libreoffice/sd/source/ui/slidesorter/cache/SlsRequestQueue.cxx

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you under the Apache
 *   License, Version 2.0 (the "License"); you may not use this file
 *   except in compliance with the License. You may obtain a copy of
 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 */


#include "SlsRequestQueue.hxx"

#include <set>

namespace sd { namespace slidesorter { namespace cache {

/** This class extends the actual request data with additional information
    that is used by the priority queues.
*/
class Request
{
public:
    Request (
        CacheKey aKey, sal_Int32 nPriority, RequestPriorityClass eClass)
        : maKey(aKey), mnPriorityInClass(nPriority), meClass(eClass)
    {}
    /** Sort requests according to priority classes and then to priorities.
    */
    class Comparator { public:
        bool operator() (const Request& rRequest1, const Request& rRequest2)
        {
            if (rRequest1.meClass == rRequest2.meClass)
                return (rRequest1.mnPriorityInClass > rRequest2.mnPriorityInClass);
            else
                return (rRequest1.meClass < rRequest2.meClass);
        }
    };
    /** Request data is compared arbitrarily by their addresses in memory.
        This just establishes an order so that the STL containers are happy.
        The order is not semantically interpreted.
    */
    class DataComparator { public:
        DataComparator (const Request&rRequest):maKey(rRequest.maKey){}
        DataComparator (const CacheKey aKey):maKey(aKey){}
        bool operator() (const Request& rRequest) { return maKey == rRequest.maKey; }
    private: const CacheKey maKey;
    };

    CacheKey maKey;
    sal_Int32 mnPriorityInClass;
    RequestPriorityClass meClass;
};


class RequestQueue::Container
    : public ::std::set<
        Request,
        Request::Comparator>
{
};




//=====  GenericRequestQueue  =================================================


RequestQueue::RequestQueue (const SharedCacheContext& rpCacheContext)
    : maMutex(),
      mpRequestQueue(new Container()),
      mpCacheContext(rpCacheContext),
      mnMinimumPriority(0),
      mnMaximumPriority(1)
{
}




RequestQueue::~RequestQueue (void)
{
}




void RequestQueue::AddRequest (
    CacheKey aKey,
    RequestPriorityClass eRequestClass,
    bool /*bInsertWithHighestPriority*/)
{
    ::osl::MutexGuard aGuard (maMutex);

    OSL_ASSERT(eRequestClass>=MIN__CLASS && eRequestClass<=MAX__CLASS);

    // If the request is already a member of the queue then remove it so
    // that the following insertion will use the new prioritization.
#if OSL_DEBUG_LEVEL >=2
    bool bRemoved =
#endif
        RemoveRequest(aKey);

    // The priority of the request inside its priority class is defined by
    // the page number.  This ensures a strict top-to-bottom, left-to-right
    // order.
    sal_Int32 nPriority (mpCacheContext->GetPriority(aKey));
    Request aRequest (aKey, nPriority, eRequestClass);
    mpRequestQueue->insert(aRequest);

    SSCD_SET_REQUEST_CLASS(aKey,eRequestClass);

#if OSL_DEBUG_LEVEL >=2
    SAL_INFO("sd.sls", OSL_THIS_FUNC << ": " << (bRemoved?"replaced":"added")
        << " request for page " << ((aKey->GetPageNum()-1)/2)
        << " with priority class " << static_cast<int>(eRequestClass));
#endif
}




bool RequestQueue::RemoveRequest (
    CacheKey aKey)
{
    bool bRequestWasRemoved (false);
    ::osl::MutexGuard aGuard (maMutex);

    while(true)
    {
        Container::const_iterator aRequestIterator = ::std::find_if (
            mpRequestQueue->begin(),
            mpRequestQueue->end(),
            Request::DataComparator(aKey));
        if (aRequestIterator != mpRequestQueue->end())
        {
            if (aRequestIterator->mnPriorityInClass == mnMinimumPriority+1)
                mnMinimumPriority++;
            else if (aRequestIterator->mnPriorityInClass == mnMaximumPriority-1)
                mnMaximumPriority--;
            mpRequestQueue->erase(aRequestIterator);
            bRequestWasRemoved = true;

            if (bRequestWasRemoved)
            {
                SSCD_SET_STATUS(aKey,NONE);
            }
        }
        else
            break;
    }

    return bRequestWasRemoved;
}




void RequestQueue::ChangeClass (
    CacheKey aKey,
    RequestPriorityClass eNewRequestClass)
{
    ::osl::MutexGuard aGuard (maMutex);

    OSL_ASSERT(eNewRequestClass>=MIN__CLASS && eNewRequestClass<=MAX__CLASS);

    Container::const_iterator iRequest (
        ::std::find_if (
            mpRequestQueue->begin(),
            mpRequestQueue->end(),
            Request::DataComparator(aKey)));
    if (iRequest!=mpRequestQueue->end() && iRequest->meClass!=eNewRequestClass)
    {
        AddRequest(aKey, eNewRequestClass, true);
        SSCD_SET_REQUEST_CLASS(aKey,eNewRequestClass);
    }
}




CacheKey RequestQueue::GetFront (void)
{
    ::osl::MutexGuard aGuard (maMutex);

    if (mpRequestQueue->empty())
        throw ::com::sun::star::uno::RuntimeException("RequestQueue::GetFront(): queue is empty",
            NULL);

    return mpRequestQueue->begin()->maKey;
}




RequestPriorityClass RequestQueue::GetFrontPriorityClass (void)
{
    ::osl::MutexGuard aGuard (maMutex);

    if (mpRequestQueue->empty())
        throw ::com::sun::star::uno::RuntimeException("RequestQueue::GetFrontPriorityClass(): queue is empty",
            NULL);

    return mpRequestQueue->begin()->meClass;
}




void RequestQueue::PopFront (void)
{
    ::osl::MutexGuard aGuard (maMutex);

    if ( ! mpRequestQueue->empty())
    {
        SSCD_SET_STATUS(maRequestQueue.begin()->mpData->GetPage(),NONE);

        mpRequestQueue->erase(mpRequestQueue->begin());

        // Reset the priority counter if possible.
        if (mpRequestQueue->empty())
        {
            mnMinimumPriority = 0;
            mnMaximumPriority = 1;
        }
    }
}




bool RequestQueue::IsEmpty (void)
{
    ::osl::MutexGuard aGuard (maMutex);
    return mpRequestQueue->empty();
}




void RequestQueue::Clear (void)
{
    ::osl::MutexGuard aGuard (maMutex);

    mpRequestQueue->clear();
    mnMinimumPriority = 0;
    mnMaximumPriority = 1;
}




::osl::Mutex& RequestQueue::GetMutex (void)
{
    return maMutex;
}


} } } // end of namespace ::sd::slidesorter::cache



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