AutoCaller.h revision 4f7bc3e9b035984d494d38afa2913fa560e259d6
/** @file
*
* VirtualBox COM base classes definition
*/
/*
* Copyright (C) 2006-2009 Sun Microsystems, Inc.
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 USA or visit http://www.sun.com if you need
* additional information or have any questions.
*/
#ifndef ____H_AUTOCALLER
#define ____H_AUTOCALLER
////////////////////////////////////////////////////////////////////////////////
//
// AutoCaller* classes
//
////////////////////////////////////////////////////////////////////////////////
/**
* Smart class that automatically increases the number of callers of the
* given VirtualBoxBase object when an instance is constructed and decreases
* it back when the created instance goes out of scope (i.e. gets destroyed).
*
* If #rc() returns a failure after the instance creation, it means that
* the managed VirtualBoxBase object is not Ready, or in any other invalid
* state, so that the caller must not use the object and can return this
* failed result code to the upper level.
*
* See VirtualBoxBase::addCaller(), VirtualBoxBase::addLimitedCaller() and
* VirtualBoxBase::releaseCaller() for more details about object callers.
*
* @param aLimited |false| if this template should use
* VirtualiBoxBase::addCaller() calls to add callers, or
* |true| if VirtualiBoxBase::addLimitedCaller() should be
* used.
*
* @note It is preferable to use the AutoCaller and AutoLimitedCaller
* classes than specify the @a aLimited argument, for better
* self-descriptiveness.
*/
{
/**
* Increases the number of callers of the given object by calling
* VirtualBoxBase::addCaller().
*
* @param aObj Object to add a caller to. If NULL, this
* instance is effectively turned to no-op (where
* rc() will return S_OK and state() will be
* NotReady).
*/
{
if (mObj)
}
/**
* If the number of callers was successfully increased, decreases it
* using VirtualBoxBase::releaseCaller(), otherwise does nothing.
*/
{
mObj->releaseCaller();
}
/**
* Stores the result code returned by VirtualBoxBase::addCaller() after
* instance creation or after the last #add() call. A successful result
* code means the number of callers was successfully increased.
*/
/**
* Returns |true| if |SUCCEEDED(rc())| is |true|, for convenience.
* |true| means the number of callers was successfully increased.
*/
/**
* Stores the object state returned by VirtualBoxBase::addCaller() after
* instance creation or after the last #add() call.
*/
/**
* Temporarily decreases the number of callers of the managed object.
* May only be called if #isOk() returns |true|. Note that #rc() will
* return E_FAIL after this method succeeds.
*/
void release()
{
{
if (mObj)
mObj->releaseCaller();
}
}
/**
* Restores the number of callers decreased by #release(). May only be
* called after #release().
*/
void add()
{
}
/**
* Attaches another object to this caller instance.
* The previous object's caller is released before the new one is added.
*
* @param aObj New object to attach, may be @c NULL.
*/
{
/* detect simple self-reattachment */
{
release();
add();
}
}
/** Verbose equivalent to <tt>attach (NULL)</tt>. */
};
/**
* Smart class that automatically increases the number of normal
* (non-limited) callers of the given VirtualBoxBase object when an instance
* is constructed and decreases it back when the created instance goes out
* of scope (i.e. gets destroyed).
*
* A typical usage pattern to declare a normal method of some object (i.e. a
* method that is valid only when the object provides its full
* functionality) is:
* <code>
* STDMETHODIMP Component::Foo()
* {
* AutoCaller autoCaller(this);
* if (FAILED(autoCaller.rc())) return autoCaller.rc();
* ...
* </code>
*
* Using this class is equivalent to using the AutoCallerBase template with
* the @a aLimited argument set to |false|, but this class is preferred
* because provides better self-descriptiveness.
*
* See AutoCallerBase for more information about auto caller functionality.
*/
/**
* Smart class that automatically increases the number of limited callers of
* the given VirtualBoxBase object when an instance is constructed and
* decreases it back when the created instance goes out of scope (i.e. gets
* destroyed).
*
* A typical usage pattern to declare a limited method of some object (i.e.
* a method that is valid even if the object doesn't provide its full
* functionality) is:
* <code>
* STDMETHODIMP Component::Bar()
* {
* AutoLimitedCaller autoCaller(this);
* if (FAILED(autoCaller.rc())) return autoCaller.rc();
* ...
* </code>
*
* Using this class is equivalent to using the AutoCallerBase template with
* the @a aLimited argument set to |true|, but this class is preferred
* because provides better self-descriptiveness.
