Windows IPC 进程间通信之共享内存

1. 必须先创建共享内存，才能够打开
2. 关闭共享内存后，就无法打开
3. 使用Global则必须是管理员权限才能创建或打开

相当于要读写一个文件，必须先创建文件才能够打开，删掉文件后就无法打开。权限不够的话就无法读写

// share_memory.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <Windows.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>

#define BUF_SIZE 256
TCHAR szName[]=TEXT("Global\\MyFileMappingObject");
TCHAR szMsg[]=TEXT("Message from first process.");

int p1();
int p2();

int _tmain(int argc, _TCHAR* argv[])
{
    if ( argc == 1 )
    {
        p1();
    }
    else
    {
        p2();
    }
    return 0;
}


int p1()
{
   HANDLE hMapFile;
   LPCTSTR pBuf;

   hMapFile = CreateFileMapping(
                 INVALID_HANDLE_VALUE, // use paging file
                 NULL, // default security
                 PAGE_READWRITE, // read/write access
                 0, // maximum object size (high-order DWORD)
                 BUF_SIZE, // maximum object size (low-order DWORD)
                 szName); // name of mapping object

   if (hMapFile == NULL)
   {
      _tprintf(TEXT("Could not create file mapping object (%d).\n"),
             GetLastError());
      return 1;
   }
   pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object
                        FILE_MAP_ALL_ACCESS, // read/write permission
                        0,
                        0,
                        BUF_SIZE);

   if (pBuf == NULL)
   {
      _tprintf(TEXT("Could not map view of file (%d).\n"),
             GetLastError());

       CloseHandle(hMapFile);

      return 1;
   }


   CopyMemory((PVOID)pBuf, szMsg, (_tcslen(szMsg) * sizeof(TCHAR)));
    _getch();

   UnmapViewOfFile(pBuf);

   CloseHandle(hMapFile);

   return 0;
}

int p2()
{
   HANDLE hMapFile;
   LPCTSTR pBuf;

   hMapFile = OpenFileMapping(
                   FILE_MAP_ALL_ACCESS, // read/write access
                   FALSE, // do not inherit the name
                   szName); // name of mapping object

   if (hMapFile == NULL)
   {
      _tprintf(TEXT("Could not open file mapping object (%d).\n"),
             GetLastError());
      return 1;
   }

   pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object
               FILE_MAP_ALL_ACCESS, // read/write permission
               0,
               0,
               BUF_SIZE);

   if (pBuf == NULL)
   {
      _tprintf(TEXT("Could not map view of file (%d).\n"),
             GetLastError());

      CloseHandle(hMapFile);

      return 1;
   }

   MessageBox(NULL, pBuf, TEXT("Process2"), MB_OK);

   UnmapViewOfFile(pBuf);

   CloseHandle(hMapFile);

   return 0;
}