面试题-多线程编程
题目:
四个线程 t1,t2,t3,t4,向 4 个文件中写入数据, t1 只能写入 1, t2 只能写入 2, t3 只能写
入 3, t4 只能写入 4,对 4 个文件 A, B, C, D 写入如下内容
A:123412341234.....
B:234123412341....
C:341234123412....
D:412341234123....
怎么实现同步可以让线程并行工作?
用windows c++实现.
// 222_thread.cpp : 定义控制台应用程序的入口点。 // #include "stdafx.h" #include <windows.h> #include <thread> #include <iostream> using namespace std; HANDLE ghMutex; HANDLE handles[4][4]; int idxx = 1; void threadA() { int idx = 0; do { DWORD res = WaitForMultipleObjects(4, handles[0], false, INFINITE); WaitForSingleObject(ghMutex, INFINITE); switch (res) { case WAIT_OBJECT_0: cout << "A" ; SetEvent(handles[1][0]); break; case WAIT_OBJECT_0+1: cout << "B"; SetEvent(handles[1][1]); break; case WAIT_OBJECT_0+2: cout << "C"; SetEvent(handles[1][2]); break; case WAIT_OBJECT_0+3: cout << "D"; SetEvent(handles[1][3]); break; } cout << 1; idxx++; ReleaseMutex(ghMutex); } while (idxx < 50); } void threadB() { int idx = 0; do { DWORD res = WaitForMultipleObjects(4, handles[1], false, INFINITE); WaitForSingleObject(ghMutex, INFINITE); switch (res) { case WAIT_OBJECT_0: cout << "A"; SetEvent(handles[2][0]); break; case WAIT_OBJECT_0 + 1: cout << "B"; SetEvent(handles[2][1]); break; case WAIT_OBJECT_0 + 2: cout << "C"; SetEvent(handles[2][2]); break; case WAIT_OBJECT_0 + 3: cout << "D"; SetEvent(handles[2][3]); break; } cout << 2; idxx++; ReleaseMutex(ghMutex); } while (idxx < 50); } void threadC() { int idx = 0; do { DWORD res = WaitForMultipleObjects(4, handles[2], false, INFINITE); WaitForSingleObject(ghMutex, INFINITE); switch (res) { case WAIT_OBJECT_0: cout << "A"; SetEvent(handles[3][0]); break; case WAIT_OBJECT_0 + 1: cout << "B"; SetEvent(handles[3][1]); break; case WAIT_OBJECT_0 + 2: cout << "C"; SetEvent(handles[3][2]); break; case WAIT_OBJECT_0 + 3: cout << "D"; SetEvent(handles[3][3]); break; } cout << 3; idxx++; ReleaseMutex(ghMutex); } while (idxx < 50); } void threadD() { int idx = 0; do { DWORD res = WaitForMultipleObjects(4, handles[3], false, INFINITE); WaitForSingleObject(ghMutex, INFINITE); switch (res) { case WAIT_OBJECT_0: cout << "A"; SetEvent(handles[0][0]); break; case WAIT_OBJECT_0 + 1: cout << "B"; SetEvent(handles[0][1]); break; case WAIT_OBJECT_0 + 2: cout << "C"; SetEvent(handles[0][2]); break; case WAIT_OBJECT_0 + 3: cout << "D"; SetEvent(handles[0][3]); break; } cout << 4; idxx++; ReleaseMutex(ghMutex); } while (idxx < 50); } void WriteA() { SetEvent(handles[0][0]); } void WriteB() { SetEvent(handles[1][1]); } void WriteC() { SetEvent(handles[2][2]); } void WriteD() { SetEvent(handles[3][3]); } int _tmain(int argc, _TCHAR* argv[]) { /* file A file B file C file D thread 1 handle[0][0] handle[0][1] handle[0][2] handle[0][3] thread 2 handle[1][0] handle[1][1] handle[1][2] handle[1][3] thread 3 handle[2][0] handle[2][1] handle[2][2] handle[2][3] thread 4 handle[3][0] handle[3][1] handle[3][2] handle[3][3] */ for (int i = 0; i < 4; i++) { for (int j = 0; j < 4; j++) { handles[i][j] = CreateEvent(NULL, false, false, NULL); } } DWORD threadID; CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)threadA, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)threadB, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)threadC, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)threadD, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)WriteA, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)WriteB, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)WriteC, NULL, 0, &threadID); CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)WriteD, NULL, 0, &threadID); ghMutex = CreateMutex( NULL, // default security attributes FALSE, // initially not owned NULL); // unnamed mutex if (ghMutex == NULL) { printf("CreateMutex error: %d\n", GetLastError()); return 1; } Sleep(60000); return 0; }
作者:
HarlanC
博客地址:
http://www.cnblogs.com/harlanc/
个人博客:
http://www.harlancn.me/
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