我有以下代码可以使用信号量连续 R/W 到 sherad 内存。但是当代码试图访问内存进行读取时，它会失败。我找不到问题所在。任何帮助都非常感谢......这是完整的代码：
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>
#include <cstdlib>
#include<iostream>
#define BUF_SIZE 255
#define TREAD_COUNT 2
#define MAX_SEM_COUNT 1
using namespace std;
char name[]="Global\\MyFileMappingObject";
char* message ="Message from first process.";
char ReadBuffer[BUF_SIZE];
char WriteBuffer[BUF_SIZE];
DWORD WINAPI ReadData( LPVOID );
DWORD WINAPI WriteData( LPVOID );
HANDLE HandleOfTreads[TREAD_COUNT];
HANDLE ghSemaphore;
HANDLE ReadHandleToMapFile;
HANDLE WriteHandleToMapFile;
DWORD ThreadID;
char* PBufForRead;
char* PBufForWrite;
string ReadString;
char PBufForReadPrev[BUF_SIZE];
int _tmain() {
/*================ Semaphore ======================= */
ghSemaphore = CreateSemaphore(
NULL, // default security attributes
MAX_SEM_COUNT, // initial count
MAX_SEM_COUNT, // maximum count
"name"); // named semaphore
if (ghSemaphore == NULL) {
printf("CreateSemaphore error: %d\n", GetLastError());
return 1;
}
/*================ Read Tread====================== */
HandleOfTreads[0] = CreateThread(
NULL, // default security attributes
0, // default stack size
(LPTHREAD_START_ROUTINE) ReadData,
NULL, // no thread function arguments
0, // default creation flags
&ThreadID); // receive thread identifier
if( HandleOfTreads[0]== NULL ) {
printf("CreateThread error: %d\n", GetLastError());
return 1;
}
/*============ Write Tread=============== */
HandleOfTreads[1]= CreateThread(
NULL, // default security attributes
0, // default stack size
(LPTHREAD_START_ROUTINE) WriteData,
NULL, // no thread function arguments
0, // default creation flags
&ThreadID); // receive thread identifier
if(HandleOfTreads[1] == NULL ) {
printf("CreateThread error: %d\n", GetLastError());
return 1;
}
/*============ close handles ============= */
// Wait for all threads to terminate
WaitForMultipleObjects(TREAD_COUNT, HandleOfTreads, TRUE, INFINITE);
// Close thread handles
for( int i=0; i < TREAD_COUNT; i++ )
CloseHandle( HandleOfTreads[i]);
return 0;
}
/*======================= Write data====================== */
DWORD WINAPI ReadData( LPVOID lpParam) {
cout<<"write"<<endl;
UNREFERENCED_PARAMETER(lpParam);
DWORD dwWaitResult;
while(1) {
dwWaitResult = WaitForSingleObject(
ghSemaphore, // handle to semaphore
INFINITE); // infinite time-out interval
cout<<"write got the semaphore"<<endl;
switch (dwWaitResult) {
// The semaphore object was signaled.
case WAIT_OBJECT_0:
WriteHandleToMapFile = 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)
name); // name of mapping object
if (WriteHandleToMapFile== NULL) {
_tprintf(TEXT("Could not create file mapping object for write(%d).\n"),
GetLastError());
return 1;
}
PBufForWrite= (LPTSTR) MapViewOfFile(WriteHandleToMapFile, // handle to map object
FILE_MAP_ALL_ACCESS, // read/write permission
0,
0,
BUF_SIZE);
if ( PBufForWrite== NULL) {
_tprintf(TEXT("Could not map view of file for write (%d).\n"),
GetLastError());
CloseHandle(WriteHandleToMapFile);
return 1;
}
getline(cin,ReadString);
strcpy(ReadBuffer,ReadString.c_str());
CopyMemory((PVOID) PBufForWrite, ReadBuffer, (_tcslen(message) * sizeof(TCHAR)));
UnmapViewOfFile((void*)PBufForWrite);
CloseHandle(WriteHandleToMapFile);
cout<<"write released the memory"<<endl;
// Release the semaphore when task is finished
if (!ReleaseSemaphore(
ghSemaphore, // handle to semaphore
1, // increase count by one
NULL) ) { // not interested in previous count
printf("ReleaseSemaphore error: %d\n", GetLastError());
}
cout<<"write released the semaphore"<<endl;
break;
// The semaphore was nonsignaled, so a time-out occurred.
case WAIT_TIMEOUT:
printf("Thread %d: wait timed out\n", GetCurrentThreadId());
break;
}
}
}
/*======================= Read data====================== */
DWORD WINAPI WriteData( LPVOID lpParam)
{
UNREFERENCED_PARAMETER(lpParam);
cout<<"read"<<endl;
DWORD dwWaitResult;
while(1)
{
dwWaitResult = WaitForSingleObject(
ghSemaphore, // handle to semaphore
INFINITE); // zero-second time-out interval
cout<<"read got the semaphore"<<endl;
switch (dwWaitResult)
{
// The semaphore object was signaled.
case WAIT_OBJECT_0:
Sleep(100);
ReadHandleToMapFile = OpenFileMapping(
FILE_MAP_ALL_ACCESS, // read/write access
FALSE, // do not inherit the name
name); // name of mapping object
if (ReadHandleToMapFile == NULL) {
printf(TEXT("Could not open file mapping object for read (%d).\n"),GetLastError());
cout<<"read exited"<<endl;
return EXIT_SUCCESS;
}
PBufForRead= (LPTSTR) MapViewOfFile(ReadHandleToMapFile, // handle to map object
FILE_MAP_ALL_ACCESS, // read/write permission
0,
0,
BUF_SIZE);
if ( PBufForRead== NULL) {
printf(TEXT("Could not map view of file for write (%d).\n"),GetLastError());
CloseHandle(ReadHandleToMapFile);
system("PAUSE");
return EXIT_SUCCESS;
}
if(strcmp( PBufForRead, PBufForReadPrev)) {
cout<< PBufForRead<<endl;
}
strcpy( PBufForReadPrev, PBufForRead);
UnmapViewOfFile((void*)PBufForRead);
CloseHandle(ReadHandleToMapFile);
cout<<"read release the memory"<<endl;
// Release the semaphore when task is finished
if (!ReleaseSemaphore(
ghSemaphore, // handle to semaphore
1, // increase count by one
NULL) ) { // not interested in previous count
printf("ReleaseSemaphore error: %d\n", GetLastError());
}
cout<<"read selased the semaphore"<<endl;
break;
// The semaphore was nonsignaled, so a time-out occurred.
case WAIT_TIMEOUT:
printf("Thread %d: wait timed out\n", GetCurrentThreadId());
break;
}
}
}