cache.cpp

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

/*
    Copyright (C) 1998 Lars Knoll ([e-mail])
    Copyright (C) 2001 Dirk Mueller ([e-mail])
    Copyright (C) 2002 Waldo Bastian ([e-mail])
    Copyright (C) 2004, 2005, 2006, 2007, 2008 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 "config.h"
#include "Cache.h"

#include "CachedCSSStyleSheet.h"
#include "CachedFont.h"
#include "CachedImage.h"
#include "CachedScript.h"
#include "CachedXSLStyleSheet.h"
#include "DocLoader.h"
#include "Document.h"
#include "FrameLoader.h"
#include "FrameView.h"
#include "Image.h"
#include "ResourceHandle.h"
#include <stdio.h>
#include <wtf/CurrentTime.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.
static const double cDefaultDecodedDataDeletionInterval = 0;

Cache* cache()
{
    static Cache* staticCache = new Cache;
    return staticCache;
}

Cache::Cache()
    : m_disabled(false)
    , m_pruneEnabled(true)
    , m_inPruneDeadResources(false)
    , m_capacity(cDefaultCacheCapacity)
    , m_minDeadCapacity(0)
    , m_maxDeadCapacity(cDefaultCacheCapacity)
    , m_deadDecodedDataDeletionInterval(cDefaultDecodedDataDeletionInterval)
    , m_liveSize(0)
    , m_deadSize(0)
{
}

static CachedResource* createResource(CachedResource::Type type, const KURL& url, const String& charset)
{
    switch (type) {
    case CachedResource::ImageResource:
        return new CachedImage(url.string());
    case CachedResource::CSSStyleSheet:
        return new CachedCSSStyleSheet(url.string(), charset);
    case CachedResource::Script:
        return new CachedScript(url.string(), charset);
    case CachedResource::FontResource:
        return new CachedFont(url.string());
#if ENABLE(XSLT)
    case CachedResource::XSLStyleSheet:
        return new CachedXSLStyleSheet(url.string());
#endif
#if ENABLE(XBL)
    case CachedResource::XBLStyleSheet:
        return new CachedXBLDocument(url.string());
#endif
    default:
        break;
    }

    return 0;
}

CachedResource* Cache::requestResource(DocLoader* docLoader, CachedResource::Type type, const KURL& url, const String& charset, bool requestIsPreload)
{
    // 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 = resourceForURL(url.string());
    
    if (resource && requestIsPreload && !resource->isPreloaded())
        return 0;
    
    if (FrameLoader::restrictAccessToLocal() && !FrameLoader::canLoad(url, String(), docLoader->doc())) {
        Document* doc = docLoader->doc();
        if (doc && !requestIsPreload)
            FrameLoader::reportLocalLoadFailed(doc->frame(), url.string());
        return 0;
    }
    
    if (!resource) {
        // The resource does not exist. Create it.
        resource = createResource(type, url, charset);
        ASSERT(resource);

        // Pretend the resource is in the cache, to prevent it from being deleted during the load() call.
        // FIXME: CachedResource should just use normal refcounting instead.
        resource->setInCache(true);
        
        resource->load(docLoader);
        
        if (!disabled())
            m_resources.set(url.string(), resource);  // The size will be added in later once the resource is loaded and calls back to us with the new size.
        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 (!disabled()) {
        // This will move the resource to the front of its LRU list and increase its access count.
        resourceAccessed(resource);
    }

    return resource;
}
    
CachedCSSStyleSheet* Cache::requestUserCSSStyleSheet(DocLoader* docLoader, const String& url, const String& charset)
{
    CachedCSSStyleSheet* userSheet;
    if (CachedResource* existing = resourceForURL(url)) {
        if (existing->type() != CachedResource::CSSStyleSheet)
            return 0;
        userSheet = static_cast<CachedCSSStyleSheet*>(existing);
    } else {
        userSheet = new CachedCSSStyleSheet(url, charset);

