unit CRC_util;

interface

function CRC16(SB: array of Byte; DataLen: integer): word;
function CheckCRC16(SB: array of Byte; DataLen: integer): Boolean;

(* Table of CRC values for high order byte *)
const
auchCRCHi: array[1..256] of Byte=(
$00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81,
$40, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0,
$80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01,
$C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41,
$00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81,
$40, $01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0,
$80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $01,
$C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40,
$00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81,
$40, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0,
$80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01,
$C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0, $80, $41,
$00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $00, $C1, $81,
$40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81, $40, $01, $C0,
$80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41, $01,
$C0, $80, $41, $00, $C1, $81, $40, $00, $C1, $81, $40, $01, $C0, $80, $41,
$00, $C1, $81, $40, $01, $C0, $80, $41, $01, $C0, $80, $41, $00, $C1, $81,
$40
);

(* Table of CRC values for low order byte *)
auchCRCLo: array[1..256] of Byte=(
$00, $C0, $C1, $01, $C3, $03, $02, $C2, $C6, $06, $07, $C7, $05, $C5, $C4,
$04, $CC, $0C, $0D, $CD, $0F, $CF, $CE, $0E, $0A, $CA, $CB, $0B, $C9, $09,
$08, $C8, $D8, $18, $19, $D9, $1B, $DB, $DA, $1A, $1E, $DE, $DF, $1F, $DD,
$1D, $1C, $DC, $14, $D4, $D5, $15, $D7, $17, $16, $D6, $D2, $12, $13, $D3,
$11, $D1, $D0, $10, $F0, $30, $31, $F1, $33, $F3, $F2, $32, $36, $F6, $F7,
$37, $F5, $35, $34, $F4, $3C, $FC, $FD, $3D, $FF, $3F, $3E, $FE, $FA, $3A,
$3B, $FB, $39, $F9, $F8, $38, $28, $E8, $E9, $29, $EB, $2B, $2A, $EA, $EE,
$2E, $2F, $EF, $2D, $ED, $EC, $2C, $E4, $24, $25, $E5, $27, $E7, $E6, $26,
$22, $E2, $E3, $23, $E1, $21, $20, $E0, $A0, $60, $61, $A1, $63, $A3, $A2,
$62, $66, $A6, $A7, $67, $A5, $65, $64, $A4, $6C, $AC, $AD, $6D, $AF, $6F,
$6E, $AE, $AA, $6A, $6B, $AB, $69, $A9, $A8, $68, $78, $B8, $B9, $79, $BB,
$7B, $7A, $BA, $BE, $7E, $7F, $BF, $7D, $BD, $BC, $7C, $B4, $74, $75, $B5,
$77, $B7, $B6, $76, $72, $B2, $B3, $73, $B1, $71, $70, $B0, $50, $90, $91,
$51, $93, $53, $52, $92, $96, $56, $57, $97, $55, $95, $94, $54, $9C, $5C,
$5D, $9D, $5F, $9F, $9E, $5E, $5A, $9A, $9B, $5B, $99, $59, $58, $98, $88,
$48, $49, $89, $4B, $8B, $8A, $4A, $4E, $8E, $8F, $4F, $8D, $4D, $4C, $8C,
$44, $84, $85, $45, $87, $47, $46, $86, $82, $42, $43, $83, $41, $81, $80,
$40
);

implementation

//CRCの計算
function CRC16(SB: array of Byte; DataLen: integer): word;
var
    uchCRCHi:Byte;  //* high byte of CRC initialized */
    uchCRCLo:Byte;  //* low byte of CRC initialized */
    uIndex:Byte; //* will index into CRC lookup table */
    i: integer;
    DataLenBuff: integer;
begin
    uchCRCHi:= $FF; //* high byte of CRC initialized */
    uchCRCLo:= $FF; //* low byte of CRC initialized */

    DataLenBuff:=DataLen;
    i:=0;
    while (DataLenBuff>0) do  //* pass through message buffer */
    begin
        uIndex := uchCRCHi xor SB[i]; //* calculate the CRC */
        uchCRCHi := uchCRCLo xor auchCRCHi[uIndex+1] ;
        uchCRCLo := auchCRCLo[uIndex+1] ;
        Inc(i);
        Dec(DataLenBuff);
    end;
    Result:=((uchCRCHi shl 8) or uchCRCLo);
end;

//CRCのチェック
function CheckCRC16(SB: array of Byte; DataLen: integer): Boolean;
var
    uchCRCHi:Byte;  //* high byte of CRC initialized */
    uchCRCLo:Byte;  //* low byte of CRC initialized */
    uIndex:Byte; //* will index into CRC lookup table */
    i: integer;
    DataLenBuff: integer;
begin
    uchCRCHi:= $FF; //* high byte of CRC initialized */
    uchCRCLo:= $FF; //* low byte of CRC initialized */

    DataLenBuff:=DataLen-2;
    i:=0;
    while (DataLenBuff>0) do  //* pass through message buffer */
    begin
        uIndex := uchCRCHi xor SB[i]; //* calculate the CRC */
        uchCRCHi := uchCRCLo xor auchCRCHi[uIndex+1] ;
        uchCRCLo := auchCRCLo[uIndex+1] ;
        Inc(i);
        Dec(DataLenBuff);
    end;

    if ((SB[DataLen-2]=uchCRCHi) and (SB[DataLen-1]=uchCRCLo)) then   Result:=True
    else                                                            Result:=False;
end;

end.