*
* See AutoCallerBase for more information about auto caller functionality.
*/
/**
* Smart class to enclose the state transition NotReady->InInit->Ready.
*
* The purpose of this span is to protect object initialization.
*
* Instances must be created as a stack-based variable taking |this| pointer
* as the argument at the beginning of init() methods of VirtualBoxBase
* subclasses. When this variable is created it automatically places the
* object to the InInit state.
*
* When the created variable goes out of scope (i.e. gets destroyed) then,
* depending on the result status of this initialization span, it either
* places the object to Ready or Limited state or calls the object's
* VirtualBoxBase::uninit() method which is supposed to place the object
* back to the NotReady state using the AutoUninitSpan class.
*
* The initial result status of the initialization span is determined by the
* @a aResult argument of the AutoInitSpan constructor (Result::Failed by
* default). Inside the initialization span, the success status can be set
* to Result::Succeeded using #setSucceeded(), to to Result::Limited using
* #setLimited() or to Result::Failed using #setFailed(). Please don't
* forget to set the correct success status before getting the AutoInitSpan
* variable destroyed (for example, by performing an early return from
* the init() method)!
*
* Note that if an instance of this class gets constructed when the object
* is in the state other than NotReady, #isOk() returns |false| and methods
* of this class do nothing: the state transition is not performed.
*
* A typical usage pattern is:
* <code>
* HRESULT Component::init()
* {
* AutoInitSpan autoInitSpan (this);
* AssertReturn (autoInitSpan.isOk(), E_FAIL);
* ...
* if (FAILED(rc))
* return rc;
* ...
* if (SUCCEEDED(rc))
* autoInitSpan.setSucceeded();
* return rc;
* }
* </code>
*
* @note Never create instances of this class outside init() methods of
* VirtualBoxBase subclasses and never pass anything other than |this|
* as the argument to the constructor!
*/
{
~AutoInitSpan();
/**
* Returns |true| if this instance has been created at the right moment
* (when the object was in the NotReady state) and |false| otherwise.
*/
/**
* Sets the initialization status to Succeeded to indicates successful
* initialization. The AutoInitSpan destructor will place the managed
* VirtualBoxBase object to the Ready state.
*/
/**
* Sets the initialization status to Succeeded to indicate limited
* (partly successful) initialization. The AutoInitSpan destructor will
* place the managed VirtualBoxBase object to the Limited state.
*/
/**
* Sets the initialization status to Failure to indicates failed
* initialization. The AutoInitSpan destructor will place the managed
* VirtualBoxBase object to the InitFailed state and will automatically
* call its uninit() method which is supposed to place the object back
* to the NotReady state using AutoUninitSpan.
*/
/** Returns the current initialization result. */
bool mOk : 1;
};
/**
* Smart class to enclose the state transition Limited->InInit->Ready.
*
* The purpose of this span is to protect object re-initialization.
*
* Instances must be created as a stack-based variable taking |this| pointer
* as the argument at the beginning of methods of VirtualBoxBase
* subclasses that try to re-initialize the object to bring it to the Ready
* state (full functionality) after partial initialization (limited
* functionality). When this variable is created, it automatically places
* the object to the InInit state.
*
* When the created variable goes out of scope (i.e. gets destroyed),
* depending on the success status of this initialization span, it either
* places the object to the Ready state or brings it back to the Limited
* state.
*
* The initial success status of the re-initialization span is |false|. In
* order to make it successful, #setSucceeded() must be called before the
* instance is destroyed.
*
* Note that if an instance of this class gets constructed when the object
* is in the state other than Limited, #isOk() returns |false| and methods
* of this class do nothing: the state transition is not performed.
*
* A typical usage pattern is:
* <code>
* HRESULT Component::reinit()
* {
* AutoReinitSpan autoReinitSpan (this);
* AssertReturn (autoReinitSpan.isOk(), E_FAIL);
* ...
* if (FAILED(rc))
* return rc;
* ...
* if (SUCCEEDED(rc))
* autoReinitSpan.setSucceeded();
* return rc;
* }
* </code>
*
* @note Never create instances of this class outside re-initialization
* methods of VirtualBoxBase subclasses and never pass anything other than
* |this| as the argument to the constructor!
*/
{
~AutoReinitSpan();
/**
* Returns |true| if this instance has been created at the right moment
* (when the object was in the Limited state) and |false| otherwise.
