   203 /* Possible values of the data_type field (though see inflate()) */

   204 

   205 #define Z_DEFLATED   8

   206 /* The deflate compression method (the only one supported in this version) */

   207 

   208 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */

   209 

   210 #define zlib_version zlibVersion()

   211 /* for compatibility with versions < 1.0.2 */

   212 

   213 

   214                         /* basic functions */

   215 

   216 ZEXTERN const char * ZEXPORT zlibVersion OF((void));

   217 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.

   218    If the first character differs, the library code actually used is not

   219    compatible with the zlib.h header file used by the application.  This check

   220    is automatically made by deflateInit and inflateInit.

   221  */

   222 

   223 /*

   224 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));

   225 

   226      Initializes the internal stream state for compression.  The fields

   227    zalloc, zfree and opaque must be initialized before by the caller.  If

   228    zalloc and zfree are set to Z_NULL, deflateInit updates them to use default

   229    allocation functions.

   230 

   231      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:

   232    1 gives best speed, 9 gives best compression, 0 gives no compression at all

   233    (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION

   234    requests a default compromise between speed and compression (currently

   235    equivalent to level 6).

   236 

   237      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough

   238    memory, Z_STREAM_ERROR if level is not a valid compression level, or

   239    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible

   240    with the version assumed by the caller (ZLIB_VERSION).  msg is set to null

   241    if there is no error message.  deflateInit does not perform any compression:

   242    this will be done by deflate().

   243 */

   244 

   245 

   246 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));

   247 /*

   248     deflate compresses as much data as possible, and stops when the input

   249   buffer becomes empty or the output buffer becomes full.  It may introduce

   250   some output latency (reading input without producing any output) except when

   251   forced to flush.

   252 

   253     The detailed semantics are as follows.  deflate performs one or both of the

   254   following actions:

   255 

   256   - Compress more input starting at next_in and update next_in and avail_in

   257     accordingly.  If not all input can be processed (because there is not

   258     enough room in the output buffer), next_in and avail_in are updated and

   259     processing will resume at this point for the next call of deflate().

   260 

   261   - Provide more output starting at next_out and update next_out and avail_out

   262     accordingly.  This action is forced if the parameter flush is non zero.

   263     Forcing flush frequently degrades the compression ratio, so this parameter

   264     should be set only when necessary (in interactive applications).  Some

   265     output may be provided even if flush is not set.

   266 

   267     Before the call of deflate(), the application should ensure that at least

   268   one of the actions is possible, by providing more input and/or consuming more

   269   output, and updating avail_in or avail_out accordingly; avail_out should

   270   never be zero before the call.  The application can consume the compressed

   271   output when it wants, for example when the output buffer is full (avail_out

   272   == 0), or after each call of deflate().  If deflate returns Z_OK and with

   273   zero avail_out, it must be called again after making room in the output

   274   buffer because there might be more output pending.

   275 

   276     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to

   277   decide how much data to accumulate before producing output, in order to

   278   maximize compression.

   279 

   280     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is

   281   flushed to the output buffer and the output is aligned on a byte boundary, so

   282   that the decompressor can get all input data available so far.  (In

   283   particular avail_in is zero after the call if enough output space has been

   284   provided before the call.) Flushing may degrade compression for some

   285   compression algorithms and so it should be used only when necessary.  This

   286   completes the current deflate block and follows it with an empty stored block

   287   that is three bits plus filler bits to the next byte, followed by four bytes

   288   (00 00 ff ff).

   289 

   290     If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the

   291   output buffer, but the output is not aligned to a byte boundary.  All of the

   292   input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.

   293   This completes the current deflate block and follows it with an empty fixed

   294   codes block that is 10 bits long.  This assures that enough bytes are output

   295   in order for the decompressor to finish the block before the empty fixed code

   296   block.

   297 

   298     If flush is set to Z_BLOCK, a deflate block is completed and emitted, as

   299   for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to

   300   seven bits of the current block are held to be written as the next byte after

   301   the next deflate block is completed.  In this case, the decompressor may not

   302   be provided enough bits at this point in order to complete decompression of

   303   the data provided so far to the compressor.  It may need to wait for the next

   304   block to be emitted.  This is for advanced applications that need to control

   305   the emission of deflate blocks.

   306 

   307     If flush is set to Z_FULL_FLUSH, all output is flushed as with

   308   Z_SYNC_FLUSH, and the compression state is reset so that decompression can

   309   restart from this point if previous compressed data has been damaged or if

   310   random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade

   311   compression.

   312 

   313     If deflate returns with avail_out == 0, this function must be called again

   314   with the same value of the flush parameter and more output space (updated

   315   avail_out), until the flush is complete (deflate returns with non-zero

   316   avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that

   317   avail_out is greater than six to avoid repeated flush markers due to

   318   avail_out == 0 on return.

   319 

   320     If the parameter flush is set to Z_FINISH, pending input is processed,

   321   pending output is flushed and deflate returns with Z_STREAM_END if there was

   322   enough output space; if deflate returns with Z_OK, this function must be

   323   called again with Z_FINISH and more output space (updated avail_out) but no

   324   more input data, until it returns with Z_STREAM_END or an error.  After

   325   deflate has returned Z_STREAM_END, the only possible operations on the stream

   326   are deflateReset or deflateEnd.

