crc如何用c++程序来计算

#include <stdio.h>

typedef unsigned short ushort

typedef unsigned char uchar

typedef union _CRC

{

ushort crc16

uchar by[2]

} CRC

//输早宽入不带CRC码的数据时，返回值是CRC码

//输前睁桐入带CRC码的数据慧坦时，则可以进行校验，返回0时CRC校验成功，否则CRC校验失败

ushort CRC16(uchar *ba, int size)

{

CRC crc

crc.crc16 = 0xffff

int i, l

for (i=0i<sizei++)

{

uchar ch = ba[i]

crc.by[0] = crc.by[0] ^ ch

for (l=0l<8l++)

{

if (crc.by[0] &0x01)

{

crc.crc16 = crc.crc16 >>1

crc.crc16 = crc.crc16 ^ 0xa001

}

else

{

crc.crc16 = crc.crc16 >>1

}

}

}

uchar swap = crc.by[0]

crc.by[0] = crc.by[1]

crc.by[1] = swap

return crc.crc16

}

void main()

{

uchar ba[8] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08}

CRC crc

//计算CRC码

crc.crc16 = CRC16(ba, 8)

printf("高字节:0x%x, 低字节:0x%x\n", crc.by[1], crc.by[0])

//CRC校验

uchar bb[10] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0xb0, 0xcf}

if (0 == CRC16(bb, 10))

{

printf("bb 校验成功！")

}

else

{

printf("bb 校验失败！")

}

}

我给你delphi的饥枣CRC算法，烂歼拆这个文改腊件可以直接使用

unit Main

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls

type

TForm1 = class(TForm)

Memo1: TMemo

Label1: TLabel

Label2: TLabel

Label3: TLabel

GenPoly8Edit: TEdit

GenPoly16Edit: TEdit

GenPoly32Edit: TEdit

TestCRC8Btn: TButton

TestCRC16Btn: TButton

TestCRC32Btn: TButton

CalCRC8Btn: TButton

CalCRC16Btn: TButton

CalCRC32Btn: TButton

CRC8ResultEdit: TEdit

CRC16ResultEdit: TEdit

CRC32ResultEdit: TEdit

procedure FormCreate(Sender: TObject)

procedure TestCRC16BtnClick(Sender: TObject)

procedure TestCRC8BtnClick(Sender: TObject)

procedure TestCRC32BtnClick(Sender: TObject)

procedure CalCRC16BtnClick(Sender: TObject)

procedure CalCRC8BtnClick(Sender: TObject)

procedure CalCRC32BtnClick(Sender: TObject)

private

public

end

var

Form1: TForm1

GenPoly32: DWord

GenPoly16: Word

GenPoly8: Byte

GenPoly4: Byte

CRC32Tab: array [0..255] of DWord

CRC16Tab: array [0..255] of Word

CRC8Tab : array [0..255] of Byte

implementation

{$R *.DFM}

function CalCRC16(data, crc, genpoly: Word): Word

var i: Integer

begin

crc := crc xor (data shl 8)

for i:=0 to 7 do

if (crc and $8000) <>0 then

crc := (crc shl 1) xor genpoly

else crc := crc shl 1

Result := crc

end

procedure InitCRC16Tab(genpoly: DWord)

var i: Integer

begin

for i:=0 to 255 do

CRC16Tab[i] := CalCRC16(i,0,genpoly)

end

function QuickCRC16(data, crc: Word): Word

begin

crc := CRC16Tab[(crc shr 8) xor data] xor (crc shl 8)

Result := crc

end

function CalCRC8(data, crc, genpoly: Byte): Byte

var i: Integer

begin

crc := crc xor data

for i:=0 to 7 do

if (crc and $01) <>0 then

crc := (crc shr 1) xor genpoly

else crc := crc shr 1

Result := crc

end

procedure InitCRC8Tab(genpoly: DWord)

var i: Integer

begin

for i:=0 to 255 do

CRC8Tab[i] := CalCRC8(i,0,genpoly)

end

function QuickCRC8(data, crc: Byte): Word

begin

crc := CRC8Tab[crc xor data]

Result := crc

end

function CalCRC32(data, crc, genpoly: DWord): DWord

var i: Integer

begin

crc := crc xor data

for i:=0 to 7 do

if (crc and $01) <>0 then

crc := (crc shr 1) xor genpoly

else crc := crc shr 1

Result := crc

end

procedure InitCRC32Tab(genpoly: DWord)

var i: Integer

begin

for i:=0 to 255 do

CRC32Tab[i] := CalCRC32(i,0,genpoly)

end

function QuickCRC32(data, crc: DWord): DWord

begin

crc := CRC32Tab[Byte(crc xor data)] xor (crc shr 8)

Result := crc

end

procedure TForm1.FormCreate(Sender: TObject)

begin

GenPoly8 := StrToInt(GenPoly8Edit.Text)

InitCRC8Tab(GenPoly8)

GenPoly16 := StrToInt(GenPoly16Edit.Text)

InitCRC16Tab(GenPoly16)

GenPoly32 := StrToInt(GenPoly32Edit.Text)

InitCRC32Tab(GenPoly32)

end

procedure TForm1.TestCRC16BtnClick(Sender: TObject)

var data, crc, crcstart: Word

begin

crcstart := $1234

Memo1.Clear

Memo1.Lines.Add('16bit CRC')

for data:=0 to 255 do

begin

crc := CalCRC16(data,crcstart,GenPoly16)

Memo1.Text := Memo1.Text + IntToHex(crc, 4) + ' '

end

Memo1.Lines.Add('')

Memo1.Lines.Add('16bit Quick CRC')

for data:=0 to 255 do

begin

crc := QuickCRC16(data,crcstart)

