文件映射操作實例

HANDLE hFile = NULL;
HANDLE hFileMap = NULL;
const viewmapsize = 8 * 1024 * 1024;//8m
DWORD highsize,lowsize,fileoffsetlow,fileoffsethigh,mapsize;
_int64 filesize,offset,remain;
int dwError;

do {
	//打開文件
	hFile= CreateFile("g:\\1289527402.png",
		GENERIC_READ,
		FILE_SHARE_READ|FILE_SHARE_WRITE,
		NULL,
		OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL,
		NULL);
	if ( hFile == INVALID_HANDLE_VALUE )
	{
		CString cs;
		cs.Format("打開文件失敗:%d",GetLastError());
		AfxMessageBox(cs);
		break;
	}
	lowsize = GetFileSize(hFile,&highsize);
	if ( lowsize == 0xFFFFFFFF && ( dwError = GetLastError() ) != NO_ERROR )
	{
		CString cs;
		cs.Format("獲取文件大小失敗:%d",dwError);
		AfxMessageBox(cs);
		break;
	}
	//文件大小
	filesize = highsize<<32 | lowsize;
	
	hFileMap = CreateFileMapping(hFile,NULL,
		PAGE_READONLY,
		highsize,
		lowsize,
		NULL);
	if ( hFileMap == NULL )
	{
		CString cs;
		cs.Format("建立CreateFileMapping失敗:%d",GetLastError());
		AfxMessageBox(cs);
		break;
	}
	offset = 0;
	
	mapsize = (int)(filesize > viewmapsize ? viewmapsize : filesize);
	fileoffsethigh = (int)(offset >> 32);
	fileoffsetlow = (int)(offset / viewmapsize * viewmapsize);
	
	LPVOID lpmap;
	while ( filesize > offset && ( lpmap = MapViewOfFile(hFileMap,FILE_MAP_READ,fileoffsethigh,fileoffsetlow,mapsize) ) != NULL )
	{
		offset += mapsize;
		remain = filesize - offset;
		
		mapsize = (int)(remain > viewmapsize ? viewmapsize : remain);
		fileoffsethigh = (int)(offset >> 32);
		fileoffsetlow = (int)(offset);
		
		UnmapViewOfFile(lpmap);
		
	}
	if ( lpmap == NULL )
	{
		CString cs;
		cs.Format("建立MapViewOfFile失敗:%d",GetLastError());
		AfxMessageBox(cs);
		break;
	}
	else
		UnmapViewOfFile(lpmap);
	
	if ( filesize == offset )
		AfxMessageBox("映射文件結束");
	
}while (0);

if ( hFileMap )
CloseHandle(hFileMap);
if (hFile)
CloseHandle(hFile);