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zlib.h (66188B)


      1 /* zlib.h -- interface of the 'zlib' general purpose compression library
      2   version 1.2.3, July 18th, 2005
      3 
      4   Copyright (C) 1995-2005 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 "1.2.3"
     41 #define ZLIB_VERNUM 0x1230
     42 
     43 /*
     44      The 'zlib' compression library provides in-memory compression and
     45   decompression functions, including integrity checks of the uncompressed
     46   data.  This version of the library supports only one compression method
     47   (deflation) but other algorithms will be added later and will have the same
     48   stream interface.
     49 
     50      Compression can be done in a single step if the buffers are large
     51   enough (for example if an input file is mmap'ed), or can be done by
     52   repeated calls of the compression function.  In the latter case, the
     53   application must provide more input and/or consume the output
     54   (providing more output space) before each call.
     55 
     56      The compressed data format used by default by the in-memory functions is
     57   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
     58   around a deflate stream, which is itself documented in RFC 1951.
     59 
     60      The library also supports reading and writing files in gzip (.gz) format
     61   with an interface similar to that of stdio using the functions that start
     62   with "gz".  The gzip format is different from the zlib format.  gzip is a
     63   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
     64 
     65      This library can optionally read and write gzip streams in memory as well.
     66 
     67      The zlib format was designed to be compact and fast for use in memory
     68   and on communications channels.  The gzip format was designed for single-
     69   file compression on file systems, has a larger header than zlib to maintain
     70   directory information, and uses a different, slower check method than zlib.
     71 
     72      The library does not install any signal handler. The decoder checks
     73   the consistency of the compressed data, so the library should never
     74   crash even in case of corrupted input.
     75 */
     76 
     77 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
     78 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
     79 
     80 struct internal_state;
     81 
     82 typedef struct z_stream_s {
     83     Bytef    *next_in;  /* next input byte */
     84     uInt     avail_in;  /* number of bytes available at next_in */
     85     uLong    total_in;  /* total nb of input bytes read so far */
     86 
     87     Bytef    *next_out; /* next output byte should be put there */
     88     uInt     avail_out; /* remaining free space at next_out */
     89     uLong    total_out; /* total nb of bytes output so far */
     90 
     91     char     *msg;      /* last error message, NULL if no error */
     92     struct internal_state FAR *state; /* not visible by applications */
     93 
     94     alloc_func zalloc;  /* used to allocate the internal state */
     95     free_func  zfree;   /* used to free the internal state */
     96     voidpf     opaque;  /* private data object passed to zalloc and zfree */
     97 
     98     int     data_type;  /* best guess about the data type: binary or text */
     99     uLong   adler;      /* adler32 value of the uncompressed data */
    100     uLong   reserved;   /* reserved for future use */
    101 } z_stream;
    102 
    103 typedef z_stream FAR *z_streamp;
    104 
    105 /*
    106      gzip header information passed to and from zlib routines.  See RFC 1952
    107   for more details on the meanings of these fields.
    108 */
    109 typedef struct gz_header_s {
    110     int     text;       /* true if compressed data believed to be text */
    111     uLong   time;       /* modification time */
    112     int     xflags;     /* extra flags (not used when writing a gzip file) */
    113     int     os;         /* operating system */
    114     Bytef   *extra;     /* pointer to extra field or Z_NULL if none */
    115     uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */
    116     uInt    extra_max;  /* space at extra (only when reading header) */
    117     Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */
    118     uInt    name_max;   /* space at name (only when reading header) */
    119     Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */
    120     uInt    comm_max;   /* space at comment (only when reading header) */
    121     int     hcrc;       /* true if there was or will be a header crc */
    122     int     done;       /* true when done reading gzip header (not used
    123                            when writing a gzip file) */
    124 } gz_header;
    125 
    126 typedef gz_header FAR *gz_headerp;
    127 
    128 /*
    129    The application must update next_in and avail_in when avail_in has
    130    dropped to zero. It must update next_out and avail_out when avail_out
    131    has dropped to zero. The application must initialize zalloc, zfree and
    132    opaque before calling the init function. All other fields are set by the
    133    compression library and must not be updated by the application.
    134 
    135    The opaque value provided by the application will be passed as the first
    136    parameter for calls of zalloc and zfree. This can be useful for custom
    137    memory management. The compression library attaches no meaning to the
    138    opaque value.
    139 
    140    zalloc must return Z_NULL if there is not enough memory for the object.
    141    If zlib is used in a multi-threaded application, zalloc and zfree must be
    142    thread safe.
    143 
    144    On 16-bit systems, the functions zalloc and zfree must be able to allocate
    145    exactly 65536 bytes, but will not be required to allocate more than this
    146    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
    147    pointers returned by zalloc for objects of exactly 65536 bytes *must*
    148    have their offset normalized to zero. The default allocation function
    149    provided by this library ensures this (see zutil.c). To reduce memory
    150    requirements and avoid any allocation of 64K objects, at the expense of
    151    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
    152 
    153    The fields total_in and total_out can be used for statistics or
    154    progress reports. After compression, total_in holds the total size of
    155    the uncompressed data and may be saved for use in the decompressor
    156    (particularly if the decompressor wants to decompress everything in
    157    a single step).
    158 */
    159 
    160                         /* constants */
    161 
    162 #define Z_NO_FLUSH      0
    163 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
    164 #define Z_SYNC_FLUSH    2
    165 #define Z_FULL_FLUSH    3
    166 #define Z_FINISH        4
    167 #define Z_BLOCK         5
    168 /* Allowed flush values; see deflate() and inflate() below for details */
    169 
    170 #define Z_OK            0
    171 #define Z_STREAM_END    1
    172 #define Z_NEED_DICT     2
    173 #define Z_ERRNO        (-1)
    174 #define Z_STREAM_ERROR (-2)
    175 #define Z_DATA_ERROR   (-3)
    176 #define Z_MEM_ERROR    (-4)
    177 #define Z_BUF_ERROR    (-5)
    178 #define Z_VERSION_ERROR (-6)
    179 /* Return codes for the compression/decompression functions. Negative
    180  * values are errors, positive values are used for special but normal events.
    181  */
    182 
    183 #define Z_NO_COMPRESSION         0
    184 #define Z_BEST_SPEED             1
    185 #define Z_BEST_COMPRESSION       9
    186 #define Z_DEFAULT_COMPRESSION  (-1)
    187 /* compression levels */
    188 
    189 #define Z_FILTERED            1
    190 #define Z_HUFFMAN_ONLY        2
    191 #define Z_RLE                 3
    192 #define Z_FIXED               4
    193 #define Z_DEFAULT_STRATEGY    0
    194 /* compression strategy; see deflateInit2() below for details */
    195 
    196 #define Z_BINARY   0
    197 #define Z_TEXT     1
    198 #define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */
    199 #define Z_UNKNOWN  2
    200 /* Possible values of the data_type field (though see inflate()) */
    201 
    202 #define Z_DEFLATED   8
    203 /* The deflate compression method (the only one supported in this version) */
    204 
    205 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
    206 
    207 #define zlib_version zlibVersion()
    208 /* for compatibility with versions < 1.0.2 */
    209 
    210                         /* basic functions */
    211 
    212 ZEXTERN const char * ZEXPORT zlibVersion OF((void));
    213 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
    214    If the first character differs, the library code actually used is
    215    not compatible with the zlib.h header file used by the application.
