strcpy实现

//#include<stdio.h>
char * strcpy(char *dst,const char *src)
{
    assert(dst != NULL && src != NULL);
    char * ret = dst;
    while ((*dst++ = *src++) != '\0');
    return ret;
}

//对于内存覆盖的情况，即src是低地址，dst是高地址，src未处理部分被dst覆盖
char * my_memcpy(char *dst,const char * src,int length)
{
    assert(dst != NULL && src != NULL);
    char * ret = dst;
    if(dst >= src && dst <= src+length-1)
    {
        dst = dst + length -1;
        src = src + length -1;
        while(length--)
        {
            *dst-- = *src --;
        }
    }
    else
    {
        while(length--)
        {
            *dst++ = * src++;
        }
    }
    return ret;
}