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

  version 1.2.11, January 15th, 2017

  Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler

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

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

  arising from the use of this software.

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

  including commercial applications, and to alter it and redistribute it

  freely, subject to the following restrictions:

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

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

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

     appreciated but is not required.

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

     misrepresented as being the original software.

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

  Jean-loup Gailly        Mark Adler

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

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

  Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950

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

*/

#ifndef ZLIB_H

#define ZLIB_H

#include "zconf.h"

#ifdef __cplusplus

extern "C" {

#endif

#define ZLIB_VERSION "1.2.11"

#define ZLIB_VERNUM 0x12b0

#define ZLIB_VER_MAJOR 1

#define ZLIB_VER_MINOR 2

#define ZLIB_VER_REVISION 11

#define ZLIB_VER_SUBREVISION 0

/*

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

  decompression functions, including integrity checks of the uncompressed data.

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

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

  interface.

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

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

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

  (providing more output space) before each call.

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

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

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

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

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

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

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

    This library can optionally read and write gzip and raw deflate streams in

  memory as well.

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

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

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

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

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

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

  even in the case of corrupted input.

*/

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

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

struct internal_state;

typedef struct z_stream_s {

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

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

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

    Bytef    *next_out; /* next output byte will go here */

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

    uLong    total_out; /* total number of bytes output so far */

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

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

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

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

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

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

                           for deflate, or the decoding state for inflate */

    uLong   adler;      /* Adler-32 or CRC-32 value of the uncompressed data */

    uLong   reserved;   /* reserved for future use */

} z_stream;

typedef z_stream FAR *z_streamp;

/*

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

  for more details on the meanings of these fields.

*/

typedef struct gz_header_s {

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

    uLong   time;       /* modification time */

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

    int     os;         /* operating system */

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

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

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

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

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

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

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

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

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

                           when writing a gzip file) */

} gz_header;

typedef gz_header FAR *gz_headerp;

/*

     The application must update next_in and avail_in when avail_in has dropped

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

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

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

   library and must not be updated by the application.

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

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

   memory management.  The compression library attaches no meaning to the

   opaque value.

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

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

   thread safe.  In that case, zlib is thread-safe.  When zalloc and zfree are

   Z_NULL on entry to the initialization function, they are set to internal

   routines that use the standard library functions malloc() and free().

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

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

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

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

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

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

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

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

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

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

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

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

*/

                        /* constants */

#define Z_NO_FLUSH      0

#define Z_PARTIAL_FLUSH 1

#define Z_SYNC_FLUSH    2

#define Z_FULL_FLUSH    3

#define Z_FINISH        4

#define Z_BLOCK         5

#define Z_TREES         6

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

#define Z_OK            0

#define Z_STREAM_END    1

#define Z_NEED_DICT     2

#define Z_ERRNO        (-1)

#define Z_STREAM_ERROR (-2)

#define Z_DATA_ERROR   (-3)

#define Z_MEM_ERROR    (-4)

#define Z_BUF_ERROR    (-5)

#define Z_VERSION_ERROR (-6)

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

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

 */

#define Z_NO_COMPRESSION         0

#define Z_BEST_SPEED             1

#define Z_BEST_COMPRESSION       9

#define Z_DEFAULT_COMPRESSION  (-1)

/* compression levels */

#define Z_FILTERED            1

#define Z_HUFFMAN_ONLY        2

#define Z_RLE                 3

#define Z_FIXED               4

#define Z_DEFAULT_STRATEGY    0

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

#define Z_BINARY   0

#define Z_TEXT     1

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

#define Z_UNKNOWN  2

/* Possible values of the data_type field for deflate() */

#define Z_DEFLATED   8

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

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

#define zlib_version zlibVersion()

/* for compatibility with versions < 1.0.2 */

                        /* basic functions */

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

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

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

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

   is automatically made by deflateInit and inflateInit.

 */

/*

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

     Initializes the internal stream state for compression.  The fields

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

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

   allocation functions.

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

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

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

   requests a default compromise between speed and compression (currently

   equivalent to level 6).

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

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

   Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible

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

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

   this will be done by deflate().

*/

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

/*

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

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

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

  forced to flush.

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

  following actions:

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

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

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

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

  - Generate more output starting at next_out and update next_out and avail_out

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

    Forcing flush frequently degrades the compression ratio, so this parameter

    should be set only when necessary.  Some output may be provided even if

    flush is zero.

