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139 lines
3.8 KiB
C++
139 lines
3.8 KiB
C++
// -*- C++ -*-
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//==========================================================================
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/**
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* @file Reverse_Lock_T.h
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*
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* $Id: Reverse_Lock_T.h 84481 2009-02-17 10:58:31Z johnnyw $
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*
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* Moved from Synch.h.
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*
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* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
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*/
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//==========================================================================
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#ifndef ACE_REVERSE_LOCK_T_H
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#define ACE_REVERSE_LOCK_T_H
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#include /**/ "ace/pre.h"
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#include "ace/Lock.h"
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#if !defined (ACE_LACKS_PRAGMA_ONCE)
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# pragma once
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#endif /* ACE_LACKS_PRAGMA_ONCE */
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ACE_BEGIN_VERSIONED_NAMESPACE_DECL
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/**
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* @namespace ACE_Acquire_Method
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*
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* @brief An enum namespace.
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*
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* These enums should have been inside the reverse lock class, but
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* some lame compilers cannot handle enums inside template classes.
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*
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* The METHOD_TYPE is used to indicate which acquire() method will be
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* called on the real lock when the release() method is called on the
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* reverse lock. REGULAR indicated the acquire() method, READ
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* indicates the acquire_read() method, and WRITE indicates the
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* acquire_write() method. Note that the try_*() methods are not
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* represented here because we have to make sure that the release()
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* method on the reverse lock acquires a lock on the real lock.
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**/
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namespace ACE_Acquire_Method
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{
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enum METHOD_TYPE
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{
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ACE_REGULAR,
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ACE_READ,
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ACE_WRITE
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};
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}
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/**
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* @class ACE_Reverse_Lock
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*
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* @brief A reverse (or anti) lock.
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*
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* This is an interesting adapter class that changes a lock into
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* a reverse lock, i.e., <acquire> on this class calls <release>
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* on the lock, and <release> on this class calls <acquire> on
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* the lock.
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* One motivation for this class is when we temporarily want to
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* release a lock (which we have already acquired) but then
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* reacquire it soon after. An alternative design would be to
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* add a Anti_Guard or Reverse_Guard class which would <release>
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* on construction and <acquire> destruction. However, there
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* are *many* varieties of the Guard class and this design
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* choice would lead to at least 6 new classes. One new
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* ACE_Reverse_Lock class seemed more reasonable.
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*/
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template <class ACE_LOCKING_MECHANISM>
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class ACE_Reverse_Lock : public ACE_Lock
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{
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public:
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typedef ACE_LOCKING_MECHANISM ACE_LOCK;
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// = Initialization/Finalization methods.
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/// Constructor. All locking requests will be forwarded to @a lock.
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ACE_Reverse_Lock (ACE_LOCKING_MECHANISM &lock,
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ACE_Acquire_Method::METHOD_TYPE acquire_method = ACE_Acquire_Method::ACE_REGULAR);
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/// Destructor. If <lock_> was not passed in by the user, it will be
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/// deleted.
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virtual ~ACE_Reverse_Lock (void);
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// = Lock accessors.
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/// Release the lock.
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virtual int acquire (void);
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/// Release the lock.
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virtual int tryacquire (void);
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/// Acquire the lock.
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virtual int release (void);
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/// Release the lock.
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virtual int acquire_read (void);
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/// Release the lock.
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virtual int acquire_write (void);
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/// Release the lock.
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virtual int tryacquire_read (void);
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/// Release the lock.
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virtual int tryacquire_write (void);
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/// Release the lock.
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virtual int tryacquire_write_upgrade (void);
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/// Explicitly destroy the lock.
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virtual int remove (void);
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private:
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/// The concrete locking mechanism that all the methods delegate to.
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ACE_LOCKING_MECHANISM &lock_;
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/// This indicates what kind of acquire method will be called.
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ACE_Acquire_Method::METHOD_TYPE acquire_method_;
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};
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ACE_END_VERSIONED_NAMESPACE_DECL
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#if defined (__ACE_INLINE__)
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#include "ace/Reverse_Lock_T.inl"
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#endif /* __ACE_INLINE__ */
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#if defined (ACE_TEMPLATES_REQUIRE_SOURCE)
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#include "ace/Reverse_Lock_T.cpp"
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#endif /* ACE_TEMPLATES_REQUIRE_SOURCE */
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#if defined (ACE_TEMPLATES_REQUIRE_PRAGMA)
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#pragma implementation ("Reverse_Lock_T.cpp")
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#endif /* ACE_TEMPLATES_REQUIRE_PRAGMA */
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#include /**/ "ace/post.h"
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#endif /* ACE_REVERSE_LOCK_T_H */
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