windows-nt/Source/XPSP1/NT/inetsrv/iis/admin/sitecreator/safecs.cpp

#include <unicode.h>
#include <windows.h>
#include "SafeCS.h"


//+-----------------------------------------------------------------------
//
// Microsoft Windows
//
// Copyright (c) Microsoft Corporation 2000
//
// File:        SafeCS.cpp
//
// Contents:    CSafeAutoCriticalSection implementation
//              CSafeLock implementation
//
//------------------------------------------------------------------------

//+--------------------------------------------------------------------------
//
//  Class:      CSafeAutoCriticalSection
//
//  Purpose:    Wrapper for initializing critical-sections.
//
//  Interface:  Lock			- locks the critical section
//				Unlock			- unlocks the critical section
//				Constructor		- initializes the critical section
//				Detructor		- uninitializes the critical section 
//
//  Notes:		This provides a convenient way to ensure that you're
//              you wrap InitializeCriticalSection and 
//              UnInitializeCriticalSection in try catches which is useful 
//              in low-mem conditions
//
//---------------------------------------------------------------------------

//+-------------------------------------------------------------------------- 
// Default constructor - Initializes the critical section and sets the state 
// flag to initialized
//+-------------------------------------------------------------------------- 

CSafeAutoCriticalSection::CSafeAutoCriticalSection()
{
    m_lState = STATE_UNINITIALIZED;
	m_dwError = ERROR_SUCCESS;

    __try
    {
	    LONG  lPreviousState;

        // try to set state flag
        lPreviousState = InterlockedCompareExchange(&m_lState,
                                                    STATE_INITIALIZED,
                                                    STATE_UNINITIALIZED);

        // if this critical section was not initialized
        if(STATE_UNINITIALIZED == lPreviousState)
        {
			//
			// Note we can call InitializeCriticalSectionAndSpinCount here
			// and thereby eliminate the need for a try catch in 
			// EnterCriticalSection. But the docs say that 
			// InitializeCriticalSectionAndSpinCount is valid on NT4.0 SP3
			// onwards and we need to run on plain NT4.0 - hence we call
			// InitializeCriticalSection
			//

			InitializeCriticalSection(&m_cs);
        }

    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
        m_dwError = _exception_code();
    }

    // failed to initialize - need to reset
    if(ERROR_SUCCESS != m_dwError)
    {
        m_lState = STATE_UNINITIALIZED;
    }

}

//+-------------------------------------------------------------------------- 
// Destructor
//+-------------------------------------------------------------------------- 

CSafeAutoCriticalSection::~CSafeAutoCriticalSection()
{
    LONG                lPreviousState;

    // try to reset the the state to uninitialized
    lPreviousState = InterlockedCompareExchange(&m_lState,
                                                STATE_UNINITIALIZED,
                                                STATE_INITIALIZED);

    // if the object was initialized delete the critical section
    if(STATE_INITIALIZED == lPreviousState)
    {
        DeleteCriticalSection(&m_cs);
    }
}

//+-------------------------------------------------------------------------- 
// Enters critical section, if needed initializes critical section
// before entering
//
// Returns 
//	DWORD -	ERROR_SUCCESS if everything is fine
//			ERROR_OUTOFMEMORY if failed to create or enter critical section
//+-------------------------------------------------------------------------- 

DWORD CSafeAutoCriticalSection::Lock()
{
    DWORD dwError = ERROR_SUCCESS;

    if(!IsInitialized())
    {
        return m_dwError;
    }

    __try
    {
        EnterCriticalSection(&m_cs);
    }
    __except(EXCEPTION_EXECUTE_HANDLER)
    {
	    dwError = _exception_code();
    }

    return dwError;
}

//+-------------------------------------------------------------------------- 
// Leaves critical section
//+-------------------------------------------------------------------------- 
DWORD CSafeAutoCriticalSection::Unlock()
{
    if(!IsInitialized())
    {
        return m_dwError;
    }

    LeaveCriticalSection(&m_cs);

    return ERROR_SUCCESS;

}

//+--------------------------------------------------------------------------
//
//  Class:      CSafeLock
//
//  Purpose:    Auto-unlocking critical-section services
//
//  Interface:  Lock			- locks the critical section
//				Unlock			- unlocks the critical section
//				Constructor		- locks the critical section (unless told 
//								  otherwise)
//				Detructor		- unlocks the critical section if its locked
//
//  Notes:		This provides a convenient way to ensure that you're
//              unlocking a CSemExclusive, which is useful if your routine
//              can be left via several returns and/or via exceptions....
//
//---------------------------------------------------------------------------

CSafeLock::CSafeLock(CSafeAutoCriticalSection* val) : 
m_pSem(val),
m_locked(FALSE)
{
}

CSafeLock::CSafeLock(CSafeAutoCriticalSection& val) : 
m_pSem(&val),
m_locked(FALSE)
{
}

CSafeLock::~CSafeLock() 
{	
	if (m_locked) 
	{
		m_pSem->Unlock(); 
	}
}

DWORD CSafeLock::Lock() 
{
	DWORD dwError = ERROR_SUCCESS;

	if(!m_locked) 
	{ 
		dwError = m_pSem->Lock(); 

		if(ERROR_SUCCESS == dwError)
		{
			m_locked = TRUE; 
		}
	}

	return dwError;
}


DWORD CSafeLock::Unlock() 
{
	DWORD dwError = ERROR_SUCCESS;

	if(m_locked) 
	{ 
		dwError = m_pSem->Unlock(); 
		m_locked = FALSE; 
	}

	return dwError;
}