/usr/include/ace/Future.h is in libace-dev 6.2.8+dfsg-1.
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//=============================================================================
/**
* @file Future.h
*
* $Id: Future.h 91626 2010-09-07 10:59:20Z johnnyw $
*
* @author Andres Kruse <Andres.Kruse@cern.ch>
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
* @author Per Andersson <Per.Andersson@hfera.ericsson.se> and
* @author John Tucker <johnny_tucker@yahoo.com>
*/
//=============================================================================
#ifndef ACE_FUTURE_H
#define ACE_FUTURE_H
#include /**/ "ace/pre.h"
#include "ace/Unbounded_Set.h"
#include "ace/Strategies_T.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#if defined (ACE_HAS_THREADS)
#include "ace/Synch_Traits.h"
#include "ace/Recursive_Thread_Mutex.h"
#include "ace/Condition_Recursive_Thread_Mutex.h"
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
// Forward decl.
template <class T> class ACE_Future_Holder;
template <class T> class ACE_Future_Observer;
template <class T> class ACE_Future_Rep;
template <class T> class ACE_Future;
/**
* @class ACE_Future_Holder
*
* @brief Implementation of object that holds an ACE_Future.
*/
template <class T>
class ACE_Future_Holder
{
public:
ACE_Future_Holder (const ACE_Future<T> &future);
~ACE_Future_Holder (void);
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
ACE_Future<T> item_;
protected:
ACE_Future_Holder (void);
};
/**
* @class ACE_Future_Observer
*
* @brief ACE_Future_Observer<T>
*
* An ACE_Future_Observer object implements an object that is
* subscribed with an ACE_Future object so that it may be notified
* when the value of the ACE_Future object is written to by a writer
* thread. It uses the Observer pattern.
*/
template <class T>
class ACE_Future_Observer
{
public:
/// Destructor
virtual ~ACE_Future_Observer (void);
/// Called by the ACE_Future in which we are subscribed to when
/// its value is written to.
virtual void update (const ACE_Future<T> &future) = 0;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
/// Constructor
ACE_Future_Observer (void);
};
/**
* @class ACE_Future_Rep
*
* @internal
*
* @brief ACE_Future_Rep<T>
*
* An ACE_Future_Rep<T> object encapsules a pointer to an object
* of class T which is the result of an asynchronous method
* invocation. It is pointed to by ACE_Future<T> object[s] and
* only accessible through them.
*/
template <class T>
class ACE_Future_Rep
{
private:
friend class ACE_Future<T>;
/**
* Set the result value. The specified @a caller represents the
* future that invoked this <set> method, which is used to notify
* the list of future observers. Returns 0 for success, -1 on error.
* This function only has an effect the first time it is called for
* the object. Subsequent calls return 0 (success) but have no effect.
*/
int set (const T &r,
ACE_Future<T> &caller);
/// Wait up to @a tv time to get the @a value. Note that @a tv must be
/// specified in absolute time rather than relative time.
int get (T &value,
ACE_Time_Value *tv) const;
/**
* Attaches the specified observer to a subject (i.e., the ACE_Future_Rep).
* The update method of the specified subject will be invoked with a copy of
* the written-to ACE_Future as input when the result gets set.
*
* Returns 0 if the observer is successfully attached, 1 if the
* observer is already attached, and -1 if failures occur.
*/
int attach (ACE_Future_Observer<T> *observer,
ACE_Future<T> &caller);
/**
* Detaches the specified observer from a subject (i.e., the ACE_Future_Rep).
* The update method of the specified subject will not be invoked when the
* ACE_Future_Reps result gets set. Returns 1 if the specified observer was
* actually attached to the subject prior to this call and 0 if was not.
*
* Returns 0 if the observer was successfully detached, and -1 if the
* observer was not attached in the first place.
*/
int detach (ACE_Future_Observer<T> *observer);
/**
* Type conversion. will block forever until the result is
* available. Note that this method is going away in a subsequent
* release since it doesn't distinguish between failure results and
* success results (exceptions should be used, but they aren't
* portable...). The <get> method should be used instead since it
* separates the error value from the result, and also permits
* timeouts.
*/
operator T ();
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
// = Encapsulate reference count and object lifetime of instances.
// These methods must go after the others to work around a bug with
// Borland's C++ Builder...
/// Allocate a new ACE_Future_Rep<T> instance, returning NULL if it
/// cannot be created.
static ACE_Future_Rep<T> *internal_create (void);
/// Create a ACE_Future_Rep<T> and initialize the reference count.
static ACE_Future_Rep<T> *create (void);
/**
* Increase the reference count and return argument. Uses the
* attribute "value_ready_mutex_" to synchronize reference count
* updating.
*
* Precondition (rep != 0).
*/
static ACE_Future_Rep<T> *attach (ACE_Future_Rep<T> *&rep);
/**
* Decreases the reference count and deletes rep if there are no
* more references to rep.
*
* Precondition (rep != 0)
*/
static void detach (ACE_Future_Rep<T> *&rep);
/**
* Decreases the rep's reference count and deletes rep if there
* are no more references to rep. Then assigns new_rep to rep.
*
* Precondition (rep != 0 && new_rep != 0)
*/
static void assign (ACE_Future_Rep<T> *&rep, ACE_Future_Rep<T> *new_rep);
/// Is result available?
int ready (void) const;
/// Pointer to the result.