        // Pretend the resource is in the cache, to prevent it from being deleted during the load() call.
        // FIXME: CachedResource should just use normal refcounting instead.
        userSheet->setInCache(true);
        // Don't load incrementally, skip load checks, don't send resource load callbacks.
        userSheet->load(docLoader, false, true, false);
        if (!disabled())
            m_resources.set(url, userSheet);
        else
            userSheet->setInCache(false);
    }

    if (!disabled()) {
        // This will move the resource to the front of its LRU list and increase its access count.
        resourceAccessed(userSheet);
    }

    return userSheet;
}
    
void Cache::revalidateResource(CachedResource* resource, DocLoader* docLoader)
{
    ASSERT(resource);
    ASSERT(!disabled());
    if (resource->resourceToRevalidate())
        return;
    if (!resource->canUseCacheValidator()) {
        evict(resource);
        return;
    }
    const String& url = resource->url();
    CachedResource* newResource = createResource(resource->type(), KURL(url), resource->encoding());
    newResource->setResourceToRevalidate(resource);
    evict(resource);
    m_resources.set(url, newResource);
    newResource->setInCache(true);
    resourceAccessed(newResource);
    newResource->load(docLoader);
}
    
void Cache::revalidationSucceeded(CachedResource* revalidatingResource, const ResourceResponse& response)
{
    CachedResource* resource = revalidatingResource->resourceToRevalidate();
    ASSERT(resource);
    ASSERT(!resource->inCache());
    ASSERT(resource->isLoaded());
    
    evict(revalidatingResource);

    ASSERT(!m_resources.get(resource->url()));
    m_resources.set(resource->url(), resource);
    resource->setInCache(true);
    resource->setExpirationDate(response.expirationDate());
    insertInLRUList(resource);
    int delta = resource->size();
    if (resource->decodedSize() && resource->hasClients())
        insertInLiveDecodedResourcesList(resource);
    if (delta)
        adjustSize(resource->hasClients(), delta);
    
    revalidatingResource->switchClientsToRevalidatedResource();
    // this deletes the revalidating resource
    revalidatingResource->clearResourceToRevalidate();
}

void Cache::revalidationFailed(CachedResource* revalidatingResource)
{
    ASSERT(revalidatingResource->resourceToRevalidate());
    revalidatingResource->clearResourceToRevalidate();
}

CachedResource* Cache::resourceForURL(const String& url)
{
    CachedResource* resource = m_resources.get(url);
    if (resource && !resource->makePurgeable(false)) {
        ASSERT(!resource->hasClients());
        evict(resource);
        return 0;
    }
    return resource;
}

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 (capacity && m_liveSize <= capacity)
        return;

    unsigned targetSize = static_cast<unsigned>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.
    double currentTime = FrameView::currentPaintTimeStamp();
    if (!currentTime) // In case prune is called directly, outside of a Frame paint.
        currentTime = WTF::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->hasClients());
        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 (targetSize && m_liveSize <= targetSize)
                return;
        }
        current = prev;
    }
}

void Cache::pruneDeadResources()
{
    if (!m_pruneEnabled)
        return;

    unsigned capacity = deadCapacity();
    if (capacity && 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();
    
    if (!m_inPruneDeadResources) {
        // See if we have any purged resources we can evict.
        for (int i = 0; i < size; i++) {
            CachedResource* current = m_allResources[i].m_tail;
            while (current) {
                CachedResource* prev = current->m_prevInAllResourcesList;
                if (current->wasPurged()) {
                    ASSERT(!current->hasClients());
                    ASSERT(!current->isPreloaded());
                    evict(current);
                }
                current = prev;
            }
        }
        if (targetSize && m_deadSize <= targetSize)
            return;
    }
    
    bool canShrinkLRULists = true;
    m_inPruneDeadResources = 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 (!current->hasClients() && !current->isPreloaded() && current->isLoaded()) {
                // 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 (targetSize && m_deadSize <= targetSize) {
                    m_inPruneDeadResources = false;
                    return;
                }
            }
            current = prev;
        }

        // Now evict objects from this queue.
        current = m_allResources[i].m_tail;
        while (current) {
            CachedResource* prev = current->m_prevInAllResourcesList;
            if (!current->hasClients() && !current->isPreloaded()) {
                evict(current);
                // If evict() caused pruneDeadResources() to be re-entered, bail out. This can happen when removing an
                // SVG CachedImage that has subresources.
                if (!m_inPruneDeadResources)
                    return;

                if (targetSize && m_deadSize <= targetSize) {
                    m_inPruneDeadResources = false;
                    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);
    }