xref: /trunk/main/framework/inc/threadhelp/readguard.hxx (revision 914d351e5f5b84e4342a86d6ab8d4aca7308b9bd)

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 * Licensed to the Apache Software Foundation (ASF) under one
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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
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#ifndef __FRAMEWORK_THREADHELP_READGUARD_HXX_
#define __FRAMEWORK_THREADHELP_READGUARD_HXX_

//_________________________________________________________________________________________________________________
//  my own includes
//_________________________________________________________________________________________________________________

#include <threadhelp/inoncopyable.h>
#include <threadhelp/irwlock.h>

//#ifndef __FRAMEWORK_THREADHELP_THREADHELPBASE_HXX_
//#include <threadhelp/threadhelpbase.hxx>
//#endif

//_________________________________________________________________________________________________________________
//  interface includes
//_________________________________________________________________________________________________________________

//_________________________________________________________________________________________________________________
//  other includes
//_________________________________________________________________________________________________________________
#include <sal/types.h>

//_________________________________________________________________________________________________________________
//  namespace
//_________________________________________________________________________________________________________________

namespace framework{

//_________________________________________________________________________________________________________________
//  const
//_________________________________________________________________________________________________________________

//_________________________________________________________________________________________________________________
//  declarations
//_________________________________________________________________________________________________________________

/*-************************************************************************************************************//**
    @short          implement a guard to set read locks
    @descr          This guard should be used to set a lock for reading object internal member.
                    Nobody can control it but don't use member after successfully locking for writing!
                    We never need a own mutex to safe our internal member access - because
                    a guard is used as function-local member only. There exists no multithreaded access to it really ...

    @attention      a) To prevent us against wrong using, the default ctor, copy ctor and the =operator are marked private!
                    b) Use interface "IRWLock" of set LockHelper only - because we must support a finer granularity of locking.
                       Interface "IMutex" should be used by easier guard implementations ... like "ResetableGuard"!

    @implements     -
    @base           INonCopyable

    @devstatus      ready to use
*//*-*************************************************************************************************************/
class ReadGuard : private INonCopyable
{
    //-------------------------------------------------------------------------------------------------------------
    //  public methods
    //-------------------------------------------------------------------------------------------------------------
    public:

        /*-****************************************************************************************************//**
            @short      ctor
            @descr      These ctors initialize the guard with a reference to used lock member of object to protect.
                        Null isn't allowed as value!

            @seealso    -

            @param      "pLock" ,reference to used lock member of object to protect
            @param      "rLock" ,reference to used lock member of object to protect
            @return     -

            @onerror    -
        *//*-*****************************************************************************************************/
        inline ReadGuard( IRWLock* pLock )
            :   m_pLock     ( pLock     )
            ,   m_bLocked   ( sal_False )
        {
            lock();
        }

        //*********************************************************************************************************
        inline ReadGuard( IRWLock& rLock )
            :   m_pLock     ( &rLock    )
            ,   m_bLocked   ( sal_False )
        {
            lock();
        }

        /*-****************************************************************************************************//**
            @short      dtor
            @descr      We unlock the used lock member automatically if user forgets it.

            @seealso    -

            @param      -
            @return     -

            @onerror    -
        *//*-*****************************************************************************************************/
        inline ~ReadGuard()
        {
            unlock();
        }

        /*-****************************************************************************************************//**
            @short      set read lock
            @descr      Call this method to set the read lock. The call will block till all current threads are synchronized!

            @seealso    method unlock()

            @param      -
            @return     -

            @onerror    -
        *//*-*****************************************************************************************************/
        inline void lock()
        {
            if( m_bLocked == sal_False )
            {
                m_pLock->acquireReadAccess();
                m_bLocked = sal_True;
            }
        }

        /*-****************************************************************************************************//**
            @short      unset read lock
            @descr      Call this method to unlock the rw-lock temp.!
                        Normally we do it at dtor automatically for you ...

            @seealso    method lock()

            @param      -
            @return     -

            @onerror    -
        *//*-*****************************************************************************************************/
        inline void unlock()
        {
            if( m_bLocked == sal_True )
            {
                m_pLock->releaseReadAccess();
                m_bLocked = sal_False;
            }
        }

    //-------------------------------------------------------------------------------------------------------------
    //  private methods
    //-------------------------------------------------------------------------------------------------------------
    private:

        /*-****************************************************************************************************//**
            @short      disable using of these functions!
            @descr      It's not allowed to use this methods. Different problems can occur otherwise.
                        That's why we disable it by making it private.

            @seealso    other ctor

            @param      -
            @return     -

            @onerror    -
        *//*-*****************************************************************************************************/
        ReadGuard();

    //-------------------------------------------------------------------------------------------------------------
    //  private member
    //-------------------------------------------------------------------------------------------------------------
    private:

        IRWLock*    m_pLock     ;   /// reference to lock-member of protected object
        sal_Bool    m_bLocked   ;   /// protection against multiple lock calls without unlock!

};      //  class ReadGuard

}       //  namespace framework

#endif  //  #ifndef __FRAMEWORK_THREADHELP_READGUARD_HXX_