// -*- C++ -*-

//==========================================================================
/**
 *  @file    Recursive_Thread_Mutex.h
 *
 *  $Id$
 *
 *   Moved from Synch.h.
 *
 *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
 */
//==========================================================================

#ifndef ACE_RECURSIVE_THREAD_MUTEX_H
#define ACE_RECURSIVE_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_Mutex.h"
#else /* ACE_HAS_THREADS */
// ACE platform supports some form of threading.

#include "ace/OS_NS_Thread.h"

/**
 * @class ACE_Recursive_Thread_Mutex
 *
 * @brief Implement a C++ wrapper that allows nested acquisition and
 * release of a mutex that occurs in the same thread.
 */
class ACE_Export ACE_Recursive_Thread_Mutex
{
public:
  /// Initialize a recursive mutex.
  ACE_Recursive_Thread_Mutex (const ACE_TCHAR *name = 0,
                              ACE_mutexattr_t *arg = 0);

  /// Implicitly release a recursive mutex.
  ~ACE_Recursive_Thread_Mutex (void);

  /**
   * Implicitly release a recursive mutex.  Note that only one thread
   * should call this method since it doesn't protect against race
   * conditions.
   */
  int remove (void);

  /**
   * Acquire a recursive mutex (will increment the nesting level and
   * not deadmutex if the owner of the mutex calls this method more
   * than once).
   */
  int acquire (void);

  /**
   * Conditionally acquire a recursive mutex (i.e., won't block).
   * Returns -1 on failure.  If we "failed" because someone else
   * already had the lock, <errno> is set to <EBUSY>.
   */
  int tryacquire (void);

  /**
   * Acquire mutex ownership.  This calls <acquire> and is only
   * here to make the <ACE_Recusive_Thread_Mutex> interface consistent
   * with the other synchronization APIs.
   */
  int acquire_read (void);

  /**
   * Acquire mutex ownership.  This calls <acquire> and is only
   * here to make the <ACE_Recusive_Thread_Mutex> interface consistent
   * with the other synchronization APIs.
   */
  int acquire_write (void);

  /**
   * Conditionally acquire mutex (i.e., won't block).  This calls
   * <tryacquire> and is only here to make the
   * <ACE_Recusive_Thread_Mutex> interface consistent with the other
   * synchronization APIs.  Returns -1 on failure.  If we "failed"
   * because someone else already had the lock, <errno> is set to
   * <EBUSY>.
   */
  int tryacquire_read (void);

  /**
   * Conditionally acquire mutex (i.e., won't block).  This calls
   * <tryacquire> and is only here to make the
   * <ACE_Recusive_Thread_Mutex> interface consistent with the other
   * synchronization APIs.  Returns -1 on failure.  If we "failed"
   * because someone else already had the lock, <errno> is set to
   * <EBUSY>.
   */
  int tryacquire_write (void);

  /**
   * This is only here to make the <ACE_Recursive_Thread_Mutex>
   * interface consistent with the other synchronization APIs.
   * Assumes the caller has already acquired the mutex using one of
   * the above calls, and returns 0 (success) always.
   */
  int tryacquire_write_upgrade (void);

  /**
   * Releases a recursive mutex (will not release mutex until all the
   * nesting level drops to 0, which means the mutex is no longer
   * held).
   */
  int release (void);

  /// Return the id of the thread that currently owns the mutex.
  ACE_thread_t get_thread_id (void);

  /**
   * Return the nesting level of the recursion.  When a thread has
   * acquired the mutex for the first time, the nesting level == 1.
   * The nesting level is incremented every time the thread acquires
   * the mutex recursively.
   */
  int get_nesting_level (void);

  /// Returns a reference to the recursive mutex;
  ACE_recursive_thread_mutex_t &mutex (void);

  /// Returns a reference to the recursive mutex's internal mutex;
  ACE_thread_mutex_t &get_nesting_mutex (void);

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

  /// Declare the dynamic allocation hooks.
  ACE_ALLOC_HOOK_DECLARE;

protected:
  // = This method should *not* be public (they hold no locks...)
  void set_thread_id (ACE_thread_t t);

  /// Recursive mutex.
  ACE_recursive_thread_mutex_t lock_;

  /// 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_Recursive_Thread_Mutex &);
  ACE_Recursive_Thread_Mutex (const ACE_Recursive_Thread_Mutex &);
};

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

#endif /* !ACE_HAS_THREADS */

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