/*

    Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)

    Copyright (C) 2001 Dirk Mueller (mueller@kde.org)

    Copyright (C) 2002 Waldo Bastian (bastian@kde.org)

    Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.

    This library is free software; you can redistribute it and/or

    modify it under the terms of the GNU Library General Public

    License as published by the Free Software Foundation; either

    version 2 of the License, or (at your option) any later version.

    This library 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

    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License

    along with this library; see the file COPYING.LIB.  If not, write to

    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

    Boston, MA 02110-1301, USA.

*/

#include "Cache.h"

#include "CachedCSSStyleSheet.h"

#include "CachedImage.h"

#include "CachedScript.h"

#include "CachedXSLStyleSheet.h"

#include "DocLoader.h"

#include "Document.h"

#include "Frame.h"

#include "FrameLoader.h"

#include "Image.h"

#include "ResourceHandle.h"

#include "SystemTime.h"

using namespace std;

namespace WebCore {

static const int cDefaultCacheCapacity = 8192 * 1024;

static const double cMinDelayBeforeLiveDecodedPrune = 1; // Seconds.

static const float cTargetPrunePercentage = .95f; // Percentage of capacity toward which we prune, to avoid immediately pruning again.

Cache* cache()

{

    static Cache* staticCache = new Cache;

    return staticCache;

}

Cache::Cache()

: m_disabled(false)

, m_pruneEnabled(true)

, m_capacity(cDefaultCacheCapacity)

, m_minDeadCapacity(0)

, m_maxDeadCapacity(cDefaultCacheCapacity)

, m_liveSize(0)

, m_deadSize(0)

{

}

{

    switch (type) {

    case CachedResource::ImageResource:

        // User agent images need to null check the docloader.  No other resources need to.

    case CachedResource::CSSStyleSheet:

    case CachedResource::Script:

#if ENABLE(XSLT)

    case CachedResource::XSLStyleSheet:

#endif

#if ENABLE(XBL)

    case CachedResource::XBLStyleSheet:

#endif

    default:

        break;

    }

    return 0;

}

#if PRELOAD_SCANNER_ENABLED

#else

#endif

{

    // FIXME: Do we really need to special-case an empty URL?

    // Would it be better to just go on with the cache code and let it fail later?

    if (url.isEmpty())

        return 0;

    // Look up the resource in our map.

    CachedResource* resource = m_resources.get(url.url());

    if (resource) {

#if PRELOAD_SCANNER_ENABLED

        if (isPreload && !resource->isPreloaded())

            return 0;

#endif

            Document* doc = docLoader->doc();

            if(doc)

                FrameLoader::reportLocalLoadFailed(doc->page(), resource->url());

            return 0;

        }

    } else {

            Document* doc = docLoader->doc();

#if PRELOAD_SCANNER_ENABLED

            if(doc && !isPreload)

#else

            if(doc)

#endif

                FrameLoader::reportLocalLoadFailed(doc->page(), url.url());

            return 0;

        }

        // The resource does not exist. Create it.

        ASSERT(resource);

        if (!disabled()) {

            m_resources.set(url.url(), resource);  // The size will be added in later once the resource is loaded and calls back to us with the new size.

            // This will move the resource to the front of its LRU list and increase its access count.

            resourceAccessed(resource);

        } else {

            // Kick the resource out of the cache, because the cache is disabled.

            resource->setInCache(false);

            resource->setDocLoader(docLoader);

            if (resource->errorOccurred()) {

                // We don't support immediate loads, but we do support immediate failure.

                // In that case we should to delete the resource now and return 0 because otherwise

                // it would leak if no ref/deref was ever done on it.

                delete resource;

                return 0;

            }

        }

    }

    if (resource->type() != type)

        return 0;

#if USE(LOW_BANDWIDTH_DISPLAY)

    // addLowBandwidthDisplayRequest() returns true if requesting CSS or JS during low bandwidth display.

    // Here, return 0 to not block parsing or layout.

    if (docLoader->frame() && docLoader->frame()->loader()->addLowBandwidthDisplayRequest(resource))

        return 0;

#endif

    return resource;

}

CachedResource* Cache::resourceForURL(const String& url)

{

    return m_resources.get(url);

}

unsigned Cache::deadCapacity() const 

{

    // Dead resource capacity is whatever space is not occupied by live resources, bounded by an independent minimum and maximum.

    unsigned capacity = m_capacity - min(m_liveSize, m_capacity); // Start with available capacity.

    capacity = max(capacity, m_minDeadCapacity); // Make sure it's above the minimum.

    capacity = min(capacity, m_maxDeadCapacity); // Make sure it's below the maximum.

    return capacity;

}

unsigned Cache::liveCapacity() const 

{ 

    // Live resource capacity is whatever is left over after calculating dead resource capacity.

    return m_capacity - deadCapacity();

}

void Cache::pruneLiveResources()

{

    if (!m_pruneEnabled)

        return;

    unsigned capacity = liveCapacity();

    if (m_liveSize <= capacity)

        return;

    unsigned targetSize = static_cast<unsigned>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.

    double currentTime = Frame::currentPaintTimeStamp();

    if (!currentTime) // In case prune is called directly, outside of a Frame paint.

        currentTime = WebCore::currentTime();

    // Destroy any decoded data in live objects that we can.