   327 

   328     Z_FINISH can be used immediately after deflateInit if all the compression

   329   is to be done in a single step.  In this case, avail_out must be at least the

   330   value returned by deflateBound (see below).  If deflate does not return

   331   Z_STREAM_END, then it must be called again as described above.

   332 

   333     deflate() sets strm->adler to the adler32 checksum of all input read

   334   so far (that is, total_in bytes).

   335 

   336     deflate() may update strm->data_type if it can make a good guess about

   337   the input data type (Z_BINARY or Z_TEXT).  In doubt, the data is considered

   338   binary.  This field is only for information purposes and does not affect the

   339   compression algorithm in any manner.

   340 

   341     deflate() returns Z_OK if some progress has been made (more input

   342   processed or more output produced), Z_STREAM_END if all input has been

   343   consumed and all output has been produced (only when flush is set to

   344   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example

   345   if next_in or next_out was Z_NULL), Z_BUF_ERROR if no progress is possible

   346   (for example avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not

   347   fatal, and deflate() can be called again with more input and more output

   348   space to continue compressing.

   349 */

   350 

   351 

   352 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));

   353 /*

   354      All dynamically allocated data structures for this stream are freed.

   355    This function discards any unprocessed input and does not flush any pending

   356    output.

   357 

   358      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the

   359    stream state was inconsistent, Z_DATA_ERROR if the stream was freed

   360    prematurely (some input or output was discarded).  In the error case, msg

   361    may be set but then points to a static string (which must not be

   362    deallocated).

   363 */

   364 

   365 

   366 /*

   367 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));

   368 

   369      Initializes the internal stream state for decompression.  The fields

   370    next_in, avail_in, zalloc, zfree and opaque must be initialized before by

   371    the caller.  If next_in is not Z_NULL and avail_in is large enough (the

   372    exact value depends on the compression method), inflateInit determines the

   373    compression method from the zlib header and allocates all data structures

   374    accordingly; otherwise the allocation will be deferred to the first call of

   375    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to

   376    use default allocation functions.

   377 

   378      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough

   379    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the

   380    version assumed by the caller, or Z_STREAM_ERROR if the parameters are

   381    invalid, such as a null pointer to the structure.  msg is set to null if

   382    there is no error message.  inflateInit does not perform any decompression

   383    apart from possibly reading the zlib header if present: actual decompression

   384    will be done by inflate().  (So next_in and avail_in may be modified, but

   385    next_out and avail_out are unused and unchanged.) The current implementation

   386    of inflateInit() does not process any header information -- that is deferred

   387    until inflate() is called.

   388 */

   389 

   390 

   391 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));

   392 /*

   393     inflate decompresses as much data as possible, and stops when the input

   394   buffer becomes empty or the output buffer becomes full.  It may introduce

   395   some output latency (reading input without producing any output) except when

   396   forced to flush.

   397 

   398   The detailed semantics are as follows.  inflate performs one or both of the

   399   following actions:

   400 

   401   - Decompress more input starting at next_in and update next_in and avail_in

   402     accordingly.  If not all input can be processed (because there is not

   403     enough room in the output buffer), next_in is updated and processing will

   404     resume at this point for the next call of inflate().

   405 

   406   - Provide more output starting at next_out and update next_out and avail_out

   407     accordingly.  inflate() provides as much output as possible, until there is

   408     no more input data or no more space in the output buffer (see below about

   409     the flush parameter).

   410 

   411     Before the call of inflate(), the application should ensure that at least

   412   one of the actions is possible, by providing more input and/or consuming more

   413   output, and updating the next_* and avail_* values accordingly.  The

   414   application can consume the uncompressed output when it wants, for example

   415   when the output buffer is full (avail_out == 0), or after each call of

   416   inflate().  If inflate returns Z_OK and with zero avail_out, it must be

   417   called again after making room in the output buffer because there might be

   418   more output pending.

   419 

   420     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,

   421   Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much

   422   output as possible to the output buffer.  Z_BLOCK requests that inflate()

   423   stop if and when it gets to the next deflate block boundary.  When decoding

   424   the zlib or gzip format, this will cause inflate() to return immediately

   425   after the header and before the first block.  When doing a raw inflate,

   426   inflate() will go ahead and process the first block, and will return when it

   427   gets to the end of that block, or when it runs out of data.

   428 

   429     The Z_BLOCK option assists in appending to or combining deflate streams.

   430   Also to assist in this, on return inflate() will set strm->data_type to the

   431   number of unused bits in the last byte taken from strm->next_in, plus 64 if

   432   inflate() is currently decoding the last block in the deflate stream, plus

   433   128 if inflate() returned immediately after decoding an end-of-block code or

   434   decoding the complete header up to just before the first byte of the deflate

   435   stream.  The end-of-block will not be indicated until all of the uncompressed

   436   data from that block has been written to strm->next_out.  The number of

   437   unused bits may in general be greater than seven, except when bit 7 of

   438   data_type is set, in which case the number of unused bits will be less than

   439   eight.  data_type is set as noted here every time inflate() returns for all

   440   flush options, and so can be used to determine the amount of currently

   441   consumed input in bits.

