spzlib.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). }

const  { constants }
   Z_NO_FLUSH      = 0;
   Z_PARTIAL_FLUSH = 1;
   Z_SYNC_FLUSH    = 2;
   Z_FULL_FLUSH    = 3;
   Z_FINISH        = 4;
{ Allowed flush values; see deflate() below for details }

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

   Z_NO_COMPRESSION         = 0;
   Z_BEST_SPEED             = 1;
   Z_BEST_COMPRESSION       = 9;
   Z_DEFAULT_COMPRESSION    = (-1);
{ compression levels }

   Z_FILTERED            = 1;
   Z_HUFFMAN_ONLY        = 2;
   Z_DEFAULT_STRATEGY    = 0;
{ compression strategy; see deflateInit2() below for details }

   Z_BINARY   = 0;
   Z_ASCII    = 1;
   Z_UNKNOWN  = 2;
{ Possible values of the data_type field }

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

   Z_NULL  = NIL;  { for initializing zalloc, zfree, opaque }

  {$IFDEF GZIO}
var
  errno : int;
  {$ENDIF}

        { common constants }


{ The three kinds of block type }
const
  STORED_BLOCK = 0;
  STATIC_TREES = 1;
  DYN_TREES = 2;
{ The minimum and maximum match lengths }
const
  MIN_MATCH = 3;
{$ifdef MAX_MATCH_IS_258}
  MAX_MATCH = 258;
{$else}
  MAX_MATCH = ??;    { deliberate syntax error }
{$endif}

  MIN_LOOKAHEAD = (MAX_MATCH+MIN_MATCH+1);

const
  PRESET_DICT = $20; { preset dictionary flag in zlib header }

  procedure Trace(x : string);
  procedure Tracev(x : string);
  procedure Tracevv(x : string);
  procedure Tracevvv(x : string);
  procedure Tracec(c : boolean; x : string);
  procedure Tracecv(c : boolean; x : string);

function zlibVersion : string;
{ 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. }

function zError(err : int) : string;

function ZALLOC (var strm : z_stream; items : uInt; size : uInt) : voidpf;

procedure ZFREE (var strm : z_stream; ptr : voidpf);

procedure TRY_FREE (var strm : z_stream; ptr : voidpf);

const
  ZLIB_VERSION : string[10] = '1.1.2';

const
  z_errbase = Z_NEED_DICT;
  z_errmsg : Array[0..9] of string[21] = { indexed by 2-zlib_error }
           ('need dictionary',     { Z_NEED_DICT       2  }
            'stream end',          { Z_STREAM_END      1  }
            '',                    { Z_OK              0  }
            'file error',          { Z_ERRNO         (-1) }
            'stream error',        { Z_STREAM_ERROR  (-2) }
            'data error',          { Z_DATA_ERROR    (-3) }
            'insufficient memory', { Z_MEM_ERROR     (-4) }
            'buffer error',        { Z_BUF_ERROR     (-5) }
            'incompatible version',{ Z_VERSION_ERROR (-6) }
            '');
const
  z_verbose : int = 1;

function adler32(adler : uLong; buf : pBytef; len : uInt) : uLong;

{    Update a running Adler-32 checksum with the bytes buf[0..len-1] and
   return the updated checksum. If buf is NIL, this function returns
   the required initial value for the checksum.
   An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
   much faster. Usage example:

   var
     adler : uLong;
   begin
     adler := adler32(0, Z_NULL, 0);

     while (read_buffer(buffer, length) <> EOF) do
       adler := adler32(adler, buffer, length);

     if (adler <> original_adler) then
       error();
   end;
}


{ Orginal: deflate.h -- internal compression state
           deflate.c -- compress data using the deflation algorithm
  Copyright (C) 1995-1996 Jean-loup Gailly.

