Question

Can someone help me with Delphi implementation of CRC-CCITT (0xFFFF)?

Already get the Java version, but confusing on how to port it to Delphi

public static int CRC16CCITT(byte[] bytes) {
    int crc = 0xFFFF;          // initial value
    int polynomial = 0x1021;   // 0001 0000 0010 0001  (0, 5, 12) 

    for (byte b : bytes) {
        for (int i = 0; i < 8; i++) {
            boolean bit = ((b   >> (7-i) & 1) == 1);
            boolean c15 = ((crc >> 15    & 1) == 1);
            crc <<= 1;
            if (c15 ^ bit) crc ^= polynomial;
         }
    }

    crc &= 0xffff;
    //System.out.println("CRC16-CCITT = " + Integer.toHexString(crc));
    return crc;
}

and for PHP implementation

<?php
function crc16($data)
 {
   $crc = 0xFFFF;
   for ($i = 0; $i < strlen($data); $i++)
   {
     $x = (($crc >> 8) ^ ord($data[$i])) & 0xFF;
     $x ^= $x >> 4;
     $crc = (($crc << 8) ^ ($x << 12) ^ ($x << 5) ^ $x) & 0xFFFF;
   }
   return $crc;
 }

Answer 1

i found some code that works:

function crc16(Buffer:String;Polynom,Initial:Cardinal):Cardinal;
var
  i,j: Integer;
begin
Result:=Initial;
for i:=1 to Length(Buffer) do begin
  Result:=Result xor (ord(buffer[i]) shl 8);
  for j:=0 to 7 do begin
    if (Result and $8000)<>0 then Result:=(Result shl 1) xor Polynom
    else Result:=Result shl 1;
    end;
  end;
Result:=Result and $ffff;
end;

source : http://www.miscel.dk/MiscEl/CRCcalculations.html