   442 

   443     The Z_TREES option behaves as Z_BLOCK does, but it also returns when the

   444   end of each deflate block header is reached, before any actual data in that

   445   block is decoded.  This allows the caller to determine the length of the

   446   deflate block header for later use in random access within a deflate block.

   447   256 is added to the value of strm->data_type when inflate() returns

   448   immediately after reaching the end of the deflate block header.

   449 

   450     inflate() should normally be called until it returns Z_STREAM_END or an

   451   error.  However if all decompression is to be performed in a single step (a

   452   single call of inflate), the parameter flush should be set to Z_FINISH.  In

   453   this case all pending input is processed and all pending output is flushed;

   454   avail_out must be large enough to hold all the uncompressed data.  (The size

   455   of the uncompressed data may have been saved by the compressor for this

   456   purpose.) The next operation on this stream must be inflateEnd to deallocate

   457   the decompression state.  The use of Z_FINISH is never required, but can be

   458   used to inform inflate that a faster approach may be used for the single

   459   inflate() call.

   460 

   461      In this implementation, inflate() always flushes as much output as

   462   possible to the output buffer, and always uses the faster approach on the

   463   first call.  So the only effect of the flush parameter in this implementation

   464   is on the return value of inflate(), as noted below, or when it returns early

   465   because Z_BLOCK or Z_TREES is used.

   466 

   467      If a preset dictionary is needed after this call (see inflateSetDictionary

   468   below), inflate sets strm->adler to the adler32 checksum of the dictionary

   469   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets

   470   strm->adler to the adler32 checksum of all output produced so far (that is,

   471   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described

   472   below.  At the end of the stream, inflate() checks that its computed adler32

   473   checksum is equal to that saved by the compressor and returns Z_STREAM_END

   474   only if the checksum is correct.

   475 

   476     inflate() can decompress and check either zlib-wrapped or gzip-wrapped

   477   deflate data.  The header type is detected automatically, if requested when

   478   initializing with inflateInit2().  Any information contained in the gzip

   479   header is not retained, so applications that need that information should

   480   instead use raw inflate, see inflateInit2() below, or inflateBack() and

   481   perform their own processing of the gzip header and trailer.

   482 

   483     inflate() returns Z_OK if some progress has been made (more input processed

   484   or more output produced), Z_STREAM_END if the end of the compressed data has

   485   been reached and all uncompressed output has been produced, Z_NEED_DICT if a

   486   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was

   487   corrupted (input stream not conforming to the zlib format or incorrect check

   488   value), Z_STREAM_ERROR if the stream structure was inconsistent (for example

   489   next_in or next_out was Z_NULL), Z_MEM_ERROR if there was not enough memory,

   490   Z_BUF_ERROR if no progress is possible or if there was not enough room in the

   491   output buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and

   492   inflate() can be called again with more input and more output space to

   493   continue decompressing.  If Z_DATA_ERROR is returned, the application may

   494   then call inflateSync() to look for a good compression block if a partial

   495   recovery of the data is desired.

   496 */

   497 

   498 

   499 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));

   500 /*

   501      All dynamically allocated data structures for this stream are freed.

   502    This function discards any unprocessed input and does not flush any pending

   503    output.

   504 

   505      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state

   506    was inconsistent.  In the error case, msg may be set but then points to a

   507    static string (which must not be deallocated).

   508 */

   509 

   510 

   511                         /* Advanced functions */

   512 

   513 /*

   514     The following functions are needed only in some special applications.

   515 */

   516 

   517 /*

   518 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,

   519                                      int  level,

   520                                      int  method,

   521                                      int  windowBits,

   522                                      int  memLevel,

   523                                      int  strategy));

   524 

   525      This is another version of deflateInit with more compression options.  The

   526    fields next_in, zalloc, zfree and opaque must be initialized before by the

   527    caller.

   528 

   529      The method parameter is the compression method.  It must be Z_DEFLATED in

   530    this version of the library.

   531 

   532      The windowBits parameter is the base two logarithm of the window size

   533    (the size of the history buffer).  It should be in the range 8..15 for this

   534    version of the library.  Larger values of this parameter result in better

   535    compression at the expense of memory usage.  The default value is 15 if

   536    deflateInit is used instead.

   537 

   538      windowBits can also be -8..-15 for raw deflate.  In this case, -windowBits

   539    determines the window size.  deflate() will then generate raw deflate data

   540    with no zlib header or trailer, and will not compute an adler32 check value.

   541 

   542      windowBits can also be greater than 15 for optional gzip encoding.  Add

   543    16 to windowBits to write a simple gzip header and trailer around the

   544    compressed data instead of a zlib wrapper.  The gzip header will have no

   545    file name, no extra data, no comment, no modification time (set to zero), no

   546    header crc, and the operating system will be set to 255 (unknown).  If a

   547    gzip stream is being written, strm->adler is a crc32 instead of an adler32.

