[fpc-pascal] Calculating CRC16?

[Jean SUZINEAU]

I couldn't verify the code but it should be  relatively close to your  
c++ example. Not sure of the width of int type, I supposed it's 16 bits 
wide:

function CRC16( crc: Word; buf: PByte; len: Word; Poly:Word=$A001): Word;
var
    pos: Word;
    i: Word;
begin
      for pos:= 0 to len-1
      do
        begin
        crc:= crc xor Word(buf[pos]);    // * XOR byte into least sig. byte of crc
        // * Loop over each bit
        for i:= 8 downto 1
        do
          begin
          // * If the LSB is set
          if ((crc and $0001) <> 0)
          then
              begin
              // * Shift right and XOR 0xA001
              crc:= crc shr 1;
                 crc:= crc xor Poly;
              end
          // * Else LSB is not set
          else
              // * Just shift right
              crc:= crc shr 1;
          end;
        end;
       Result:= crc;
end;
var
    S: String;
begin
      Readln( S);
      WriteLn( IntToHex( CRC16( 0, PByte(@S[1]), Length(S), $8005), 4));
end.

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