/*演示如何使用semaphore進行互斥訪問說明: read1, read2, read3互斥訪問, write等三個read讀完后才能寫，通過信息量進行控制 */#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 << "讀線程1開始讀取...\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 << "讀線程2開始讀取...\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 << "讀線程3開始讀取...\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 << "寫線程開始寫入...\n";pparams->a = rand() % 256;cout << "寫入" << (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; }/*程序運行情況：================= 寫線程開始寫入... 寫入41 讀線程2開始讀取... 41 讀線程1開始讀取... 41 讀線程3開始讀取... 41================= 寫線程開始寫入... 寫入35 讀線程1開始讀取... 35 讀線程3開始讀取... 35 讀線程2開始讀取... 35================= 寫線程開始寫入... 寫入190 讀線程1開始讀取... 190 讀線程3開始讀取... 190 讀線程2開始讀取... 190================= 寫線程開始寫入... 寫入132 讀線程1開始讀取... 132 讀線程3開始讀取... 132 讀線程2開始讀取... 132================= 寫線程開始寫入... 寫入225 讀線程1開始讀取... 225 讀線程3開始讀取... 225 讀線程2開始讀取... 225================= 寫線程開始寫入... 寫入108 讀線程1開始讀取... 108 讀線程3開始讀取... 108 讀線程2開始讀取... 108================= 寫線程開始寫入... 寫入214 讀線程1開始讀取... 214 讀線程3開始讀取... 214 讀線程2開始讀取... 214================= 寫線程開始寫入... 寫入174 讀線程2開始讀取... 174 讀線程1開始讀取... 174 讀線程3開始讀取... 174================= 寫線程開始寫入... 寫入82 讀線程1開始讀取... 82 讀線程3開始讀取... 82 讀線程2開始讀取... 82================= 寫線程開始寫入... 寫入144 讀線程3開始讀取... 144 讀線程2開始讀取... 144 讀線程1開始讀取... 144*/

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