在字符串S1中删除字符串S2中所包含的字符【转】

/*************************************************************************
    > File Name: test.c
    > Author: ToLiMit
    > Mail: 348958453@qq.com 
    > Created Time: Sun 04 Jan 2015 06:20:05 PM PST
 ************************************************************************/

#include<stdio.h>

void delete_str_char (char * main_str, char * sub_str)
{
    if ((main_str == NULL) || (sub_str == NULL))
        return;

    char * sub_index = sub_str;
    char * main_index = main_str;
    char bitmap[32] = {0};
    char * str = (char *)malloc (strlen (str) + 1);
    char * index = str;
    memset (str, 0, strlen (str) + 1);

    while (*sub_index != '\0') {
        char suffix = ((*sub_index) / 8) - 1;
        char offset = (*sub_index) % 8;

        bitmap[suffix] |= (0x1 << (8 - offset));
        sub_index++;
    }

    while (*main_index != '\0') {
        char suffix = ((*main_index) / 8) - 1;
        char offset = (*main_index) % 8;

        if ((bitmap[suffix] & (0x1 << (8 - offset))) == 0) {
            *index = *main_index;
            index++;
        }
        main_index++;
    }

    *index = '\0';
    memcpy (main_str, str, strlen (str) + 1);
    free (str);
    return;
}

int main (int argc, char * argv[])
{
    char test[] = "aabcdaaaaabcaacb";

    delete_str_char (test, "bcd");
    printf ("%s\n", test);
    return 0;
}