{** TZStreamRec ***********************************************************}

  TZStreamRec = packed record
    next_in  : PChar;     // next input byte
    avail_in : Longint;   // number of bytes available at next_in
    total_in : Longint;   // total nb of input bytes read so far

    next_out : PChar;     // next output byte should be put here
    avail_out: Longint;   // remaining free space at next_out
    total_out: Longint;   // total nb of bytes output so far

    msg      : PChar;     // last error message, NULL if no error
    state    : Pointer;   // not visible by applications

    zalloc   : TZAlloc;   // used to allocate the internal state
    zfree    : TZFree;    // used to free the internal state
    opaque   : Pointer;   // private data object passed to zalloc and zfree

    data_type: Integer;   // best guess about the data type: ascii or binary
    adler    : Longint;   // adler32 value of the uncompressed data
    reserved : Longint;   // reserved for future use
  end;

procedure ZDecompress(const inBuffer: Pointer; inSize: Integer;
 out outBuffer: Pointer; out outSize: Integer; outEstimate: Integer = 0);


function ZDecompressCheck(code: Integer): Integer;
begin
  Result := code;

  if code < 0 then
  begin
     raise EZDecompressionError.Create(_z_errmsg[2 - code];
  end;
end;


{*****************************************************************************
*  ZDecompress                                                               *
*                                                                            *
*  pre-conditions                                                            *
*    inBuffer    = pointer to compressed data                                *
*    inSize      = size of inBuffer (bytes)                                  *
*    outBuffer   = pointer (unallocated)                                     *
*    outEstimate = estimated size of uncompressed data (bytes)               *
*                                                                            *
*  post-conditions                                                           *
*    outBuffer = pointer to decompressed data (allocated)                    *
*    outSize   = size of outBuffer (bytes)                                   *
*****************************************************************************}

procedure ZDecompress(const inBuffer: Pointer; inSize: Integer;
  out outBuffer: Pointer; out outSize: Integer; outEstimate: Integer);
var
  zstream: TZStreamRec;
  delta  : Integer;
begin
  FillChar(zstream,SizeOf(TZStreamRec),0);

  delta := (inSize + 255) and not 255;

  if outEstimate = 0 then outSize := delta
  else outSize := outEstimate;

  GetMem(outBuffer,outSize);

  try
    zstream.next_in := inBuffer;
    zstream.avail_in := inSize;
    zstream.next_out := outBuffer;
    zstream.avail_out := outSize;

    ZDecompressCheck(InflateInit(zstream));

    try
      while ZDecompressCheck(inflate(zstream,Z_NO_FLUSH)) <> Z_STREAM_END do
      begin
        Inc(outSize,delta);
        ReallocMem(outBuffer,outSize);

        zstream.next_out := PChar(Integer(outBuffer) + zstream.total_out);
        zstream.avail_out := delta;
      end;
    finally
      ZDecompressCheck(inflateEnd(zstream));
    end;

    ReallocMem(outBuffer,zstream.total_out);
    outSize := zstream.total_out;
  except
    FreeMem(outBuffer);
    raise;
  end;
end;

type
  TZAlloc = function (opaque: Pointer; items, size: Integer): Pointer;
  TZFree  = procedure (opaque, block: Pointer);

  TZCompressionLevel = (zcNone, zcFastest, zcDefault, zcMax);

  {** TZStreamRec ***********************************************************}

  TZStreamRec = packed record
    next_in  : PChar;     // next input byte
    avail_in : Longint;   // number of bytes available at next_in
    total_in : Longint;   // total nb of input bytes read so far

    next_out : PChar;     // next output byte should be put here
    avail_out: Longint;   // remaining free space at next_out
    total_out: Longint;   // total nb of bytes output so far

    msg      : PChar;     // last error message, NULL if no error
    state    : Pointer;   // not visible by applications

    zalloc   : TZAlloc;   // used to allocate the internal state
    zfree    : TZFree;    // used to free the internal state
    opaque   : Pointer;   // private data object passed to zalloc and zfree

    data_type: Integer;   // best guess about the data type: ascii or binary
    adler    : Longint;   // adler32 value of the uncompressed data
    reserved : Longint;   // reserved for future use
  end;

typedef struct z_stream_s {
    Bytef    *next_in;  /* next input byte */
    uInt     avail_in;  /* number of bytes available at next_in */
    uLong    total_in;  /* total nb of input bytes read so far */

    Bytef    *next_out; /* next output byte should be put there */
    uInt     avail_out; /* remaining free space at next_out */
    uLong    total_out; /* total nb of bytes output so far */

    char     *msg;      /* last error message, NULL if no error */
    struct internal_state FAR *state; /* not visible by applications */

    alloc_func zalloc;  /* used to allocate the internal state */
    free_func  zfree;   /* used to free the internal state */
    voidpf     opaque;  /* private data object passed to zalloc and zfree */

    int     data_type;  /* best guess about the data type: ascii or binary */
    uLong   adler;      /* adler32 value of the uncompressed data */
    uLong   reserved;   /* reserved for future use */
} z_stream ;