字符串函数

size_t str_len(const char* str)
{
    if(NULL == str) return 0;
    assert(NULL != str);
    const char* temp = str;
    while(*temp) temp++;
    return temp - str;
}

char* str_cpy(char* src1,const char* src2)
{
    if(NULL == src1 || NULL == src2) return NULL;
    char* temp = src1;
    while(*temp++ = *src2++);
    return src1;
}

char* str_cat(char* src1,const char* src2)
{
    char* temp = src1;
    while(*temp) temp++;
    while(*temp++ = *src2++);
    return dest;
}

int str_cmp(const char* s1,const char* s2)
{
    while(*s1 && *s1 == *s2) s1++,s2++;
    return *s1 - *s2;
}