进程间通信：信号量

//main.cpp
#include <iostream>
#include <semaphore.h>
#include <pthread.h>
#include <string.h>
#include <signal.h>
#include <stdlib.h>
#define _SIZE_ 10
using namespace std;

void EXIT(int arg)//注册信号处理函数。
{
    cout<<"Come Over!"<<endl;
    exit(0);
}
class sem
{
  public:
    sem(int Default = _SIZE_)
    {
        start = 0;
        end = 0;

        sem_init(&empty_size,0,0);
        sem_init(&exit_size,Default,0);

    }
    void SetStr(string s)
    {
        sem_post(&exit_size);
        str[end]=s;
        end = (end+1)%_SIZE_;
        sem_wait(&empty_size);
    }
    string GetStr()
    {
        string s;
        sem_wait(&exit_size);
        s = str[start];
        start = (start+1)%_SIZE_;
        sem_post(&empty_size);
        return s;
    }
    ~sem()
    {
        sem_destroy(&empty_size);
        sem_destroy(&exit_size);
    }
    private:
    int start;
  int end;
  string str[_SIZE_];
    sem_t empty_size;
    sem_t exit_size;
};

void* Write(void  *arg)
{
    sem *sm = (sem *)arg;
    while(1)
    {
        sm->SetStr("this is semaphore message!!");
        sleep(1);//让线程写的速度慢于线程读的速度，可以
             //看到互斥等待访问并不影响正常的需求。
    }
    return (void*) 0;
}

void* Read(void *arg)
{
    sem *sm = (sem *)arg;
    while(1)
    {
        cout<<sm->GetStr().c_str()<<endl;
    }
    return (void*) 0;
}

int main()
{
    sem sm;
    pthread_t idone,idtwe;
    signal(SIGINT,EXIT);//遇到2号信号SIGINT作出相应的处理。
    pthread_create(&idone,NULL,Write,&sm);
    pthread_create(&idtwe,NULL,Read,&sm);

    pthread_join(idone,NULL);
    pthread_join(idtwe,NULL);

    return 0;
}

//下面是Makefile

OUT=a.out
MAINCPP=main.cpp
MAINO=main.o
CC=g++
LIB=-lpthread

$(OUT):$(MAINO)
    @$(CC) -o [email protected] $^ $(LIB)
$(MAINO):$(MAINCPP)
    @$(CC) -c $<

.PHONY:clean
clean:
    rm -rf $(OUT) $(MIANO)

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