/*演示如何使用semaphore进行互斥访问说明: read1, read2, read3互斥访问, write等三个read读完后才能写，通过信息量进行控制
*/#include<windows.h>
#include<process.h>
#include<iostream>using namespace std;CRITICAL_SECTION cs;				// critical section objecttypedef struct
{HANDLE h1;HANDLE h2;HANDLE h3;HANDLE h4;int a;
}PARAMS, *PPARAMS;void read1(PVOID pvoid)
{while(TRUE){		volatile PPARAMS pparams=(PPARAMS)pvoid;WaitForSingleObject(pparams->h2, INFINITE);EnterCriticalSection(&cs);cout << "读线程1开始读取...\n";cout << (pparams->a) << endl;LeaveCriticalSection(&cs);Sleep(1000);ReleaseSemaphore(pparams->h1, 1, NULL);			// increase count of h1}
}void read2(PVOID pvoid)
{while(TRUE){	volatile PPARAMS pparams=(PPARAMS)pvoid;WaitForSingleObject(pparams->h3, INFINITE);EnterCriticalSection(&cs);cout << "读线程2开始读取...\n";cout << (pparams->a) << endl;LeaveCriticalSection(&cs);Sleep(1000);ReleaseSemaphore(pparams->h1, 1, NULL);}
}void read3(PVOID pvoid)
{while(TRUE){	volatile PPARAMS pparams=(PPARAMS)pvoid;WaitForSingleObject(pparams->h4, INFINITE);		// decrease count of h4EnterCriticalSection(&cs);cout << "读线程3开始读取...\n";cout << (pparams->a) << endl;LeaveCriticalSection(&cs);Sleep(1000);ReleaseSemaphore(pparams->h1, 1, NULL);			// increase count of h1}
}void write(PVOID pvoid)
{while(TRUE){	volatile PPARAMS pparams=(PPARAMS)pvoid;WaitForSingleObject(pparams->h1, INFINITE);		// decrease count of h1WaitForSingleObject(pparams->h1, INFINITE);WaitForSingleObject(pparams->h1, INFINITE);cout << "\n=================\n";cout << "写线程开始写入...\n";pparams->a = rand() % 256;cout << "写入" << (pparams->a) << endl;ReleaseSemaphore(pparams->h2, 1, NULL);			// increase count of h2ReleaseSemaphore(pparams->h3, 1, NULL);ReleaseSemaphore(pparams->h4, 1, NULL);}
}int main()
{PARAMS params;params.h1 = CreateSemaphore(NULL, 3, 3, NULL);	// create semaphore1params.h2 = CreateSemaphore(NULL, 0, 1, NULL);	// create semaphore2params.h3 = CreateSemaphore(NULL, 0, 1, NULL);params.h4 = CreateSemaphore(NULL, 0, 1, NULL);InitializeCriticalSection(&cs);					// init critical section object_beginthread(read1, 0, ¶ms);				// create thread to execute read1()_beginthread(read2, 0, ¶ms);_beginthread(read3, 0, ¶ms);_beginthread(write, 0, ¶ms);Sleep(10 * 1000);								// sleep 10 seconds, waiting for the above threads to running,// or the main thread will quickly exit, then these sub-threads have no time to run// so you will see no outputDeleteCriticalSection(&cs);return 0;
}/*程序运行情况：=================
写线程开始写入...
写入41
读线程2开始读取...
41
读线程1开始读取...
41
读线程3开始读取...
41=================
写线程开始写入...
写入35
读线程1开始读取...
35
读线程3开始读取...
35
读线程2开始读取...
35=================
写线程开始写入...
写入190
读线程1开始读取...
190
读线程3开始读取...
190
读线程2开始读取...
190=================
写线程开始写入...
写入132
读线程1开始读取...
132
读线程3开始读取...
132
读线程2开始读取...
132=================
写线程开始写入...
写入225
读线程1开始读取...
225
读线程3开始读取...
225
读线程2开始读取...
225=================
写线程开始写入...
写入108
读线程1开始读取...
108
读线程3开始读取...
108
读线程2开始读取...
108=================
写线程开始写入...
写入214
读线程1开始读取...
214
读线程3开始读取...
214
读线程2开始读取...
214=================
写线程开始写入...
写入174
读线程2开始读取...
174
读线程1开始读取...
174
读线程3开始读取...
174=================
写线程开始写入...
写入82
读线程1开始读取...
82
读线程3开始读取...
82
读线程2开始读取...
82=================
写线程开始写入...
写入144
读线程3开始读取...
144
读线程2开始读取...
144
读线程1开始读取...
144*/