【Linux】信号量基于环形队列的生产消费模型

信号量

信号量的本质是一个计数器，可以用来衡量临界资源中资源数量多少

信号量的PV操作

P操作：申请信号量称为P操作，P操作的本质就是让计数器减1。

V操作：释放信号量称为V操作，V操作的本质就是让计数器加1

POSIX信号量相关的接口函数

初始化信号量

int sem_init(sem_t *sem, int pshared, unsigned int value);

sem：需要初始化的信号量。

pshared：0表示线程间共享，非0表示进程间共享。

value：信号量的初始值（特定资源的初始数量）。

等待信号量（P操作)

int sem_wait(sem_t *sem);

发布信号量（V操作)

int sem_post(sem_t *sem);

销毁信号量

int sem_destroy(sem_t *sem);

基于环形队列的生产消费模型代码

RingQueue.hpp

#pragma once#include <iostream>
#include <vector>
#include <cassert>
#include <semaphore.h>
#include <pthread.h>static const int gcap = 5;template<class T>
class RingQueue
{
private:void P(sem_t &sem){int n = sem_wait(&sem);assert(n == 0); // if(void)n;}void V(sem_t &sem){int n = sem_post(&sem);assert(n == 0);(void)n;}
public:RingQueue(const int &cap = gcap): _queue(cap), _cap(cap){int n = sem_init(&_spaceSem, 0, _cap);assert(n == 0);n = sem_init(&_dataSem, 0, 0);assert(n == 0);_productorStep = _consumerStep = 0;pthread_mutex_init(&_pmutex, nullptr);pthread_mutex_init(&_cmutex, nullptr);}// 生产者void Push(const T &in){//先申请信号量，在加锁P(_spaceSem); pthread_mutex_lock(&_pmutex);        _queue[_productorStep++] = in;_productorStep %= _cap;pthread_mutex_unlock(&_pmutex);V(_dataSem);}// 消费者void Pop(T *out){//先申请信号量，在加锁P(_dataSem);pthread_mutex_lock(&_cmutex);*out = _queue[_consumerStep++];_consumerStep %= _cap;pthread_mutex_unlock(&_cmutex);V(_spaceSem);}~RingQueue(){sem_destroy(&_spaceSem);sem_destroy(&_dataSem);pthread_mutex_destroy(&_pmutex);pthread_mutex_destroy(&_cmutex);}
private:std::vector<T> _queue;int _cap;sem_t _spaceSem; // 生产者的空间资源sem_t _dataSem;  // 消费者的数据资源int _productorStep;int _consumerStep;pthread_mutex_t _pmutex;pthread_mutex_t _cmutex;
};

Task.hpp

#pragma once#include <iostream>
#include <string>
#include <cstdio>
#include <functional>class Task
{using func_t = std::function<int(int,int,char)>;// typedef std::function<int(int,int)> func_t;
public:Task(){}Task(int x, int y, char op, func_t func):_x(x), _y(y), _op(op), _callback(func){}std::string operator()(){int result = _callback(_x, _y, _op);char buffer[1024];snprintf(buffer, sizeof buffer, "%d %c %d = %d", _x, _op, _y, result);return buffer;}std::string toTaskString(){char buffer[1024];snprintf(buffer, sizeof buffer, "%d %c %d = ?", _x, _op, _y);return buffer;}
private:int _x;int _y;char _op;func_t _callback;
};const std::string oper = "+-*/%";int mymath(int x, int y, char op)
{int result = 0;switch (op){case '+':result = x + y;break;case '-':result = x - y;break;case '*':result = x * y;break;case '/':{if (y == 0){std::cerr << "div zero error!" << std::endl;result = -1;}elseresult = x / y;}break;case '%':{if (y == 0){std::cerr << "mod zero error!" << std::endl;result = -1;}elseresult = x % y;}break;default:// do nothingbreak;}return result;
}

main.cc

#include "RingQueue.hpp"
#include "Task.hpp"
#include <pthread.h>
#include <ctime>
#include <cstdlib>
#include <sys/types.h>
#include <unistd.h>std::string SelfName()
{char name[128];snprintf(name, sizeof(name), "thread[0x%x]", pthread_self());return name;
}void *ProductorRoutine(void *rq)
{RingQueue<Task> *ringqueue = static_cast<RingQueue<Task> *>(rq);while(true){int x = rand() % 10;int y = rand() % 5;char op = oper[rand()%oper.size()];Task t(x, y, op, mymath);// 生产任务ringqueue->Push(t);// 输出提示std::cout <<  SelfName() << ", 生产者派发了一个任务: " << t.toTaskString() << std::endl;sleep(1);}
}void *ConsumerRoutine(void *rq)
{RingQueue<Task> *ringqueue = static_cast<RingQueue<Task> *>(rq);while(true){Task t;//消费任务ringqueue->Pop(&t);std::string result = t(); std::cout <<  SelfName() << ", 消费者消费了一个任务: " << result << std::endl;}
}int main()
{srand((unsigned int)time(nullptr) ^ getpid() ^ pthread_self() ^ 0x71727374);RingQueue<Task> *rq = new RingQueue<Task>();pthread_t p[4], c[8];for(int i = 0; i < 4; i++) pthread_create(p+i, nullptr, ProductorRoutine, rq);for(int i = 0; i < 8; i++) pthread_create(c+i, nullptr, ConsumerRoutine, rq);for(int i = 0; i < 4; i++) pthread_join(p[i], nullptr);for(int i = 0; i < 8; i++) pthread_join(c[i], nullptr);delete rq;return 0;
}