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zlib.inc -- interface of the 'zlib' general purpose compression library

  version 1.2.8, April 28th, 2013

  Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler

 basic functions

const char * 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.

int 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().

int 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().

  - Provide 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 (in interactive applications).  Some

    output may be provided even if flush is not set.

    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.

    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 code

  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, 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 immediately after deflateInit if all the compression

  is to be done in a single step.  In this case, 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 adler32 checksum of all input read

  so far (that is, total_in bytes).

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

  the input data type (Z_BINARY or Z_TEXT).  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), 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.

int 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).

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

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

   compression method from the zlib header and allocates all data structures

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

   inflate.  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

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

   until inflate() is called.

int 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), next_in is updated and processing will

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

  - Provide 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.  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.

  Also to assist in this, on return inflate() will set 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 adler32

  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, so applications that need that information should

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

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

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

  producted so far.  The CRC-32 is checked against the gzip trailer.

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

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

  Z_BUF_ERROR if no progress is 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 desired.

int 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, Z_STREAM_ERROR if the stream state

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

   static string (which must not be deallocated).

 Advanced functions

    The following functions are needed only in some special applications.

int 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.

     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 an adler32 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 255 (unknown).  If a

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

     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().

int 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 adler32 value

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

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

   adler32 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().

int 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.

int deflateReset OF((z_streamp strm));

     This function is equivalent to deflateEnd followed by deflateInit,

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

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

   may have been set by deflateInit2.

     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).

int 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 level is changed, the input available so far is

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

   effect only at the next call of deflate().

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

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

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

     deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source

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

   strm->avail_out was zero.

int 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.

uLong 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.

int 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.

int 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.

int 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.

int 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 adler32 or a crc32 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

   crc32 instead of an adler32.

     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.

int 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 adler32 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 adler32 value).  inflateSetDictionary does not

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

   inflate().

int 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.

int 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.

int 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.

int inflateReset OF((z_streamp strm));

     This function is equivalent to inflateEnd followed by inflateInit,

   but does not free and reallocate all 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).

int 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.

     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.

int 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.

long 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 -1 << 16 if the provided

   source stream state was inconsistent.

int 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.

int 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));

int 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 normal

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

   cannot return Z_OK.

int inflateBackEnd OF((z_streamp strm));

     All memory allocated by inflateBackInit() is freed.

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

   state was inconsistent.

uLong zlibCompileFlags OF((void));

 Return flags indicating compile-time options.

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

     1.0: size of uInt

     3.2: size of uLong

     5.4: size of voidpf (pointer)

     7.6: size of z_off_t

    Compiler, assembler, and debug options:

     8: DEBUG

     9: ASMV or ASMINF -- use ASM code

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

     11: 0 (reserved)

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

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

     13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed

     14,15: 0 (reserved)

    Library content (indicates missing functionality):

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

                          deflate code when not needed)

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

                    and decode gzip streams (to avoid linking crc code)

     18-19: 0 (reserved)

    Operation variations (changes in library functionality):

     20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate

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

     22,23: 0 (reserved)

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

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

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

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

    Remainder:

     27-31: 0 (reserved)

#ifndef Z_SOLO

                         utility functions

     The following utility functions are implemented on top of the basic

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

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

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

   you need special options.

int compress OF((Bytef *dest,   uLongf *destLen,

                                 const Bytef *source, uLong sourceLen));

     Compresses the source buffer into the destination buffer.  sourceLen is

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

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

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

   compressed buffer.

     compress returns Z_OK if success, Z_MEM_ERROR if there was not

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

   buffer.

int compress2 OF((Bytef *dest,   uLongf *destLen,

                                  const Bytef *source, uLong sourceLen,

                                  int level));

     Compresses the source buffer into the destination buffer.  The level

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

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

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

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

   compressed buffer.

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

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

   Z_STREAM_ERROR if the level parameter is invalid.

uLong compressBound OF((uLong sourceLen));

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

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

   compress() or compress2() call to allocate the destination buffer.

int uncompress OF((Bytef *dest,   uLongf *destLen,

                                   const Bytef *source, uLong sourceLen));

     Decompresses the source buffer into the destination buffer.  sourceLen is

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

   of the destination buffer, which must be large enough to hold the entire

   uncompressed data.  (The size of the uncompressed data must have been saved

   previously by the compressor and transmitted to the decompressor by some

   mechanism outside the scope of this compression library.) Upon exit, destLen

   is the actual size of the uncompressed buffer.

     uncompress returns Z_OK if success, Z_MEM_ERROR if there was not

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

   buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In

   the case where there is not enough room, uncompress() will fill the output

   buffer with the uncompressed data up to that point.

