win32 pv操作 读者写者问题

p操作对应着WaitForSingleObject

v操作对应着ReleaseSemaphore

CRITICAL_SECTION就是临界区，你懂的

写者写一次，读者read1，read2，read3都读一次之后，write才能再次写。一下是win32源代码。例子比较简单，不过网上现成的例子貌似不太多，要有也是很杂乱的那种，所以写下来

#include<windows.h>
#include<process.h>
#include<iostream>
using namespace std;

CRITICAL_SECTION cs;

typedef struct{
HANDLE h1;
HANDLE h2;
HANDLE h3;
HANDLE h4;
int a;
}PARAMS,*PPARAMS;

void read1(PVOID pvoid){
while(TRUE){

volatile PPARAMS pparams=(PPARAMS)pvoid;
WaitForSingleObject(pparams->h2,INFINITE);

EnterCriticalSection(&cs);
cout<<"读线程1开始读取...\n";
cout<<(pparams->a)<<endl;
LeaveCriticalSection(&cs);

Sleep(1000);
ReleaseSemaphore(pparams->h1,1,NULL);

}
}

void read2(PVOID pvoid){
while(TRUE){

volatile PPARAMS pparams=(PPARAMS)pvoid;
WaitForSingleObject(pparams->h3,INFINITE);

EnterCriticalSection(&cs);
cout<<"读线程2开始读取...\n";
cout<<(pparams->a)<<endl;
LeaveCriticalSection(&cs);

Sleep(1000);
ReleaseSemaphore(pparams->h1,1,NULL);

}
}

void read3(PVOID pvoid){
while(TRUE){

volatile PPARAMS pparams=(PPARAMS)pvoid;
WaitForSingleObject(pparams->h4,INFINITE);

EnterCriticalSection(&cs);
cout<<"读线程3开始读取...\n";
cout<<(pparams->a)<<endl;
LeaveCriticalSection(&cs);

Sleep(1000);
ReleaseSemaphore(pparams->h1,1,NULL);

}
}

void write(PVOID pvoid){
while(TRUE){

volatile PPARAMS pparams=(PPARAMS)pvoid;
WaitForSingleObject(pparams->h1,INFINITE);
WaitForSingleObject(pparams->h1,INFINITE);
WaitForSingleObject(pparams->h1,INFINITE);

cout<<"=================\n";
cout<<"写线程开始写入...\n";
pparams->a=rand()%256;
cout<<"写入"<<(pparams->a)<<endl;

ReleaseSemaphore(pparams->h2,1,NULL);
ReleaseSemaphore(pparams->h3,1,NULL);
ReleaseSemaphore(pparams->h4,1,NULL);

}
}

int main(){
PARAMS params;
params.h1=CreateSemaphore(NULL,3,3,NULL);
params.h2=CreateSemaphore(NULL,0,1,NULL);
params.h3=CreateSemaphore(NULL,0,1,NULL);
params.h4=CreateSemaphore(NULL,0,1,NULL);

InitializeCriticalSection(&cs);

_beginthread(read1,0,¶ms);
_beginthread(read2,0,¶ms);
_beginthread(read3,0,¶ms);
_beginthread(write,0,¶ms);

// HANDLE hEvent;
// hEvent=CreateEvent(NULL,FALSE,FALSE,NULL);
// WaitForSingleObject(hEvent,INFINITE);

int a;cin>>a;

DeleteCriticalSection(&cs);

return 0;
}