
{******************************************}
{                                          }
{             FastReport v3.0              }
{         GZIP compress/decompress         }
{                                          }
{            Copyright (c) 2004            }
{          by Alexander Fediachov,         }
{             Fast Reports, Inc.           }
{                                          }
{******************************************}

unit frxGZip;

interface

{$I frx.inc}

uses Windows, Classes, SysUtils, frxZLib, frxClass;

type
  TfrxCompressionLevel = (gzNone, gzFastest, gzDefault, gzMax);

  TfrxGZipCompressor = class(TfrxCustomCompressor)
  public
    procedure Compress(Dest: TStream); override;
    procedure Decompress(Source: TStream); override;
  end;


procedure frxCompressStream(Source, Dest: TStream;
  Compression: TfrxCompressionLevel = gzDefault; FileName: String = '');
function frxDecompressStream(Source, Dest: TStream): String;
function frxStreamCRC32(Stream: TStream): Cardinal;
procedure frxDeflateStream(Source, Dest: TStream;
  Compression: TfrxCompressionLevel = gzDefault);
procedure frxInflateStream(Source, Dest: TStream);


implementation

const
  CRCTable: array [0..255] of Cardinal = (
 0000000000, 1996959894, 3993919788, 2567524794,
 0124634137, 1886057615, 3915621685, 2657392035,
 0249268274, 2044508324, 3772115230, 2547177864,
 0162941995, 2125561021, 3887607047, 2428444049,
 0498536548, 1789927666, 4089016648, 2227061214,
 0450548861, 1843258603, 4107580753, 2211677639,
 0325883990, 1684777152, 4251122042, 2321926636,
 0335633487, 1661365465, 4195302755, 2366115317,
 0997073096, 1281953886, 3579855332, 2724688242,
 1006888145, 1258607687, 3524101629, 2768942443,
 0901097722, 1119000684, 3686517206, 2898065728,
 0853044451, 1172266101, 3705015759, 2882616665,
 0651767980, 1373503546, 3369554304, 3218104598,
 0565507253, 1454621731, 3485111705, 3099436303,
 0671266974, 1594198024, 3322730930, 2970347812,
 0795835527, 1483230225, 3244367275, 3060149565,
 1994146192, 0031158534, 2563907772, 4023717930,
 1907459465, 0112637215, 2680153253, 3904427059,
 2013776290, 0251722036, 2517215374, 3775830040,
 2137656763, 0141376813, 2439277719, 3865271297,
 1802195444, 0476864866, 2238001368, 4066508878,
 1812370925, 0453092731, 2181625025, 4111451223,
 1706088902, 0314042704, 2344532202, 4240017532,
 1658658271, 0366619977, 2362670323, 4224994405,
 1303535960, 0984961486, 2747007092, 3569037538,
 1256170817, 1037604311, 2765210733, 3554079995,
 1131014506, 0879679996, 2909243462, 3663771856,
 1141124467, 0855842277, 2852801631, 3708648649,
 1342533948, 0654459306, 3188396048, 3373015174,
 1466479909, 0544179635, 3110523913, 3462522015,
 1591671054, 0702138776, 2966460450, 3352799412,
 1504918807, 0783551873, 3082640443, 3233442989,
 3988292384, 2596254646, 0062317068, 1957810842,
 3939845945, 2647816111, 0081470997, 1943803523,
 3814918930, 2489596804, 0225274430, 2053790376,
 3826175755, 2466906013, 0167816743, 2097651377,
 4027552580, 2265490386, 0503444072, 1762050814,
 4150417245, 2154129355, 0426522225, 1852507879,
 4275313526, 2312317920, 0282753626, 1742555852,
 4189708143, 2394877945, 0397917763, 1622183637,
 3604390888, 2714866558, 0953729732, 1340076626,
 3518719985, 2797360999, 1068828381, 1219638859,
 3624741850, 2936675148, 0906185462, 1090812512,
 3747672003, 2825379669, 0829329135, 1181335161,
 3412177804, 3160834842, 0628085408, 1382605366,
 3423369109, 3138078467, 0570562233, 1426400815,
 3317316542, 2998733608, 0733239954, 1555261956,
 3268935591, 3050360625, 0752459403, 1541320221,
 2607071920, 3965973030, 1969922972, 0040735498,
 2617837225, 3943577151, 1913087877, 0083908371,
 2512341634, 3803740692, 2075208622, 0213261112,
 2463272603, 3855990285, 2094854071, 0198958881,
 2262029012, 4057260610, 1759359992, 0534414190,
 2176718541, 4139329115, 1873836001, 0414664567,
 2282248934, 4279200368, 1711684554, 0285281116,
 2405801727, 4167216745, 1634467795, 0376229701,
 2685067896, 3608007406, 1308918612, 0956543938,
 2808555105, 3495958263, 1231636301, 1047427035,
 2932959818, 3654703836, 1088359270, 0936918000,
 2847714899, 3736837829, 1202900863, 0817233897,
 3183342108, 3401237130, 1404277552, 0615818150,
 3134207493, 3453421203, 1423857449, 0601450431,
 3009837614, 3294710456, 1567103746, 0711928724,
 3020668471, 3272380065, 1510334235, 0755167117);

function frxStreamCRC32(Stream: TStream): Cardinal;
var
  OldPos: Integer;
  b: Byte;
  c: Cardinal;
begin
  OldPos := Stream.Position;
  Stream.Position := 0;
  c := $ffffffff;
  while Stream.Position < Stream.Size do
  begin
    Stream.Read(b,1);
    c := CrcTable[(c xor Cardinal(b)) and $ff] xor (c shr 8);
  end;
  Stream.Position := OldPos;
  Result := c xor $ffffffff;
end;

procedure frxCompressStream(Source, Dest: TStream;
  Compression: TfrxCompressionLevel = gzDefault; FileName: String = '');
var
  header: array [0..3] of Byte;
  Compressor: TZCompressionStream;
  Size: Cardinal;
  CRC: Cardinal;
begin
  CRC := frxStreamCRC32(Source);
  Size := Source.Size;
  if FileName = '' then
    FileName := '1';
  FileName := FileName + #0;