                         gzip file access functions

     This library 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.

typedef struct gzFile_s *gzFile;    ;semi-opaque gzip file descriptor

gzFile gzopen OF((const char *path, const char *mode));

     Opens a gzip (.gz) file for reading or writing.  The mode parameter is as

   in fopen ("rb" or "wb") but can also include a compression level ("wb9") or

   a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman-only

   compression as in "wb1h", 'R' for run-length encoding as in "wb1R", or 'F'

   for fixed code compression as in "wb9F".  (See the description of

   deflateInit2 for more information about the strategy parameter.)  'T' will

   request transparent writing or appending with no compression and not using

   the gzip format.

     "a" can be used instead of "w" to request that the gzip stream that will

   be written be appended to the file.  "+" will result in an error, since

   reading and writing to the same gzip file is not supported.  The addition of

   "x" when writing will create the file exclusively, which fails if the file

   already exists.  On systems that support it, the addition of "e" when

   reading or writing will set the flag to close the file on an execve() call.

     These functions, as well as gzip, will read and decode a sequence of gzip

   streams in a file.  The append function of gzopen() can be used to create

   such a file.  (Also see gzflush() for another way to do this.)  When

   appending, gzopen does not test whether the file begins with a gzip stream,

   nor does it look for the end of the gzip streams to begin appending.  gzopen

   will simply append a gzip stream to the existing file.

     gzopen can be used to read a file which is not in gzip format; in this

   case gzread will directly read from the file without decompression.  When

   reading, this will be detected automatically by looking for the magic two-

   byte gzip header.

     gzopen returns NULL if the file could not be opened, if there was

   insufficient memory to allocate the gzFile state, or if an invalid mode was

   specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).

   errno can be checked to determine if the reason gzopen failed was that the

   file could not be opened.

gzFile gzdopen OF((int fd, const char *mode));

     gzdopen associates a gzFile with the file descriptor fd.  File descriptors

   are obtained from calls like open, dup, creat, pipe or fileno (if the file

   has been previously opened with fopen).  The mode parameter is as in gzopen.

     The next call of gzclose on the returned gzFile will also close the file

   descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor

   fd.  If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,

   mode);.  The duplicated descriptor should be saved to avoid a leak, since

   gzdopen does not close fd if it fails.  If you are using fileno() to get the

   file descriptor from a FILE *, then you will have to use dup() to avoid

   double-close()ing the file descriptor.  Both gzclose() and fclose() will

   close the associated file descriptor, so they need to have different file

   descriptors.

     gzdopen returns NULL if there was insufficient memory to allocate the

   gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not

   provided, or '+' was provided), or if fd is -1.  The file descriptor is not

   used until the next gz* read, write, seek, or close operation, so gzdopen

   will not detect if fd is invalid (unless fd is -1).

int gzbuffer OF((gzFile file, unsigned size));

     Set the internal buffer size used by this library's functions.  The

   default buffer size is 8192 bytes.  This function must be called after

   gzopen() or gzdopen(), and before any other calls that read or write the

   file.  The buffer memory allocation is always deferred to the first read or

   write.  Two buffers are allocated, either both of the specified size when

   writing, or one of the specified size and the other twice that size when

   reading.  A larger buffer size of, for example, 64K or 128K bytes will

   noticeably increase the speed of decompression (reading).

     The new buffer size also affects the maximum length for gzprintf().

     gzbuffer() returns 0 on success, or -1 on failure, such as being called

   too late.

int gzsetparams OF((gzFile file, int level, int strategy));

     Dynamically update the compression level or strategy.  See the description

   of deflateInit2 for the meaning of these parameters.

     gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not

   opened for writing.

int gzread OF((gzFile file, voidp buf, unsigned len));

     Reads the given number of uncompressed bytes from the compressed file.  If

   the input file is not in gzip format, gzread copies the given number of

   bytes into the buffer directly from the file.

     After reaching the end of a gzip stream in the input, gzread will continue

   to read, looking for another gzip stream.  Any number of gzip streams may be

   concatenated in the input file, and will all be decompressed by gzread().

   If something other than a gzip stream is encountered after a gzip stream,

   that remaining trailing garbage is ignored (and no error is returned).

     gzread can be used to read a gzip file that is being concurrently written.

   Upon reaching the end of the input, gzread will return with the available

   data.  If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then

   gzclearerr can be used to clear the end of file indicator in order to permit

   gzread to be tried again.  Z_OK indicates that a gzip stream was completed

   on the last gzread.  Z_BUF_ERROR indicates that the input file ended in the

   middle of a gzip stream.  Note that gzread does not return -1 in the event

   of an incomplete gzip stream.  This error is deferred until gzclose(), which

   will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip

   stream.  Alternatively, gzerror can be used before gzclose to detect this

   case.

     gzread returns the number of uncompressed bytes actually read, less than

   len for end of file, or -1 for error.

int gzwrite OF((gzFile file,

                                voidpc buf, unsigned len));

     Writes the given number of uncompressed bytes into the compressed file.

   gzwrite returns the number of uncompressed bytes written or 0 in case of

   error.