对象池模式在软件中广泛使用，例如，线程池，连接池，内存池等。Boost库中的pool实现了内存池，thread_group实现了简单的线程池。
以下实现的线程池与boost无关，只是提供一种思路。
Task类：
对应要执行的任务Task::run, 任务入参Task::mParam.
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class Task {
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public:
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Task(
int val=
0):
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mParam(val)
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{
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}
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virtual ~Task() {
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}
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void setParam(int val) {
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mParam = val;
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}
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void run() {
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thread::id threadId =
std::this_thread::get_id();
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cout <<
"param = " << mParam <<
" ThreadId = " << threadId <<
endl;
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string data =
"param = " +
std::to_string(mParam)+
" ThreadId = "+ getThreadIdOfString(threadId) +
"\n";
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myLogger.logData(data);
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}
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private:
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int mParam;
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};
threadPool类：
成员变量vector<shared_ptr<thread>> threadCache保存构造函数中开辟的线程；构造函数中开辟线程，各个线程的入口函数都是threadFunc，如果任务队列为空则线程bolck，等待任务。
std::queue<Task> mTasksQueue保存外界传入的要执行的task.
std::condition_variable mCondVar用于当任务队列mTasksQueue不为空时，唤醒一个线程，从队列头取出一个task执行。
stopAllThreads()用于停止所有线程；
joinThreads()用于等待所有线程结束，在析构函数中被调用。
Note:
threadFunc函数中的线程唤醒条件while (mTasksQueue.empty() && !mReceStopOrder)， 不加mReceStopOrder的判断，易导致stopAllThreads()可能不起作用（调用stopAllThreads函数时，taskQueue已经为空）。
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//c++实现线程池：
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class threadPool {
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public:
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threadPool(
int maxThreadsNum=
1):
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mMaxThreadsNum(maxThreadsNum){
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mReceStopOrder =
false;
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//creat threads:
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for (
int i =
0; i < mMaxThreadsNum; ++i) {
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shared_ptr<thread> th =
std::make_shared<thread>(&threadPool::threadFunc,
this);
//Ok
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//shared_ptr<thread> th = std::make_shared<thread>(std::bind(&threadPool::threadFunc, this)); //Ok
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//shared_ptr<thread> th = std::make_shared<thread>(std::bind(&threadPool::threadFunc, *this));//build error
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//newThread.detach();
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threadCache.push_back(th);
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}
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}
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void joinThreads() {
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for (
auto& it : threadCache) {
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it->join();
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}
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}
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virtual ~threadPool() {
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joinThreads();
//等待所有线程结束
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}
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void pushTask(Task task) {
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std::lock_guard<std::mutex> lk(mMux);
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mTasksQueue.push(task);
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mCondVar.notify_one();
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}
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//构造函数中开辟的多个线程的入口
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void threadFunc() {
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while (
true)
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{
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//终止函数,停止线程
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if (mReceStopOrder) {
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myLogger.logData(
"break---");
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break;
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}
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std::unique_lock<std::mutex> lk(mMux);
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while (mTasksQueue.empty() && !mReceStopOrder)
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{
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mCondVar.wait(lk);
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}
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if (mReceStopOrder) {
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myLogger.logData(
"break");
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break;
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}
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//get a task and execute it:
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Task task = mTasksQueue.front();
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mTasksQueue.pop();
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lk.unlock();
//显式地解锁.
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task.run();
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}
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thread::id threadId =
std::this_thread::get_id();
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string data =
"ThreadId "+ getThreadIdOfString(threadId) +
" exit \n";
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myLogger.logData(data);
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}
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void stopAllThreads() {
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myLogger.logData(
"stopAllThreads was called!");
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mReceStopOrder =
true;
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mCondVar.notify_all();
//可能有的线程处于wait状态
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}
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private:
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unsigned
int mMaxThreadsNum;
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std::
queue<Task> mTasksQueue;
//缓存各个任务
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vector<
shared_ptr<thread>> threadCache;
//保存开辟的各个线程
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std::mutex mMux;
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std::condition_variable mCondVar;
//当任务队列mTasksQueue不为空时，唤醒一个线程，从队列头取出一个task执行。
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std::atomic<
bool> mReceStopOrder;
//用于控制线程的停止
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};
logger类 & std::thread::id转换为string的函数：
log数据到文件，如果用屏幕打印的话，由于多线程，容易出现穿插打印。
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std::string getThreadIdOfString(const std::thread::id& id)
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{
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std::
stringstream ss;
//#include<sstream>
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ss << id;
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return ss.str();
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}
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class logger {
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public:
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logger(
string path =
"") :filePath(path) {
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ofs.open(filePath, ios::out);
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}
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virtual ~logger() {
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ofs.close();
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}
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void logData(string a) {
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std::lock_guard<mutex> lkguard(mMut);
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ofs << a <<
endl;
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}
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private:
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mutex mMut;
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string filePath =
"";
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ofstream ofs;
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};
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logger myLogger("C:\\Users\\xxx\\Desktop\\goodVideo\\1.txt");
//全局变量
Test:
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#include <iostream>
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#include <stack>
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#include <vector>
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#include <list>
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#include <unordered_map>
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#include <queue>
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#include <functional>
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#include <mutex>
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#include <atomic>
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#include <thread>
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#include <string>
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#include <fstream>
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#include <sstream>
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#include <memory>
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int main() {
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threadPool myThreadPools(5);
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for (
int i =
0; i <
5; i++) {
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Task myTempTask(i);
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myThreadPools.pushTask(myTempTask);
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std::this_thread::sleep_for(
std::chrono::milliseconds(
1));
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}
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std::this_thread::sleep_for(
std::chrono::seconds(
2));
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myThreadPools.stopAllThreads();
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}
Related：
https://blog.csdn.net/FlushHip/article/details/81902188 -- thread_id
https://blog.csdn.net/FlushHip/article/details/81902188 -- good idea and implemented with linux api
转载：https://blog.csdn.net/qq_35865125/article/details/115773774
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