/////////////////////////////////////////////////////////////////////////////
// MemMapFile.cpp   內存映射的 - 文件操作 ( Memory Mapping File )          //
// CopyRight(C)   1996,2008   TCSY 公司                                    //
// Pentium Working Room   ShanChengKun   2003.10.28   更新                 //
/////////////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "MemMapFile.h"

//===========================================================================
// 執著地按指定大小映射文件，沒有則創建，有則直接打開，覆蓋只讀文件會失敗
//===========================================================================
void * CMemMapFile::CreateNewFile (LPCTSTR szFileName, DWORD dwMaxFileSize)
{
	this->UnMapFile () ;
	m_hFile = ::CreateFile (szFileName, GENERIC_READ | GENERIC_WRITE,
							FILE_SHARE_READ, NULL, CREATE_ALWAYS,
							FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL) ;
	if (m_hFile == INVALID_HANDLE_VALUE)
		return NULL ;

	m_hFileMap = ::CreateFileMapping (m_hFile, NULL, PAGE_READWRITE, 0, dwMaxFileSize, NULL) ;
	if (m_hFileMap == NULL)
	{
		::CloseHandle (m_hFile) ;
		m_hFile = INVALID_HANDLE_VALUE ;
		return NULL ;
	}

	m_pMapAddress = ::MapViewOfFile (m_hFileMap, FILE_MAP_ALL_ACCESS, 0, 0, 0) ;
	if (m_pMapAddress == NULL)
		this->UnMapFile () ;
	return (void *)m_pMapAddress ;
}

//===========================================================================
// 執著地按指定大小映射文件，沒有則創建，有則直接打開，覆蓋只讀文件會失敗
//===========================================================================
void * CMemMapFile::OpenExistFile (LPCTSTR szFileName, DWORD dwMaxFileSize)
{
	this->UnMapFile () ;
	m_hFile = ::CreateFile (szFileName, GENERIC_READ | GENERIC_WRITE,
							FILE_SHARE_READ, NULL, OPEN_ALWAYS,
							FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL) ;
	if (m_hFile == INVALID_HANDLE_VALUE)
		return NULL ;

	m_hFileMap = ::CreateFileMapping (m_hFile, NULL, PAGE_READWRITE, 0, dwMaxFileSize, NULL) ;
	if (m_hFileMap == NULL)
	{
		::CloseHandle (m_hFile) ;
		m_hFile = INVALID_HANDLE_VALUE ;
		return NULL ;
	}

	m_pMapAddress = ::MapViewOfFile (m_hFileMap, FILE_MAP_ALL_ACCESS, 0, 0, 0) ;
	if (m_pMapAddress == NULL)
		this->UnMapFile () ;
	return (void *)m_pMapAddress ;
}

//===========================================================================
// 只讀方式打開并映射指定的已經存在的文件，并發的程序可以只讀的方式訪問
//===========================================================================
void * CMemMapFile::OpenReadFile (LPCTSTR szFileName)
{
	this->UnMapFile () ;
	m_hFile = ::CreateFile (szFileName, GENERIC_READ, FILE_SHARE_READ, NULL,
							OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL) ;
	if (m_hFile == INVALID_HANDLE_VALUE)
		return NULL ;

	m_hFileMap = ::CreateFileMapping (m_hFile, NULL, PAGE_READONLY, 0, 0, NULL) ;
	if (m_hFileMap == NULL)
	{
		::CloseHandle (m_hFile) ;
		m_hFile = INVALID_HANDLE_VALUE ;
		return NULL ;
	}

	m_pMapAddress = ::MapViewOfFile (m_hFileMap, FILE_MAP_READ, 0, 0, 0) ;
	if (m_pMapAddress == NULL)
		this->UnMapFile () ;
	return (void *)m_pMapAddress ;
}

/////////////////////////////////////////////////////////////////////////////