crc16.pas

楠楠写的DBiocp例子都是源码

unit crc16;

interface

  procedure CalcCRC16( p: PByte; nbyte: word; var CRCvalue: word );
  procedure CalcFileCRC16( FromName: string; var CRCvalue: word;
                           var IOBuffer: PByte; BufferSize: word; var error: word);

implementation

  const
    table:  array[0..255] of word =
     ($0000,$C0C1,$C181,$0140,$C301,$03C0,$0280,$C241,$C601,$06C0,$0780,
      $C741,$0500,$C5C1,$C481,$0440,$CC01,$0CC0,$0D80,$CD41,$0F00,$CFC1,
      $CE81,$0E40,$0A00,$CAC1,$CB81,$0B40,$C901,$09C0,$0880,$C841,$D801,
      $18C0,$1980,$D941,$1B00,$DBC1,$DA81,$1A40,$1E00,$DEC1,$DF81,$1F40,
      $DD01,$1DC0,$1C80,$DC41,$1400,$D4C1,$D581,$1540,$D701,$17C0,$1680,
      $D641,$D201,$12C0,$1380,$D341,$1100,$D1C1,$D081,$1040,$F001,$30C0,
      $3180,$F141,$3300,$F3C1,$F281,$3240,$3600,$F6C1,$F781,$3740,$F501,
      $35C0,$3480,$F441,$3C00,$FCC1,$FD81,$3D40,$FF01,$3FC0,$3E80,$FE41,
      $FA01,$3AC0,$3B80,$FB41,$3900,$F9C1,$F881,$3840,$2800,$E8C1,$E981,
      $2940,$EB01,$2BC0,$2A80,$EA41,$EE01,$2EC0,$2F80,$EF41,$2D00,$EDC1,
      $EC81,$2C40,$E401,$24C0,$2580,$E541,$2700,$E7C1,$E681,$2640,$2200,
      $E2C1,$E381,$2340,$E101,$21C0,$2080,$E041,$A001,$60C0,$6180,$A141,
      $6300,$A3C1,$A281,$6240,$6600,$A6C1,$A781,$6740,$A501,$65C0,$6480,
      $A441,$6C00,$ACC1,$AD81,$6D40,$AF01,$6FC0,$6E80,$AE41,$AA01,$6AC0,
      $6B80,$AB41,$6900,$A9C1,$A881,$6840,$7800,$B8C1,$B981,$7940,$BB01,
      $7BC0,$7A80,$BA41,$BE01,$7EC0,$7F80,$BF41,$7D00,$BDC1,$BC81,$7C40,
      $B401,$74C0,$7580,$B541,$7700,$B7C1,$B681,$7640,$7200,$B2C1,$B381,
      $7340,$B101,$71C0,$7080,$B041,$5000,$90C1,$9181,$5140,$9301,$53C0,
      $5280,$9241,$9601,$56C0,$5780,$9741,$5500,$95C1,$9481,$5440,$9C01,
      $5CC0,$5D80,$9D41,$5F00,$9FC1,$9E81,$5E40,$5A00,$9AC1,$9B81,$5B40,
      $9901,$59C0,$5880,$9841,$8801,$48C0,$4980,$8941,$4B00,$8BC1,$8A81,
      $4A40,$4E00,$8EC1,$8F81,$4F40,$8D01,$4DC0,$4C80,$8C41,$4400,$84C1,
      $8581,$4540,$8701,$47C0,$4680,$8641,$8201,$42C0,$4380,$8341,$4100,
      $81C1,$8081,$4040);

type
  buffer = array[1..65521] of byte;

  procedure CalcCRC16(p: PByte; nbyte: word; var CRCvalue: word);
  var
    i: word;
    q: PByte;
  begin
    q := p;
    for  i := 1 TO nBYTE do
    begin
      CRCvalue := Hi(CRCvalue)  XOR  Table[ q^ XOR Lo(CRCvalue) ];
      inc(q)
    end
  end;


  procedure CalcFileCRC16 (FromName:  string; var CRCvalue:  word;
              var IOBuffer:  PByte;  BufferSize:  word; var error:  word);
    var
      BytesRead:  INTEGER;
      FromFile :  FILE;
  begin
    FileMode := 0;
    CRCValue := $FFFF;
    ASSIGN (FromFile,FromName);
    {$I-} RESET (FromFile,1); {$I+}
    error := IOResult;
    if   error = 0
    then begin
      repeat
        BlockRead (FromFile,IOBuffer^,BufferSize,BytesRead);
        CalcCRC16 (IOBuffer,BytesRead,CRCvalue)
      until BytesRead = 0;

      CRCvalue := NOT CRCvalue;
      CLOSE (FromFile)
    end
  end;

end.