  // put gzip header
  header[0] := $1f; // ID1 (IDentification 1)
  header[1] := $8b; // ID2 (IDentification 2)
  header[2] := $8;  // CM (Compression Method) CM = 8 denotes the "deflate"
  header[3] := $8;  // FLG (FLaGs) bit 3   FNAME
  Dest.Write(header, 4);

  // reserve 4 bytes in MTIME field
  Dest.Write(header, 4);

  header[0] := 0; // XFL (eXtra FLags) XFL = 2 - compressor used maximum compression
  header[1] := 0; // OS (Operating System) 0 - FAT filesystem (MS-DOS, OS/2, NT/Win32)
  Dest.Write(header, 2);

  // original file name, zero-terminated
  Dest.Write(FileName[1], Length(FileName));

  // seek back to skip 2 bytes zlib header
  Dest.Seek(-2, soFromCurrent);

  // put compressed data
  Compressor := TZCompressionStream.Create(Dest, TZCompressionLevel(Compression));
  try
    Compressor.CopyFrom(Source, 0);
  finally
    Compressor.Free;
  end;

  // get adler32 checksum
  Dest.Seek(-4, soFromEnd);
  Dest.Read(header, 4);
  // write it to the header (to MTIME field)
  Dest.Position := 4;
  Dest.Write(header, 4);

  // restore original file name (it was corrupted by zlib header)
  Dest.Seek(2, soFromCurrent);
  Dest.Write(FileName[1], Length(FileName));

  // put crc32 and length
  Dest.Seek(-4, soFromEnd);
  Dest.Write(CRC, 4);
  Dest.Write(Size, 4);
end;

function frxDecompressStream(Source, Dest: TStream): String;
var
  s: String;
  header: array [0..3] of byte;
  adler32: Integer;
  FTempStream: TMemoryStream;
  UnknownPtr: Pointer;
  NewSize: Integer;
begin
  s := '';

  // read gzip header
  Source.Read(header, 4);
  if (header[0] = $1f) and (header[1] = $8b) and (header[2] = $8) then
  begin
    Source.Read(adler32, 4);
    Source.Read(header, 2);
    if (header[3] and $8) <> 0 then
    begin
      Source.Read(header, 1);
      while header[0] <> 0 do
      begin
        s := s + Char(header[0]);
        Source.Read(header, 1);
      end;
    end;
  end;

  FTempStream := TMemoryStream.Create;
  try
    // put zlib header
    s := #$78#$DA;
    FTempStream.Write(s[1], 2);
    // put compressed data, skip gzip's crc32 and filelength
    FTempStream.CopyFrom(Source, Source.Size - Source.Position - 8);
    // put adler32
    FTempStream.Write(adler32, 4);

    // uncompress data and save it to the Dest
    ZDeCompress(FTempStream.Memory, FTempStream.Size, UnknownPtr, NewSize);
    Dest.Write(UnknownPtr^, NewSize);
    FreeMem(UnknownPtr, NewSize);
  finally
    FTempStream.Free;
  end;
  Result := s;
end;

procedure frxDeflateStream(Source, Dest: TStream;
  Compression: TfrxCompressionLevel = gzDefault);
var
  Compressor: TZCompressionStream;
begin
  Compressor := TZCompressionStream.Create(Dest, TZCompressionLevel(Compression));
  try
    Compressor.CopyFrom(Source, 0);
  finally
    Compressor.Free;
  end;
end;

procedure frxInflateStream(Source, Dest: TStream);
var
  FTempStream: TMemoryStream;
  UnknownPtr: Pointer;
  NewSize: Integer;
begin
  FTempStream := TMemoryStream.Create;
  try
    FTempStream.CopyFrom(Source, 0);
    // uncompress data and save it to the Dest
    ZDeCompress(FTempStream.Memory, FTempStream.Size, UnknownPtr, NewSize);
    Dest.Write(UnknownPtr^, NewSize);
    FreeMem(UnknownPtr, NewSize);
  finally
    FTempStream.Free;
  end;
end;


{ TfrxGZipCompressor }

procedure TfrxGZipCompressor.Compress(Dest: TStream);
var
  Compression: TfrxCompressionLevel;
  FileName: String;
begin
  if IsFR3File then
  begin
    Compression := gzMax;
    FileName := '1.fr3';
  end
  else
  begin
    Compression := gzDefault;
    FileName := '1.fp3';
  end;
  frxCompressStream(Stream, Dest, Compression, FileName);
end;

procedure TfrxGZipCompressor.Decompress(Source: TStream);
var
  Signature: array[0..1] of Byte;
begin
  Source.Read(Signature, 2);
  Source.Seek(-2, soFromCurrent);
  if (Signature[0] = $1F) and (Signature[1] = $8B) then
    frxDecompressStream(Source, Stream) else
    Stream.CopyFrom(Source, 0);
  Stream.Position := 0;
end;


end.


//<censored>