Memo1.Text := Memo1.Text + IntToHex(crc, 4) + ' '

end

end

procedure TForm1.TestCRC8BtnClick(Sender: TObject)

var data, crc, crcstart: Byte

begin

crcstart := $12

Memo1.Clear

Memo1.Lines.Add('8bit CRC')

for data:=0 to 255 do

begin

crc := CalCRC8(data,crcstart,GenPoly8)

Memo1.Text := Memo1.Text + IntToHex(crc, 2) + ' '

end

Memo1.Lines.Add('')

Memo1.Lines.Add('8bit Quick CRC')

for data:=0 to 255 do

begin

crc := QuickCRC8(data,crcstart)

Memo1.Text := Memo1.Text + IntToHex(crc, 2) + ' '

end

end

procedure TForm1.TestCRC32BtnClick(Sender: TObject)

var data, crc, crcstart: DWord

begin

crcstart := $12345678

Memo1.Clear

Memo1.Lines.Add('32bit CRC')

for data:=0 to 255 do

begin

crc := CalCRC32(data,crcstart,GenPoly32)

Memo1.Text := Memo1.Text + IntToHex(crc, 8) + ' '

end

Memo1.Lines.Add('')

Memo1.Lines.Add('32bit Quick CRC')

for data:=0 to 255 do

begin

crc := QuickCRC32(data,crcstart)

Memo1.Text := Memo1.Text + IntToHex(crc, 8) + ' '

end

end

function GetDataFromText(str: String): String

var i, p1, p2: Integer

begin

Result := ''

while str <>'' do

begin

i := 0

p1 := Pos(' ',str)

p2 := Pos(#13#10,str)

if p1=1 then

begin Delete(str,1,1)continueend

if p2=1 then

begin Delete(str,1,2)continueend

if (p1=0) and (p2=0) and (str<>'') then

begin

i := StrToIntDef('$'+str,0)

Delete(str,1,Length(str))

end

if ((p1>0) and (p2=0)) or

((p1>0) and (p2>0) and (p1<p2)) then

begin

i := StrToIntDef('$'+Copy(str,1,p1-1),0)

Delete(str,1,p1)

end

if ((p1=0) and (p2>0)) or

((p1>0) and (p2>0) and (p1>p2)) then

begin

i := StrToIntDef('$'+Copy(str,1,p2-1),0)

Delete(str,1,p2+1)

end

Result := Result + Chr(i)

end

end

procedure TForm1.CalCRC16BtnClick(Sender: TObject)

var

i: Integer

databuf: String

data, crc: Word

begin

databuf := GetDataFromText(Memo1.Text)

crc := 0

for i:=1 to Length(databuf) do

begin

data := Ord(databuf[i])

crc := CalCRC16(data,crc,GenPoly16)

end

CRC16ResultEdit.Text := 'CRC16 = ' + IntToHex(crc,4)

end

procedure TForm1.CalCRC8BtnClick(Sender: TObject)

var

i: Integer

databuf: String

data, crc: Byte

begin

databuf := GetDataFromText(Memo1.Text)

crc := 0

for i:=1 to Length(databuf) do

begin

data := Ord(databuf[i])

crc := CalCRC8(data,crc,GenPoly8)

end

CRC8ResultEdit.Text := 'CRC8 = ' + IntToHex(crc,2)

end

procedure TForm1.CalCRC32BtnClick(Sender: TObject)

var

i: Integer

databuf: String

data, crc: DWord

begin

databuf := GetDataFromText(Memo1.Text)

crc := 0

for i:=1 to Length(databuf) do

begin

data := Ord(databuf[i])

crc := CalCRC32(data,crc,GenPoly32)

end

CRC32ResultEdit.Text := 'CRC32 = ' + IntToHex(crc,8)

end

end.

按位计算CRC采用CRC-CCITT多项式，多项式为0x11021，C语言编程时，参与计算为0x1021。当按位计算CRC时，例如计算二进制序列为1001 1010 1010 1111时，将二进制序列数左移16位，即为1001 1010 1010 1111 (0000 0000 0000 0000)，实际上该二进制序列可拆分为1000 0000 0000 0000 (0000 0000 0000 0000) + 000 0000 0000 0000 (0000 0000 0000 0000) + 00 0000 0000 0000 (0000 0000 0000 0000) + 1 0000 0000 0000 (0000 0000 0000 0000) + ……

现在开始分析运算：

<1>对第一个二进制分序列求余数，竖式除激肢法即为0x10000 ^ 0x11021运算，后面的0位保留；

<2>接着对第二个二进制分序列求余数，将第一步运算的余数*2后再和第二个二进制分序列一起对0x11021求余，这一步理解应该没什么问题。如果该分序列为0，无需计算。

<3>对其余的二进制序列求余与上面两步相同。

<4>计算到最后一位时即为整个二进制序列的余数，即为CRC校验码。

该计算岩衡方法相当于对每一位计算，运算过程很容易理解，所占内存少，缺点是一位一位计算粗铅做比较耗时。

下面给出C语言实现方法：

代码如下:

unsigned char test[16] = {0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x99,0xaa,0xbb,0xcc,0xdd,0xee,0xff}

unsigned char len = 16

void main( void )

{

unsigned long temp = 0

unsigned int crc

unsigned char i

unsigned char *ptr = test

while( len-- ) {

for(i = 0x80i != 0i = i >>1) {

temp = temp * 2

if((temp &0x10000) != 0)

temp = temp ^ 0x11021

if((*ptr &i) != 0)

temp = temp ^ (0x10000 ^ 0x11021)

}

ptr++

}

crc = temp

printf("0x%x ",crc)

}

---