   548 

   549      The memLevel parameter specifies how much memory should be allocated

   550    for the internal compression state.  memLevel=1 uses minimum memory but is

   551    slow and reduces compression ratio; memLevel=9 uses maximum memory for

   552    optimal speed.  The default value is 8.  See zconf.h for total memory usage

   553    as a function of windowBits and memLevel.

   554 

   555      The strategy parameter is used to tune the compression algorithm.  Use the

   556    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a

   557    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no

   558    string match), or Z_RLE to limit match distances to one (run-length

   559    encoding).  Filtered data consists mostly of small values with a somewhat

   560    random distribution.  In this case, the compression algorithm is tuned to

   561    compress them better.  The effect of Z_FILTERED is to force more Huffman

   562    coding and less string matching; it is somewhat intermediate between

   563    Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as

   564    fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The

   565    strategy parameter only affects the compression ratio but not the

   566    correctness of the compressed output even if it is not set appropriately.

   567    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler

   568    decoder for special applications.

   569 

   570      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough

   571    memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid

   572    method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is

   573    incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is

   574    set to null if there is no error message.  deflateInit2 does not perform any

   575    compression: this will be done by deflate().

   576 */

   577 

   578 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,

   579                                              const Bytef *dictionary,

   580                                              uInt  dictLength));

   581 /*

   582      Initializes the compression dictionary from the given byte sequence

   583    without producing any compressed output.  This function must be called

   584    immediately after deflateInit, deflateInit2 or deflateReset, before any call

   585    of deflate.  The compressor and decompressor must use exactly the same

   586    dictionary (see inflateSetDictionary).

   587 

   588      The dictionary should consist of strings (byte sequences) that are likely

   589    to be encountered later in the data to be compressed, with the most commonly

   590    used strings preferably put towards the end of the dictionary.  Using a

   591    dictionary is most useful when the data to be compressed is short and can be

   592    predicted with good accuracy; the data can then be compressed better than

   593    with the default empty dictionary.

   594 

   595      Depending on the size of the compression data structures selected by

   596    deflateInit or deflateInit2, a part of the dictionary may in effect be

   597    discarded, for example if the dictionary is larger than the window size

   598    provided in deflateInit or deflateInit2.  Thus the strings most likely to be

   599    useful should be put at the end of the dictionary, not at the front.  In

   600    addition, the current implementation of deflate will use at most the window

   601    size minus 262 bytes of the provided dictionary.

   602 

   603      Upon return of this function, strm->adler is set to the adler32 value

   604    of the dictionary; the decompressor may later use this value to determine

   605    which dictionary has been used by the compressor.  (The adler32 value

   606    applies to the whole dictionary even if only a subset of the dictionary is

   607    actually used by the compressor.) If a raw deflate was requested, then the

   608    adler32 value is not computed and strm->adler is not set.

   609 

   610      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a

   611    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is

   612    inconsistent (for example if deflate has already been called for this stream

   613    or if the compression method is bsort).  deflateSetDictionary does not

   614    perform any compression: this will be done by deflate().

   615 */

   616 

   617 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,

   618                                     z_streamp source));

   619 /*

   620      Sets the destination stream as a complete copy of the source stream.

   621 

   622      This function can be useful when several compression strategies will be

   623    tried, for example when there are several ways of pre-processing the input

   624    data with a filter.  The streams that will be discarded should then be freed

   625    by calling deflateEnd.  Note that deflateCopy duplicates the internal

   626    compression state which can be quite large, so this strategy is slow and can

   627    consume lots of memory.

   628 

   629      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not

   630    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent

   631    (such as zalloc being Z_NULL).  msg is left unchanged in both source and

   632    destination.

   633 */

   634 

   635 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));

   636 /*

   637      This function is equivalent to deflateEnd followed by deflateInit,

   638    but does not free and reallocate all the internal compression state.  The

   639    stream will keep the same compression level and any other attributes that

   640    may have been set by deflateInit2.

   641 

   642      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source

   643    stream state was inconsistent (such as zalloc or state being Z_NULL).

   644 */

   645 

   646 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,

   647                                       int level,

   648                                       int strategy));

   649 /*

   650      Dynamically update the compression level and compression strategy.  The

   651    interpretation of level and strategy is as in deflateInit2.  This can be

   652    used to switch between compression and straight copy of the input data, or

   653    to switch to a different kind of input data requiring a different strategy.

   654    If the compression level is changed, the input available so far is

   655    compressed with the old level (and may be flushed); the new level will take

   656    effect only at the next call of deflate().

   657 

   658      Before the call of deflateParams, the stream state must be set as for

   659    a call of deflate(), since the currently available input may have to be

   660    compressed and flushed.  In particular, strm->avail_out must be non-zero.

   661 

   662      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source

   663    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if

   664    strm->avail_out was zero.