    216    This check is automatically made by deflateInit and inflateInit.
    217  */
    218 
    219 /*
    220 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
    221 
    222      Initializes the internal stream state for compression. The fields
    223    zalloc, zfree and opaque must be initialized before by the caller.
    224    If zalloc and zfree are set to Z_NULL, deflateInit updates them to
    225    use default allocation functions.
    226 
    227      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
    228    1 gives best speed, 9 gives best compression, 0 gives no compression at
    229    all (the input data is simply copied a block at a time).
    230    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
    231    compression (currently equivalent to level 6).
    232 
    233      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
    234    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
    235    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
    236    with the version assumed by the caller (ZLIB_VERSION).
    237    msg is set to null if there is no error message.  deflateInit does not
    238    perform any compression: this will be done by deflate().
    239 */
    240 
    241 
    242 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
    243 /*
    244     deflate compresses as much data as possible, and stops when the input
    245   buffer becomes empty or the output buffer becomes full. It may introduce some
    246   output latency (reading input without producing any output) except when
    247   forced to flush.
    248 
    249     The detailed semantics are as follows. deflate performs one or both of the
    250   following actions:
    251 
    252   - Compress more input starting at next_in and update next_in and avail_in
    253     accordingly. If not all input can be processed (because there is not
    254     enough room in the output buffer), next_in and avail_in are updated and
    255     processing will resume at this point for the next call of deflate().
    256 
    257   - Provide more output starting at next_out and update next_out and avail_out
    258     accordingly. This action is forced if the parameter flush is non zero.
    259     Forcing flush frequently degrades the compression ratio, so this parameter
    260     should be set only when necessary (in interactive applications).
    261     Some output may be provided even if flush is not set.
    262 
    263   Before the call of deflate(), the application should ensure that at least
    264   one of the actions is possible, by providing more input and/or consuming
    265   more output, and updating avail_in or avail_out accordingly; avail_out
    266   should never be zero before the call. The application can consume the
    267   compressed output when it wants, for example when the output buffer is full
    268   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
    269   and with zero avail_out, it must be called again after making room in the
    270   output buffer because there might be more output pending.
    271 
    272     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
    273   decide how much data to accumualte before producing output, in order to
    274   maximize compression.
    275 
    276     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
    277   flushed to the output buffer and the output is aligned on a byte boundary, so
    278   that the decompressor can get all input data available so far. (In particular
    279   avail_in is zero after the call if enough output space has been provided
    280   before the call.)  Flushing may degrade compression for some compression
    281   algorithms and so it should be used only when necessary.
    282 
    283     If flush is set to Z_FULL_FLUSH, all output is flushed as with
    284   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
    285   restart from this point if previous compressed data has been damaged or if
    286   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
    287   compression.
    288 
    289     If deflate returns with avail_out == 0, this function must be called again
    290   with the same value of the flush parameter and more output space (updated
    291   avail_out), until the flush is complete (deflate returns with non-zero
    292   avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
    293   avail_out is greater than six to avoid repeated flush markers due to
    294   avail_out == 0 on return.
    295 
    296     If the parameter flush is set to Z_FINISH, pending input is processed,
    297   pending output is flushed and deflate returns with Z_STREAM_END if there
    298   was enough output space; if deflate returns with Z_OK, this function must be
    299   called again with Z_FINISH and more output space (updated avail_out) but no
    300   more input data, until it returns with Z_STREAM_END or an error. After
    301   deflate has returned Z_STREAM_END, the only possible operations on the
    302   stream are deflateReset or deflateEnd.
    303 
    304     Z_FINISH can be used immediately after deflateInit if all the compression
    305   is to be done in a single step. In this case, avail_out must be at least
    306   the value returned by deflateBound (see below). If deflate does not return
    307   Z_STREAM_END, then it must be called again as described above.
    308 
    309     deflate() sets strm->adler to the adler32 checksum of all input read
    310   so far (that is, total_in bytes).
    311 
    312     deflate() may update strm->data_type if it can make a good guess about
    313   the input data type (Z_BINARY or Z_TEXT). In doubt, the data is considered
    314   binary. This field is only for information purposes and does not affect
    315   the compression algorithm in any manner.
    316 
    317     deflate() returns Z_OK if some progress has been made (more input
    318   processed or more output produced), Z_STREAM_END if all input has been
    319   consumed and all output has been produced (only when flush is set to
    320   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
    321   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
    322   (for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not
    323   fatal, and deflate() can be called again with more input and more output
    324   space to continue compressing.
    325 */
    326 
    327 
    328 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
    329 /*
    330      All dynamically allocated data structures for this stream are freed.
    331    This function discards any unprocessed input and does not flush any
    332    pending output.
    333 
    334      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
    335    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
    336    prematurely (some input or output was discarded). In the error case,
    337    msg may be set but then points to a static string (which must not be
    338    deallocated).
    339 */
    340 
    341 
    342 /*
    343 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
    344 
    345      Initializes the internal stream state for decompression. The fields
    346    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
    347    the caller. If next_in is not Z_NULL and avail_in is large enough (the exact
    348    value depends on the compression method), inflateInit determines the
    349    compression method from the zlib header and allocates all data structures
    350    accordingly; otherwise the allocation will be deferred to the first call of
    351    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
    352    use default allocation functions.
    353 
    354      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
    355    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
    356    version assumed by the caller.  msg is set to null if there is no error
    357    message. inflateInit does not perform any decompression apart from reading
    358    the zlib header if present: this will be done by inflate().  (So next_in and
    359    avail_in may be modified, but next_out and avail_out are unchanged.)
    360 */
    361 
    362 
    363 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
    364 /*
    365     inflate decompresses as much data as possible, and stops when the input
    366   buffer becomes empty or the output buffer becomes full. It may introduce
    367   some output latency (reading input without producing any output) except when
    368   forced to flush.
    369 
    370   The detailed semantics are as follows. inflate performs one or both of the
    371   following actions:
    372 
    373   - Decompress more input starting at next_in and update next_in and avail_in
    374     accordingly. If not all input can be processed (because there is not
    375     enough room in the output buffer), next_in is updated and processing
    376     will resume at this point for the next call of inflate().
