WebCore/loader/CachedResource.cpp

/*
    Copyright (C) 1998 Lars Knoll (knoll (at) mpi-hd.mpg.de)
    Copyright (C) 2001 Dirk Mueller (mueller (at) kde.org)
    Copyright (C) 2002 Waldo Bastian (bastian (at) kde.org)
    Copyright (C) 2006 Samuel Weinig (sam.weinig (at) gmail.com)
    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 "CachedResource.h"

#include "Cache.h"
#include "CachedResourceHandle.h"
#include "DocLoader.h"
#include "Frame.h"
#include "FrameLoader.h"
#include "KURL.h"
#include "PurgeableBuffer.h"
#include "Request.h"
#include <wtf/CurrentTime.h>
#include <wtf/MathExtras.h>
#include <wtf/RefCountedLeakCounter.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>

using namespace WTF;

namespace WebCore {

#ifndef NDEBUG
static RefCountedLeakCounter cachedResourceLeakCounter("CachedResource");
#endif

CachedResource::CachedResource(const String& url, Type type)
    : m_url(url)
    , m_responseTimestamp(currentTime())
    , m_lastDecodedAccessTime(0)
    , m_sendResourceLoadCallbacks(true)
    , m_preloadCount(0)
    , m_preloadResult(PreloadNotReferenced)
    , m_requestedFromNetworkingLayer(false)
    , m_inCache(false)
    , m_loading(false)
    , m_docLoader(0)
    , m_handleCount(0)
    , m_resourceToRevalidate(0)
    , m_proxyResource(0)
{
#ifndef NDEBUG
    cachedResourceLeakCounter.increment();
#endif

    m_type = type;
    m_status = Pending;
    m_encodedSize = 0;
    m_decodedSize = 0;
    m_request = 0;

    m_accessCount = 0;
    m_inLiveDecodedResourcesList = false;

    m_nextInAllResourcesList = 0;
    m_prevInAllResourcesList = 0;

    m_nextInLiveResourcesList = 0;
    m_prevInLiveResourcesList = 0;

#ifndef NDEBUG
    m_deleted = false;
    m_lruIndex = 0;
#endif
    m_errorOccurred = false;
}

CachedResource::~CachedResource()
{
    ASSERT(!m_resourceToRevalidate); // Should be true because canDelete() checks this.
    ASSERT(canDelete());
    ASSERT(!inCache());
    ASSERT(!m_deleted);
    ASSERT(url().isNull() || cache()->resourceForURL(url()) != this);
#ifndef NDEBUG
    m_deleted = true;
    cachedResourceLeakCounter.decrement();
#endif

    if (m_docLoader)
        m_docLoader->removeCachedResource(this);
}

void CachedResource::load(DocLoader* docLoader, bool incremental, SecurityCheckPolicy securityCheck, bool sendResourceLoadCallbacks)
{
    m_sendResourceLoadCallbacks = sendResourceLoadCallbacks;
    cache()->loader()->load(docLoader, this, incremental, securityCheck, sendResourceLoadCallbacks);
    m_loading = true;
}

void CachedResource::finish()
{
    m_status = Cached;
}

bool CachedResource::isExpired() const
{
    if (m_response.isNull())
        return false;

    return currentAge() > freshnessLifetime();
}

double CachedResource::currentAge() const
{
    // RFC2616 13.2.3
    // No compensation for latency as that is not terribly important in practice
    double dateValue = m_response.date();
    double apparentAge = isfinite(dateValue) ? max(0., m_responseTimestamp - dateValue) : 0;
    double ageValue = m_response.age();
    double correctedReceivedAge = isfinite(ageValue) ? max(apparentAge, ageValue) : apparentAge;
    double residentTime = currentTime() - m_responseTimestamp;
    return correctedReceivedAge + residentTime;
}

double CachedResource::freshnessLifetime() const
{
    // Cache non-http resources liberally
    if (!m_response.url().protocolInHTTPFamily())
        return std::numeric_limits<double>::max();