  Pascal tranlastion
  Copyright (C) 1998 by Jacques Nomssi Nzali
  For conditions of distribution and use, see copyright notice in readme.txt
}


{  ALGORITHM

       The "deflation" process depends on being able to identify portions
       of the input text which are identical to earlier input (within a
       sliding window trailing behind the input currently being processed).

       The most straightforward technique turns out to be the fastest for
       most input files: try all possible matches and select the longest.
       The key feature of this algorithm is that insertions into the string
       dictionary are very simple and thus fast, and deletions are avoided
       completely. Insertions are performed at each input character, whereas
       string matches are performed only when the previous match ends. So it
       is preferable to spend more time in matches to allow very fast string
       insertions and avoid deletions. The matching algorithm for small
       strings is inspired from that of Rabin & Karp. A brute force approach
       is used to find longer strings when a small match has been found.
       A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
       (by Leonid Broukhis).
          A previous version of this file used a more sophisticated algorithm
       (by Fiala and Greene) which is guaranteed to run in linear amortized
       time, but has a larger average cost, uses more memory and is patented.
       However the F&G algorithm may be faster for some highly redundant
       files if the parameter max_chain_length (described below) is too large.

   ACKNOWLEDGEMENTS

       The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
       I found it in 'freeze' written by Leonid Broukhis.
       Thanks to many people for bug reports and testing.

   REFERENCES

       Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
       Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc

       A description of the Rabin and Karp algorithm is given in the book
          "Algorithms" by R. Sedgewick, Addison-Wesley, p252.

       Fiala,E.R., and Greene,D.H.
          Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595}

function deflateInit_(strm : z_streamp;
                      level : int;
                      const version : string;
                      stream_size : int) : int;


function deflateInit (var strm : z_stream; level : int) : int;

{  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(). }


{EXPORT}
function deflate (var strm : z_stream; flush : int) : int;

{ 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_PARTIAL_FLUSH, the current compression
  block is terminated and flushed to the output buffer so that the
  decompressor can get all input data available so far. For method 9, a future
  variant on method 8, the current block will be flushed but not terminated.
  Z_SYNC_FLUSH has the same effect as partial flush except that the compressed
  output is byte aligned (the compressor can clear its internal bit buffer)
  and the current block is always terminated; this can be useful if the
  compressor has to be restarted from scratch after an interruption (in which
  case the internal state of the compressor may be lost).
    If flush is set to Z_FULL_FLUSH, the compression block is terminated, a
  special marker is output and the compression dictionary is discarded; this
  is useful to allow the decompressor to synchronize if one compressed block
  has been damaged (see inflateSync below).  Flushing degrades compression and
  so should be used only when necessary.  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).

    If the parameter flush is set to Z_FINISH, all pending input is processed,
  all 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
  0.1% larger than avail_in plus 12 bytes.  If deflate does not return
  Z_STREAM_END, then it must be called again as described above.

    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. }


function deflateEnd (var strm : z_stream) : int;

{     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). }




                        { Advanced functions }

{ The following functions are needed only in some special applications. }


{EXPORT}
function deflateInit2 (var strm : z_stream;
                       level : int;
                       method : int;
                       windowBits : int;
                       memLevel : int;
                       strategy : int) : int;

{  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. (Method 9 will allow a 64K history buffer and
   partial block flushes.)

     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 (the value 16 will be allowed for method 9). 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.

     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), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
   string match).  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. The strategy parameter only affects
   the compression ratio but not the correctness of the compressed output even
   if it is not set appropriately.

     If next_in is not null, the library will use this buffer to hold also
   some history information; the buffer must either hold the entire input
   data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in
   is null, the library will allocate its own history buffer (and leave next_in
   null). next_out need not be provided here but must be provided by the
   application for the next call of deflate().

     If the history buffer is provided by the application, next_in must
   must never be changed by the application since the compressor maintains
   information inside this buffer from call to call; the application
   must provide more input only by increasing avail_in. next_in is always
   reset by the library in this case.

      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(). }


{EXPORT}
function deflateSetDictionary (var strm : z_stream;