   665 */

   666 

   667 ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,

   668                                     int good_length,

   669                                     int max_lazy,

   670                                     int nice_length,

   671                                     int max_chain));

   672 /*

   673      Fine tune deflate's internal compression parameters.  This should only be

   674    used by someone who understands the algorithm used by zlib's deflate for

   675    searching for the best matching string, and even then only by the most

   676    fanatic optimizer trying to squeeze out the last compressed bit for their

   677    specific input data.  Read the deflate.c source code for the meaning of the

   678    max_lazy, good_length, nice_length, and max_chain parameters.

   679 

   680      deflateTune() can be called after deflateInit() or deflateInit2(), and

   681    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.

   682  */

   683 

   684 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,

   685                                        uLong sourceLen));

   686 /*

   687      deflateBound() returns an upper bound on the compressed size after

   688    deflation of sourceLen bytes.  It must be called after deflateInit() or

   689    deflateInit2(), and after deflateSetHeader(), if used.  This would be used

   690    to allocate an output buffer for deflation in a single pass, and so would be

   691    called before deflate().

   692 */

   693 

   694 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,

   695                                      int bits,

   696                                      int value));

   697 /*

   698      deflatePrime() inserts bits in the deflate output stream.  The intent

   699    is that this function is used to start off the deflate output with the bits

   700    leftover from a previous deflate stream when appending to it.  As such, this

   701    function can only be used for raw deflate, and must be used before the first

   702    deflate() call after a deflateInit2() or deflateReset().  bits must be less

   703    than or equal to 16, and that many of the least significant bits of value

   704    will be inserted in the output.

   705 

   706      deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source

   707    stream state was inconsistent.

   708 */

   709 

   710 ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,

   711                                          gz_headerp head));

   712 /*

   713      deflateSetHeader() provides gzip header information for when a gzip

   714    stream is requested by deflateInit2().  deflateSetHeader() may be called

   715    after deflateInit2() or deflateReset() and before the first call of

   716    deflate().  The text, time, os, extra field, name, and comment information

   717    in the provided gz_header structure are written to the gzip header (xflag is

   718    ignored -- the extra flags are set according to the compression level).  The

   719    caller must assure that, if not Z_NULL, name and comment are terminated with

   720    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are

   721    available there.  If hcrc is true, a gzip header crc is included.  Note that

   722    the current versions of the command-line version of gzip (up through version

   723    1.3.x) do not support header crc's, and will report that it is a "multi-part

   724    gzip file" and give up.

   725 

   726      If deflateSetHeader is not used, the default gzip header has text false,

   727    the time set to zero, and os set to 255, with no extra, name, or comment

   728    fields.  The gzip header is returned to the default state by deflateReset().

   729 

   730      deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source

   731    stream state was inconsistent.

   732 */

   733 

   734 /*

   735 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,

   736                                      int  windowBits));

   737 

   738      This is another version of inflateInit with an extra parameter.  The

   739    fields next_in, avail_in, zalloc, zfree and opaque must be initialized

   740    before by the caller.

   741 

   742      The windowBits parameter is the base two logarithm of the maximum window

   743    size (the size of the history buffer).  It should be in the range 8..15 for

   744    this version of the library.  The default value is 15 if inflateInit is used

   745    instead.  windowBits must be greater than or equal to the windowBits value

   746    provided to deflateInit2() while compressing, or it must be equal to 15 if

   747    deflateInit2() was not used.  If a compressed stream with a larger window

   748    size is given as input, inflate() will return with the error code

   749    Z_DATA_ERROR instead of trying to allocate a larger window.

   750 

   751      windowBits can also be zero to request that inflate use the window size in

   752    the zlib header of the compressed stream.

   753 

   754      windowBits can also be -8..-15 for raw inflate.  In this case, -windowBits

   755    determines the window size.  inflate() will then process raw deflate data,

   756    not looking for a zlib or gzip header, not generating a check value, and not

   757    looking for any check values for comparison at the end of the stream.  This

   758    is for use with other formats that use the deflate compressed data format

   759    such as zip.  Those formats provide their own check values.  If a custom

   760    format is developed using the raw deflate format for compressed data, it is

   761    recommended that a check value such as an adler32 or a crc32 be applied to

   762    the uncompressed data as is done in the zlib, gzip, and zip formats.  For

   763    most applications, the zlib format should be used as is.  Note that comments

   764    above on the use in deflateInit2() applies to the magnitude of windowBits.

   765 

   766      windowBits can also be greater than 15 for optional gzip decoding.  Add

   767    32 to windowBits to enable zlib and gzip decoding with automatic header

   768    detection, or add 16 to decode only the gzip format (the zlib format will

   769    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a

   770    crc32 instead of an adler32.

   771 

   772      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough

   773    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the

   774    version assumed by the caller, or Z_STREAM_ERROR if the parameters are

   775    invalid, such as a null pointer to the structure.  msg is set to null if

   776    there is no error message.  inflateInit2 does not perform any decompression

   777    apart from possibly reading the zlib header if present: actual decompression

   778    will be done by inflate().  (So next_in and avail_in may be modified, but

   779    next_out and avail_out are unused and unchanged.) The current implementation

   780    of inflateInit2() does not process any header information -- that is

   781    deferred until inflate() is called.