    // RFC2616 13.2.4
    double maxAgeValue = m_response.cacheControlMaxAge();
    if (isfinite(maxAgeValue))
        return maxAgeValue;
    double expiresValue = m_response.expires();
    double dateValue = m_response.date();
    double creationTime = isfinite(dateValue) ? dateValue : m_responseTimestamp;
    if (isfinite(expiresValue))
        return expiresValue - creationTime;
    double lastModifiedValue = m_response.lastModified();
    if (isfinite(lastModifiedValue))
        return (creationTime - lastModifiedValue) * 0.1;
    // If no cache headers are present, the specification leaves the decision to the UA. Other browsers seem to opt for 0.
    return 0;
}

void CachedResource::setResponse(const ResourceResponse& response)
{
    m_response = response;
    m_responseTimestamp = currentTime();
}

void CachedResource::setRequest(Request* request)
{
    if (request && !m_request)
        m_status = Pending;
    m_request = request;
    if (canDelete() && !inCache())
        delete this;
}

void CachedResource::addClient(CachedResourceClient* client)
{
    addClientToSet(client);
    didAddClient(client);
}

void CachedResource::addClientToSet(CachedResourceClient* client)
{
    ASSERT(!isPurgeable());

    if (m_preloadResult == PreloadNotReferenced) {
        if (isLoaded())
            m_preloadResult = PreloadReferencedWhileComplete;
        else if (m_requestedFromNetworkingLayer)
            m_preloadResult = PreloadReferencedWhileLoading;
        else
            m_preloadResult = PreloadReferenced;
    }
    if (!hasClients() && inCache())
        cache()->addToLiveResourcesSize(this);
    m_clients.add(client);
}

void CachedResource::removeClient(CachedResourceClient* client)
{
    ASSERT(m_clients.contains(client));
    m_clients.remove(client);

    if (canDelete() && !inCache())
        delete this;
    else if (!hasClients() && inCache()) {
        cache()->removeFromLiveResourcesSize(this);
        cache()->removeFromLiveDecodedResourcesList(this);
        allClientsRemoved();
        if (response().cacheControlContainsNoStore()) {
            // RFC2616 14.9.2:
            // "no-store: ...MUST make a best-effort attempt to remove the information from volatile storage as promptly as possible"
            cache()->remove(this);
        } else
            cache()->prune();
    }
    // This object may be dead here.
}

void CachedResource::deleteIfPossible()
{
    if (canDelete() && !inCache())
        delete this;
}

void CachedResource::setDecodedSize(unsigned size)
{
    if (size == m_decodedSize)
        return;

    int delta = size - m_decodedSize;

    // The object must now be moved to a different queue, since its size has been changed.
    // We have to remove explicitly before updating m_decodedSize, so that we find the correct previous
    // queue.
    if (inCache())
        cache()->removeFromLRUList(this);

    m_decodedSize = size;

    if (inCache()) {
        // Now insert into the new LRU list.
        cache()->insertInLRUList(this);

        // Insert into or remove from the live decoded list if necessary.
        // When inserting into the LiveDecodedResourcesList it is possible
        // that the m_lastDecodedAccessTime is still zero or smaller than
        // the m_lastDecodedAccessTime of the current list head. This is a
        // violation of the invariant that the list is to be kept sorted
        // by access time. The weakening of the invariant does not pose
        // a problem. For more details please see: https://bugs.webkit.org/show_bug.cgi?id=30209
        if (m_decodedSize && !m_inLiveDecodedResourcesList && hasClients())
            cache()->insertInLiveDecodedResourcesList(this);
        else if (!m_decodedSize && m_inLiveDecodedResourcesList)
            cache()->removeFromLiveDecodedResourcesList(this);

        // Update the cache's size totals.
        cache()->adjustSize(hasClients(), delta);
    }
}

void CachedResource::setEncodedSize(unsigned size)
{
    if (size == m_encodedSize)
        return;

