多個進(jìn)程可以通過在系統(tǒng)頁面文件中存儲的內(nèi)存映射文件來實(shí)現(xiàn)多個進(jìn)程共享數(shù)據(jù)。
第一個進(jìn)程
The first process creates the file mapping object by calling the CreateFileMapping function with INVALID_HANDLE_VALUE and a name for the object. By using the PAGE_READWRITE flag, the process has read/write permission to the memory through any file views that are created.
Then the process uses the file mapping object handle that CreateFileMapping returns in a call to MapViewOfFile to create a view of the file in the process address space. The MapViewOfFile function returns a pointer to the file view, pBuf. The process then uses the CopyMemory function to write a string to the view that can be accessed by other processes.
When the process no longer needs access to the file mapping object, it should call the CloseHandle function. When all handles are closed, the system can free the section of the paging file that the object uses.
第一個進(jìn)程通過調(diào)用以INVALID_HANDLE_VALUE 為參數(shù)的CreateFileMapping方法創(chuàng)建一個命名的內(nèi)存映射文件對象。通過使用PAGE_READWRITE 標(biāo)識，進(jìn)程可通過任何以創(chuàng)建文件視圖獲得文件讀寫權(quán)限。
然后進(jìn)程使用
CreateFileMapping 返回的對象句柄作為參數(shù)調(diào)用
MapViewOfFile 方法在進(jìn)程地址空間內(nèi)創(chuàng)建一個文件視圖。
MapViewOfFile 返回一個文件視圖的指針。進(jìn)程可以調(diào)用
CopyMemory 方法寫一段字串到文件視圖，而該視圖可以被其他進(jìn)程訪問。
當(dāng)進(jìn)程不在需要訪文件映射對象是，應(yīng)該調(diào)用
CloseHandle 方法。當(dāng)所有的進(jìn)程都關(guān)閉后，系統(tǒng)會釋放對象所使用的頁面文件。
1
#include <windows.h>
2#include <stdio.h>
3#include <conio.h>
4
5#define BUF_SIZE 256
6TCHAR szName[]=TEXT("Global\\MyFileMappingObject");
7TCHAR szMsg[]=TEXT("Message from first process");
8
9int main()
10
{
11
HANDLE hMapFile;
12 LPCTSTR pBuf;
13
14 hMapFile = CreateFileMapping(
15 INVALID_HANDLE_VALUE, // use paging file使用系統(tǒng)頁面文件
16 NULL, // default security
17 PAGE_READWRITE, // read/write access
18 0, // max. object size
19 BUF_SIZE, // buffer size
20 szName); // name of mapping object
21
22 if (hMapFile == NULL)
23
{
24 printf("Could not create file mapping object (%d).\n",
25 GetLastError());
26 return 1;
27
}
28 pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object
29 FILE_MAP_ALL_ACCESS, // read/write permission
30 0,
31 0,
32 BUF_SIZE);
33
34 if (pBuf == NULL)
35 {
36 printf("Could not map view of file (%d).\n",
37 GetLastError());
38 return 2;
39 }
40
41
42 CopyMemory((PVOID)pBuf, szMsg, strlen(szMsg));
43 _getch();
44
45 UnmapViewOfFile(pBuf);
46
47 CloseHandle(hMapFile);
48
49 return 0;
50
}
51
第二個進(jìn)程
A second process can access the string written to the shared memory by the first process by calling the OpenFileMapping function specifying the same name for the mapping object as the first process. Then it can use the MapViewOfFile function to obtain a pointer to the file view, pBuf. The process can display this string as it would any other string. In this example, the message box displayed contains the message "Message from first process" that was written by the first process.
第二個進(jìn)程可以通過OpenFileMapping 方法并且指定與第一個進(jìn)程中相同的內(nèi)存映射文件對象名稱來訪問共享內(nèi)存中的字串。然后可通過MapViewOfFile 方法得到文件視圖的指針pBuf
1#include <windows.h>
2#include <stdio.h>
3#include <conio.h>
4
5#define BUF_SIZE 256
6TCHAR szName[]=TEXT("Global\\MyFileMappingObject");
7
8int main()
9{
10 HANDLE hMapFile;
11 LPCTSTR pBuf;
12
13 hMapFile = OpenFileMapping(
14 FILE_MAP_ALL_ACCESS, // read/write access
15 FALSE, // do not inherit the name
16 szName); // name of mapping object
17
18 if (hMapFile == NULL)
19 {
20 printf("Could not open file mapping object (%d).\n",
21 GetLastError());
22 return 1;
23 }
24
25 pBuf = (LPTSTR) MapViewOfFile(hMapFile, // handle to map object
26 FILE_MAP_ALL_ACCESS, // read/write permission
27 0,
28 0,
29 BUF_SIZE);
30
31 if (pBuf == NULL)
32 {
33 printf("Could not map view of file (%d).\n",
34 GetLastError());
35 return 2;
36 }
37
38 MessageBox(NULL, pBuf, TEXT("Process2"), MB_OK);
39
40 UnmapViewOfFile(pBuf);
41
42 CloseHandle(hMapFile);
43
44 return 0;
45}
46
更多內(nèi)容參照
http://baike.baidu.com/view/394293.htm