libreoffice/framework/inc/threadhelp/readguard.hxx

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 *   Licensed to the Apache Software Foundation (ASF) under one or more
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#ifndef __FRAMEWORK_THREADHELP_READGUARD_HXX_
#define __FRAMEWORK_THREADHELP_READGUARD_HXX_

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

#include <sal/types.h>


namespace framework{

/*-************************************************************************************************************//**
    @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 successfuly 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 exist no multithreaded access to it realy ...

    @attention      a) To prevent us against wrong using, the default ctor, copy ctor and the =operator are maked 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 automaticly if user forget 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.!
                        Normaly we do it at dtor automaticly 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 problem can occure otherwise.
                        Thats why we disable it by make 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_

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