    // The size cannot ever shrink (unless it is being nulled out because of an error).  If it ever does, assert.
    ASSERT(size == 0 || size >= m_encodedSize);

    int delta = size - m_encodedSize;

    // The object must now be moved to a different queue, since its size has been changed.
    // We have to remove explicitly before updating m_encodedSize, so that we find the correct previous
    // queue.
    if (inCache())
        cache()->removeFromLRUList(this);

    m_encodedSize = size;

    if (inCache()) {
        // Now insert into the new LRU list.
        cache()->insertInLRUList(this);

        // Update the cache's size totals.
        cache()->adjustSize(hasClients(), delta);
    }
}

void CachedResource::didAccessDecodedData(double timeStamp)
{
    m_lastDecodedAccessTime = timeStamp;

    if (inCache()) {
        if (m_inLiveDecodedResourcesList) {
            cache()->removeFromLiveDecodedResourcesList(this);
            cache()->insertInLiveDecodedResourcesList(this);
        }
        cache()->prune();
    }
}

void CachedResource::setResourceToRevalidate(CachedResource* resource)
{
    ASSERT(resource);
    ASSERT(!m_resourceToRevalidate);
    ASSERT(resource != this);
    ASSERT(m_handlesToRevalidate.isEmpty());
    ASSERT(resource->type() == type());

    // The following assert should be investigated whenever it occurs. Although it should never fire, it currently does in rare circumstances.
    // https://bugs.webkit.org/show_bug.cgi?id=28604.
    // So the code needs to be robust to this assert failing thus the "if (m_resourceToRevalidate->m_proxyResource == this)" in CachedResource::clearResourceToRevalidate.
    ASSERT(!resource->m_proxyResource);

    resource->m_proxyResource = this;
    m_resourceToRevalidate = resource;
}

void CachedResource::clearResourceToRevalidate()
{
    ASSERT(m_resourceToRevalidate);
    // A resource may start revalidation before this method has been called, so check that this resource is still the proxy resource before clearing it out.
    if (m_resourceToRevalidate->m_proxyResource == this) {
        m_resourceToRevalidate->m_proxyResource = 0;
        m_resourceToRevalidate->deleteIfPossible();
    }
    m_handlesToRevalidate.clear();
    m_resourceToRevalidate = 0;
    deleteIfPossible();
}

void CachedResource::switchClientsToRevalidatedResource()
{
    ASSERT(m_resourceToRevalidate);
    ASSERT(m_resourceToRevalidate->inCache());
    ASSERT(!inCache());

    HashSet<CachedResourceHandleBase*>::iterator end = m_handlesToRevalidate.end();
    for (HashSet<CachedResourceHandleBase*>::iterator it = m_handlesToRevalidate.begin(); it != end; ++it) {
        CachedResourceHandleBase* handle = *it;
        handle->m_resource = m_resourceToRevalidate;
        m_resourceToRevalidate->registerHandle(handle);
        --m_handleCount;
    }
    ASSERT(!m_handleCount);
    m_handlesToRevalidate.clear();

    Vector<CachedResourceClient*> clientsToMove;
    HashCountedSet<CachedResourceClient*>::iterator end2 = m_clients.end();
    for (HashCountedSet<CachedResourceClient*>::iterator it = m_clients.begin(); it != end2; ++it) {
        CachedResourceClient* client = it->first;
        unsigned count = it->second;
        while (count) {
            clientsToMove.append(client);
            --count;
        }
    }
    // Equivalent of calling removeClient() for all clients
    m_clients.clear();

    unsigned moveCount = clientsToMove.size();
    for (unsigned n = 0; n < moveCount; ++n)
        m_resourceToRevalidate->addClientToSet(clientsToMove[n]);
    for (unsigned n = 0; n < moveCount; ++n) {
        // Calling didAddClient for a client may end up removing another client. In that case it won't be in the set anymore.
        if (m_resourceToRevalidate->m_clients.contains(clientsToMove[n]))
            m_resourceToRevalidate->didAddClient(clientsToMove[n]);
    }
}

void CachedResource::updateResponseAfterRevalidation(const ResourceResponse& validatingResponse)
{
    m_responseTimestamp = currentTime();

