zlibh.pas

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  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 the
  uncompressed data. (The size of the uncompressed data may have been saved
  by the compressor for this purpose.) The next operation on this stream must
  be inflateEnd to deallocate the decompression state. The use of Z_FINISH
  is never required, but can be used to inform inflate that a faster approach
  may be used for the single inflate() call.

     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 only effect of the flush parameter in this implementation
  is on the return value of inflate(), as noted below, or when it returns early
  because Z_BLOCK is used.

     If a preset dictionary is needed after this call (see inflateSetDictionary
  below), inflate sets strm-adler to the adler32 checksum of the dictionary
  chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
  strm->adler to the adler32 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() will decompress and check either zlib-wrapped or gzip-wrapped
  deflate data.  The header type is detected automatically.  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.

    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
  if next_in or next_out was 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.
*}

{$EXTERNALSYM inflateEnd}
function inflateEnd(var strm: TZStreamRec): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     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.
*}

{$EXTERNALSYM deflateInit2}
function deflateInit2(var strm: TZStreamRec;
                      level: Integer;
                      method: Integer;
                      windowBits: Integer;
                      memLevel: Integer;
                      strategy: Integer): Integer; // macro
{*
     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).

     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 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.

      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
   memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
   method). msg is set to null if there is no error message.  deflateInit2 does
   not perform any compression: this will be done by deflate().
*}

{$EXTERNALSYM deflateSetDictionary}
function deflateSetDictionary(var strm: TZStreamRec;
                              {const} dictionary: PBytef;
                              dictLength:uInt): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     Initializes the compression dictionary from the given byte sequence
   without producing any compressed output. This function must be called
   immediately after deflateInit, deflateInit2 or deflateReset, before any
   call of deflate. 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 in
   deflate or deflate2. Thus the strings most likely to be useful should be
   put at the end of the dictionary, not at the front.

     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 (such as NULL dictionary) or the stream state is
   inconsistent (for example if deflate has already been called for this stream
   or if the compression method is bsort). deflateSetDictionary does not
   perform any compression: this will be done by deflate().
*}

{$EXTERNALSYM deflateCopy}
function deflateCopy(var dest: TZStreamRec;
                     var source: TZStreamRec): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     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 NULL). msg is left unchanged in both source and
   destination.
*}

{$EXTERNALSYM deflateReset}
function deflateReset(var strm: TZStreamRec): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     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 NULL).
*}

{$EXTERNALSYM deflateParams}
function deflateParams(var strm: TZStreamRec;
                       level: Integer;
                       strategy: Integer): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     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.
*}

{$EXTERNALSYM deflateBound}
function deflateBound(var strm: TZStreamRec;
                      sourceLen:uLong):uLong;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     deflateBound() returns an upper bound on the compressed size after
   deflation of sourceLen bytes.  It must be called after deflateInit()
   or deflateInit2().  This would be used to allocate an output buffer
   for deflation in a single pass, and so would be called before deflate().
*}

{$EXTERNALSYM deflatePrime}
function deflatePrime(var strm: TZStreamRec;
                      bits: Integer;
                      value: Integer): Integer;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{*
     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, or Z_STREAM_ERROR if the source
   stream state was inconsistent.
*}

{$EXTERNALSYM inflateInit2}
function inflateInit2(var strm: TZStreamRec;
                      windowBits: Integer): Integer; // macro
{*
     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 -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).

     inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
   memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
   memLevel). msg is set to null if there is no error message.  inflateInit2
   does not perform any decompression apart from reading the zlib header if
   present: this will be done by inflate(). (So next_in and avail_in may be
   modified, but next_out and avail_out are unchanged.)
*}

{$EXTERNALSYM inflateSetDictionary}
function inflateSetDictionary(var strm: TZStreamRec;
                              {const} dictionary: PBytef;