third_party/WebKit/Source/platform/loader/fetch/Resource.cpp

/*
    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) 2006 Samuel Weinig (sam.weinig@gmail.com)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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 "platform/loader/fetch/Resource.h"

#include "platform/Histogram.h"
#include "platform/InstanceCounters.h"
#include "platform/RuntimeEnabledFeatures.h"
#include "platform/SharedBuffer.h"
#include "platform/WebTaskRunner.h"
#include "platform/instrumentation/tracing/TraceEvent.h"
#include "platform/loader/fetch/CachedMetadata.h"
#include "platform/loader/fetch/CrossOriginAccessControl.h"
#include "platform/loader/fetch/FetchInitiatorTypeNames.h"
#include "platform/loader/fetch/FetchRequest.h"
#include "platform/loader/fetch/IntegrityMetadata.h"
#include "platform/loader/fetch/MemoryCache.h"
#include "platform/loader/fetch/ResourceClient.h"
#include "platform/loader/fetch/ResourceClientWalker.h"
#include "platform/loader/fetch/ResourceLoader.h"
#include "platform/network/HTTPParsers.h"
#include "platform/weborigin/KURL.h"
#include "public/platform/Platform.h"
#include "public/platform/WebCachePolicy.h"
#include "public/platform/WebScheduler.h"
#include "public/platform/WebSecurityOrigin.h"
#include "wtf/CurrentTime.h"
#include "wtf/MathExtras.h"
#include "wtf/StdLibExtras.h"
#include "wtf/Vector.h"
#include "wtf/text/CString.h"
#include "wtf/text/StringBuilder.h"
#include <algorithm>
#include <cassert>
#include <memory>
#include <stdint.h>

namespace blink {

// These response headers are not copied from a revalidated response to the
// cached response headers. For compatibility, this list is based on Chromium's
// net/http/http_response_headers.cc.
const char* const headersToIgnoreAfterRevalidation[] = {
    "allow",
    "connection",
    "etag",
    "expires",
    "keep-alive",
    "last-modified",
    "proxy-authenticate",
    "proxy-connection",
    "trailer",
    "transfer-encoding",
    "upgrade",
    "www-authenticate",
    "x-frame-options",
    "x-xss-protection",
};

// Some header prefixes mean "Don't copy this header from a 304 response.".
// Rather than listing all the relevant headers, we can consolidate them into
// this list, also grabbed from Chromium's net/http/http_response_headers.cc.
const char* const headerPrefixesToIgnoreAfterRevalidation[] = {
    "content-", "x-content-", "x-webkit-"};

static inline bool shouldUpdateHeaderAfterRevalidation(
    const AtomicString& header) {
  for (size_t i = 0; i < WTF_ARRAY_LENGTH(headersToIgnoreAfterRevalidation);
       i++) {
    if (equalIgnoringCase(header, headersToIgnoreAfterRevalidation[i]))
      return false;
  }
  for (size_t i = 0;
       i < WTF_ARRAY_LENGTH(headerPrefixesToIgnoreAfterRevalidation); i++) {
    if (header.startsWith(headerPrefixesToIgnoreAfterRevalidation[i],
                          TextCaseASCIIInsensitive))
      return false;
  }
  return true;
}

class Resource::CachedMetadataHandlerImpl : public CachedMetadataHandler {
 public:
  static Resource::CachedMetadataHandlerImpl* create(Resource* resource) {
    return new CachedMetadataHandlerImpl(resource);
  }
  ~CachedMetadataHandlerImpl() override {}
  DECLARE_VIRTUAL_TRACE();
  void setCachedMetadata(uint32_t, const char*, size_t, CacheType) override;
  void clearCachedMetadata(CacheType) override;
  PassRefPtr<CachedMetadata> cachedMetadata(uint32_t) const override;
  String encoding() const override;
  // Sets the serialized metadata retrieved from the platform's cache.
  void setSerializedCachedMetadata(const char*, size_t);

 protected:
  explicit CachedMetadataHandlerImpl(Resource*);
  virtual void sendToPlatform();
  const ResourceResponse& response() const { return m_resource->response(); }