    377 
    378   - Provide more output starting at next_out and update next_out and avail_out
    379     accordingly.  inflate() provides as much output as possible, until there
    380     is no more input data or no more space in the output buffer (see below
    381     about the flush parameter).
    382 
    383   Before the call of inflate(), the application should ensure that at least
    384   one of the actions is possible, by providing more input and/or consuming
    385   more output, and updating the next_* and avail_* values accordingly.
    386   The application can consume the uncompressed output when it wants, for
    387   example when the output buffer is full (avail_out == 0), or after each
    388   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
    389   must be called again after making room in the output buffer because there
    390   might be more output pending.
    391 
    392     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
    393   Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
    394   output as possible to the output buffer. Z_BLOCK requests that inflate() stop
    395   if and when it gets to the next deflate block boundary. When decoding the
    396   zlib or gzip format, this will cause inflate() to return immediately after
    397   the header and before the first block. When doing a raw inflate, inflate()
    398   will go ahead and process the first block, and will return when it gets to
    399   the end of that block, or when it runs out of data.
    400 
    401     The Z_BLOCK option assists in appending to or combining deflate streams.
    402   Also to assist in this, on return inflate() will set strm->data_type to the
    403   number of unused bits in the last byte taken from strm->next_in, plus 64
    404   if inflate() is currently decoding the last block in the deflate stream,
    405   plus 128 if inflate() returned immediately after decoding an end-of-block
    406   code or decoding the complete header up to just before the first byte of the
    407   deflate stream. The end-of-block will not be indicated until all of the
    408   uncompressed data from that block has been written to strm->next_out.  The
    409   number of unused bits may in general be greater than seven, except when
    410   bit 7 of data_type is set, in which case the number of unused bits will be
    411   less than eight.
    412 
    413     inflate() should normally be called until it returns Z_STREAM_END or an
    414   error. However if all decompression is to be performed in a single step
    415   (a single call of inflate), the parameter flush should be set to
    416   Z_FINISH. In this case all pending input is processed and all pending
    417   output is flushed; avail_out must be large enough to hold all the
    418   uncompressed data. (The size of the uncompressed data may have been saved
    419   by the compressor for this purpose.) The next operation on this stream must
    420   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
    421   is never required, but can be used to inform inflate that a faster approach
    422   may be used for the single inflate() call.
    423 
    424      In this implementation, inflate() always flushes as much output as
    425   possible to the output buffer, and always uses the faster approach on the
    426   first call. So the only effect of the flush parameter in this implementation
    427   is on the return value of inflate(), as noted below, or when it returns early
    428   because Z_BLOCK is used.
    429 
    430      If a preset dictionary is needed after this call (see inflateSetDictionary
    431   below), inflate sets strm->adler to the adler32 checksum of the dictionary
    432   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
    433   strm->adler to the adler32 checksum of all output produced so far (that is,
    434   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
    435   below. At the end of the stream, inflate() checks that its computed adler32
    436   checksum is equal to that saved by the compressor and returns Z_STREAM_END
    437   only if the checksum is correct.
    438 
    439     inflate() will decompress and check either zlib-wrapped or gzip-wrapped
    440   deflate data.  The header type is detected automatically.  Any information
    441   contained in the gzip header is not retained, so applications that need that
    442   information should instead use raw inflate, see inflateInit2() below, or
    443   inflateBack() and perform their own processing of the gzip header and
    444   trailer.
    445 
    446     inflate() returns Z_OK if some progress has been made (more input processed
    447   or more output produced), Z_STREAM_END if the end of the compressed data has
    448   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
    449   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
    450   corrupted (input stream not conforming to the zlib format or incorrect check
    451   value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
    452   if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
    453   Z_BUF_ERROR if no progress is possible or if there was not enough room in the
    454   output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
    455   inflate() can be called again with more input and more output space to
    456   continue decompressing. If Z_DATA_ERROR is returned, the application may then
    457   call inflateSync() to look for a good compression block if a partial recovery
    458   of the data is desired.
    459 */
    460 
    461 
    462 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
    463 /*
    464      All dynamically allocated data structures for this stream are freed.
    465    This function discards any unprocessed input and does not flush any
    466    pending output.
    467 
    468      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
    469    was inconsistent. In the error case, msg may be set but then points to a
    470    static string (which must not be deallocated).
    471 */
    472 
    473                         /* Advanced functions */
    474 
    475 /*
    476     The following functions are needed only in some special applications.
    477 */
    478 
    479 /*
    480 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
    481                                      int  level,
    482                                      int  method,
    483                                      int  windowBits,
    484                                      int  memLevel,
    485                                      int  strategy));
    486 
    487      This is another version of deflateInit with more compression options. The
    488    fields next_in, zalloc, zfree and opaque must be initialized before by
    489    the caller.
    490 
    491      The method parameter is the compression method. It must be Z_DEFLATED in
    492    this version of the library.
    493 
    494      The windowBits parameter is the base two logarithm of the window size
    495    (the size of the history buffer). It should be in the range 8..15 for this
    496    version of the library. Larger values of this parameter result in better
    497    compression at the expense of memory usage. The default value is 15 if
    498    deflateInit is used instead.
    499 
    500      windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
    501    determines the window size. deflate() will then generate raw deflate data
    502    with no zlib header or trailer, and will not compute an adler32 check value.
    503 
    504      windowBits can also be greater than 15 for optional gzip encoding. Add
    505    16 to windowBits to write a simple gzip header and trailer around the
    506    compressed data instead of a zlib wrapper. The gzip header will have no
    507    file name, no extra data, no comment, no modification time (set to zero),
    508    no header crc, and the operating system will be set to 255 (unknown).  If a
    509    gzip stream is being written, strm->adler is a crc32 instead of an adler32.
    510 
    511      The memLevel parameter specifies how much memory should be allocated
    512    for the internal compression state. memLevel=1 uses minimum memory but
    513    is slow and reduces compression ratio; memLevel=9 uses maximum memory
    514    for optimal speed. The default value is 8. See zconf.h for total memory
    515    usage as a function of windowBits and memLevel.
    516 
    517      The strategy parameter is used to tune the compression algorithm. Use the
    518    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
    519    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
    520    string match), or Z_RLE to limit match distances to one (run-length
    521    encoding). Filtered data consists mostly of small values with a somewhat
    522    random distribution. In this case, the compression algorithm is tuned to
    523    compress them better. The effect of Z_FILTERED is to force more Huffman
    524    coding and less string matching; it is somewhat intermediate between
    525    Z_DEFAULT and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as fast as
    526    Z_HUFFMAN_ONLY, but give better compression for PNG image data. The strategy
    527    parameter only affects the compression ratio but not the correctness of the
    528    compressed output even if it is not set appropriately.  Z_FIXED prevents the
    529    use of dynamic Huffman codes, allowing for a simpler decoder for special
    530    applications.