    // Start from the tail, since this is the least recently accessed of the objects.

    CachedResource* current = m_liveDecodedResources.m_tail;

    while (current) {

        CachedResource* prev = current->m_prevInLiveResourcesList;

        ASSERT(current->referenced());

        if (current->isLoaded() && current->decodedSize()) {

            // Check to see if the remaining resources are too new to prune.

            double elapsedTime = currentTime - current->m_lastDecodedAccessTime;

            if (elapsedTime < cMinDelayBeforeLiveDecodedPrune)

                return;

            // Destroy our decoded data. This will remove us from 

            // m_liveDecodedResources, and possibly move us to a differnt LRU 

            // list in m_allResources.

            current->destroyDecodedData();

            if (m_liveSize <= targetSize)

                return;

        }

        current = prev;

    }

}

void Cache::pruneDeadResources()

{

    if (!m_pruneEnabled)

        return;

    unsigned capacity = deadCapacity();

    if (m_deadSize <= capacity)

        return;

    unsigned targetSize = static_cast<unsigned>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.

    int size = m_allResources.size();

    bool canShrinkLRULists = true;

    for (int i = size - 1; i >= 0; i--) {

        // Remove from the tail, since this is the least frequently accessed of the objects.

        CachedResource* current = m_allResources[i].m_tail;

        // First flush all the decoded data in this queue.

        while (current) {

            CachedResource* prev = current->m_prevInAllResourcesList;

#if PRELOAD_SCANNER_ENABLED

            if (!current->referenced() && !current->isPreloaded() && current->isLoaded() && current->decodedSize()) {

#else

            if (!current->referenced() && current->isLoaded() && current->decodedSize()) {

#endif

                // Destroy our decoded data. This will remove us from 

                // m_liveDecodedResources, and possibly move us to a differnt 

                // LRU list in m_allResources.

                current->destroyDecodedData();

                if (m_deadSize <= targetSize)

                    return;

            }

            current = prev;

        }

        // Now evict objects from this queue.

        current = m_allResources[i].m_tail;

        while (current) {

            CachedResource* prev = current->m_prevInAllResourcesList;

#if PRELOAD_SCANNER_ENABLED

            if (!current->referenced() && !current->isPreloaded()) {

#else

            if (!current->referenced()) {

#endif

                remove(current);

                if (m_deadSize <= targetSize)

                    return;

            }

            current = prev;

        }

        // Shrink the vector back down so we don't waste time inspecting

        // empty LRU lists on future prunes.

        if (m_allResources[i].m_head)

            canShrinkLRULists = false;

        else if (canShrinkLRULists)

            m_allResources.resize(i);

    }

}

void Cache::setCapacities(unsigned minDeadBytes, unsigned maxDeadBytes, unsigned totalBytes)

{

    ASSERT(minDeadBytes <= maxDeadBytes);

    ASSERT(maxDeadBytes <= totalBytes);

    m_minDeadCapacity = minDeadBytes;

    m_maxDeadCapacity = maxDeadBytes;

    m_capacity = totalBytes;

    prune();

}

void Cache::remove(CachedResource* resource)

{

    // The resource may have already been removed by someone other than our caller,

    // who needed a fresh copy for a reload. See <http://bugs.webkit.org/show_bug.cgi?id=12479#c6>.

    if (resource->inCache()) {

        // Remove from the resource map.

        m_resources.remove(resource->url());

        resource->setInCache(false);

        // Remove from the appropriate LRU list.

        removeFromLRUList(resource);

        removeFromLiveDecodedResourcesList(resource);

        // Notify all doc loaders that might be observing this object still that it has been

        // extracted from the set of resources.

