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// -*- C++ -*-
//==========================================================================
/**
* @file Lock.h
*
* Moved from Synch.h.
*
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
*/
//==========================================================================
#ifndef ACE_LOCK_H
#define ACE_LOCK_H
#include /**/ "ace/pre.h"
#include /**/ "ace/ACE_export.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
/**
* @class ACE_Lock
*
* @brief This is the abstract base class that contains the uniform
* locking API that is supported by all the ACE synchronization
* mechanisms.
*
* This class is typically used in conjunction with the
* ACE_Lock_Adapter in order to provide a polymorphic
* interface to the ACE synchronization mechanisms (e.g.,
* ACE_Mutex, ACE_Semaphore, ACE_RW_Mutex, etc). Note that
* the reason that all of ACE doesn't use polymorphic locks is
* that (1) they add ~20% extra overhead for virtual function
* calls and (2) objects with virtual functions can't be placed
* into shared memory.
*/
class ACE_Export ACE_Lock
{
public:
/// CE needs a default constructor here.
ACE_Lock (void);
/// Noop virtual destructor
virtual ~ACE_Lock (void);
/**
* Explicitly destroy the lock. Note that only one thread should
* call this method since it doesn't protect against race
* conditions.
*/
virtual int remove (void) = 0;
/// Block the thread until the lock is acquired. Returns -1 on
/// failure.
virtual int acquire (void) = 0;
/**
* Conditionally acquire the lock (i.e., won't block). Returns -1
* on failure. If we "failed" because someone else already had the
* lock, @c errno is set to @c EBUSY.
*/
virtual int tryacquire (void) = 0;
/// Release the lock. Returns -1 on failure.
virtual int release (void) = 0;
/**
* Block until the thread acquires a read lock. If the locking
* mechanism doesn't support read locks then this just calls
* acquire(). Returns -1 on failure.
*/
virtual int acquire_read (void) = 0;
/**
* Block until the thread acquires a write lock. If the locking
* mechanism doesn't support read locks then this just calls
* acquire(). Returns -1 on failure.
*/
virtual int acquire_write (void) = 0;
/**
* Conditionally acquire a read lock. If the locking mechanism
* doesn't support read locks then this just calls acquire().
* Returns -1 on failure. If we "failed" because someone else
* already had the lock, @c errno is set to @c EBUSY.
*/
virtual int tryacquire_read (void) = 0;
/**
* Conditionally acquire a write lock. If the locking mechanism
* doesn't support read locks then this just calls acquire().
* Returns -1 on failure. If we "failed" because someone else
* already had the lock, @c errno is set to @c EBUSY.
*/
virtual int tryacquire_write (void) = 0;
/**
* Conditionally try to upgrade a lock held for read to a write lock.
* If the locking mechanism doesn't support read locks then this just
* calls acquire(). Returns 0 on success, -1 on failure.
*/
virtual int tryacquire_write_upgrade (void) = 0;
};
/**
* @class ACE_Adaptive_Lock
*
* @brief An adaptive general locking class that defers the decision of
* lock type to run time.
*
* This class, as ACE_Lock, provide a set of general locking APIs.
* However, it defers our decision of what kind of lock to use
* to the run time and delegates all locking operations to the actual
* lock. Users must define a constructor in their subclass to
* initialize @c lock_.
*/
class ACE_Export ACE_Adaptive_Lock : public ACE_Lock
{
public:
/// You must also override the destructor function to match with how
/// you construct the underneath @c lock_.
virtual ~ACE_Adaptive_Lock (void);
// = Lock/unlock operations.
virtual int remove (void);
virtual int acquire (void);
virtual int tryacquire (void);
virtual int release (void);
virtual int acquire_read (void);
virtual int acquire_write (void);
virtual int tryacquire_read (void);
virtual int tryacquire_write (void);
virtual int tryacquire_write_upgrade (void);
void dump (void) const;
protected:
/**
* Create and initialize create the actual lock used in the class.
* The default constructor simply set the @c lock_ to 0 (null). You
* must overwrite this method for this class to work.
*/
ACE_Adaptive_Lock (void);
ACE_Lock *lock_;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/Lock.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* ACE_LOCK_H */
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