    531 
    532       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
    533    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
    534    method). msg is set to null if there is no error message.  deflateInit2 does
    535    not perform any compression: this will be done by deflate().
    536 */
    537 
    538 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
    539                                              const Bytef *dictionary,
    540                                              uInt  dictLength));
    541 /*
    542      Initializes the compression dictionary from the given byte sequence
    543    without producing any compressed output. This function must be called
    544    immediately after deflateInit, deflateInit2 or deflateReset, before any
    545    call of deflate. The compressor and decompressor must use exactly the same
    546    dictionary (see inflateSetDictionary).
    547 
    548      The dictionary should consist of strings (byte sequences) that are likely
    549    to be encountered later in the data to be compressed, with the most commonly
    550    used strings preferably put towards the end of the dictionary. Using a
    551    dictionary is most useful when the data to be compressed is short and can be
    552    predicted with good accuracy; the data can then be compressed better than
    553    with the default empty dictionary.
    554 
    555      Depending on the size of the compression data structures selected by
    556    deflateInit or deflateInit2, a part of the dictionary may in effect be
    557    discarded, for example if the dictionary is larger than the window size in
    558    deflate or deflate2. Thus the strings most likely to be useful should be
    559    put at the end of the dictionary, not at the front. In addition, the
    560    current implementation of deflate will use at most the window size minus
    561    262 bytes of the provided dictionary.
    562 
    563      Upon return of this function, strm->adler is set to the adler32 value
    564    of the dictionary; the decompressor may later use this value to determine
    565    which dictionary has been used by the compressor. (The adler32 value
    566    applies to the whole dictionary even if only a subset of the dictionary is
    567    actually used by the compressor.) If a raw deflate was requested, then the
    568    adler32 value is not computed and strm->adler is not set.
    569 
    570      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
    571    parameter is invalid (such as NULL dictionary) or the stream state is
    572    inconsistent (for example if deflate has already been called for this stream
    573    or if the compression method is bsort). deflateSetDictionary does not
    574    perform any compression: this will be done by deflate().
    575 */
    576 
    577 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
    578                                     z_streamp source));
    579 /*
    580      Sets the destination stream as a complete copy of the source stream.
    581 
    582      This function can be useful when several compression strategies will be
    583    tried, for example when there are several ways of pre-processing the input
    584    data with a filter. The streams that will be discarded should then be freed
    585    by calling deflateEnd.  Note that deflateCopy duplicates the internal
    586    compression state which can be quite large, so this strategy is slow and
    587    can consume lots of memory.
    588 
    589      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
    590    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
    591    (such as zalloc being NULL). msg is left unchanged in both source and
    592    destination.
    593 */
    594 
    595 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
    596 /*
    597      This function is equivalent to deflateEnd followed by deflateInit,
    598    but does not free and reallocate all the internal compression state.
    599    The stream will keep the same compression level and any other attributes
    600    that may have been set by deflateInit2.
    601 
    602       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
    603    stream state was inconsistent (such as zalloc or state being NULL).
    604 */
    605 
    606 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
    607                                       int level,
    608                                       int strategy));
    609 /*
    610      Dynamically update the compression level and compression strategy.  The
    611    interpretation of level and strategy is as in deflateInit2.  This can be
    612    used to switch between compression and straight copy of the input data, or
    613    to switch to a different kind of input data requiring a different
    614    strategy. If the compression level is changed, the input available so far
    615    is compressed with the old level (and may be flushed); the new level will
    616    take effect only at the next call of deflate().
    617 
    618      Before the call of deflateParams, the stream state must be set as for
    619    a call of deflate(), since the currently available input may have to
    620    be compressed and flushed. In particular, strm->avail_out must be non-zero.
    621 
    622      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
    623    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
    624    if strm->avail_out was zero.
    625 */
    626 
    627 ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,
    628                                     int good_length,
    629                                     int max_lazy,
    630                                     int nice_length,
    631                                     int max_chain));
    632 /*
    633      Fine tune deflate's internal compression parameters.  This should only be
    634    used by someone who understands the algorithm used by zlib's deflate for
    635    searching for the best matching string, and even then only by the most
    636    fanatic optimizer trying to squeeze out the last compressed bit for their
    637    specific input data.  Read the deflate.c source code for the meaning of the
    638    max_lazy, good_length, nice_length, and max_chain parameters.
    639 
    640      deflateTune() can be called after deflateInit() or deflateInit2(), and
    641    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
    642  */
    643 
    644 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
    645                                        uLong sourceLen));
    646 /*
    647      deflateBound() returns an upper bound on the compressed size after
    648    deflation of sourceLen bytes.  It must be called after deflateInit()
    649    or deflateInit2().  This would be used to allocate an output buffer
    650    for deflation in a single pass, and so would be called before deflate().
    651 */
    652 
    653 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
    654                                      int bits,
    655                                      int value));
    656 /*
    657      deflatePrime() inserts bits in the deflate output stream.  The intent
    658   is that this function is used to start off the deflate output with the
    659   bits leftover from a previous deflate stream when appending to it.  As such,
    660   this function can only be used for raw deflate, and must be used before the
    661   first deflate() call after a deflateInit2() or deflateReset().  bits must be
    662   less than or equal to 16, and that many of the least significant bits of
    663   value will be inserted in the output.
    664 
    665       deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
    666    stream state was inconsistent.
    667 */
    668 
    669 ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,
    670                                          gz_headerp head));
    671 /*
    672       deflateSetHeader() provides gzip header information for when a gzip
    673    stream is requested by deflateInit2().  deflateSetHeader() may be called
    674    after deflateInit2() or deflateReset() and before the first call of
    675    deflate().  The text, time, os, extra field, name, and comment information
    676    in the provided gz_header structure are written to the gzip header (xflag is
    677    ignored -- the extra flags are set according to the compression level).  The
    678    caller must assure that, if not Z_NULL, name and comment are terminated with
    679    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
    680    available there.  If hcrc is true, a gzip header crc is included.  Note that
    681    the current versions of the command-line version of gzip (up through version
    682    1.3.x) do not support header crc's, and will report that it is a "multi-part
    683    gzip file" and give up.
    684 
    685       If deflateSetHeader is not used, the default gzip header has text false,
    686    the time set to zero, and os set to 255, with no extra, name, or comment
    687    fields.  The gzip header is returned to the default state by deflateReset().
    688 
    689       deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
    690    stream state was inconsistent.
    691 */
    692 
    693 /*
    694 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
    695                                      int  windowBits));
    696 
    697      This is another version of inflateInit with an extra parameter. The
    698    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
    699    before by the caller.
