读写锁在对资源进行保护的同时，还能区分想要读取资源值的线程（读取者线程）和想要更新资源的线程（写入者线程）。
对于读取者线程，读写锁会允许他们并发的执行。当有写入者线程在占有资源时，读写锁会让其它写入者线程和读取者线程等待。
用读写锁来解决读者写者问题会使代码非常清晰和简洁。
typedef RTL_SRWLOCK SRWLOCK, *PSRWLOCK;
typedef struct _RTL_SRWLOCK {
PVOID Ptr;
} RTL_SRWLOCK, *PRTL_SRWLOCK; // 初始化读写锁
WINBASEAPI
VOID
WINAPI
InitializeSRWLock (
__out PSRWLOCK SRWLock
); // 独占式访问
WINBASEAPI
VOID
WINAPI
AcquireSRWLockExclusive (
__inout PSRWLOCK SRWLock
); // 共享式访问
WINBASEAPI
VOID
WINAPI
AcquireSRWLockShared (
__inout PSRWLOCK SRWLock
); // 独占式释放
WINBASEAPI
VOID
WINAPI
ReleaseSRWLockExclusive (
__inout PSRWLOCK SRWLock
); // 共享式释放
WINBASEAPI
VOID
WINAPI
ReleaseSRWLockShared (
__inout PSRWLOCK SRWLock
);
// SRWLock.cpp : 定义控制台应用程序的入口点。
// #include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <process.h> using namespace std;
unsigned int __stdcall ReadThread(PVOID ParameterData);
unsigned int __stdcall WriteThread(PVOID ParameterData); const int NUM = 30, READER_SIZE = 10;
HANDLE ThreadRead[NUM], ThreadWrite[NUM];
SRWLOCK __SRWLock; int main()
{
InitializeSRWLock(&__SRWLock); int i = 0;
for (; i<NUM; i++) {
ThreadRead[i] = (HANDLE)_beginthreadex(NULL, 0, ReadThread, NULL, 0, NULL);
ThreadWrite[i] = (HANDLE)_beginthreadex(NULL, 0, WriteThread, NULL, 0, NULL);
} WaitForMultipleObjects(NUM, ThreadRead, TRUE, INFINITE);
WaitForMultipleObjects(NUM, ThreadWrite, TRUE, INFINITE); cout << "运行完毕" << endl;
getchar();
return 0;
} unsigned int __stdcall ReadThread(PVOID ParameterData) {
AcquireSRWLockShared(&__SRWLock); cout << "ID" << GetCurrentThreadId() << " Read Thread Begin!" << endl;
Sleep(100);
cout << "ID" << GetCurrentThreadId() << " Read Thread Terminate!" << endl; ReleaseSRWLockShared(&__SRWLock);
return 0;
} unsigned int __stdcall WriteThread(PVOID ParameterData) {
AcquireSRWLockExclusive(&__SRWLock);
cout << "ID" << GetCurrentThreadId() << " WRITE Thread Begin~~~~~~~~~~" << endl;
Sleep(200);
cout << "ID" << GetCurrentThreadId() << " WRITE Thread Terminate~~~~~~" << endl;
ReleaseSRWLockExclusive(&__SRWLock);
return 0;
}