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

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

  output, and updating avail_in or avail_out accordingly; avail_out should

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

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

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

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

  buffer because there might be more output pending. See deflatePending(),

  which can be used if desired to determine whether or not there is more ouput

  in that case.

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

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

  maximize compression.

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

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

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

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

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

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

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

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

  (00 00 ff ff).

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

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

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

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

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

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

  codes block.

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

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

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

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

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

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

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

  the emission of deflate blocks.

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

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

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

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

  compression.

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

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

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

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

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

  avail_out == 0 on return.

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

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

  enough output space.  If deflate returns with Z_OK or Z_BUF_ERROR, this

  function must be called again with Z_FINISH and more output space (updated

  avail_out) but no more input data, until it returns with Z_STREAM_END or an

  error.  After deflate has returned Z_STREAM_END, the only possible operations

  on the stream are deflateReset or deflateEnd.

    Z_FINISH can be used in the first deflate call after deflateInit if all the

  compression is to be done in a single step.  In order to complete in one

  call, avail_out must be at least the value returned by deflateBound (see

  below).  Then deflate is guaranteed to return Z_STREAM_END.  If not enough

  output space is provided, deflate will not return Z_STREAM_END, and it must

  be called again as described above.

    deflate() sets strm->adler to the Adler-32 checksum of all input read

  so far (that is, total_in bytes).  If a gzip stream is being generated, then

  strm->adler will be the CRC-32 checksum of the input read so far.  (See

  deflateInit2 below.)

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

  the input data type (Z_BINARY or Z_TEXT).  If in doubt, the data is

  considered binary.  This field is only for information purposes and does not

  affect the compression algorithm in any manner.

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

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

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

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

  if next_in or next_out was Z_NULL or the state was inadvertently written over

  by the application), or Z_BUF_ERROR if no progress is possible (for example

  avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not fatal, and

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

  continue compressing.

*/

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

/*

     All dynamically allocated data structures for this stream are freed.

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

   output.

     deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the

   stream state was inconsistent, Z_DATA_ERROR if the stream was freed

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

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

   deallocated).

*/

/*

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

     Initializes the internal stream state for decompression.  The fields

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

   the caller.  In the current version of inflate, the provided input is not

   read or consumed.  The allocation of a sliding window will be deferred to

   the first call of inflate (if the decompression does not complete on the

   first call).  If zalloc and zfree are set to Z_NULL, inflateInit updates

   them to use default allocation functions.

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

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

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

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

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

   Actual decompression will be done by inflate().  So next_in, and avail_in,

   next_out, and avail_out are unused and unchanged.  The current

   implementation of inflateInit() does not process any header information --

   that is deferred until inflate() is called.

*/

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

/*

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

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

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

  forced to flush.

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

  following actions:

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

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

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

    accordingly, and processing will resume at this point for the next call of

    inflate().

  - Generate more output starting at next_out and update next_out and avail_out

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

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

    the flush parameter).

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

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

  output, and updating the next_* and avail_* values accordingly.  If the

  caller of inflate() does not provide both available input and available

  output space, it is possible that there will be no progress made.  The

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

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

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

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

  more output pending.

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

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

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

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

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

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

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

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

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

  To assist in this, on return inflate() always sets strm->data_type to the

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

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

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

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

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

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

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

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

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

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

  consumed input in bits.

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

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

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

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

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

  immediately after reaching the end of the deflate block header.

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

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

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

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

  avail_out must be large enough to hold all of the uncompressed data for the

  operation to complete.  (The size of the uncompressed data may have been

  saved by the compressor for this purpose.)  The use of Z_FINISH is not

  required to perform an inflation in one step.  However it may be used to

  inform inflate that a faster approach can be used for the single inflate()

  call.  Z_FINISH also informs inflate to not maintain a sliding window if the

  stream completes, which reduces inflate's memory footprint.  If the stream

  does not complete, either because not all of the stream is provided or not

  enough output space is provided, then a sliding window will be allocated and

  inflate() can be called again to continue the operation as if Z_NO_FLUSH had

  been used.

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

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

  first call.  So the effects of the flush parameter in this implementation are

  on the return value of inflate() as noted below, when inflate() returns early

  when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of

  memory for a sliding window when Z_FINISH is used.