   782 */

   783 

   784 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,

   785                                              const Bytef *dictionary,

   786                                              uInt  dictLength));

   787 /*

   788      Initializes the decompression dictionary from the given uncompressed byte

   789    sequence.  This function must be called immediately after a call of inflate,

   790    if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor

   791    can be determined from the adler32 value returned by that call of inflate.

   792    The compressor and decompressor must use exactly the same dictionary (see

   793    deflateSetDictionary).  For raw inflate, this function can be called

   794    immediately after inflateInit2() or inflateReset() and before any call of

   795    inflate() to set the dictionary.  The application must insure that the

   796    dictionary that was used for compression is provided.

   797 

   798      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a

   799    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is

   800    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the

   801    expected one (incorrect adler32 value).  inflateSetDictionary does not

   802    perform any decompression: this will be done by subsequent calls of

   803    inflate().

   804 */

   805 

   806 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));

   807 /*

   808      Skips invalid compressed data until a full flush point (see above the

   809    description of deflate with Z_FULL_FLUSH) can be found, or until all

   810    available input is skipped.  No output is provided.

   811 

   812      inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR

   813    if no more input was provided, Z_DATA_ERROR if no flush point has been

   814    found, or Z_STREAM_ERROR if the stream structure was inconsistent.  In the

   815    success case, the application may save the current current value of total_in

   816    which indicates where valid compressed data was found.  In the error case,

   817    the application may repeatedly call inflateSync, providing more input each

   818    time, until success or end of the input data.

   819 */

   820 

   821 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,

   822                                     z_streamp source));

   823 /*

   824      Sets the destination stream as a complete copy of the source stream.

   825 

   826      This function can be useful when randomly accessing a large stream.  The

   827    first pass through the stream can periodically record the inflate state,

   828    allowing restarting inflate at those points when randomly accessing the

   829    stream.

   830 

   831      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not

   832    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent

   833    (such as zalloc being Z_NULL).  msg is left unchanged in both source and

   834    destination.

   835 */

   836 

   837 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));

   838 /*

   839      This function is equivalent to inflateEnd followed by inflateInit,

   840    but does not free and reallocate all the internal decompression state.  The

   841    stream will keep attributes that may have been set by inflateInit2.

   842 

   843      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source

   844    stream state was inconsistent (such as zalloc or state being Z_NULL).

   845 */

   846 

   847 ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,

   848                                       int windowBits));

   849 /*

   850      This function is the same as inflateReset, but it also permits changing

   851    the wrap and window size requests.  The windowBits parameter is interpreted

   852    the same as it is for inflateInit2.

   853 

   854      inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source

   855    stream state was inconsistent (such as zalloc or state being Z_NULL), or if

   856    the windowBits parameter is invalid.

   857 */

   858 

   859 ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,

   860                                      int bits,

   861                                      int value));

   862 /*

   863      This function inserts bits in the inflate input stream.  The intent is

   864    that this function is used to start inflating at a bit position in the

   865    middle of a byte.  The provided bits will be used before any bytes are used

   866    from next_in.  This function should only be used with raw inflate, and

   867    should be used before the first inflate() call after inflateInit2() or

   868    inflateReset().  bits must be less than or equal to 16, and that many of the

   869    least significant bits of value will be inserted in the input.

   870 

   871      If bits is negative, then the input stream bit buffer is emptied.  Then

   872    inflatePrime() can be called again to put bits in the buffer.  This is used

   873    to clear out bits leftover after feeding inflate a block description prior

   874    to feeding inflate codes.

   875 

   876      inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source

   877    stream state was inconsistent.

   878 */

   879 

   880 ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm));

   881 /*

   882      This function returns two values, one in the lower 16 bits of the return

   883    value, and the other in the remaining upper bits, obtained by shifting the

   884    return value down 16 bits.  If the upper value is -1 and the lower value is

   885    zero, then inflate() is currently decoding information outside of a block.

   886    If the upper value is -1 and the lower value is non-zero, then inflate is in

   887    the middle of a stored block, with the lower value equaling the number of

   888    bytes from the input remaining to copy.  If the upper value is not -1, then

   889    it is the number of bits back from the current bit position in the input of

   890    the code (literal or length/distance pair) currently being processed.  In

   891    that case the lower value is the number of bytes already emitted for that

   892    code.

   893 

   894      A code is being processed if inflate is waiting for more input to complete

   895    decoding of the code, or if it has completed decoding but is waiting for

   896    more output space to write the literal or match data.

   897 

   898      inflateMark() is used to mark locations in the input data for random

   899    access, which may be at bit positions, and to note those cases where the

   900    output of a code may span boundaries of random access blocks.  The current

   901    location in the input stream can be determined from avail_in and data_type

   902    as noted in the description for the Z_BLOCK flush parameter for inflate.

   903 

   904      inflateMark returns the value noted above or -1 << 16 if the provided

   905    source stream state was inconsistent.

   906 */

   907 

   908 ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,

   909                                          gz_headerp head));

   910 /*

   911      inflateGetHeader() requests that gzip header information be stored in the

   912    provided gz_header structure.  inflateGetHeader() may be called after

   913    inflateInit2() or inflateReset(), and before the first call of inflate().