    700 
    701      The windowBits parameter is the base two logarithm of the maximum window
    702    size (the size of the history buffer).  It should be in the range 8..15 for
    703    this version of the library. The default value is 15 if inflateInit is used
    704    instead. windowBits must be greater than or equal to the windowBits value
    705    provided to deflateInit2() while compressing, or it must be equal to 15 if
    706    deflateInit2() was not used. If a compressed stream with a larger window
    707    size is given as input, inflate() will return with the error code
    708    Z_DATA_ERROR instead of trying to allocate a larger window.
    709 
    710      windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
    711    determines the window size. inflate() will then process raw deflate data,
    712    not looking for a zlib or gzip header, not generating a check value, and not
    713    looking for any check values for comparison at the end of the stream. This
    714    is for use with other formats that use the deflate compressed data format
    715    such as zip.  Those formats provide their own check values. If a custom
    716    format is developed using the raw deflate format for compressed data, it is
    717    recommended that a check value such as an adler32 or a crc32 be applied to
    718    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
    719    most applications, the zlib format should be used as is. Note that comments
    720    above on the use in deflateInit2() applies to the magnitude of windowBits.
    721 
    722      windowBits can also be greater than 15 for optional gzip decoding. Add
    723    32 to windowBits to enable zlib and gzip decoding with automatic header
    724    detection, or add 16 to decode only the gzip format (the zlib format will
    725    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is
    726    a crc32 instead of an adler32.
    727 
    728      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
    729    memory, Z_STREAM_ERROR if a parameter is invalid (such as a null strm). msg
    730    is set to null if there is no error message.  inflateInit2 does not perform
    731    any decompression apart from reading the zlib header if present: this will
    732    be done by inflate(). (So next_in and avail_in may be modified, but next_out
    733    and avail_out are unchanged.)
    734 */
    735 
    736 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
    737                                              const Bytef *dictionary,
    738                                              uInt  dictLength));
    739 /*
    740      Initializes the decompression dictionary from the given uncompressed byte
    741    sequence. This function must be called immediately after a call of inflate,
    742    if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
    743    can be determined from the adler32 value returned by that call of inflate.
    744    The compressor and decompressor must use exactly the same dictionary (see
    745    deflateSetDictionary).  For raw inflate, this function can be called
    746    immediately after inflateInit2() or inflateReset() and before any call of
    747    inflate() to set the dictionary.  The application must insure that the
    748    dictionary that was used for compression is provided.
    749 
    750      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
    751    parameter is invalid (such as NULL dictionary) or the stream state is
    752    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
    753    expected one (incorrect adler32 value). inflateSetDictionary does not
    754    perform any decompression: this will be done by subsequent calls of
    755    inflate().
    756 */
    757 
    758 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
    759 /*
    760     Skips invalid compressed data until a full flush point (see above the
    761   description of deflate with Z_FULL_FLUSH) can be found, or until all
    762   available input is skipped. No output is provided.
    763 
    764     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
    765   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
    766   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
    767   case, the application may save the current current value of total_in which
    768   indicates where valid compressed data was found. In the error case, the
    769   application may repeatedly call inflateSync, providing more input each time,
    770   until success or end of the input data.
    771 */
    772 
    773 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
    774                                     z_streamp source));
    775 /*
    776      Sets the destination stream as a complete copy of the source stream.
    777 
    778      This function can be useful when randomly accessing a large stream.  The
    779    first pass through the stream can periodically record the inflate state,
    780    allowing restarting inflate at those points when randomly accessing the
    781    stream.
    782 
    783      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
    784    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
    785    (such as zalloc being NULL). msg is left unchanged in both source and
    786    destination.
    787 */
    788 
    789 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
    790 /*
    791      This function is equivalent to inflateEnd followed by inflateInit,
    792    but does not free and reallocate all the internal decompression state.
    793    The stream will keep attributes that may have been set by inflateInit2.
    794 
    795       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
    796    stream state was inconsistent (such as zalloc or state being NULL).
    797 */
    798 
    799 ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,
    800                                      int bits,
    801                                      int value));
    802 /*
    803      This function inserts bits in the inflate input stream.  The intent is
    804   that this function is used to start inflating at a bit position in the
    805   middle of a byte.  The provided bits will be used before any bytes are used
    806   from next_in.  This function should only be used with raw inflate, and
    807   should be used before the first inflate() call after inflateInit2() or
    808   inflateReset().  bits must be less than or equal to 16, and that many of the
    809   least significant bits of value will be inserted in the input.
    810 
    811       inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
    812    stream state was inconsistent.
    813 */
    814 
    815 ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
    816                                          gz_headerp head));
    817 /*
    818       inflateGetHeader() requests that gzip header information be stored in the
    819    provided gz_header structure.  inflateGetHeader() may be called after
    820    inflateInit2() or inflateReset(), and before the first call of inflate().
    821    As inflate() processes the gzip stream, head->done is zero until the header
    822    is completed, at which time head->done is set to one.  If a zlib stream is
    823    being decoded, then head->done is set to -1 to indicate that there will be
    824    no gzip header information forthcoming.  Note that Z_BLOCK can be used to
    825    force inflate() to return immediately after header processing is complete
    826    and before any actual data is decompressed.
    827 
    828       The text, time, xflags, and os fields are filled in with the gzip header
    829    contents.  hcrc is set to true if there is a header CRC.  (The header CRC
    830    was valid if done is set to one.)  If extra is not Z_NULL, then extra_max
    831    contains the maximum number of bytes to write to extra.  Once done is true,
    832    extra_len contains the actual extra field length, and extra contains the
    833    extra field, or that field truncated if extra_max is less than extra_len.
    834    If name is not Z_NULL, then up to name_max characters are written there,
    835    terminated with a zero unless the length is greater than name_max.  If
    836    comment is not Z_NULL, then up to comm_max characters are written there,
    837    terminated with a zero unless the length is greater than comm_max.  When
    838    any of extra, name, or comment are not Z_NULL and the respective field is
    839    not present in the header, then that field is set to Z_NULL to signal its
    840    absence.  This allows the use of deflateSetHeader() with the returned
    841    structure to duplicate the header.  However if those fields are set to
    842    allocated memory, then the application will need to save those pointers
    843    elsewhere so that they can be eventually freed.
    844 
    845       If inflateGetHeader is not used, then the header information is simply
    846    discarded.  The header is always checked for validity, including the header
    847    CRC if present.  inflateReset() will reset the process to discard the header
    848    information.  The application would need to call inflateGetHeader() again to
    849    retrieve the header from the next gzip stream.
    850 
    851       inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
    852    stream state was inconsistent.