  RefPtr<CachedMetadata> m_cachedMetadata;

 private:
  Member<Resource> m_resource;
};

Resource::CachedMetadataHandlerImpl::CachedMetadataHandlerImpl(
    Resource* resource)
    : m_resource(resource) {}

DEFINE_TRACE(Resource::CachedMetadataHandlerImpl) {
  visitor->trace(m_resource);
  CachedMetadataHandler::trace(visitor);
}

void Resource::CachedMetadataHandlerImpl::setCachedMetadata(
    uint32_t dataTypeID,
    const char* data,
    size_t size,
    CachedMetadataHandler::CacheType cacheType) {
  // Currently, only one type of cached metadata per resource is supported. If
  // the need arises for multiple types of metadata per resource this could be
  // enhanced to store types of metadata in a map.
  DCHECK(!m_cachedMetadata);
  m_cachedMetadata = CachedMetadata::create(dataTypeID, data, size);
  if (cacheType == CachedMetadataHandler::SendToPlatform)
    sendToPlatform();
}

void Resource::CachedMetadataHandlerImpl::clearCachedMetadata(
    CachedMetadataHandler::CacheType cacheType) {
  m_cachedMetadata.clear();
  if (cacheType == CachedMetadataHandler::SendToPlatform)
    sendToPlatform();
}

PassRefPtr<CachedMetadata> Resource::CachedMetadataHandlerImpl::cachedMetadata(
    uint32_t dataTypeID) const {
  if (!m_cachedMetadata || m_cachedMetadata->dataTypeID() != dataTypeID)
    return nullptr;
  return m_cachedMetadata.get();
}

String Resource::CachedMetadataHandlerImpl::encoding() const {
  return m_resource->encoding();
}

void Resource::CachedMetadataHandlerImpl::setSerializedCachedMetadata(
    const char* data,
    size_t size) {
  // We only expect to receive cached metadata from the platform once. If this
  // triggers, it indicates an efficiency problem which is most likely
  // unexpected in code designed to improve performance.
  DCHECK(!m_cachedMetadata);
  m_cachedMetadata = CachedMetadata::createFromSerializedData(data, size);
}

void Resource::CachedMetadataHandlerImpl::sendToPlatform() {
  if (m_cachedMetadata) {
    const Vector<char>& serializedData = m_cachedMetadata->serializedData();
    Platform::current()->cacheMetadata(
        response().url(), response().responseTime(), serializedData.data(),
        serializedData.size());
  } else {
    Platform::current()->cacheMetadata(response().url(),
                                       response().responseTime(), nullptr, 0);
  }
}

class Resource::ServiceWorkerResponseCachedMetadataHandler
    : public Resource::CachedMetadataHandlerImpl {
 public:
  static Resource::CachedMetadataHandlerImpl* create(
      Resource* resource,
      SecurityOrigin* securityOrigin) {
    return new ServiceWorkerResponseCachedMetadataHandler(resource,
                                                          securityOrigin);
  }
  ~ServiceWorkerResponseCachedMetadataHandler() override {}
  DECLARE_VIRTUAL_TRACE();

 protected:
  void sendToPlatform() override;

 private:
  explicit ServiceWorkerResponseCachedMetadataHandler(Resource*,
                                                      SecurityOrigin*);
  String m_cacheStorageCacheName;
  RefPtr<SecurityOrigin> m_securityOrigin;
};

Resource::ServiceWorkerResponseCachedMetadataHandler::
    ServiceWorkerResponseCachedMetadataHandler(Resource* resource,
                                               SecurityOrigin* securityOrigin)
    : CachedMetadataHandlerImpl(resource), m_securityOrigin(securityOrigin) {}