   914    As inflate() processes the gzip stream, head->done is zero until the header

   915    is completed, at which time head->done is set to one.  If a zlib stream is

   916    being decoded, then head->done is set to -1 to indicate that there will be

   917    no gzip header information forthcoming.  Note that Z_BLOCK or Z_TREES can be

   918    used to force inflate() to return immediately after header processing is

   919    complete and before any actual data is decompressed.

   920 

   921      The text, time, xflags, and os fields are filled in with the gzip header

   922    contents.  hcrc is set to true if there is a header CRC.  (The header CRC

   923    was valid if done is set to one.) If extra is not Z_NULL, then extra_max

   924    contains the maximum number of bytes to write to extra.  Once done is true,

   925    extra_len contains the actual extra field length, and extra contains the

   926    extra field, or that field truncated if extra_max is less than extra_len.

   927    If name is not Z_NULL, then up to name_max characters are written there,

   928    terminated with a zero unless the length is greater than name_max.  If

   929    comment is not Z_NULL, then up to comm_max characters are written there,

   930    terminated with a zero unless the length is greater than comm_max.  When any

   931    of extra, name, or comment are not Z_NULL and the respective field is not

   932    present in the header, then that field is set to Z_NULL to signal its

   933    absence.  This allows the use of deflateSetHeader() with the returned

   934    structure to duplicate the header.  However if those fields are set to

   935    allocated memory, then the application will need to save those pointers

   936    elsewhere so that they can be eventually freed.

   937 

   938      If inflateGetHeader is not used, then the header information is simply

   939    discarded.  The header is always checked for validity, including the header

   940    CRC if present.  inflateReset() will reset the process to discard the header

   941    information.  The application would need to call inflateGetHeader() again to

   942    retrieve the header from the next gzip stream.

   943 

   944      inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source

   945    stream state was inconsistent.

   946 */

   947 

   948 /*

   949 ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,

   950                                         unsigned char FAR *window));

   951 

   952      Initialize the internal stream state for decompression using inflateBack()

   953    calls.  The fields zalloc, zfree and opaque in strm must be initialized

   954    before the call.  If zalloc and zfree are Z_NULL, then the default library-

   955    derived memory allocation routines are used.  windowBits is the base two

   956    logarithm of the window size, in the range 8..15.  window is a caller

   957    supplied buffer of that size.  Except for special applications where it is

   958    assured that deflate was used with small window sizes, windowBits must be 15

   959    and a 32K byte window must be supplied to be able to decompress general

   960    deflate streams.

   961 

   962      See inflateBack() for the usage of these routines.

   963 

   964      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of

   965    the paramaters are invalid, Z_MEM_ERROR if the internal state could not be

   966    allocated, or Z_VERSION_ERROR if the version of the library does not match

   967    the version of the header file.

   968 */

   969 

   970 typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));

   971 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));

   972 

   973 ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,

   974                                     in_func in, void FAR *in_desc,

   975                                     out_func out, void FAR *out_desc));

   976 /*

   977      inflateBack() does a raw inflate with a single call using a call-back

   978    interface for input and output.  This is more efficient than inflate() for

   979    file i/o applications in that it avoids copying between the output and the

   980    sliding window by simply making the window itself the output buffer.  This

   981    function trusts the application to not change the output buffer passed by

   982    the output function, at least until inflateBack() returns.

   983 

   984      inflateBackInit() must be called first to allocate the internal state

   985    and to initialize the state with the user-provided window buffer.

   986    inflateBack() may then be used multiple times to inflate a complete, raw

   987    deflate stream with each call.  inflateBackEnd() is then called to free the

   988    allocated state.

   989 

   990      A raw deflate stream is one with no zlib or gzip header or trailer.

   991    This routine would normally be used in a utility that reads zip or gzip

   992    files and writes out uncompressed files.  The utility would decode the

   993    header and process the trailer on its own, hence this routine expects only

   994    the raw deflate stream to decompress.  This is different from the normal

   995    behavior of inflate(), which expects either a zlib or gzip header and

   996    trailer around the deflate stream.

   997 

   998      inflateBack() uses two subroutines supplied by the caller that are then

   999    called by inflateBack() for input and output.  inflateBack() calls those

  1000    routines until it reads a complete deflate stream and writes out all of the

  1001    uncompressed data, or until it encounters an error.  The function's

  1002    parameters and return types are defined above in the in_func and out_func

  1003    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the

  1004    number of bytes of provided input, and a pointer to that input in buf.  If

  1005    there is no input available, in() must return zero--buf is ignored in that

  1006    case--and inflateBack() will return a buffer error.  inflateBack() will call

  1007    out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].  out()

  1008    should return zero on success, or non-zero on failure.  If out() returns

  1009    non-zero, inflateBack() will return with an error.  Neither in() nor out()

  1010    are permitted to change the contents of the window provided to

  1011    inflateBackInit(), which is also the buffer that out() uses to write from.