    DEFINE_STATIC_LOCAL(const AtomicString, contentHeaderPrefix, ("content-"));
    // RFC2616 10.3.5
    // Update cached headers from the 304 response
    const HTTPHeaderMap& newHeaders = validatingResponse.httpHeaderFields();
    HTTPHeaderMap::const_iterator end = newHeaders.end();
    for (HTTPHeaderMap::const_iterator it = newHeaders.begin(); it != end; ++it) {
        // Don't allow 304 response to update content headers, these can't change but some servers send wrong values.
        if (it->first.startsWith(contentHeaderPrefix, false))
            continue;
        m_response.setHTTPHeaderField(it->first, it->second);
    }
}

bool CachedResource::canUseCacheValidator() const
{
    if (m_loading || m_errorOccurred)
        return false;

    if (m_response.cacheControlContainsNoStore())
        return false;

    DEFINE_STATIC_LOCAL(const AtomicString, lastModifiedHeader, ("last-modified"));
    DEFINE_STATIC_LOCAL(const AtomicString, eTagHeader, ("etag"));
    return !m_response.httpHeaderField(lastModifiedHeader).isEmpty() || !m_response.httpHeaderField(eTagHeader).isEmpty();
}

bool CachedResource::mustRevalidate(CachePolicy cachePolicy) const
{
    if (m_errorOccurred)
        return true;

    if (m_loading)
        return false;

    if (m_response.cacheControlContainsNoCache() || m_response.cacheControlContainsNoStore())
        return true;

    if (cachePolicy == CachePolicyCache)
        return m_response.cacheControlContainsMustRevalidate() && isExpired();

    return isExpired();
}

bool CachedResource::isSafeToMakePurgeable() const
{
    return !hasClients() && !m_proxyResource && !m_resourceToRevalidate;
}

bool CachedResource::makePurgeable(bool purgeable)
{
    if (purgeable) {
        ASSERT(isSafeToMakePurgeable());

        if (m_purgeableData) {
            ASSERT(!m_data);
            return true;
        }
        if (!m_data)
            return false;

        // Should not make buffer purgeable if it has refs other than this since we don't want two copies.
        if (!m_data->hasOneRef())
            return false;

        // Purgeable buffers are allocated in multiples of the page size (4KB in common CPUs) so it does not make sense for very small buffers.
        const size_t purgeableThreshold = 4 * 4096;
        if (m_data->size() < purgeableThreshold)
            return false;

        if (m_data->hasPurgeableBuffer()) {
            m_purgeableData.set(m_data->releasePurgeableBuffer());
        } else {
            m_purgeableData.set(PurgeableBuffer::create(m_data->data(), m_data->size()));
            if (!m_purgeableData)
                return false;
        }

        m_purgeableData->makePurgeable(true);
        m_data.clear();
        return true;
    }

    if (!m_purgeableData)
        return true;
    ASSERT(!m_data);
    ASSERT(!hasClients());

    if (!m_purgeableData->makePurgeable(false))
        return false;

    m_data = SharedBuffer::adoptPurgeableBuffer(m_purgeableData.release());
    return true;
}

bool CachedResource::isPurgeable() const
{
    return m_purgeableData && m_purgeableData->isPurgeable();
}

bool CachedResource::wasPurged() const
{
    return m_purgeableData && m_purgeableData->wasPurged();
}

unsigned CachedResource::overheadSize() const
{
    return sizeof(CachedResource) + m_response.memoryUsage() + 576;
    /*
        576 = 192 +                   // average size of m_url
              384;                    // average size of m_clients hash map
    */
}

}