内联汇编实现 memcpy 和 memset

#pragma check_stack( off)

LPVOID   __cdecl _memcpy(void * dst, void* src,  size_t size)
{
	int dwSize = size/4;
	int byteSize = size%4;
	__asm{
		mov edi,dst
		mov esi,src
		mov ecx,dwSize
		rep movs dword ptr es:[edi],dword ptr ds:[esi]
		mov ecx,byteSize
		rep movs byte  ptr es:[edi],byte ptr ds:[esi]
	}

	return dst;
}
#pragma check_stack( off)
LPVOID    __cdecl  __memset( void * dst,  int val,  size_t size)
{ 

	int dwSize = size/4;
	int byteSize = size%4;
	int fixVal;
	__asm{
		mov eax,val
		lea edi,  fixVal
		mov ecx,4 
		rep stos byte ptr es:[edi]
		
		mov eax, fixVal
		mov ecx, dwSize
		mov edi,dst
		rep stos dword ptr es:[edi]
		mov ecx, byteSize
		rep stos byte ptr es:[edi]
	}

	return dst;

}

  

posted on 2015-07-01 10:44  透明色~  阅读(1750)  评论(0编辑  收藏  举报

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