    853 */
    854 
    855 /*
    856 ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
    857                                         unsigned char FAR *window));
    858 
    859      Initialize the internal stream state for decompression using inflateBack()
    860    calls.  The fields zalloc, zfree and opaque in strm must be initialized
    861    before the call.  If zalloc and zfree are Z_NULL, then the default library-
    862    derived memory allocation routines are used.  windowBits is the base two
    863    logarithm of the window size, in the range 8..15.  window is a caller
    864    supplied buffer of that size.  Except for special applications where it is
    865    assured that deflate was used with small window sizes, windowBits must be 15
    866    and a 32K byte window must be supplied to be able to decompress general
    867    deflate streams.
    868 
    869      See inflateBack() for the usage of these routines.
    870 
    871      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
    872    the paramaters are invalid, Z_MEM_ERROR if the internal state could not
    873    be allocated, or Z_VERSION_ERROR if the version of the library does not
    874    match the version of the header file.
    875 */
    876 
    877 typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));
    878 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
    879 
    880 ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,
    881                                     in_func in, void FAR *in_desc,
    882                                     out_func out, void FAR *out_desc));
    883 /*
    884      inflateBack() does a raw inflate with a single call using a call-back
    885    interface for input and output.  This is more efficient than inflate() for
    886    file i/o applications in that it avoids copying between the output and the
    887    sliding window by simply making the window itself the output buffer.  This
    888    function trusts the application to not change the output buffer passed by
    889    the output function, at least until inflateBack() returns.
    890 
    891      inflateBackInit() must be called first to allocate the internal state
    892    and to initialize the state with the user-provided window buffer.
    893    inflateBack() may then be used multiple times to inflate a complete, raw
    894    deflate stream with each call.  inflateBackEnd() is then called to free
    895    the allocated state.
    896 
    897      A raw deflate stream is one with no zlib or gzip header or trailer.
    898    This routine would normally be used in a utility that reads zip or gzip
    899    files and writes out uncompressed files.  The utility would decode the
    900    header and process the trailer on its own, hence this routine expects
    901    only the raw deflate stream to decompress.  This is different from the
    902    normal behavior of inflate(), which expects either a zlib or gzip header and
    903    trailer around the deflate stream.
    904 
    905      inflateBack() uses two subroutines supplied by the caller that are then
    906    called by inflateBack() for input and output.  inflateBack() calls those
    907    routines until it reads a complete deflate stream and writes out all of the
    908    uncompressed data, or until it encounters an error.  The function's
    909    parameters and return types are defined above in the in_func and out_func
    910    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
    911    number of bytes of provided input, and a pointer to that input in buf.  If
    912    there is no input available, in() must return zero--buf is ignored in that
    913    case--and inflateBack() will return a buffer error.  inflateBack() will call
    914    out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].  out()
    915    should return zero on success, or non-zero on failure.  If out() returns
    916    non-zero, inflateBack() will return with an error.  Neither in() nor out()
    917    are permitted to change the contents of the window provided to
    918    inflateBackInit(), which is also the buffer that out() uses to write from.
    919    The length written by out() will be at most the window size.  Any non-zero
    920    amount of input may be provided by in().
    921 
    922      For convenience, inflateBack() can be provided input on the first call by
    923    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
    924    in() will be called.  Therefore strm->next_in must be initialized before
    925    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
    926    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
    927    must also be initialized, and then if strm->avail_in is not zero, input will
    928    initially be taken from strm->next_in[0 .. strm->avail_in - 1].
    929 
    930      The in_desc and out_desc parameters of inflateBack() is passed as the
    931    first parameter of in() and out() respectively when they are called.  These
    932    descriptors can be optionally used to pass any information that the caller-
    933    supplied in() and out() functions need to do their job.
    934 
    935      On return, inflateBack() will set strm->next_in and strm->avail_in to
    936    pass back any unused input that was provided by the last in() call.  The
    937    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
    938    if in() or out() returned an error, Z_DATA_ERROR if there was a format
    939    error in the deflate stream (in which case strm->msg is set to indicate the
    940    nature of the error), or Z_STREAM_ERROR if the stream was not properly
    941    initialized.  In the case of Z_BUF_ERROR, an input or output error can be
    942    distinguished using strm->next_in which will be Z_NULL only if in() returned
    943    an error.  If strm->next is not Z_NULL, then the Z_BUF_ERROR was due to
    944    out() returning non-zero.  (in() will always be called before out(), so
    945    strm->next_in is assured to be defined if out() returns non-zero.)  Note
    946    that inflateBack() cannot return Z_OK.
    947 */
    948 
    949 ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));
    950 /*
    951      All memory allocated by inflateBackInit() is freed.
    952 
    953      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
    954    state was inconsistent.
    955 */
    956 
    957 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
    958 /* Return flags indicating compile-time options.
    959 
    960     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
    961      1.0: size of uInt
    962      3.2: size of uLong
    963      5.4: size of voidpf (pointer)
    964      7.6: size of z_off_t
    965 
    966     Compiler, assembler, and debug options:
    967      8: DEBUG
    968      9: ASMV or ASMINF -- use ASM code
    969      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
    970      11: 0 (reserved)
    971 
    972     One-time table building (smaller code, but not thread-safe if true):
    973      12: BUILDFIXED -- build static block decoding tables when needed
    974      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
    975      14,15: 0 (reserved)
    976 
    977     Library content (indicates missing functionality):
    978      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
    979                           deflate code when not needed)
    980      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
    981                     and decode gzip streams (to avoid linking crc code)
    982      18-19: 0 (reserved)
    983 
    984     Operation variations (changes in library functionality):
    985      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
    986      21: FASTEST -- deflate algorithm with only one, lowest compression level
    987      22,23: 0 (reserved)
    988 
    989     The sprintf variant used by gzprintf (zero is best):
    990      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
    991      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
    992      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
    993 
    994     Remainder:
    995      27-31: 0 (reserved)
    996  */
    997 
    998 
    999                         /* utility functions */
   1000 
   1001 /*
   1002      The following utility functions are implemented on top of the
   1003    basic stream-oriented functions. To simplify the interface, some
   1004    default options are assumed (compression level and memory usage,
   1005    standard memory allocation functions). The source code of these
   1006    utility functions can easily be modified if you need special options.
   1007 */
   1008 
   1009 ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,
   1010                                  const Bytef *source, uLong sourceLen));
   1011 /*
   1012      Compresses the source buffer into the destination buffer.  sourceLen is
   1013    the byte length of the source buffer. Upon entry, destLen is the total
   1014    size of the destination buffer, which must be at least the value returned
   1015    by compressBound(sourceLen). Upon exit, destLen is the actual size of the
   1016    compressed buffer.
   1017      This function can be used to compress a whole file at once if the
   1018    input file is mmap'ed.
   1019      compress returns Z_OK if success, Z_MEM_ERROR if there was not
   1020    enough memory, Z_BUF_ERROR if there was not enough room in the output
   1021    buffer.
