/*
    Scan Tailor - Interactive post-processing tool for scanned pages.
    Copyright (C)  Joseph Artsimovich <joseph.artsimovich@gmail.com>

    This program 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.

    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "OutOfMemoryHandler.h"

#include <QMutexLocker>
#include <QMetaObject>
#include <Qt>

OutOfMemoryHandler::OutOfMemoryHandler()
    :   m_hadOOM(false)
{
}

OutOfMemoryHandler&
OutOfMemoryHandler::instance()
{
    // Depending on the compiler, this may not be thread-safe.
    // However, because we insist an instance of this object to be created early on,
    // the only case that might get us into trouble is an out-of-memory situation
    // after main() has returned and this instance got destroyed.  This scenario
    // sounds rather fantastic, and is not a big deal, as the project would have
    // already been saved.
    static OutOfMemoryHandler object;

    return object;
}

void
OutOfMemoryHandler::allocateEmergencyMemory(size_t bytes)
{
    QMutexLocker const locker(&m_mutex);

    boost::scoped_array<char>(new char[bytes]).swap(m_emergencyBuffer);
}

void
OutOfMemoryHandler::handleOutOfMemorySituation()
{
    QMutexLocker const locker(&m_mutex);

    if (m_hadOOM) {
        return;
    }

    m_hadOOM = true;
    boost::scoped_array<char>().swap(m_emergencyBuffer);
    QMetaObject::invokeMethod(this, "outOfMemory", Qt::QueuedConnection);
}

bool
OutOfMemoryHandler::hadOutOfMemorySituation() const
{
    QMutexLocker const locker(&m_mutex);
    return m_hadOOM;
}
