CRC8算法DELPHI源码

　　最近做个程序需要用到CRC8校验，网上找了一堆资料都看得头晕脑胀的，最终还是搞不懂它的算法，惭愧。最后找了个C源码请高手翻译成DELPHI的才解决问题。在这感谢　老鸨。。他写的DELPHI程序如下：

unit Crc8;

interface

Uses
Classes, Windows;

Function Crc_8n(p : array of BYTE; len : BYTE) : Byte;

implementation

Function Crc_8n(p : array of BYTE; len : BYTE) : Byte;
Var
j, cbit, aout, crc, crc_a, crc_b : Byte;
i : integer;
begin
crc := 0;
i := 0;

// 取移位的位
repeat
crc_a := p[i];
inc(i);
j := 8;
cbit := 1;
repeat
crc_b := crc_a;
crc_b := crc_b xor crc; // ?????
aout := crc_b and cbit;
if aout<>0 then begin
crc := crc xor $18; // ?????
crc := crc shr 1;
crc := crc or $80;
end else begin
crc := crc shr 1;
end;
crc_a := crc_a shr 1;
dec(j);
until j = 0;
dec(len);
until len = 0;

result := crc;
end;

end.

=================================

unit main;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls,
Crc8;

type
TForm1 = class(TForm)
Edit1: TEdit;
Memo1: TMemo;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

const MinBase = 2;
MaxBase = 36;

function StrToNum (const s: string; base: Integer;
neg: Boolean; max: Integer): Integer;
// s = 要转换的字符串
// base = 进制数
// neg = 是否为负数

// max = 要转换的最大数//
// 用法:
// i:= StrToNum (''''''''00101101'''''''', 2, false, MaxInt);
// i:= StrToNum (''''''''002D'''''''', 16, false, MaxInt);
// i:= StrToNum (''''''''-45'''''''', 10, true, MaxInt);
// i:= StrToNum (''''''''ZZ'''''''', 36, true, MaxInt);
//
var negate, done: Boolean;
i, len, digit, mmb: Integer;
c: Char;
mdb, res: Integer;
begin
res:= 0; i:= 1; digit:= 0;
if (base >= MinBase) and (base <= MaxBase) then begin
mmb:= max mod base;
mdb:= max div base;
len:= Length (s);
negate:= False;
while (i <= len) and (s[i] = '''' '''') do Inc (i);
if neg then begin
case s[i] of
'''' '''': Inc (i);
''''-'''': begin Inc (i); negate:= TRUE; end;
end; (* CASE *)
end; (* IF neg *)
done:= len > i;
while (i <= len) and done do begin
c:= Upcase (s[i]);
case c of
''''0''''..''''9'''': digit:= ORD(c) - 48;
''''A''''..''''Z'''': digit:= ORD(c) - 55;
else done:= FALSE
end; (* CASE *)
done:= done and (digit < base);
if done then begin
done:= (res < mdb) or ((res = mdb) and (digit <= mmb));
IF done then begin
res:= res * base digit;
Inc (i);
end; (* IF done *)
end; (* IF done *)
end; (* WHILE *)
if negate then res:= - res;
end; (* IF done *)
Result:= res;
end;

procedure TForm1.Button1Click(Sender: TObject);
Var
S : String;
P : Array[0..255] of Byte;
Len : Byte;
R : Byte;
I : Integer;
begin
S := Edit1.Text;

if length(s) mod 2 = 1 then s := s ''''0'''';

Memo1.Lines.Add(S '''' :'''');
for i:=1 to length(s) div 2 do begin
p[i-1] := BYTE(StrToNum(copy(s, (i-1)*2 1, 2), 16, false, 500));
Memo1.Lines.Add(IntToStr(I) '''' --> '''' IntToHex(p[i-1], 2));
end;

Len := length(s) div 2;

R := Crc_8n(P, Len);
Memo1.Lines.Add(''''Crc8 Result: '''' IntToHex(R, 2));
end;

end.

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