memcpy手写实现

memcpy手写实现：

void *Memcpy(void *dst, const void *src, size_t size){if (dst == NULL || src == NULL)return NULL;char *psrc;char *pdst;//地址重叠的情况if ((src < dst) && (char*)src + size > (char *)dst){psrc = (char*)src + size - 1;pdst = (char*)dst + size - 1;while(size--){*pdst-- = *pdst--;}}else {psrc = (char*)src;pdst = (char*)dst;while(size--){*pdst++ = *psrc++;}}return dst;}