        HashSet<DocLoader*>::iterator end = m_docLoaders.end();

        for (HashSet<DocLoader*>::iterator itr = m_docLoaders.begin(); itr != end; ++itr)

            (*itr)->removeCachedResource(resource);

        // Subtract from our size totals.

        int delta = -static_cast<int>(resource->size());

        if (delta)

            adjustSize(resource->referenced(), delta);

    if (resource->canDelete())

        delete resource;

}

void Cache::addDocLoader(DocLoader* docLoader)

{

    m_docLoaders.add(docLoader);

}

void Cache::removeDocLoader(DocLoader* docLoader)

{

    m_docLoaders.remove(docLoader);

}

static inline unsigned fastLog2(unsigned i)

{

    unsigned log2 = 0;

    if (i & (i - 1))

        log2 += 1;

    if (i >> 16)

        log2 += 16, i >>= 16;

    if (i >> 8)

        log2 += 8, i >>= 8;

    if (i >> 4)

        log2 += 4, i >>= 4;

    if (i >> 2)

        log2 += 2, i >>= 2;

    if (i >> 1)

        log2 += 1;

    return log2;

}

Cache::LRUList* Cache::lruListFor(CachedResource* resource)

{

    unsigned accessCount = max(resource->accessCount(), 1U);

    unsigned queueIndex = fastLog2(resource->size() / accessCount);

#ifndef NDEBUG

    resource->m_lruIndex = queueIndex;

#endif

    if (m_allResources.size() <= queueIndex)

        m_allResources.resize(queueIndex + 1);

    return &m_allResources[queueIndex];

}

void Cache::removeFromLRUList(CachedResource* resource)

{

    // If we've never been accessed, then we're brand new and not in any list.

    if (resource->accessCount() == 0)

        return;

#ifndef NDEBUG

    unsigned oldListIndex = resource->m_lruIndex;

#endif

    LRUList* list = lruListFor(resource);

#ifndef NDEBUG

    // Verify that the list we got is the list we want.

    ASSERT(resource->m_lruIndex == oldListIndex);

    // Verify that we are in fact in this list.

    bool found = false;

    for (CachedResource* current = list->m_head; current; current = current->m_nextInAllResourcesList) {

        if (current == resource) {

            found = true;

            break;

        }

    }

    ASSERT(found);

#endif

    CachedResource* next = resource->m_nextInAllResourcesList;

    CachedResource* prev = resource->m_prevInAllResourcesList;

    if (next == 0 && prev == 0 && list->m_head != resource)

        return;

    resource->m_nextInAllResourcesList = 0;

    resource->m_prevInAllResourcesList = 0;

    if (next)

        next->m_prevInAllResourcesList = prev;

    else if (list->m_tail == resource)

        list->m_tail = prev;

    if (prev)

        prev->m_nextInAllResourcesList = next;

    else if (list->m_head == resource)

        list->m_head = next;

}

void Cache::insertInLRUList(CachedResource* resource)

{

    // Make sure we aren't in some list already.

    ASSERT(!resource->m_nextInAllResourcesList && !resource->m_prevInAllResourcesList);

    ASSERT(resource->inCache());

    LRUList* list = lruListFor(resource);

    resource->m_nextInAllResourcesList = list->m_head;

    if (list->m_head)

        list->m_head->m_prevInAllResourcesList = resource;

    list->m_head = resource;

    if (!resource->m_nextInAllResourcesList)

        list->m_tail = resource;

#ifndef NDEBUG

    // Verify that we are in now in the list like we should be.

    list = lruListFor(resource);

    bool found = false;

    for (CachedResource* current = list->m_head; current; current = current->m_nextInAllResourcesList) {

        if (current == resource) {

            found = true;

            break;

        }

    }

    ASSERT(found);

#endif

}

void Cache::resourceAccessed(CachedResource* resource)

{

    ASSERT(resource->inCache());

    // Need to make sure to remove before we increase the access count, since

    // the queue will possibly change.

    removeFromLRUList(resource);

    // Add to our access count.

    resource->increaseAccessCount();

    // Now insert into the new queue.

    insertInLRUList(resource);

}

void Cache::removeFromLiveDecodedResourcesList(CachedResource* resource)

{

    // If we've never been accessed, then we're brand new and not in any list.

    if (!resource->m_inLiveDecodedResourcesList)

        return;

    resource->m_inLiveDecodedResourcesList = false;

#ifndef NDEBUG

    // Verify that we are in fact in this list.

    bool found = false;

    for (CachedResource* current = m_liveDecodedResources.m_head; current; current = current->m_nextInLiveResourcesList) {

        if (current == resource) {

            found = true;

            break;

        }

    }

    ASSERT(found);

#endif

    CachedResource* next = resource->m_nextInLiveResourcesList;

    CachedResource* prev = resource->m_prevInLiveResourcesList;

    if (next == 0 && prev == 0 && m_liveDecodedResources.m_head != resource)

        return;

    resource->m_nextInLiveResourcesList = 0;

    resource->m_prevInLiveResourcesList = 0;

    if (next)