DEFINE_TRACE(Resource::ServiceWorkerResponseCachedMetadataHandler) {
  CachedMetadataHandlerImpl::trace(visitor);
}

void Resource::ServiceWorkerResponseCachedMetadataHandler::sendToPlatform() {
  // We don't support sending the metadata to the platform when the response was
  // directly fetched via a ServiceWorker (eg:
  // FetchEvent.respondWith(fetch(FetchEvent.request))) to prevent an attacker's
  // Service Worker from poisoning the metadata cache of HTTPCache.
  if (response().cacheStorageCacheName().isNull())
    return;

  if (m_cachedMetadata) {
    const Vector<char>& serializedData = m_cachedMetadata->serializedData();
    Platform::current()->cacheMetadataInCacheStorage(
        response().url(), response().responseTime(), serializedData.data(),
        serializedData.size(), WebSecurityOrigin(m_securityOrigin),
        response().cacheStorageCacheName());
  } else {
    Platform::current()->cacheMetadataInCacheStorage(
        response().url(), response().responseTime(), nullptr, 0,
        WebSecurityOrigin(m_securityOrigin),
        response().cacheStorageCacheName());
  }
}

// This class cannot be on-heap because the first callbackHandler() call
// instantiates the singleton object while we can call it in the
// pre-finalization step.
class Resource::ResourceCallback final {
 public:
  static ResourceCallback& callbackHandler();
  void schedule(Resource*);
  void cancel(Resource*);
  bool isScheduled(Resource*) const;

 private:
  ResourceCallback();

  void runTask();
  TaskHandle m_taskHandle;
  HashSet<Persistent<Resource>> m_resourcesWithPendingClients;
};

Resource::ResourceCallback& Resource::ResourceCallback::callbackHandler() {
  DEFINE_STATIC_LOCAL(ResourceCallback, callbackHandler, ());
  return callbackHandler;
}

Resource::ResourceCallback::ResourceCallback() {}

void Resource::ResourceCallback::schedule(Resource* resource) {
  if (!m_taskHandle.isActive()) {
    // WTF::unretained(this) is safe because a posted task is canceled when
    // |m_taskHandle| is destroyed on the dtor of this ResourceCallback.
    m_taskHandle =
        Platform::current()
            ->currentThread()
            ->scheduler()
            ->loadingTaskRunner()
            ->postCancellableTask(
                BLINK_FROM_HERE,
                WTF::bind(&ResourceCallback::runTask, WTF::unretained(this)));
  }
  m_resourcesWithPendingClients.insert(resource);
}

void Resource::ResourceCallback::cancel(Resource* resource) {
  m_resourcesWithPendingClients.erase(resource);
  if (m_taskHandle.isActive() && m_resourcesWithPendingClients.isEmpty())
    m_taskHandle.cancel();
}

bool Resource::ResourceCallback::isScheduled(Resource* resource) const {
  return m_resourcesWithPendingClients.contains(resource);
}

void Resource::ResourceCallback::runTask() {
  HeapVector<Member<Resource>> resources;
  for (const Member<Resource>& resource : m_resourcesWithPendingClients)
    resources.push_back(resource.get());
  m_resourcesWithPendingClients.clear();

  for (const auto& resource : resources)
    resource->finishPendingClients();
}

Resource::Resource(const ResourceRequest& request,
                   Type type,
                   const ResourceLoaderOptions& options)
    : m_loadFinishTime(0),
      m_identifier(0),
      m_encodedSize(0),
      m_encodedSizeMemoryUsage(0),
      m_decodedSize(0),
      m_overheadSize(calculateOverheadSize()),
      m_preloadCount(0),
      m_preloadDiscoveryTime(0.0),
      m_cacheIdentifier(MemoryCache::defaultCacheIdentifier()),
      m_preloadResult(PreloadNotReferenced),
      m_type(type),
      m_status(ResourceStatus::NotStarted),
      m_needsSynchronousCacheHit(false),
      m_linkPreload(false),
      m_isRevalidating(false),
      m_isAlive(false),
      m_isAddRemoveClientProhibited(false),
      m_integrityDisposition(ResourceIntegrityDisposition::NotChecked),
      m_options(options),
      m_responseTimestamp(currentTime()),
      m_cancelTimer(Platform::current()->mainThread()->getWebTaskRunner(),
                    this,
                    &Resource::cancelTimerFired),
      m_resourceRequest(request) {
  InstanceCounters::incrementCounter(InstanceCounters::ResourceCounter);

