MapViewOfFile 问题

[shawn]

	HANDLE hFile = CreateFile("media.mp3",
		GENERIC_READ | GENERIC_WRITE,
		FILE_SHARE_READ | FILE_SHARE_WRITE,
		NULL,
		OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL,
		NULL);

	if (hFile == INVALID_HANDLE_VALUE)
	{
		printf("invalid handle value\n");
	}
	DWORD fileSize = GetFileSize(hFile,NULL);
	printf("file size is: %d GB",((fileSize/1024)/1024)/1024);

	HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
		0,fileSize + sizeof(char),NULL);

	if (hFileMap == NULL)
	{
		printf("create file mapping object failed.\n");
	}
	else
	{
		DWORD dwNumberOfBytesToMap = 1024 * 64 * 1024 * 10;
		DWORD dwNum = 0;
		DWORD offset = 0;
		while (fileSize)
		{
			dwNum = dwNumberOfBytesToMap > fileSize? fileSize : dwNumberOfBytesToMap;
	
			LPVOID pvFile = MapViewOfFile(hFileMap,FILE_MAP_WRITE,offset>>32,offset&0xffffffff,dwNum);
			if (pvFile == NULL)
			{
				printf("create map view of file is failed, error code is :%d",GetLastError());
			}
			else
			{
				fileSize -= dwNum;
				offset += dwNum;
				PSTR pchAnsi = (PSTR)pvFile;
			//	pchAnsi[dwNum/sizeof(char)] = 0;

				//_strrev(pchAnsi);
				UnmapViewOfFile(pvFile);
			}
		}
			
		CloseHandle(hFileMap);
	}

	CloseHandle(hFile);

为什么以上的代码第二次调用MapViewOfFile时会出现5，就是拒绝访问的意思吧，media.mp3大小是好几个GB大小 。。。

[海盗医生]

DWORD dwNumberOfBytesToMap = 1024 * 64 * 1024 * 10;
定义个小点看看

[stonewater]

DWORD offset = 0;
->
DWORD64 offset = 0;

[stonewater]

DWORD fileSize = GetFileSize(hFile,NULL);
这句有问题,文件比较大,最后一个参数不能为NULL,你看看GetFileSize的msdn

HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
0,fileSize + sizeof(char),NULL);

这句也有问题,相同的问题

[stonewater]

HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
0,fileSize + sizeof(char),NULL);

可以改为

HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
0,0,NULL);

[shawn]

[Quote=引用 3 楼 stonewater 的回复:]

DWORD fileSize = GetFileSize(hFile,NULL);
这句有问题,文件比较大,最后一个参数不能为NULL,你看看GetFileSize的msdn

HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
0,fileSize + sizeof(char),NULL);

……
[/Quote]

GetFileSize返回的值是正确的，所以这点是没问题的 。。。

[shawn]

[Quote=引用 2 楼 stonewater 的回复:]

DWORD offset = 0;
->
DWORD64 offset = 0;
[/Quote]

问大虾DWORD 和DWORD64的差距在哪里 ？

[shawn]

[Quote=引用 2 楼 stonewater 的回复:]

DWORD offset = 0;
->
DWORD64 offset = 0;
[/Quote]

抱歉，还以为DWORD是两个机器字长的长度呢 。。。

[Eleven]

DWORD
32-bit unsigned integer. The range is 0 through 4294967295 decimal.

This type is declared in WinDef.h as follows:


typedef unsigned long DWORD;


DWORD64
64-bit unsigned integer.

This type is declared in BaseTsd.h as follows:


typedef unsigned __int64 DWORD64;

[yiruirui0507]

改动2个地方你先测试一下吧：
1 HANDLE hFileMap = CreateFileMapping(hFile,NULL,PAGE_READWRITE,
0,0,NULL);
2 LPVOID pvFile = MapViewOfFile(hFileMap,FILE_MAP_WRITE,offset>>32,offset&0xffffffff,0);