实现字符串函数，strlen(),strcpy(),strcmp(),strcat()

实现字符串函数，strlen(),strcpy(),strcmp(),strcat()

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

int my_strlen(char *str);
char *my_strcpy(char *dest, char *src);
char *my_strcat(char *dest, char *src);
int my_strcmp(char *str1,char *str2);

int main()
{
    char dest[32] = "chen";
    char src[32] = "chengha";
    int res;
    //printf("strlen(%s) = %d
",str,my_strlen(str));
    res = my_strcmp(dest,src);
    printf("res = %d
",res);
    //puts(dest);
    system("pause");
    return 0;
}

int my_strlen(char *str)
{
    int len = 0;
    while(*str != '')
    {
        len++;
        str++;
    }
    return len;
}

char *my_strcpy(char *dest, char *src)
{
    char *address = dest;
    while((*dest = *src) != '')
    {
        dest++;
        src++;
    }
    return address;
}

char *my_strcat(char *dest, char *src)
{
    char *address = dest;
    while(*dest != '')
        dest++;
    while((*dest = *src) != '')
    {
        dest++;
        src++;
    }
    return address;
}

int my_strcmp(char *str1,char *str2)
{
    for(; *str1 == *str2; str1++, str2++)
        if(*str1 == '')
            return 0;
    return *str1 - *str2;
}