strcmp strcpy strcat源代码

strcmp函数：

下面听说是微软源代码：

int strcmp(const char * src, const char * dest)
{
    int ret = 0;
    while (!(ret = *(unsigned char *)src - *(unsigned char *)dest) && *dest)
    {
         src++;
         dest++;
    }
    if (ret < 0)
         return -1;
    if (ret > 0)
         return 1;
    return (ret);
}

下面是另外一个：

int strcmp(const char * src, const char * dest)
{
    for ( ; *src == *dest;)
    {
         if (!*dest)
             return 0;
         src++;
         dest++;
     }
     return (*src - *dest);
}

接下来是strcpy函数的源代码：

char * strcpy(char * dest, const char * src)
{
    char * tmp = dest;
    while ((*tmp++ = *src++) != '\0')
        ;
    return dest;
}

strcat的源代码

void strcat(char * p1, char * p2)
{
    char * p = p1;
    while (*p1)
    {
         p1++;
    }
    while (*p2)
    {
        *p1 = *p2;
        p1++;
        p2++;
    }
    p1 = '\0';
    p1 = p
}