进程间通信：信号量

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//main.cpp#include <iostream>#include <semaphore.h>#include <pthread.h>#include <string.h>#include <signal.h>#include <stdlib.h>#define _SIZE_ 10using 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.outMAINCPP=main.cppMAINO=main.oCC=g++LIB=-lpthread$(OUT):$(MAINO)    @$(CC) -o $@ $^ $(LIB)$(MAINO):$(MAINCPP)    @$(CC) -c $<.PHONY:cleanclean:    rm -rf $(OUT) $(MIANO)

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