crc.c

MSP430单片机C语言应用程序设计实例精讲

#include "CRC.h"
#include "table16.h"
#include "table32.h"

unsigned short crc16Bitwise(unsigned short crc, 
							unsigned short poly, 
							unsigned char *pmsg, 
							unsigned int msg_size)
{
    unsigned int i, j, carry;
    unsigned char msg;
    unsigned short temp;

	temp = *pmsg++ << 8;
	temp |= *pmsg++;
	crc ^= temp;
    
    for(i = 0 ; i < msg_size ; i ++)
    {
        msg = *pmsg++;
        
		for(j = 0 ; j < 8 ; j++)
        {
			carry = crc & 0x8000;
			crc = (crc << 1) | (msg >> 7);
			if(carry) crc ^= poly;
			msg <<= 1;
        }
    }
   
    return(crc ^ CRC16_FINAL_XOR);
}
unsigned short crc16Bitwise2(unsigned short crc, 
							 unsigned short poly,
							 unsigned char *pmsg, 
							 unsigned int msg_size)
{
    unsigned int i, j;
    unsigned short msg;
    
    for(i = 0 ; i < msg_size ; i ++)
    {
        msg = (*pmsg++ << 8);
        
		for(j = 0 ; j < 8 ; j++)
        {
            if((msg ^ crc) >> 15) crc = (crc << 1) ^ poly;
			else crc <<= 1;
	
			msg <<= 1;
        }
    }
   
    return(crc ^ CRC16R_FINAL_XOR);
}
unsigned long crc32Bitwise(unsigned long crc, 
						   unsigned long poly, 
						   unsigned char *pmsg, 
						   unsigned int msg_size)
{
    unsigned int i, j, carry;
    unsigned char msg;
    unsigned long temp;

	temp = (unsigned long)(*pmsg++) << 24;
	temp |= (unsigned long)(*pmsg++) << 16;
	temp |= (unsigned long)(*pmsg++) << 8;
	temp |= (unsigned long)(*pmsg++);
	crc ^= temp;

    for(i = 0 ; i < msg_size ; i ++)
    {
        msg = *pmsg++;

		for(j = 0 ; j < 8 ; j++)
        {
			carry = crc >> 31;
			crc = (crc << 1) | (msg >> 7);
			if(carry) crc ^= poly;
			msg <<= 1;
        }
    }
   
    return(crc ^ CRC32_FINAL_XOR);
}
unsigned long crc32Bitwise2(unsigned long crc, 
							unsigned long poly, 
							unsigned char *pmsg, 
							unsigned int msg_size)
{
    unsigned int i, j;
    unsigned long msg;
            
    for(i = 0 ; i < msg_size ; i++)
    {
        msg = *pmsg++;
        msg <<= 24;
        
        for(j = 0 ; j < 8 ; j++)
        {
            if((msg ^ crc) >> 31) crc = (crc << 1) ^ poly;
			else crc <<= 1;
	
			msg <<= 1;
        }
    }
    
    return(crc ^ CRC32R_FINAL_XOR);
}

unsigned short crc16TableMethod(unsigned short crc, 
								unsigned short *table,
								unsigned char *pbuffer, 
								unsigned int length)
{
    while(length--) 
        crc = table[((crc >> 8) ^ *pbuffer++)] ^ (crc << 8);

    return(crc ^ CRC16_FINAL_XOR);
}

unsigned short crc16rTableMethod(unsigned short crc, 
								 unsigned short *table,
								 unsigned char *pbuffer, 
								 unsigned int length)
{
    while(length--) 
        crc = table[(crc & 0xFF) ^ *pbuffer++] ^ (crc >> 8);

    return(crc ^ CRC16R_FINAL_XOR);
}

unsigned long crc32TableMethod(unsigned long crc, 
							   unsigned long *table, 
							   unsigned char *pbuffer, 
							   unsigned int length)
{
    while(length--) 
        crc = table[((crc >> 24) ^ *pbuffer++)] ^ (crc << 8);

    return(crc ^ CRC32_FINAL_XOR);
}

unsigned long crc32rTableMethod(unsigned long crc, 
							   unsigned long *table, 
							   unsigned char *pbuffer, 
							   unsigned int length)
{
    while(length--) 
        crc = table[(crc ^ *pbuffer++) & 0xFFL] ^ (crc >> 8);

    return(crc ^ CRC32R_FINAL_XOR);
}
void crc16BuildTable(unsigned short *ptable, unsigned short poly)
{
	unsigned int i, j;

    for(i = 0; i <= 255; i++)
    {
        ptable[i] = i << 8;
        for(j = 0; j < 8; j++)
            ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x8000 ? poly : 0);
    }
}

void crc32BuildTable(unsigned long *ptable, unsigned long poly)
{
	unsigned int i, j;

    for(i = 0; i <= 255; i++)
    {
        ptable[i] = (long)i << 24;        
        for(j = 0; j < 8; j++)
            ptable[i] = (ptable[i] << 1) ^ (ptable[i] & 0x80000000 ? poly : 0);
    }
}

unsigned long bitReflect(unsigned long data, unsigned int width)
{
    unsigned long result = 0;
	unsigned int i;

    for (i = 1; i < (width + 1); i++)
    {
        if(data & 1) result |= 0x1L << (width - i);
        data >>= 1;
    } 	

    return result;
}
void main(void)
{
	unsigned long crc32;
	unsigned short crc16;
	unsigned char msg[8] = "12345678";
	crc16 = crc16Bitwise(CRC16_INIT_REM, CRC16_POLY, msg, 8);
	crc32 = crc32Bitwise(CRC32_INIT_REM, CRC32_POLY, msg, 8);
	crc32 = crc32TableMethod(CRC32_INIT_REM, table32, msg, 8);
}