   1022 */
   1023 
   1024 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,
   1025                                   const Bytef *source, uLong sourceLen,
   1026                                   int level));
   1027 /*
   1028      Compresses the source buffer into the destination buffer. The level
   1029    parameter has the same meaning as in deflateInit.  sourceLen is the byte
   1030    length of the source buffer. Upon entry, destLen is the total size of the
   1031    destination buffer, which must be at least the value returned by
   1032    compressBound(sourceLen). Upon exit, destLen is the actual size of the
   1033    compressed buffer.
   1034 
   1035      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
   1036    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
   1037    Z_STREAM_ERROR if the level parameter is invalid.
   1038 */
   1039 
   1040 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
   1041 /*
   1042      compressBound() returns an upper bound on the compressed size after
   1043    compress() or compress2() on sourceLen bytes.  It would be used before
   1044    a compress() or compress2() call to allocate the destination buffer.
   1045 */
   1046 
   1047 ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
   1048                                    const Bytef *source, uLong sourceLen));
   1049 /*
   1050      Decompresses the source buffer into the destination buffer.  sourceLen is
   1051    the byte length of the source buffer. Upon entry, destLen is the total
   1052    size of the destination buffer, which must be large enough to hold the
   1053    entire uncompressed data. (The size of the uncompressed data must have
   1054    been saved previously by the compressor and transmitted to the decompressor
   1055    by some mechanism outside the scope of this compression library.)
   1056    Upon exit, destLen is the actual size of the compressed buffer.
   1057      This function can be used to decompress a whole file at once if the
   1058    input file is mmap'ed.
   1059 
   1060      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
   1061    enough memory, Z_BUF_ERROR if there was not enough room in the output
   1062    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.
   1063 */
   1064 
   1065 
   1066 typedef voidp gzFile;
   1067 
   1068 ZEXTERN gzFile ZEXPORT gzopen  OF((const char *path, const char *mode));
   1069 /*
   1070      Opens a gzip (.gz) file for reading or writing. The mode parameter
   1071    is as in fopen ("rb" or "wb") but can also include a compression level
   1072    ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
   1073    Huffman only compression as in "wb1h", or 'R' for run-length encoding
   1074    as in "wb1R". (See the description of deflateInit2 for more information
   1075    about the strategy parameter.)
   1076 
   1077      gzopen can be used to read a file which is not in gzip format; in this
   1078    case gzread will directly read from the file without decompression.
   1079 
   1080      gzopen returns NULL if the file could not be opened or if there was
   1081    insufficient memory to allocate the (de)compression state; errno
   1082    can be checked to distinguish the two cases (if errno is zero, the
   1083    zlib error is Z_MEM_ERROR).  */
   1084 
   1085 ZEXTERN gzFile ZEXPORT gzdopen  OF((int fd, const char *mode));
   1086 /*
   1087      gzdopen() associates a gzFile with the file descriptor fd.  File
   1088    descriptors are obtained from calls like open, dup, creat, pipe or
   1089    fileno (in the file has been previously opened with fopen).
   1090    The mode parameter is as in gzopen.
   1091      The next call of gzclose on the returned gzFile will also close the
   1092    file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
   1093    descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
   1094      gzdopen returns NULL if there was insufficient memory to allocate
   1095    the (de)compression state.
   1096 */
   1097 
   1098 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
   1099 /*
   1100      Dynamically update the compression level or strategy. See the description
   1101    of deflateInit2 for the meaning of these parameters.
   1102      gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
   1103    opened for writing.
   1104 */
   1105 
   1106 ZEXTERN int ZEXPORT    gzread  OF((gzFile file, voidp buf, unsigned len));
   1107 /*
   1108      Reads the given number of uncompressed bytes from the compressed file.
   1109    If the input file was not in gzip format, gzread copies the given number
   1110    of bytes into the buffer.
   1111      gzread returns the number of uncompressed bytes actually read (0 for
   1112    end of file, -1 for error). */
   1113 
   1114 ZEXTERN int ZEXPORT    gzwrite OF((gzFile file,
   1115                                    voidpc buf, unsigned len));
   1116 /*
   1117      Writes the given number of uncompressed bytes into the compressed file.
   1118    gzwrite returns the number of uncompressed bytes actually written
   1119    (0 in case of error).
   1120 */
   1121 
   1122 ZEXTERN int ZEXPORTVA   gzprintf OF((gzFile file, const char *format, ...));
   1123 /*
   1124      Converts, formats, and writes the args to the compressed file under
   1125    control of the format string, as in fprintf. gzprintf returns the number of
   1126    uncompressed bytes actually written (0 in case of error).  The number of
   1127    uncompressed bytes written is limited to 4095. The caller should assure that
   1128    this limit is not exceeded. If it is exceeded, then gzprintf() will return
   1129    return an error (0) with nothing written. In this case, there may also be a
   1130    buffer overflow with unpredictable consequences, which is possible only if
   1131    zlib was compiled with the insecure functions sprintf() or vsprintf()
   1132    because the secure snprintf() or vsnprintf() functions were not available.
   1133 */
   1134 
   1135 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
   1136 /*
   1137       Writes the given null-terminated string to the compressed file, excluding
   1138    the terminating null character.
   1139       gzputs returns the number of characters written, or -1 in case of error.
   1140 */
   1141 
   1142 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
   1143 /*
   1144       Reads bytes from the compressed file until len-1 characters are read, or
   1145    a newline character is read and transferred to buf, or an end-of-file
   1146    condition is encountered.  The string is then terminated with a null
   1147    character.
   1148       gzgets returns buf, or Z_NULL in case of error.
   1149 */
   1150 
   1151 ZEXTERN int ZEXPORT    gzputc OF((gzFile file, int c));
   1152 /*
   1153       Writes c, converted to an unsigned char, into the compressed file.
   1154    gzputc returns the value that was written, or -1 in case of error.
   1155 */
   1156 
   1157 ZEXTERN int ZEXPORT    gzgetc OF((gzFile file));
   1158 /*
   1159       Reads one byte from the compressed file. gzgetc returns this byte
   1160    or -1 in case of end of file or error.
   1161 */
   1162 
   1163 ZEXTERN int ZEXPORT    gzungetc OF((int c, gzFile file));
   1164 /*
   1165       Push one character back onto the stream to be read again later.
   1166    Only one character of push-back is allowed.  gzungetc() returns the
   1167    character pushed, or -1 on failure.  gzungetc() will fail if a
   1168    character has been pushed but not read yet, or if c is -1. The pushed
   1169    character will be discarded if the stream is repositioned with gzseek()
   1170    or gzrewind().
   1171 */
   1172 
   1173 ZEXTERN int ZEXPORT    gzflush OF((gzFile file, int flush));
   1174 /*
   1175      Flushes all pending output into the compressed file. The parameter
   1176    flush is as in the deflate() function. The return value is the zlib
   1177    error number (see function gzerror below). gzflush returns Z_OK if
   1178    the flush parameter is Z_FINISH and all output could be flushed.
