Linux下用C语言将一个字符串格式(char*)的MAC地址转换为十六进制数组

#include <stdio.h>
#include <stdlib.h>

unsigned char a2x(const char c)
{
	switch(c) {
	case '0'...'9':
		return (unsigned char)atoi(&c);
	case 'a'...'f':
		return 0xa + (c-'a');
	case 'A'...'F':
		return 0xa + (c-'A');
	default:
		goto error;
	}
error:
	exit(0);
}

/*convert a string,which length is 18, to a macaddress data type.*/
#define MAC_LEN_IN_BYTE 6
#define COPY_STR2MAC(mac,str)  \
	do { \
		for(int i = 0; i < MAC_LEN_IN_BYTE; i++) {\
  			mac[i] = (a2x(str[i*3]) << 4) + a2x(str[i*3 + 1]);\
		}\
	} while(0)

int main(int argc, char **argv)
{
	unsigned char macaddr[8] = {0};
	char macaddr_str[18] = "8e:b2:cf:89:00:4a";
	COPY_STR2MAC(macaddr,macaddr_str);
	printf("0x%02x 0x%02x\n",macaddr[0],macaddr[1]);

	return 0;
}