读写锁的实现

读写锁的实现

 

#include " stdafx.h "
#include < windows.h >
/**/ /*对于一块临界区
**可以同时读
**当要写时，等待所有的读者离开，后来的读者不允许进入
**因为在同一个进程中
**所以使用临界区，而不是使用互斥对象，因为这样比较节省资源
*/
class  __declspec(novtable) auto_RWLock
{
public:
    auto_RWLock(void);
    ~auto_RWLock(void);

    void LockForRead(void);
    void UnLockForRead(void);

    void LockForWrite(void);
    void UnLockForWrite(void);

private:
    long readerCount;
    CRITICAL_SECTION critical_section;
    CRITICAL_SECTION reader_all_leave;
} ;

#include " stdafx.h "
#include " auto_RWLock.h "

auto_RWLock::auto_RWLock( void ):readerCount( 0 )
{
    InitializeCriticalSection(&critical_section);
    InitializeCriticalSection(&reader_all_leave);
}
auto_RWLock:: ~ auto_RWLock( void )
{
    DeleteCriticalSection(&critical_section);
    DeleteCriticalSection(&reader_all_leave);
}

void  auto_RWLock::LockForRead( void )
{
    EnterCriticalSection(&critical_section);
    
    if(InterlockedIncrement(&readerCount) ==1)
        EnterCriticalSection(&reader_all_leave);

    LeaveCriticalSection(&critical_section);
}

void  auto_RWLock::UnLockForRead( void )
{
    if(InterlockedDecrement(&readerCount)==0)
        LeaveCriticalSection(&reader_all_leave);
}

void  auto_RWLock::LockForWrite( void )
{
    EnterCriticalSection(&critical_section);
    EnterCriticalSection(&reader_all_leave);
}

void  auto_RWLock::UnLockForWrite( void )
{
    LeaveCriticalSection(&critical_section);
    LeaveCriticalSection(&reader_all_leave);
}