firemonkey android crc16 result mismatch with delphi for windows - delphi

Question

in two different project i need to use crc16 checksum.one in windows and other in android.i used a code for windows and it worked prefect.
showmessage( bin2crc16(HexToBin('1234')) ); //---> 0EC9
here is used function for winsows
function Pow(i, k: Integer): Integer;
var
j, Count: Integer;
begin
if k>0 then j:=2
else j:=1;
for Count:=1 to k-1 do
j:=j*2;
Result:=j;
end;
function BinToDec(Str: string): Integer;
var
Len, Res, i: Integer;
Error: Boolean;
begin
Error:=False;
Len:=Length(Str);
Res:=0;
for i:=1 to Len do
if (Str[i]='0')or(Str[i]='1') then
Res:=Res+Pow(2, Len-i)*StrToInt(Str[i])
else
begin
//MessageDlg('It is not a binary number', mtInformation, [mbOK], 0);
Error:=True;
Break;
end;
if Error=True then Result:=0
else Result:=Res;
end;
//------------------------------------------------------------------------------
function CRC16CCITT(bytes: array of Byte): Word;
const
polynomial = $1021;
var
crc: Word;
I, J: Integer;
b: Byte;
bit, c15: Boolean;
begin
crc := $FFFF;
for I := 0 to High(bytes) do
begin
b := bytes[I];
for J := 0 to 7 do
begin
bit := (((b shr (7-J)) and 1) = 1);
c15 := (((crc shr 15) and 1) = 1);
crc := crc shl 1;
if ((c15 xor bit) <> false) then crc := crc xor polynomial;
end;
end;
Result := crc and $ffff;
end;
//------------------------------------------------------------------------------
function HexToDec(const Str: string): Integer;
begin
if (Str <> '') and ((Str[1] = '-') or (Str[1] = '+')) then
Result := StrToInt(Str[1] + '$' + Copy(Str, 2, MaxInt))
else
Result := StrToInt('$' + Str);
end;
//------------------------------------------------------------------------------
function bin2crc16(str: string): string;
var
I:integer;
lengthCount : integer;
crcByteArr : array of Byte;
crcOut : Word;
begin
lengthCount := Trunc(length(str)/8);
setlength(crcByteArr , lengthCount );
for I := 0 to lengthCount-1 do
begin
crcByteArr[I] := BinToDec(copy(str, I*8+1, 8));
end;
crcOut := CRC16CCITT(crcByteArr);
result := crcOut.ToHexString;
end;
//------------------------------------------------------------------------------
function HexToBin(Hexadecimal: string): string;
const
BCD: array [0..15] of string =
('0000', '0001', '0010', '0011', '0100', '0101', '0110', '0111',
'1000', '1001', '1010', '1011', '1100', '1101', '1110', '1111');
var
i: integer;
begin
Result := '';
for i := Length(Hexadecimal) downto 1 do
Result := BCD[StrToInt('$' + Hexadecimal[i])] + Result;
end;
but for android i changed the code to handle zero index string.
the result is different
memo2.Lines.Add( bin2crc16(HexToBin('1234')) ); //-----> 1AFa
here is used functions in android
function BinToDec(Str: string): Integer;
var
Len, Res, i: Integer;
Error: Boolean;
begin
Error:=False;
Len:=Length(Str);
Res:=0;
for i:=0 to Len-1 do
if (Str[i]='0')or(Str[i]='1') then
Res:=Res+Pow(2, Len-i)*StrToInt(Str[i])
else
begin
Error:=True;
Break;
end;
if Error=True then Result:=0
else Result:=Res;
end;
//------------------------------------------------------------------------------
function CRC16CCITT(bytes: array of Byte): Word;
const
polynomial = $1021;
var
crc: Word;
I, J: Integer;
b: Byte;
bit, c15: Boolean;
begin
crc := $FFFF;
for I := 0 to High(bytes) do
begin
b := bytes[I];
for J := 0 to 7 do
begin
bit := (((b shr (7-J)) and 1) = 1);
c15 := (((crc shr 15) and 1) = 1);
crc := crc shl 1;
if ((c15 xor bit) <> false) then crc := crc xor polynomial;
end;
end;
Result := crc and $ffff;
end;
//------------------------------------------------------------------------------
function bin2crc16(str: string): string;
var
I:integer;
lengthCount : integer;
crcByteArr : array of Byte;
crcOut : Word;
begin
lengthCount := Trunc(length(str)/8);
setlength(crcByteArr , lengthCount );
for I := 0 to lengthCount-1 do
begin
crcByteArr[I] := BinToDec(copy(str, I*8, 8));
end;
crcOut := CRC16CCITT(crcByteArr);
result := crcOut.ToHexString;
end;
//-----------------------------------------------------------------------------------
function HexToBin(Hexadecimal: string): string;
const
BCD: array [0..15] of string =
('0000', '0001', '0010', '0011', '0100', '0101', '0110', '0111',
'1000', '1001', '1010', '1011', '1100', '1101', '1110', '1111');
var
i: integer;
begin
Result := '';
for i := Length(Hexadecimal)-1 downto 0 do
Result := BCD[StrToInt('$' + Hexadecimal[i])] + Result;
end;
//---------------------------------------------------------------------------------
function Pow(i, k: Integer): Integer;
var
j, Count: Integer;
begin
if k>0 then j:=2
else j:=1;
for Count:=1 to k-1 do
j:=j*2;
Result:=j;
end;
how can i fix my problem !?

Answer 1

You have not adjusted your HexToBin function for zero length strings.
There is also an issue in your BinToDec function. Your power calculation is wrong because the index into the string has changed. Possibly the simplest way to deal with it is as follows, although you could also adjust the index in the POW function
function BinToDec(Str: string): Integer;
var
Len, Res, i: Integer;
Error: Boolean;
begin
Error:=False;
Len:=Length(Str);
Res:=0;
for i:=1 to Len do
if (Str[I - 1]='0')or(Str[I - 1]='1') then
Res:=Res+Pow(2, Len-i)*StrToInt(Str[I - 1])
else
begin
Error:=True;
Break;
end;
if Error=True then Result:=0
else Result:=Res;
end;
The last thing to note is that 'Copy' uses One based indexing even on zero based strings, but you have assumed that it is zero indexed. I agree it is confusing, but there it is.