zlibh.pas

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   the uncompressed data and may be saved for use in the decompressor
   (particularly if the decompressor wants to decompress everything in
   a single step).
*}

                        {* constants *}

const
  {$EXTERNALSYM Z_NO_FLUSH}
  Z_NO_FLUSH      = 0;
  {$EXTERNALSYM Z_PARTIAL_FLUSH}
  Z_PARTIAL_FLUSH = 1; // will be removed, use Z_SYNC_FLUSH instead
  {$EXTERNALSYM Z_SYNC_FLUSH}
  Z_SYNC_FLUSH    = 2;
  {$EXTERNALSYM Z_FULL_FLUSH}
  Z_FULL_FLUSH    = 3;
  {$EXTERNALSYM Z_FINISH}
  Z_FINISH        = 4;
  {$EXTERNALSYM Z_BLOCK}
  Z_BLOCK         = 5;

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

  {$EXTERNALSYM Z_OK}
  Z_OK            = 0;
  {$EXTERNALSYM Z_STREAM_END}
  Z_STREAM_END    = 1;
  {$EXTERNALSYM Z_NEED_DICT}
  Z_NEED_DICT     = 2;
  {$EXTERNALSYM Z_ERRNO}
  Z_ERRNO        = -1;
  {$EXTERNALSYM Z_STREAM_ERROR}
  Z_STREAM_ERROR = -2;
  {$EXTERNALSYM Z_DATA_ERROR}
  Z_DATA_ERROR   = -3;
  {$EXTERNALSYM Z_MEM_ERROR}
  Z_MEM_ERROR    = -4;
  {$EXTERNALSYM Z_BUF_ERROR}
  Z_BUF_ERROR    = -5;
  {$EXTERNALSYM Z_VERSION_ERROR}
  Z_VERSION_ERROR = -6;
{* Return codes for the compression/decompression functions. Negative
 * values are errors, positive values are used for special but normal events.
 *}

  {$EXTERNALSYM Z_NO_COMPRESSION}
  Z_NO_COMPRESSION       = 0;
  {$EXTERNALSYM Z_BEST_SPEED}
  Z_BEST_SPEED           = 1;
  {$EXTERNALSYM Z_BEST_COMPRESSION}
  Z_BEST_COMPRESSION     = 9;
  {$EXTERNALSYM Z_DEFAULT_COMPRESSION}
  Z_DEFAULT_COMPRESSION = -1;

{* compression levels *}

  {$EXTERNALSYM Z_FILTERED}
  Z_FILTERED           = 1;
  {$EXTERNALSYM Z_HUFFMAN_ONLY}
  Z_HUFFMAN_ONLY       = 2;
  {$EXTERNALSYM Z_RLE}
  Z_RLE                = 3;
  {$EXTERNALSYM Z_DEFAULT_STRATEGY}
  Z_DEFAULT_STRATEGY   = 0;
{* compression strategy; see deflateInit2() below for details *}

  {$EXTERNALSYM Z_BINARY}
  Z_BINARY  = 0;
  {$EXTERNALSYM Z_ASCII}
  Z_ASCII   = 1;
  {$EXTERNALSYM Z_UNKNOWN}
  Z_UNKNOWN = 2;
{* Possible values of the data_type field (though see inflate()) *}

  {$EXTERNALSYM Z_DEFLATED}
  Z_DEFLATED  = 8;
{* The deflate compression method (the only one supported in this version) *}

  {$EXTERNALSYM Z_NULL}
  Z_NULL  = 0;  {* for initializing zalloc, zfree, opaque *}

{* for compatibility with versions < 1.0.2 *}

                        {* basic functions *}

{$EXTERNALSYM zlibVersion}
function zlibVersion(): PChar;
{$IFDEF ZEXPORT_CDECL} cdecl; {$ENDIF}
{* 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.
 *}

{$EXTERNALSYM deflateInit}
function deflateInit(var strm: TZStreamRec; level: Integer): Integer; // macro
{*
     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,
   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().
*}

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

    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.

    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
  the 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). If deflate does not return
  Z_STREAM_END, then 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 data_type if it can make a good guess about
  the input data type (Z_ASCII or Z_BINARY). 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 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.
*}

{$EXTERNALSYM deflateEnd}
function deflateEnd(var strm: TZStreamRec): Integer;
{$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.

     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).
*}

{$EXTERNALSYM inflateInit}
function inflateInit(var strm: TZStreamRec): Integer; // macro
{*

     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.  msg is set to null if there is no error
   message. inflateInit 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 inflate}
function inflate(strm: TZStreamRec; flush: Integer): Integer;
{*
    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, or Z_BLOCK. 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 get 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.

    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