CRC16校验的实现

操作系统：Debian7.5

前言
    很多设备的通信命令中，都会用到校验，常用的有crc8，crc16等。现在封装一下crc16的实现。

一，源码
    1，《crc.h》

#ifndef CRC_H
#define CRC_H


#include "commontypes.h"

#define CRC_INIT 0xFFFF


uint16 crc_polynomial(uint8 b, uint16 acc);
uint16 crc_sum(uint8* message, uint16 length, uint16 crc);
uint32 crc_verify(uint8* message, uint16 length);
void crc_append(uint8* message, uint16 length);

#endif

    2，《crc.c》

//!-------------------------------------------------------------------
//! Include Files
//!-------------------------------------------------------------------
//#include "PR9200.h"
#include "crc.h"


//!-------------------------------------------------------------------
//! Definitions
//!-------------------------------------------------------------------



//!-------------------------------------------------------------------
//! Global Data Declaration
//!-------------------------------------------------------------------


//!-------------------------------------------------------------------
//! Fuction Definitions
//!-------------------------------------------------------------------


//!---------------------------------------------------------------
//!    @brief
//!        Polynomial functions for CRC (X16 + X12 + X5 + 1)
//!
//! @param
//!        b: a byte data
//!        acc: accumulated value
//!
//! @return
//!        accumulated value
//!
//!---------------------------------------------------------------
uint16 crc_polynomial(uint8 b, uint16 acc)
{
    acc = (uint8)(acc >> 8) | (acc << 8);
    acc ^= b;
    acc ^= (uint8)(acc & 0xff) >> 4;
    acc ^= (acc << 8) << 4;
    acc ^= ((acc & 0xff) << 4) << 1;

    return acc;
}

//!---------------------------------------------------------------
//!    @brief
//!        Caculate 16-bit CRC on all the messages
//!
//! @param
//!        * msg:    data pointer
//!        length: data length
//!     crc: CRC initial value(0xFFFF)
//!
//! @return
//!        crc value
//!
//!---------------------------------------------------------------
uint16 crc_sum(uint8* msg, uint16 length, uint16 crc)
{
    uint16 i;

    for(i = 0; i < length; i++) {
        crc = crc_polynomial(msg[i],crc);
    }
    return crc;
}

//!---------------------------------------------------------------
//!    @brief
//!        Check the CRC validity
//!
//! @param
//!        * msg: data pointer
//!        length: data length
//!
//! @return
//!        valid(0) / invalid(Not 0)
//!
//!---------------------------------------------------------------
uint32 crc_verify(uint8* msg, uint16 length)
{
    uint16 expected;

    expected = crc_sum(msg, length - 2, CRC_INIT);
    return !( ( expected & 0xff) == msg[length - 1] &&
              ((expected >> 8) & 0xff) == msg[length - 2] );
}


//!---------------------------------------------------------------
//!    @brief
//!        Append the CRC value to the end of data
//!
//! @param
//!        * message: data pointer
//!        length: data length
//!
//! @return
//!        None
//!
//!---------------------------------------------------------------
void crc_append(uint8* message, uint16 length)
{
#ifdef    __FEATURE_ENABLE_RCP_CRC__

    uint16 crc;

    crc = crc_sum(message, length, CRC_INIT);
    message[length+1] = (uint8)(crc & 0xff);
    message[length] = (uint8)((crc >> 8) & 0xff);

#endif
}

二，测试结果



三，源码包
    crc16.rar