字符串转十六进行制

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

int ctoh(char * str)
{
    unsigned long var = 0;
    unsigned long t;
    char * tmp,* tmp_head;
    int i,len;

    len = strlen(str);
    tmp = malloc(len + 1);

    tmp_head = tmp;

    if (len > 8) //最长8位
    {
        free(tmp);
        return -1;
    }

    for (i = 0;*str;i++)
    {
        tmp[i] = toupper(*str++);//统一大写
    }
    tmp[i] = '\0';
    printf("str %s tmp %s\n",str,tmp);

    for (; *tmp != '\0'; tmp++)
    {
        if (*tmp >='A' && *tmp <='F')
            t = *tmp-55;    //a-f之间的ascii与对应数值相差55如'A'为65,65-55即为A
        else
            t = *tmp-48;    //字符0-9 之间的ascii与对应数值相差为48;
        var <<= 4;
        var |= t;
     }

    free(tmp_head);

    return var;
}


int main(void)
{
    int id;
    char * test = "1a";
    char * test1 = "11";

    id = atoi(test1);  //只能适用于0-9的数字
    printf("%d \n",id);

    id = ctoh(test);
    printf(" test %s, 0x%x \n",test,id);


    return 0;
}