【MUDUO】Thread封装

 开启线程 sem_t信号量

假如说started这个线程走的快，要开启这个线程了，主线程直接就到sem_wait(&sem),由于子线程在创建还没走到sem_post(&sem), 还没给信号资源加1，所以sem_wait根本就获取不到信号量资源，主线程就会被阻塞在sem_wait。子线程只要创建成功执行到sem_post，信号量的资源就会加1，这个时候tid就有了

#include <semaphore.h>

void Thread::start()
{
    started_ = true;

    sem_t sem;
    sem_init(&sem,false,0);

    //开启线程
    thread_ = std::shared_ptr<std::thread>(new std::thread(
        [&](){
            ...
            sem_post(&sem); //线程信号
            ...
        }
    ));

    //这里必须要等待获取上面新创建的线程tid值
    sem_wait(&sem); //会把主线程阻塞，直到线程创建成功
}

Thread.h

#pragma once
#include "noncopyable.h"

#include <functional>
#include <thread>
#include <memory>
#include <unistd.h>
#include <atomic>
class Thread:noncopyable
{
    public:
        using ThreadFunc = std::function<void()>;
    
    public:
        explicit Thread(ThreadFunc, const std::string &name = std::string() );
        ~Thread();
        void start();
        void join();

        bool started()const { return started_; }
        pid_t pid() const {return tid_; }

        const std::string &name() const {return name_; }

        static int numCreated() { return numCreated_; }
    private:
        void setDautleName();

        bool started_;
        bool joined_;
        std::shared_ptr<std::thread> thread_; 
        pid_t tid_;
        ThreadFunc func_;
        std::string name_;
        static std::atomic_int numCreated_;
};

 Thread.cc

#include "Thread.h"
#include "CurrenThread.h"

#include <semaphore.h>

std::atomic_int Thread::numCreated_(0);

Thread::Thread(ThreadFunc func, const std::string &name )
    :started_(false)
    ,joined_(false)
    ,tid_(0)
    ,func_(std::move(func))
    ,name_(name)
{
    setDautleName();
}
Thread::~Thread()
{ 
    if(started_ && !joined_)
    {
        thread_->detach();
    }
}
void Thread::start() //一个Thread对象，记录的就是一个新线程的详细信息
{
    started_ = true;

    sem_t sem;
    sem_init(&sem,false,0);

    //开启线程
    thread_ = std::shared_ptr<std::thread>(new std::thread(
        [&](){
            //获取线程ID值
            tid_ = CurrenThread::tid();
            sem_post(&sem); //线程信号
            //开启一个新的线程，专门执行该线程函数
            func_();
        }
    ));

    //这里必须要等待获取上面新创建的线程tid值
    sem_wait(&sem); //会把主线程阻塞，直到线程创建成功
}
void Thread::join()
{
    joined_ = true;
    thread_->join();
}


void Thread::setDautleName()
{
    int num = ++numCreated_;
    if(name_.empty())
    {
        char buf[32] = {0};
        snprintf(buf,sizeof buf, "Thread %d", num);
        name_ = buf;
    }
}