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

  below), inflate sets strm->adler to the Adler-32 checksum of the dictionary

  chosen by the compressor and returns Z_NEED_DICT; otherwise it sets

  strm->adler to the Adler-32 checksum of all output produced so far (that is,

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

  below.  At the end of the stream, inflate() checks that its computed Adler-32

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

  only if the checksum is correct.

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

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

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

  header is not retained unless inflateGetHeader() is used.  When processing

  gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output

  produced so far.  The CRC-32 is checked against the gzip trailer, as is the

  uncompressed length, modulo 2^32.

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

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

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

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

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

  value, in which case strm->msg points to a string with a more specific

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

  next_in or next_out was Z_NULL, or the state was inadvertently written over

  by the application), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR

  if no progress was possible or if there was not enough room in the output

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

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

  continue decompressing.  If Z_DATA_ERROR is returned, the application may

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

  recovery of the data is to be attempted.

*/

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

/*

     All dynamically allocated data structures for this stream are freed.

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

   output.

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

   was inconsistent.

*/

                        /* Advanced functions */

/*

    The following functions are needed only in some special applications.

*/

/*

ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,

                                     int  level,

                                     int  method,

                                     int  windowBits,

                                     int  memLevel,

                                     int  strategy));

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

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

   caller.

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

   this version of the library.

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

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

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

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

   deflateInit is used instead.

     For the current implementation of deflate(), a windowBits value of 8 (a

   window size of 256 bytes) is not supported.  As a result, a request for 8

   will result in 9 (a 512-byte window).  In that case, providing 8 to

   inflateInit2() will result in an error when the zlib header with 9 is

   checked against the initialization of inflate().  The remedy is to not use 8

   with deflateInit2() with this initialization, or at least in that case use 9

   with inflateInit2().

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

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

   with no zlib header or trailer, and will not compute a check value.

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

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

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

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

   header crc, and the operating system will be set to the appropriate value,

   if the operating system was determined at compile time.  If a gzip stream is

   being written, strm->adler is a CRC-32 instead of an Adler-32.

     For raw deflate or gzip encoding, a request for a 256-byte window is

   rejected as invalid, since only the zlib header provides a means of

   transmitting the window size to the decompressor.

     The memLevel parameter specifies how much memory should be allocated

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

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

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

   as a function of windowBits and memLevel.

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

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

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

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

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

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

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

   coding and less string matching; it is somewhat intermediate between

   Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as

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

   strategy parameter only affects the compression ratio but not the

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

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

   decoder for special applications.

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

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

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

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

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

   compression: this will be done by deflate().

*/

ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,

                                             const Bytef *dictionary,

                                             uInt  dictLength));

/*

     Initializes the compression dictionary from the given byte sequence

   without producing any compressed output.  When using the zlib format, this

   function must be called immediately after deflateInit, deflateInit2 or

   deflateReset, and before any call of deflate.  When doing raw deflate, this

   function must be called either before any call of deflate, or immediately

   after the completion of a deflate block, i.e. after all input has been

   consumed and all output has been delivered when using any of the flush

   options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The

   compressor and decompressor must use exactly the same dictionary (see

   inflateSetDictionary).

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

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

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

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

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

   with the default empty dictionary.

     Depending on the size of the compression data structures selected by

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

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

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

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

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

   size minus 262 bytes of the provided dictionary.

     Upon return of this function, strm->adler is set to the Adler-32 value

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

   which dictionary has been used by the compressor.  (The Adler-32 value

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

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

   Adler-32 value is not computed and strm->adler is not set.

     deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a

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

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

   or if not at a block boundary for raw deflate).  deflateSetDictionary does

   not perform any compression: this will be done by deflate().

*/

ZEXTERN int ZEXPORT deflateGetDictionary OF((z_streamp strm,

                                             Bytef *dictionary,

                                             uInt  *dictLength));

/*

     Returns the sliding dictionary being maintained by deflate.  dictLength is

   set to the number of bytes in the dictionary, and that many bytes are copied

   to dictionary.  dictionary must have enough space, where 32768 bytes is

   always enough.  If deflateGetDictionary() is called with dictionary equal to

   Z_NULL, then only the dictionary length is returned, and nothing is copied.

   Similary, if dictLength is Z_NULL, then it is not set.

     deflateGetDictionary() may return a length less than the window size, even

   when more than the window size in input has been provided. It may return up

   to 258 bytes less in that case, due to how zlib's implementation of deflate

   manages the sliding window and lookahead for matches, where matches can be

   up to 258 bytes long. If the application needs the last window-size bytes of

   input, then that would need to be saved by the application outside of zlib.

     deflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the

   stream state is inconsistent.

