Celartem::Locker Class Reference

#include <cel_lockable.h>

Public Member Functions
	Locker ()
	Locker (const Lockable &inLockable)
	Locker (const Locker &inLocker)
	~Locker ()
Locker &	operator= (const Lockable &inLockable)
Locker &	operator= (const Locker &inLocker)
void	lock (const Lockable &inLockable)
void	unlock ()
void	swap (Locker &inLocker)

Detailed Description

This class is to lock Lockable instances.
This class is introduced to make the code exception-safe. Since the scheme of calling lock method in the first of a function and unlock on return is usually not easy to be exception-safe and the programmers may happen to introduce dirty try-catch hack to recover from it. The Locker object is to get rid of such dirty temporary hacks; all you have to do is to initialize the instance of Locker class directly in the local scope. (This class is intended to be initialized as auto variable or class member variable.) The following code shows how to use Locker class.

void someOperation(Mutex& mutex)
{
    // Locking the mutex; Locker is initialized as an auto object.
    Locker lock(mutex);

    // do something
    ....

    if(err)
    {
        // At the time the exception is thrown, the instance of
        // the Locker class is automatically deleted and the mutex
        // is released.
        celThrow(errOperationFailed);
    }
}

The code which does same operation but in the old syntax:

void someOperation(Mutex& mutex)
{
    mutex->lock(); // lock the mutex

    try
    {
        // do something; it may throw some exception...
        ....
    }
    catch(...)
    {
        mutex->unlock();
        throw; // re-throw
    }

    // place unlock here to deal with both of error and non-error
    // cases.
    mutex->unlock();

    if(err)
        celThrow(errOperationFailed);
}

See Also

Lockable, Mutex, Semaphore

Constructor & Destructor Documentation

Celartem::Locker::Locker ( )

inline

Initializes the instance without any lockable instances.

Celartem::Locker::Locker ( const Lockable &  inLockable )

inline

This constructor it to lock the specified lockable instance.

Parameters

inLockable

An instance to lock.

Celartem::Locker::Locker ( const Locker &  inLocker )

inline

This constructor duplicates the lock; it is dengerous when you are deal with non-recursive Mutex.

Parameters

inLocker

An instance of Locker.

Celartem::Locker::~Locker ( )

inline

Unlocks the lockable.

Member Function Documentation

void Celartem::Locker::lock ( const Lockable &  inLockable )

inline

This method locks the specified Lockable instance.

Parameters

inLockable

An instance to lock. You can also pass NULL to release the currently locked Lockable instance.

Locker& Celartem::Locker::operator= ( const Lockable &  inLockable )

inline

This method sets the lockable instance to lock.

Parameters

inLockable

An instance to lock. You can also pass NULL to release the currently locked Lockable instance.

Returns

This instance (*this ).

Locker& Celartem::Locker::operator= ( const Locker &  inLocker )

inline

This method duplicates the lock; it is dengerous when you are deal with non-recursive Mutex.

Parameters

inLocker

An instance of Locker.

Returns

This instance (*this ).

void Celartem::Locker::swap ( Locker &  inLocker )

inline

This method swaps the locked instances of the two Locker instances.

Parameters

inLocker

The locker to exchange the locked instance with.

void Celartem::Locker::unlock ( )

inline

This method unlocks the currently locked instance.

Referenced by ~Locker().

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The documentation for this class was generated from the following file:

• cel_lockable.h