1. 线程池要求
我们创建线程池的目的本质上是用空间换取时间，而我们选择于 C++ 的类内包装原生线程库的形式来创建，其具体实行逻辑如图
可以看到，整个线程池其实就是一个大型的 CP 模型，接下来我们来完成它
2. 整体模板
cpp
#pragma once
#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <pthread.h>
struct ThreadInfo
{
pthread_t tid;
std::string name;
};
static const int defalutnum = 5;
template<class T>
class ThreadPool
{
public:
ThreadPoo1(int num = defalutnum)
:threads_(num)
{
pthread_mutex_init(&mutex_, nullptr);
pthread_cond_init(&cond_, nullptr);
}
~ThreadPoo1()
{
pthread_mutex_destroy(&mutex_);
pthread_mutex_destroy(&cond_);
}
private:
std::vector<ThreadInfo> threads_;
std::queue<T>tasks_;
pthread_mutex_t mutex_;
pthread_cond_t cond_;
};3. 具体实现
cpp
#pragma once
#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <pthread.h>
// 存储线程池中各个线程信息
struct ThreadInfo
{
pthread_t tid;
std::string name;
};
// 默认线程池容量
static const int defalutnum = 5;
template<class T>
class ThreadPool
{
private:
// 加锁
void Lock()
{
pthread_mutex_lock(&mutex_);
}
// 释放锁
void Unlock()
{
pthread_mutex_unlock (&mutex_);
}
// 唤醒线程
void Wakeup()
{
pthread_cond_signal(&cond_);
}
// 资源不就绪, 线程同步
void ThreadSleep()
{
pthread_cond_wait(&cond_, &mutex_);
}
// 对当前任务列表判空
bool IsQueueEmpty()
{
return tasks_.size() == 0 ? true : false;
}
// 获取线程 name
std::string GetThreadName(pthread_t tid)
{
for (const auto &ti : threads_)
{
if (ti.tid == tid)
return ti.name;
}
return "None";
}
public:
ThreadPool(int num = defalutnum)
:threads_(num)
{
pthread_mutex_init(&mutex_, nullptr);
pthread_cond_init(&cond_, nullptr);
}
// 由于 pthread_create 函数的特殊性
// 只能将 HandlerTask 设置为静态函数
// 同时将 this 指针以参数的形式传入
static void *HandlerTask(void *args)
{
ThreadPool<T> *tp = static_cast<ThreadPool<T> *>(args);
while (true)
{
// 确保同一时刻只有一个线程在进行消费
tp->Lock();
// 如果当前任务列表为空就让线程等待资源
// 为防止伪唤醒的情况, 使用 while
while (tp->IsQueueEmpty())
{
tp->ThreadSleep();
}
T t = tp->Pop();
tp->Unlock();
// 执行任务
// 注: 需要任务中重载 operator()
t();
}
}
// 启动线程池
void Start()
{
int num = threads_.size();
for (int i = 0; i < num; i++)
{
threads_[i].name = "thread-" + std::to_string(i+1);
pthread_create(&(threads_[i].tid), nullptr, HandlerTask, this);
}
}
// Pop 函数在锁内执行因此不需要单独加锁
T Pop()
{
T t = tasks_.front();
tasks_.pop();
return t;
}
// 将外界资源投入线程池
void Push(const T &t)
{
Lock();
tasks_.push(t);
Wakeup(); // 投入资源成功后唤醒线程
Unlock();
}
~ThreadPool()
{
pthread_mutex_destroy(&mutex_);
pthread_cond_destroy(&cond_);
}
private:
std::vector<ThreadInfo> threads_; // 线程池中所有线程的信息
std::queue<T> tasks_; // 任务队列
pthread_mutex_t mutex_; // 互斥锁
pthread_cond_t cond_; // 条件变量
};4. 使用测试
在这里我们引用一个 Task.hpp 的任务工具，如下
cpp
#pragma once
#include "Log.hpp"
#include <iostream>
#include <string>
std::string opers = "+-*/%";
enum ErrorCode
{
DevideZero,
ModZero,
Unknown,
Normal
};
class Task
{
public:
Task(int x, int y, char op)
:a(x), b(y), op_(op)
{}
void operator()()
{
run();
lg(Info, "run a task: %s", GetResult().c_str());
}
void run()
{
switch(op_)
{
case '+':
answer = a + b;
break;
case '-':
answer = a - b;
break;
case '*':
answer = a * b;
break;
case '/':
if (b != 0) answer = a / b;
else exitcode = DevideZero;
break;
case '%':
if (b != 0) answer = a % b;
else exitcode = ModZero;
break;
default:
lg(Error, "Using correct operation: + - * / %");
exitcode = Unknown;
break;
}
}
std::string GetTask()
{
std::string ret;
ret += "Task: ";
ret += std::to_string(a);
ret += " ";
ret += op_;
ret += " ";
ret += std::to_string(b);
ret += " ";
ret += "= ?";
return ret;
}
std::string GetResult()
{
std::string ret;
if (exitcode <= Unknown)
{
ret += "run the task fail, reason: ";
switch (exitcode)
{
case DevideZero:
ret += "DevideZero";
break;
case ModZero:
ret += "ModZero";
break;
case Unknown:
ret += "Unknown";
break;
default:
break;
}
}
else
{
ret += "run the task success, result: ";
ret += std::to_string(a);
ret += " ";
ret += op_;
ret += " ";
ret += std::to_string(b);
ret += " ";
ret += "= ";
ret += std::to_string(answer);
}
return ret;
}
~Task()
{}
private:
int a;
int b;
char op_;
int answer = 0;
ErrorCode exitcode = Normal;
};main 函数如下
cpp
#include <iostream>
#include <time.h>
#include "ThreadPool.hpp"
#include "Task.hpp"
extern std::string opers;
int main()
{
ThreadPool<Task>* tp = new ThreadPool<Task>(5);
tp->Start();
srand(time(nullptr)^ getpid());
while(true)
{
//1．构建任务
int x = rand() % 10 + 1;
usleep(10);
int y =rand() % 5;
char op = opers[rand()%opers.size()];
Task t(x, y, op);
tp->Push(t);
// 2.交给线程池处理
lg(Info, "main thread make task: %s", t.GetTask().c_str());
sleep(1);
}
return 0;
}运行效果如下
也就是说我们想要使用这个线程池，只需要
创建一个固定容量的进程池
调用 Start() 函数启动进程池
调用 Push() 函数向进程池中添加任务
即可！