*/

ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,

                                    z_streamp source));

/*

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

     This function can be useful when several compression strategies will be

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

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

   by calling deflateEnd.  Note that deflateCopy duplicates the internal

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

   consume lots of memory.

     deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not

   enough memory, Z_STREAM_ERROR if the source stream state was inconsistent

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

   destination.

*/

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

/*

     This function is equivalent to deflateEnd followed by deflateInit, but

   does not free and reallocate the internal compression state.  The stream

   will leave the compression level and any other attributes that may have been

   set unchanged.

     deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source

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

*/

ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,

                                      int level,

                                      int strategy));

/*

     Dynamically update the compression level and compression strategy.  The

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

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

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

   If the compression approach (which is a function of the level) or the

   strategy is changed, and if any input has been consumed in a previous

   deflate() call, then the input available so far is compressed with the old

   level and strategy using deflate(strm, Z_BLOCK).  There are three approaches

   for the compression levels 0, 1..3, and 4..9 respectively.  The new level

   and strategy will take effect at the next call of deflate().

     If a deflate(strm, Z_BLOCK) is performed by deflateParams(), and it does

   not have enough output space to complete, then the parameter change will not

   take effect.  In this case, deflateParams() can be called again with the

   same parameters and more output space to try again.

     In order to assure a change in the parameters on the first try, the

   deflate stream should be flushed using deflate() with Z_BLOCK or other flush

   request until strm.avail_out is not zero, before calling deflateParams().

   Then no more input data should be provided before the deflateParams() call.

   If this is done, the old level and strategy will be applied to the data

   compressed before deflateParams(), and the new level and strategy will be

   applied to the the data compressed after deflateParams().

     deflateParams returns Z_OK on success, Z_STREAM_ERROR if the source stream

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

   there was not enough output space to complete the compression of the

   available input data before a change in the strategy or approach.  Note that

   in the case of a Z_BUF_ERROR, the parameters are not changed.  A return

   value of Z_BUF_ERROR is not fatal, in which case deflateParams() can be

   retried with more output space.

*/

ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,

                                    int good_length,

                                    int max_lazy,

                                    int nice_length,

                                    int max_chain));

/*

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

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

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

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

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

   max_lazy, good_length, nice_length, and max_chain parameters.

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

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

 */

ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,

                                       uLong sourceLen));

/*

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

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

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

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

   called before deflate().  If that first deflate() call is provided the

   sourceLen input bytes, an output buffer allocated to the size returned by

   deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed

   to return Z_STREAM_END.  Note that it is possible for the compressed size to

   be larger than the value returned by deflateBound() if flush options other

   than Z_FINISH or Z_NO_FLUSH are used.

*/

ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm,

                                       unsigned *pending,

                                       int *bits));

/*

     deflatePending() returns the number of bytes and bits of output that have

   been generated, but not yet provided in the available output.  The bytes not

   provided would be due to the available output space having being consumed.

   The number of bits of output not provided are between 0 and 7, where they

   await more bits to join them in order to fill out a full byte.  If pending

   or bits are Z_NULL, then those values are not set.

     deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source

   stream state was inconsistent.

 */

ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,

                                     int bits,

                                     int value));

/*

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

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

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

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

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

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

   will be inserted in the output.

     deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough

   room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the

   source stream state was inconsistent.

*/

ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,

                                         gz_headerp head));

/*

     deflateSetHeader() provides gzip header information for when a gzip

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

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

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

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

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

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

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

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

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

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

   gzip file" and give up.

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

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

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

     deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source

   stream state was inconsistent.

*/

/*

ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,

                                     int  windowBits));

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

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

   before by the caller.

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

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

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

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

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

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

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

   Z_DATA_ERROR instead of trying to allocate a larger window.

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

   the zlib header of the compressed stream.

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

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

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

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

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

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

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

   recommended that a check value such as an Adler-32 or a CRC-32 be applied to

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

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

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

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

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

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

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

   CRC-32 instead of an Adler-32.  Unlike the gunzip utility and gzread() (see

   below), inflate() will not automatically decode concatenated gzip streams.

   inflate() will return Z_STREAM_END at the end of the gzip stream.  The state

   would need to be reset to continue decoding a subsequent gzip stream.