*/
/**
* Sets the re-initialization status to Succeeded to indicates
* successful re-initialization. The AutoReinitSpan destructor will place
* the managed VirtualBoxBase object to the Ready state.
*/
void setSucceeded() { mSucceeded = true; }
bool mSucceeded : 1;
bool mOk : 1;
};
/**
* Smart class to enclose the state transition Ready->InUnnit->NotReady,
* InitFailed->InUnnit->NotReady or WillUninit->InUnnit->NotReady.
*
* The purpose of this span is to protect object uninitialization.
*
* Instances must be created as a stack-based variable taking |this| pointer
* as the argument at the beginning of uninit() methods of VirtualBoxBase
* subclasses. When this variable is created it automatically places the
* object to the InUninit state, unless it is already in the NotReady state
* as indicated by #uninitDone() returning |true|. In the latter case, the
* uninit() method must immediately return because there should be nothing
* to uninitialize.
*
* When this variable goes out of scope (i.e. gets destroyed), it places the
* object to NotReady state.
*
* A typical usage pattern is:
* <code>
* void Component::uninit()
* {
* AutoUninitSpan autoUninitSpan (this);
* if (autoUninitSpan.uninitDone())
* return;
* ...
* }
* </code>
*
* @note The constructor of this class blocks the current thread execution
* until the number of callers added to the object using #addCaller()
* or AutoCaller drops to zero. For this reason, it is forbidden to
* create instances of this class (or call uninit()) within the
* AutoCaller or #addCaller() scope because it is a guaranteed
* deadlock.
*
* @note Never create instances of this class outside uninit() methods and
* never pass anything other than |this| as the argument to the
* constructor!
*/
{
~AutoUninitSpan();
/** |true| when uninit() is called as a result of init() failure */
bool initFailed() { return mInitFailed; }
/** |true| when uninit() has already been called (so the object is NotReady) */
bool uninitDone() { return mUninitDone; }
bool mInitFailed : 1;
bool mUninitDone : 1;
};
/**
* Smart class to enclose the state transition Ready->MayUninit->NotReady or
* Ready->MayUninit->WillUninit.
*
* The purpose of this span is to safely check if unintialization is
* possible at the given moment and seamlessly perform it if so.
*
* Instances must be created as a stack-based variable taking |this| pointer
* as the argument at the beginning of methods of VirtualBoxBase
* subclasses that want to uninitialize the object if a necessary set of
* criteria is met and leave it Ready otherwise.
*
* When this variable is created it automatically places the object to the
* MayUninit state if it is Ready, does nothing but returns |true| in
* response to #alreadyInProgress() if it is already in MayUninit, or
* returns a failure in response to #rc() in any other case. The example
* below shows how the user must react in latter two cases.
*
* When this variable goes out of scope (i.e. gets destroyed), it places the
* object back to Ready state unless #acceptUninit() is called in which case
* the object is placed to WillUninit state and uninit() is immediately
* called after that.
*
* A typical usage pattern is:
* <code>
* void Component::uninit()
* {
* AutoMayUninitSpan mayUninitSpan (this);
* if (FAILED(mayUninitSpan.rc())) return mayUninitSpan.rc();
* if (mayUninitSpan.alreadyInProgress())
* return S_OK;
* ...
* if (FAILED(rc))
* return rc; // will go back to Ready
* ...
* if (SUCCEEDED(rc))
* mayUninitSpan.acceptUninit(); // will call uninit()
* return rc;
* }
* </code>
*
* @note The constructor of this class blocks the current thread execution
* until the number of callers added to the object using #addCaller()
* or AutoCaller drops to zero. For this reason, it is forbidden to
* create instances of this class (or call uninit()) within the
* AutoCaller or #addCaller() scope because it is a guaranteed
* deadlock.
*/
{
/**
* Returns a failure if the AutoMayUninitSpan variable was constructed
* at an improper time. If there is a failure, do nothing but return
* it to the caller.
*/
/**
* Returns |true| if AutoMayUninitSpan is already in progress on some
* other thread. If it's the case, do nothing but return S_OK to
* the caller.
*/
bool alreadyInProgress() { return mAlreadyInProgress; }
/*
* Accepts uninitialization and causes the destructor to go to
* WillUninit state and call uninit() afterwards.
*/
void acceptUninit() { mAcceptUninit = true; }
bool mAlreadyInProgress : 1;
bool mAcceptUninit : 1;
};
#endif // !____H_AUTOCALLER