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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2012-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING. If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////
#if ! defined (octave_event_queue_h)
#define octave_event_queue_h 1
#include "octave-config.h"
#include <queue>
#include <memory>
#include "action-container.h"
namespace octave
{
class
event_queue : public action_container
{
public:
event_queue (void) : fifo () { }
// No copying!
event_queue (const event_queue&) = delete;
event_queue& operator = (const event_queue&) = delete;
// Destructor should not raise an exception, so all actions
// registered should be exception-safe. If you're not sure, see
// event_queue_safe.
~event_queue (void) { run (); }
void run_first (void)
{
if (! empty ())
{
// No leak on exception!
std::unique_ptr<elem> ptr (fifo.front ());
fifo.pop ();
ptr->run ();
}
}
void discard_first (void)
{
if (! empty ())
{
elem *ptr = fifo.front ();
fifo.pop ();
delete ptr;
}
}
size_t size (void) const { return fifo.size (); }
protected:
void add_action (elem *new_elem)
{
fifo.push (new_elem);
}
std::queue<elem *> fifo;
};
// Like event_queue, but this one will guard against the
// possibility of seeing an exception (or interrupt) in the cleanup actions.
// Not that we can do much about it, but at least we won't crash.
class
event_queue_safe : public event_queue
{
private:
void warn_unhandled_exception (void) const;
public:
event_queue_safe (void) : event_queue () { }
// No copying!
event_queue_safe (const event_queue_safe&) = delete;
event_queue_safe& operator = (const event_queue_safe&) = delete;
~event_queue_safe (void)
{
while (! empty ())
{
try
{
run_first ();
}
catch (...) // Yes, the black hole. Remember we're in a dtor.
{
warn_unhandled_exception ();
}
}
}
};
}
#endif
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