memcpy momove strcmp源码实现

void *memcpy(void *des, void *src, int count)

{

    assert(des!=NULL||src!=NULL);

    char *d = (char*)des;

    char *s = (char*)src;

    while(count--)

    {

        *d++=*s++;

    }

    

    return des;

}

 

void *memove(void *des, void *src, int count)

{

    assert(des!=NULL||src!=NULL);

    char *d = (char*)des;

    char *s = (char*)src;

    if ((d <= s) || d>=s+n))

    {

        while(count--)

        {

            *d++=*s++;

        }

    }

    else

    {

        s+=count;

        d+=count;

        while(count--）

        {

            *d-- = *s--

        }

    }    

    return des;

}

char *strcpy(char *des, const char *src)

{

    assert(des!=NULL||src!=NULL);

    char *d = des;

    while((*d++=*src++) != '\0');

    

    return des;

}