  1012    The length written by out() will be at most the window size.  Any non-zero

  1013    amount of input may be provided by in().

  1014 

  1015      For convenience, inflateBack() can be provided input on the first call by

  1016    setting strm->next_in and strm->avail_in.  If that input is exhausted, then

  1017    in() will be called.  Therefore strm->next_in must be initialized before

  1018    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called

  1019    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in

  1020    must also be initialized, and then if strm->avail_in is not zero, input will

  1021    initially be taken from strm->next_in[0 ..  strm->avail_in - 1].

  1022 

  1023      The in_desc and out_desc parameters of inflateBack() is passed as the

  1024    first parameter of in() and out() respectively when they are called.  These

  1025    descriptors can be optionally used to pass any information that the caller-

  1026    supplied in() and out() functions need to do their job.

  1027 

  1028      On return, inflateBack() will set strm->next_in and strm->avail_in to

  1029    pass back any unused input that was provided by the last in() call.  The

  1030    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR

  1031    if in() or out() returned an error, Z_DATA_ERROR if there was a format error

  1032    in the deflate stream (in which case strm->msg is set to indicate the nature

  1033    of the error), or Z_STREAM_ERROR if the stream was not properly initialized.

  1034    In the case of Z_BUF_ERROR, an input or output error can be distinguished

  1035    using strm->next_in which will be Z_NULL only if in() returned an error.  If

  1036    strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning

  1037    non-zero.  (in() will always be called before out(), so strm->next_in is

  1038    assured to be defined if out() returns non-zero.) Note that inflateBack()

  1039    cannot return Z_OK.

  1040 */

  1041 

  1042 ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));

  1043 /*

  1044      All memory allocated by inflateBackInit() is freed.

  1045 

  1046      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream

  1047    state was inconsistent.

  1048 */

  1049 

  1050 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));

  1051 /* Return flags indicating compile-time options.

  1052 

  1053     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:

  1054      1.0: size of uInt

  1055      3.2: size of uLong

  1056      5.4: size of voidpf (pointer)

  1057      7.6: size of z_off_t

  1058 

  1059     Compiler, assembler, and debug options:

  1060      8: DEBUG

  1061      9: ASMV or ASMINF -- use ASM code

  1062      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention

  1063      11: 0 (reserved)

  1064 

  1065     One-time table building (smaller code, but not thread-safe if true):

  1066      12: BUILDFIXED -- build static block decoding tables when needed

  1067      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed

  1068      14,15: 0 (reserved)

  1069 

  1070     Library content (indicates missing functionality):

  1071      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking

  1072                           deflate code when not needed)

  1073      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect

  1074                     and decode gzip streams (to avoid linking crc code)

  1075      18-19: 0 (reserved)

  1076 

  1077     Operation variations (changes in library functionality):

  1078      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate

  1079      21: FASTEST -- deflate algorithm with only one, lowest compression level

  1080      22,23: 0 (reserved)

  1081 

  1082     The sprintf variant used by gzprintf (zero is best):

  1083      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format

  1084      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!

  1085      26: 0 = returns value, 1 = void -- 1 means inferred string length returned

  1086 

  1087     Remainder:

  1088      27-31: 0 (reserved)

  1089  */

  1090 

  1091 

  1092                         /* utility functions */

  1093 

  1094 /*

  1095      The following utility functions are implemented on top of the basic

  1096    stream-oriented functions.  To simplify the interface, some default options

  1097    are assumed (compression level and memory usage, standard memory allocation

  1098    functions).  The source code of these utility functions can be modified if

  1099    you need special options.

  1100 */

  1101 

  1102 ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,

  1103                                  const Bytef *source, uLong sourceLen));

  1104 /*

  1105      Compresses the source buffer into the destination buffer.  sourceLen is

  1106    the byte length of the source buffer.  Upon entry, destLen is the total size

  1107    of the destination buffer, which must be at least the value returned by

  1108    compressBound(sourceLen).  Upon exit, destLen is the actual size of the

  1109    compressed buffer.

  1110 

  1111      compress returns Z_OK if success, Z_MEM_ERROR if there was not

  1112    enough memory, Z_BUF_ERROR if there was not enough room in the output

  1113    buffer.

  1114 */

  1115 

  1116 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,

  1117                                   const Bytef *source, uLong sourceLen,

  1118                                   int level));

  1119 /*

  1120      Compresses the source buffer into the destination buffer.  The level

  1121    parameter has the same meaning as in deflateInit.  sourceLen is the byte

  1122    length of the source buffer.  Upon entry, destLen is the total size of the

  1123    destination buffer, which must be at least the value returned by

  1124    compressBound(sourceLen).  Upon exit, destLen is the actual size of the

  1125    compressed buffer.

  1126 

  1127      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough

  1128    memory, Z_BUF_ERROR if there was not enough room in the output buffer,

  1129    Z_STREAM_ERROR if the level parameter is invalid.

  1130 */

  1131 

  1132 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));

  1133 /*

  1134      compressBound() returns an upper bound on the compressed size after

  1135    compress() or compress2() on sourceLen bytes.  It would be used before a