// -*- C++ -*-

//==========================================================================
/**
 *  @file    Condition_Thread_Mutex.h
 *
 *  Condition_Thread_Mutex.h,v 4.2 2004/05/18 11:31:49 jwillemsen Exp
 *
 *   Moved from Synch.h.
 *
 *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
 */
//==========================================================================

#ifndef ACE_CONDITION_THREAD_MUTEX_H
#define ACE_CONDITION_THREAD_MUTEX_H
#include /**/ "ace/pre.h"

#include "ace/ACE_export.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

#if !defined (ACE_HAS_THREADS)
#  include "ace/Null_Condition.h"
#else /* ACE_HAS_THREADS */
// ACE platform supports some form of threading.

#include "ace/Thread_Mutex.h"

class ACE_Time_Value;

class ACE_Export ACE_Condition_Attributes
{
public:
  /// Constructor
  ACE_Condition_Attributes (int type = ACE_DEFAULT_SYNCH_TYPE);

  /// Destructor
  ~ACE_Condition_Attributes (void);

private:
  friend class ACE_Condition_Thread_Mutex;

  /// The attributes
  ACE_condattr_t attributes_;

private:
  // = Prevent assignment and initialization.
  void operator= (const ACE_Condition_Attributes &);
  ACE_Condition_Attributes (const ACE_Condition_Attributes &);
};

/**
 * @class ACE_Condition_Thread_Mutex
 *
 * @brief ACE_Condition variable wrapper written using ACE_Mutexes This
 * allows threads to block until shared data changes state.
 * A condition variable enables threads to atomically block and
 * test the condition under the protection of a mutual exclu-
 * sion lock (mutex) until the condition is satisfied.  That is,
 * the mutex must have been held by the thread before calling
 * wait or signal on the condition.  If the condition is false,
 * a thread blocks on a condition variable and atomically
 * releases the mutex that is waiting for the condition to
 * change.  If another thread changes the condition, it may wake
 * up waiting threads by signaling the associated condition
 * variable.  The waiting threads, upon awakening, reacquire the
 * mutex and re-evaluate the condition.
 *
 * This should be an instantiation of ACE_Condition but problems
 * with compilers precludes this...
 */
class ACE_Export ACE_Condition_Thread_Mutex
{
public:
  /// Initialize the condition variable.
  ACE_Condition_Thread_Mutex (const ACE_Thread_Mutex &m,
                              const ACE_TCHAR *name = 0,
                              void *arg = 0);

  /// Initialize the condition variable.
  ACE_Condition_Thread_Mutex (const ACE_Thread_Mutex &m,
                              ACE_Condition_Attributes &attributes,
                              const ACE_TCHAR *name = 0,
                              void *arg = 0);

  /// Implicitly destroy the condition variable.
  ~ACE_Condition_Thread_Mutex (void);

  /**
   * Explicitly destroy the condition variable.  Note that only one
   * thread should call this method since it doesn't protect against
   * race conditions.
   */
  int remove (void);

  /**
   * Block on condition, or until absolute time-of-day has passed.  If
   * abstime == 0 use "blocking" <wait> semantics.  Else, if <abstime>
   * != 0 and the call times out before the condition is signaled
   * <wait> returns -1 and sets errno to ETIME.
   */
  int wait (const ACE_Time_Value *abstime);

  /// Block on condition.
  int wait (void);

  /**
   * Block on condition or until absolute time-of-day has passed.  If
   * abstime == 0 use "blocking" wait() semantics on the <mutex>
   * passed as a parameter (this is useful if you need to store the
   * <Condition> in shared memory).  Else, if <abstime> != 0 and the
   * call times out before the condition is signaled <wait> returns -1
   * and sets errno to ETIME.
   */
  int wait (ACE_Thread_Mutex &mutex, const ACE_Time_Value *abstime = 0);

  /// Signal one waiting thread.
  int signal (void);

  /// Signal *all* waiting threads.
  int broadcast (void);

  /// Returns a reference to the underlying mutex;
  ACE_Thread_Mutex &mutex (void);

  /// Dump the state of an object.
  void dump (void) const;

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

protected:
  /// Condition variable.
  ACE_cond_t cond_;

  /// Reference to mutex lock.
  ACE_Thread_Mutex &mutex_;

  /// Keeps track of whether <remove> has been called yet to avoid
  /// multiple <remove> calls, e.g., explicitly and implicitly in the
  /// destructor.  This flag isn't protected by a lock, so make sure
  /// that you don't have multiple threads simultaneously calling
  /// <remove> on the same object, which is a bad idea anyway...
  int removed_;

private:
  // = Prevent assignment and initialization.
  void operator= (const ACE_Condition_Thread_Mutex &);
  ACE_Condition_Thread_Mutex (const ACE_Condition_Thread_Mutex &);
};

#if 0
// The following class is commented out since there doesn't
// appear to be a portable and robust means of implementing this
// functionality across platforms.  If you know of a portable and
// robust way to implement this functionality please let us know.

/**
 * @class ACE_Process_Condition
 *
 * @brief ACE_Condition variable wrapper that works across processes.
 */
class ACE_Export ACE_Process_Condition
{
public:
  ACE_Process_Condition (MUTEX &m, const ACE_TCHAR *name = 0, void *arg = 0);

  /// Dump the state of an object.
  void dump (void) const;

  // ACE_ALLOC_HOOK_DECLARE;
  // Declare the dynamic allocation hooks.
};
#endif /* 0 */

#if defined (__ACE_INLINE__)
#include "ace/Condition_Thread_Mutex.inl"
#endif /* __ACE_INLINE__ */

#endif /* !ACE_HAS_THREADS */

#include /**/ "ace/post.h"
#endif /* ACE_CONDITION_THREAD_MUTEX_H */
