C中自己的memcpy

memory_cpy
// 版本 1
void *memcpy(void *dest, const void *src, size_t count)
{
 char *tmp = dest;
 const char *s = src;
 
 while (count--)
    *tmp++ = *s++ ; // 先取出s的内容，后s+1
  
 return dest;
}
//版本 2 考虑重叠
void *memcpy(void *dest, const void *src, size_t count)
{
 char *d;
 const char *s;
 
 if (dest > (src+size)) || (dest < src))
    {
    d = dest;
    s = src;
    while (count--)
        *d++ = *s++;        
    }
 else /* overlap 重叠情况从高位到低位复制*/
    {
    d = (char *)(dest + count - 1); /* offset of pointer is from 0 */
    s = (char *)(src + count -1);
    while (count --)
        *d-- = *s--;
    }
  
 return dest;
}