内存映射文件

内存映射文件 (windows许多方法用此来在进程间传送数据）
1.CreateFile
2.CreateFileMapping //对含有SEC_LARGE_PAGES标志时用户必须具有启用内存锁定页面用户权限，否则会失败
3.MapViewOfFile
4. //FlushViewOfFile //确保所做的修改已经被写入到磁盘中，如果最初是FILE_MAP_COPY,将修改页交换文件中的文件数据副本，如果是这样的话ummapviewoffile后数据丢失。可以再做个PAGE_READWRITE视图，再MoveMemory从前一视图拷到这个视图。
5.UnmapViewOfFile
6.CloseHandle(hMap);CloseHandle(hFile); //先后顺序无关，MapViewOfFile副作用是增加hFile引用计数。

对多个进程共享同一个文件映射对象来说，所有进程使用的文件映射对象的名称必须完全相同。

CreateFileMapping传入INVALID_HANDLE_VALUE时映射页交换文件，不再映射磁盘文件。

#include <Windows.h>
#include <string>
#include <iostream>
using namespace std;

bool FileReverse(const wchar_t* pcFileName)
{
	BOOL bIsUnicode = false;
	HANDLE hFile = CreateFileW(pcFileName,GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
	if( hFile == INVALID_HANDLE_VALUE )	//here must check, because createfilemapping can accept INVALID_HANDLE_VALUE, and different map view 
	{
		cout<<"CreateFileW fail"<<endl;
		return false;
	}
	DWORD dwFileSize = GetFileSize(hFile,NULL);
	HANDLE hMap = CreateFileMappingW(hFile,NULL,PAGE_READWRITE,0,dwFileSize*sizeof(wchar_t),NULL);
	if( hMap == NULL )
	{
		cout<<"CreateFileMappingW fail"<<endl;
		CloseHandle(hFile);
		return false;
	}
	PVOID pvFile = MapViewOfFile(hMap,FILE_MAP_WRITE,0,0,0);
	if( pvFile == NULL )
	{
		cout<<"MapViewOfFile fail"<<endl;
		CloseHandle(hMap);
		CloseHandle(hFile);
		return false;
	}
	
	int iUnicodeTestFlag = -1;
	bIsUnicode = IsTextUnicode(pvFile,dwFileSize,&iUnicodeTestFlag);
	if(!bIsUnicode)
	{
		char *pchar = (char*)pvFile;
		pchar[dwFileSize/sizeof(char)] = '\0';
		_strrev(pchar);
		
		pchar = strstr(pchar,"\n\r");	//find first \r\n
		while( pchar != NULL )
		{
			*pchar++ = '\r';
			*pchar++ = '\n';
			pchar = strstr(pchar,"\n\r");
		}
	}
	else
	{
		wchar_t *pwchar = (wchar_t*)pvFile;
		pwchar[dwFileSize/sizeof(wchar_t)] = L'\0';
		if((iUnicodeTestFlag & IS_TEXT_UNICODE_SIGNATURE) != 0)
		{
			pwchar++;
		}
		_wcsrev(pwchar);
		
		pwchar = wcsstr(pwchar,L"\n\r");	//find first \r\n
		while( pwchar != NULL )
		{
			*pwchar++ = L'\r';
			*pwchar++ = L'\n';
			pwchar = wcsstr(pwchar,L"\n\r");
		}
	}

	UnmapViewOfFile(pvFile);
	CloseHandle(hMap);

	//delete manuly append '\0'
	SetFilePointer(hFile,dwFileSize,NULL,FILE_BEGIN);
	SetEndOfFile(hFile);
	CloseHandle(hFile);
	return true;
}

void wmain()
{
	FileReverse(L"testu.txt");
}