T *value_;
/// Reference count.
int ref_count_;
typedef ACE_Future_Observer<T> OBSERVER;
typedef ACE_Unbounded_Set<OBSERVER *> OBSERVER_COLLECTION;
/// Keep a list of ACE_Future_Observers unread by client's reader thread.
OBSERVER_COLLECTION observer_collection_;
// = Condition variable and mutex that protect the <value_>.
mutable ACE_SYNCH_RECURSIVE_MUTEX value_ready_mutex_;
mutable ACE_SYNCH_RECURSIVE_CONDITION value_ready_;
private:
ACE_Future_Rep (void);
protected:
~ACE_Future_Rep (void);
};
/**
* @class ACE_Future
*
* @brief This class implements a ``single write, multiple read''
* pattern that can be used to return results from asynchronous
* method invocations.
*/
template <class T>
class ACE_Future
{
public:
// = Initialization and termination methods.
/// Constructor.
ACE_Future (void);
/// Copy constructor binds @a this and @a r to the same
/// ACE_Future_Rep. An ACE_Future_Rep is created if necessary.
ACE_Future (const ACE_Future<T> &r);
/// Constructor that initialises an ACE_Future to point to the
/// result @a r immediately.
ACE_Future (const T &r);
/// Destructor.
~ACE_Future (void);
/// Assignment operator that binds @a this and @a r to the same
/// ACE_Future_Rep. An ACE_Future_Rep is created if necessary.
void operator = (const ACE_Future<T> &r);
/// Cancel an ACE_Future and assign the value @a r. It is used if a
/// client does not want to wait for the value to be produced.
int cancel (const T &r);
/**
* Cancel an ACE_Future. Put the future into its initial
* state. Returns 0 on succes and -1 on failure. It is now possible
* to reuse the ACE_Future. But remember, the ACE_Future
* is now bound to a new ACE_Future_Rep.
*/
int cancel (void);
/**
* Equality operator that returns @c true if both ACE_Future objects
* point to the same ACE_Future_Rep object.
*
* @note It also returns @c true if both objects have just been
* instantiated and not used yet.
*/
bool operator == (const ACE_Future<T> &r) const;
/// Inequality operator, which is the opposite of equality.
bool operator != (const ACE_Future<T> &r) const;
/**
* Make the result available. Is used by the server thread to give
* the result to all waiting clients. Returns 0 for success, -1 on failure.
* This function only has an effect the first time it is called for
* the object (actually, the first time the underlying ACE_Future_Rep has a
* value assigned to it). Subsequent calls return 0 (success) but have no
* effect.
*/
int set (const T &r);
/**
* Wait to get the object's value.
*
* @param value Receives the value of this ACE_Future when it is set.
* @param tv Pointer to an ACE_Time_Value containing the absolute
* time to wait until for the value to be set. If @a tv
* is 0, the call waits indefinitely for the value to be
* set, unless an error occurs.
*
* @retval 0 Success; @a value contains the value of the ACE_Future.
* @retval -1 Error; check ACE_OS::last_error() for an error code.
*/
int get (T &value, ACE_Time_Value *tv = 0) const;
/**
* @deprecated Note that this method is going away in a subsequent
* release since it doesn't distinguish between failure
* results and success results (exceptions should be
* used, but they aren't portable...).
* Type conversion, which obtains the result of the asynchronous
* method invocation. Will block forever. The get() method should be
* used instead since it separates the error value from the result,
* and also permits timeouts.
*/
operator T ();
/// Check if the result is available.
int ready (void) const;
/**
* Attaches the specified observer to a subject (this ACE_Future).
* The update method of the specified subject will be invoked with a copy of
* the associated ACE_Future as input when the result gets set. If the
* result is already set when this method gets invoked, then the update
* method of the specified subject will be invoked immediately.
*
* @param observer The observer to attach to the subject.
*
* @retval 0 Success.
* @retval 1 The observer was already attached.
* @retval -1 Error; check ACE_OS::last_error() for an error code.
*/
int attach (ACE_Future_Observer<T> *observer);
/**
* Detaches the specified observer from a subject (this ACE_Future).
* The update method of the specified subject will not be invoked when the
* ACE_Future_Rep result gets set.
*
* @param observer The observer to attach to the subject.
*
* @retval 0 The observer was successfully detached.
* @retval -1 Error, including the observer not attached prior
* to calling this method.
*/
int detach (ACE_Future_Observer<T> *observer);
/// Dump the state of an object.
void dump (void) const;
/**
* Get the underlying ACE_Future_Rep pointer. Note that this method should
* rarely, if ever, be used and that modifying the underlying
* ACE_Future_Rep should be done with extreme caution.
*/
ACE_Future_Rep<T> *get_rep (void);
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
private:
/// The ACE_Future_Rep
/// Protect operations on the <Future>.
typedef ACE_Future_Rep<T> FUTURE_REP;
FUTURE_REP *future_rep_;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (ACE_TEMPLATES_REQUIRE_SOURCE)
#include "ace/Future.cpp"
#endif /* ACE_TEMPLATES_REQUIRE_SOURCE */
#if defined (ACE_TEMPLATES_REQUIRE_PRAGMA)
#pragma implementation ("Future.cpp")
#endif /* ACE_TEMPLATES_REQUIRE_PRAGMA */
#endif /* ACE_HAS_THREADS */
#include /**/ "ace/post.h"
#endif /* ACE_FUTURE_H */
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