不用MFC的CMemFile类如何创建内存文件？

[bilbo0214]

我想使用内存文件，但不知道如何创建。
那位朋友能够举个简单的例子。

[bilbo0214]

有个问题，如果不用SDK，难道就不能实现吗？

[yndfcd]

CreateFileMapping(0xFFFFFFFF, NULL, PAGE_READWRIT, 0, SIZELOW, szFileName);

[Skt32]

sdk

[Skt32]

hMap = CreateFileMapping(...);

if (hMap != NULL && GetLastError() == ERROR_ALREADY_EXISTS)
{
CloseHandle(hMap);
hMap = NULL;
}
return hMap;

[Skt32]

Below is the complete source code for MeteredSection.h and MeteredSection.c. This is the same code that you can copy from the link at the top of this article.

/************************************************************
Module Name: MeteredSection.h
Author: Dan Chou
Description: Defines the metered section synchronization object
************************************************************/

#ifndef _METERED_SECTION_H_
#define _METERED_SECTION_H_

#define MAX_METSECT_NAMELEN 128

#ifdef __cplusplus
extern "C"
{
#endif // __cplusplus

// Shared info needed for metered section
typedef struct _METSECT_SHARED_INFO {
BOOL fInitialized; // Is the metered section initialized?
LONG lSpinLock; // Used to gain access to this structure
LONG lThreadsWaiting; // Count of threads waiting
LONG lAvailableCount; // Available resource count
LONG lMaximumCount; // Maximum resource count
} METSECT_SHARED_INFO, *LPMETSECT_SHARED_INFO;

// The opaque Metered Section data structure
typedef struct _METERED_SECTION {
HANDLE hEvent; // Handle to a kernel event object
HANDLE hFileMap; // Handle to memory mapped file
LPMETSECT_SHARED_INFO lpSharedInfo;
} METERED_SECTION, *LPMETERED_SECTION;

// Interface functions
LPMETERED_SECTION
CreateMeteredSection(LONG lInitialCount, LONG lMaximumCount, LPCTSTR lpName);

#ifndef _WIN32_WCE
LPMETERED_SECTION OpenMeteredSection(LPCTSTR lpName);
#endif

DWORD EnterMeteredSection(LPMETERED_SECTION lpMetSect, DWORD dwMilliseconds);
BOOL LeaveMeteredSection(LPMETERED_SECTION lpMetSect, LONG lReleaseCount, LPLONG lpPreviousCount);
void CloseMeteredSection(LPMETERED_SECTION lpMetSect);

#ifdef __cplusplus
}
#endif // __cplusplus

#endif // _METERED_SECTION_H_

/************************************************************
Module Name: MeteredSection.c
Author: Dan Chou
Description: Implements the metered section synchronization object
************************************************************/

#include <windows.h>
#include <tchar.h>
#include "MeteredSection.h"

// Internal function declarations
BOOL InitMeteredSection(LPMETERED_SECTION lpMetSect, LONG lInitialCount, LONG lMaximumCount, LPCTSTR lpName, BOOL bOpenOnly);
BOOL CreateMetSectEvent(LPMETERED_SECTION lpMetSect, LPCTSTR lpName, BOOL bOpenOnly);
BOOL CreateMetSectFileView(LPMETERED_SECTION lpMetSect, LONG lInitialCount, LONG lMaximumCount, LPCTSTR lpName, BOOL bOpenOnly);
void GetMeteredSectionLock(LPMETERED_SECTION lpMetSect);
void ReleaseMeteredSectionLock(LPMETERED_SECTION lpMetSect);

/*
* CreateMeteredSection
*/
LPMETERED_SECTION CreateMeteredSection(LONG lInitialCount, LONG lMaximumCount, LPCTSTR lpName)
{
LPMETERED_SECTION lpMetSect;

// Verify the parameters
if ((lMaximumCount < 1) ||
(lInitialCount > lMaximumCount) ||
(lInitialCount < 0) ||
((lpName) && (_tcslen(lpName) > MAX_METSECT_NAMELEN)))
{
SetLastError(ERROR_INVALID_PARAMETER);
return NULL;
}

// Allocate memory for the metered section
lpMetSect = (LPMETERED_SECTION)malloc(sizeof(METERED_SECTION));

// If the memory for the metered section was allocated okay, initialize it
if (lpMetSect)
{
if (!InitMeteredSection(lpMetSect, lInitialCount, lMaximumCount, lpName, FALSE))
{
CloseMeteredSection(lpMetSect);
lpMetSect = NULL;
}
}
return lpMetSect;
}

/*
* OpenMeteredSection
*/
#ifndef _WIN32_WCE
LPMETERED_SECTION OpenMeteredSection(LPCTSTR lpName)
{
LPMETERED_SECTION lpMetSect = NULL;

if (lpName)
{
lpMetSect = (LPMETERED_SECTION)malloc(sizeof(METERED_SECTION));

// If the memory for the metered section was allocated okay
if (lpMetSect)
{
if (!InitMeteredSection(lpMetSect, 0, 0, lpName, TRUE))
{
// Metered section failed to initialize
CloseMeteredSection(lpMetSect);
lpMetSect = NULL;
}
}
}
return lpMetSect;
}
#endif

/*
* EnterMeteredSection
*/
DWORD EnterMeteredSection(LPMETERED_SECTION lpMetSect, DWORD dwMilliseconds)
{
while (TRUE)
{
GetMeteredSectionLock(lpMetSect);

// We have access to the metered section, everything we do now will be atomic
if (lpMetSect->lpSharedInfo->lAvailableCount >= 1)
{
lpMetSect->lpSharedInfo->lAvailableCount--;
ReleaseMeteredSectionLock(lpMetSect);
return WAIT_OBJECT_0;
}

// Couldn't get in. Wait on the event object
lpMetSect->lpSharedInfo->lThreadsWaiting++;
ResetEvent(lpMetSect->hEvent);
ReleaseMeteredSectionLock(lpMetSect);
if (WaitForSingleObject(lpMetSect->hEvent, dwMilliseconds) == WAIT_TIMEOUT)
{
return WAIT_TIMEOUT;
}
}
}

/*
* LeaveMeteredSection
*/
BOOL LeaveMeteredSection(LPMETERED_SECTION lpMetSect, LONG lReleaseCount, LPLONG lpPreviousCount)
{
int iCount;
GetMeteredSectionLock(lpMetSect);

// Save the old value if they want it
if (lpPreviousCount)
{
*lpPreviousCount = lpMetSect->lpSharedInfo->lAvailableCount;
}

// We have access to the metered section, everything we do now will be atomic
if ((lReleaseCount < 0) ||
(lpMetSect->lpSharedInfo->lAvailableCount+lReleaseCount >
lpMetSect->lpSharedInfo->lMaximumCount))
{
ReleaseMeteredSectionLock(lpMetSect);
SetLastError(ERROR_INVALID_PARAMETER);
return FALSE;
}
lpMetSect->lpSharedInfo->lAvailableCount += lReleaseCount;

// Set the event the appropriate number of times
lReleaseCount = min(lReleaseCount,lpMetSect->lpSharedInfo->lThreadsWaiting);
if (lpMetSect->lpSharedInfo->lThreadsWaiting)
{
for (iCount=0; iCount < lReleaseCount ; iCount++)
{
lpMetSect->lpSharedInfo->lThreadsWaiting--;
SetEvent(lpMetSect->hEvent);
}
}
ReleaseMeteredSectionLock(lpMetSect);
return TRUE;
}

/*
* CloseMeteredSection
*/

[bilbo0214]

请继续