   1179      gzflush should be called only when strictly necessary because it can
   1180    degrade compression.
   1181 */
   1182 
   1183 ZEXTERN z_off_t ZEXPORT    gzseek OF((gzFile file,
   1184                                       z_off_t offset, int whence));
   1185 /*
   1186       Sets the starting position for the next gzread or gzwrite on the
   1187    given compressed file. The offset represents a number of bytes in the
   1188    uncompressed data stream. The whence parameter is defined as in lseek(2);
   1189    the value SEEK_END is not supported.
   1190      If the file is opened for reading, this function is emulated but can be
   1191    extremely slow. If the file is opened for writing, only forward seeks are
   1192    supported; gzseek then compresses a sequence of zeroes up to the new
   1193    starting position.
   1194 
   1195       gzseek returns the resulting offset location as measured in bytes from
   1196    the beginning of the uncompressed stream, or -1 in case of error, in
   1197    particular if the file is opened for writing and the new starting position
   1198    would be before the current position.
   1199 */
   1200 
   1201 ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
   1202 /*
   1203      Rewinds the given file. This function is supported only for reading.
   1204 
   1205    gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
   1206 */
   1207 
   1208 ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
   1209 /*
   1210      Returns the starting position for the next gzread or gzwrite on the
   1211    given compressed file. This position represents a number of bytes in the
   1212    uncompressed data stream.
   1213 
   1214    gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
   1215 */
   1216 
   1217 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
   1218 /*
   1219      Returns 1 when EOF has previously been detected reading the given
   1220    input stream, otherwise zero.
   1221 */
   1222 
   1223 ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
   1224 /*
   1225      Returns 1 if file is being read directly without decompression, otherwise
   1226    zero.
   1227 */
   1228 
   1229 ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
   1230 /*
   1231      Flushes all pending output if necessary, closes the compressed file
   1232    and deallocates all the (de)compression state. The return value is the zlib
   1233    error number (see function gzerror below).
   1234 */
   1235 
   1236 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
   1237 /*
   1238      Returns the error message for the last error which occurred on the
   1239    given compressed file. errnum is set to zlib error number. If an
   1240    error occurred in the file system and not in the compression library,
   1241    errnum is set to Z_ERRNO and the application may consult errno
   1242    to get the exact error code.
   1243 */
   1244 
   1245 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
   1246 /*
   1247      Clears the error and end-of-file flags for file. This is analogous to the
   1248    clearerr() function in stdio. This is useful for continuing to read a gzip
   1249    file that is being written concurrently.
   1250 */
   1251 
   1252                         /* checksum functions */
   1253 
   1254 /*
   1255      These functions are not related to compression but are exported
   1256    anyway because they might be useful in applications using the
   1257    compression library.
   1258 */
   1259 
   1260 ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
   1261 /*
   1262      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
   1263    return the updated checksum. If buf is NULL, this function returns
   1264    the required initial value for the checksum.
   1265    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
   1266    much faster. Usage example:
   1267 
   1268      uLong adler = adler32(0L, Z_NULL, 0);
   1269 
   1270      while (read_buffer(buffer, length) != EOF) {
   1271        adler = adler32(adler, buffer, length);
   1272      }
   1273      if (adler != original_adler) error();
   1274 */
   1275 
   1276 ZEXTERN uLong ZEXPORT adler32_combine OF((uLong adler1, uLong adler2,
   1277                                           z_off_t len2));
   1278 /*
   1279      Combine two Adler-32 checksums into one.  For two sequences of bytes, seq1
   1280    and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
   1281    each, adler1 and adler2.  adler32_combine() returns the Adler-32 checksum of
   1282    seq1 and seq2 concatenated, requiring only adler1, adler2, and len2.
   1283 */
   1284 
   1285 ZEXTERN uLong ZEXPORT crc32   OF((uLong crc, const Bytef *buf, uInt len));
   1286 /*
   1287      Update a running CRC-32 with the bytes buf[0..len-1] and return the
   1288    updated CRC-32. If buf is NULL, this function returns the required initial
   1289    value for the for the crc. Pre- and post-conditioning (one's complement) is
   1290    performed within this function so it shouldn't be done by the application.
   1291    Usage example:
   1292 
   1293      uLong crc = crc32(0L, Z_NULL, 0);
   1294 
   1295      while (read_buffer(buffer, length) != EOF) {
   1296        crc = crc32(crc, buffer, length);
   1297      }
   1298      if (crc != original_crc) error();
   1299 */
   1300 
   1301 ZEXTERN uLong ZEXPORT crc32_combine OF((uLong crc1, uLong crc2, z_off_t len2));
   1302 
   1303 /*
   1304      Combine two CRC-32 check values into one.  For two sequences of bytes,
   1305    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
   1306    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
   1307    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
   1308    len2.
   1309 */
   1310 
   1311 
   1312                         /* various hacks, don't look :) */
   1313 
   1314 /* deflateInit and inflateInit are macros to allow checking the zlib version
   1315  * and the compiler's view of z_stream:
   1316  */
   1317 ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
   1318                                      const char *version, int stream_size));
   1319 ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
   1320                                      const char *version, int stream_size));
   1321 ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int  level, int  method,
   1322                                       int windowBits, int memLevel,
   1323                                       int strategy, const char *version,
   1324                                       int stream_size));
   1325 ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int  windowBits,
   1326                                       const char *version, int stream_size));
   1327 ZEXTERN int ZEXPORT inflateBackInit_ OF((z_streamp strm, int windowBits,
   1328                                          unsigned char FAR *window,
   1329                                          const char *version,
   1330                                          int stream_size));
   1331 #define deflateInit(strm, level) \
   1332         deflateInit_((strm), (level),       ZLIB_VERSION, sizeof(z_stream))
   1333 #define inflateInit(strm) \
   1334         inflateInit_((strm),                ZLIB_VERSION, sizeof(z_stream))
   1335 #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
   1336         deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
   1337                       (strategy),           ZLIB_VERSION, sizeof(z_stream))
   1338 #define inflateInit2(strm, windowBits) \
   1339         inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
   1340 #define inflateBackInit(strm, windowBits, window) \
   1341         inflateBackInit_((strm), (windowBits), (window), \
   1342         ZLIB_VERSION, sizeof(z_stream))
   1343 
   1344 
   1345 #if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
   1346     struct internal_state {int dummy;}; /* hack for buggy compilers */
   1347 #endif
   1348 
   1349 ZEXTERN const char   * ZEXPORT zError           OF((int));
   1350 ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp z));
   1351 ZEXTERN const uLongf * ZEXPORT get_crc_table    OF((void));
   1352 
   1353 #ifdef __cplusplus
   1354 }
   1355 #endif
   1356 
   1357 #endif /* ZLIB_H */