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

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

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

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

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

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

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

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

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

   deferred until inflate() is called.

*/

ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,

                                             const Bytef *dictionary,

                                             uInt  dictLength));

/*

     Initializes the decompression dictionary from the given uncompressed byte

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

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

   can be determined from the Adler-32 value returned by that call of inflate.

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

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

   time to set the dictionary.  If the provided dictionary is smaller than the

   window and there is already data in the window, then the provided dictionary

   will amend what's there.  The application must insure that the dictionary

   that was used for compression is provided.

     inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a

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

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

   expected one (incorrect Adler-32 value).  inflateSetDictionary does not

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

   inflate().

*/

ZEXTERN int ZEXPORT inflateGetDictionary OF((z_streamp strm,

                                             Bytef *dictionary,

                                             uInt  *dictLength));

/*

     Returns the sliding dictionary being maintained by inflate.  dictLength is

   set to the number of bytes in the dictionary, and that many bytes are copied

   to dictionary.  dictionary must have enough space, where 32768 bytes is

   always enough.  If inflateGetDictionary() is called with dictionary equal to

   Z_NULL, then only the dictionary length is returned, and nothing is copied.

   Similary, if dictLength is Z_NULL, then it is not set.

     inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the

   stream state is inconsistent.

*/

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

/*

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

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

   available input is skipped.  No output is provided.

     inflateSync searches for a 00 00 FF FF pattern in the compressed data.

   All full flush points have this pattern, but not all occurrences of this

   pattern are full flush points.

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

   Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point

   has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.

   In the success case, the application may save the current current value of

   total_in which indicates where valid compressed data was found.  In the

   error case, the application may repeatedly call inflateSync, providing more

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

*/

ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,

                                    z_streamp source));

/*

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

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

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

   allowing restarting inflate at those points when randomly accessing the

   stream.

     inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not

   enough memory, Z_STREAM_ERROR if the source stream state was inconsistent

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

   destination.

*/

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

/*

     This function is equivalent to inflateEnd followed by inflateInit,

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

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

     inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source

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

*/

ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,

                                      int windowBits));

/*

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

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

   the same as it is for inflateInit2.  If the window size is changed, then the

   memory allocated for the window is freed, and the window will be reallocated

   by inflate() if needed.

     inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source

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

   the windowBits parameter is invalid.

*/

ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,

                                     int bits,

                                     int value));

/*

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

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

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

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

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

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

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

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

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

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

   to feeding inflate codes.

     inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source

   stream state was inconsistent.

*/

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

/*

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

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

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

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

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

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

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

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

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

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

   code.

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

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

   more output space to write the literal or match data.

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

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

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

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

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

     inflateMark returns the value noted above, or -65536 if the provided

   source stream state was inconsistent.

*/

ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,

                                         gz_headerp head));

/*

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

   provided gz_header structure.  inflateGetHeader() may be called after

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

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

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

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

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

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

   complete and before any actual data is decompressed.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

   elsewhere so that they can be eventually freed.

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

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

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

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

   retrieve the header from the next gzip stream.

     inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source

   stream state was inconsistent.

*/

/*

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

                                        unsigned char FAR *window));

     Initialize the internal stream state for decompression using inflateBack()

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

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

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

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

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

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

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

   deflate streams.

     See inflateBack() for the usage of these routines.

     inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of

   the parameters are invalid, Z_MEM_ERROR if the internal state could not be

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

   the version of the header file.

*/

typedef unsigned (*in_func) OF((void FAR *,

                                z_const unsigned char FAR * FAR *));

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

ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,

                                    in_func in, void FAR *in_desc,

                                    out_func out, void FAR *out_desc));

/*

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

   interface for input and output.  This is potentially more efficient than

   inflate() for file i/o applications, in that it avoids copying between the

   output and the sliding window by simply making the window itself the output

   buffer.  inflate() can be faster on modern CPUs when used with large

   buffers.  inflateBack() trusts the application to not change the output

   buffer passed by the output function, at least until inflateBack() returns.

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

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

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

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

   allocated state.

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

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

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

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

   the raw deflate stream to decompress.  This is different from the default

   behavior of inflate(), which expects a zlib header and trailer around the

   deflate stream.

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

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

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

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

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

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

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

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

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

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

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

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

   out() are permitted to change the contents of the window provided to

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

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

   amount of input may be provided by in().

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