  // Currently we support the metadata caching only for HTTP family.
  if (resourceRequest().url().protocolIsInHTTPFamily())
    m_cacheHandler = CachedMetadataHandlerImpl::create(this);
  MemoryCoordinator::instance().registerClient(this);
}

Resource::~Resource() {
  InstanceCounters::decrementCounter(InstanceCounters::ResourceCounter);
}

DEFINE_TRACE(Resource) {
  visitor->trace(m_loader);
  visitor->trace(m_cacheHandler);
  visitor->trace(m_clients);
  visitor->trace(m_clientsAwaitingCallback);
  visitor->trace(m_finishedClients);
  MemoryCoordinatorClient::trace(visitor);
}

void Resource::setLoader(ResourceLoader* loader) {
  CHECK(!m_loader);
  DCHECK(stillNeedsLoad());
  m_loader = loader;
  m_status = ResourceStatus::Pending;
}

void Resource::checkNotify() {
  if (isLoading())
    return;

  ResourceClientWalker<ResourceClient> w(m_clients);
  while (ResourceClient* c = w.next()) {
    markClientFinished(c);
    c->notifyFinished(this);
  }
}

void Resource::markClientFinished(ResourceClient* client) {
  if (m_clients.contains(client)) {
    m_finishedClients.insert(client);
    m_clients.erase(client);
  }
}

void Resource::appendData(const char* data, size_t length) {
  TRACE_EVENT0("blink", "Resource::appendData");
  DCHECK(!m_isRevalidating);
  DCHECK(!errorOccurred());
  if (m_options.dataBufferingPolicy == DoNotBufferData)
    return;
  if (m_data)
    m_data->append(data, length);
  else
    m_data = SharedBuffer::create(data, length);
  setEncodedSize(m_data->size());
}

void Resource::setResourceBuffer(PassRefPtr<SharedBuffer> resourceBuffer) {
  DCHECK(!m_isRevalidating);
  DCHECK(!errorOccurred());
  DCHECK_EQ(m_options.dataBufferingPolicy, BufferData);
  m_data = std::move(resourceBuffer);
  setEncodedSize(m_data->size());
}

void Resource::clearData() {
  m_data.clear();
  m_encodedSizeMemoryUsage = 0;
}

void Resource::setDataBufferingPolicy(DataBufferingPolicy dataBufferingPolicy) {
  m_options.dataBufferingPolicy = dataBufferingPolicy;
  clearData();
  setEncodedSize(0);
}

void Resource::error(const ResourceError& error) {
  DCHECK(!error.isNull());
  m_error = error;
  m_isRevalidating = false;

  if (m_error.isCancellation() || !isPreloaded())
    memoryCache()->remove(this);

  if (!errorOccurred())
    setStatus(ResourceStatus::LoadError);
  DCHECK(errorOccurred());
  clearData();
  m_loader = nullptr;
  checkNotify();
}

void Resource::finish(double loadFinishTime) {
  DCHECK(!m_isRevalidating);
  m_loadFinishTime = loadFinishTime;
  if (!errorOccurred())
    m_status = ResourceStatus::Cached;
  m_loader = nullptr;
  checkNotify();
}

AtomicString Resource::httpContentType() const {
  return response().httpContentType();
}

bool Resource::passesAccessControlCheck(
    const SecurityOrigin* securityOrigin) const {
  StoredCredentials storedCredentials =
      lastResourceRequest().allowStoredCredentials()
          ? AllowStoredCredentials
          : DoNotAllowStoredCredentials;
  CrossOriginAccessControl::AccessStatus status =
      CrossOriginAccessControl::checkAccess(response(), storedCredentials,
                                            securityOrigin);

  return status == CrossOriginAccessControl::kAccessAllowed;
}

bool Resource::isEligibleForIntegrityCheck(
    SecurityOrigin* securityOrigin) const {
  return securityOrigin->canRequest(resourceRequest().url()) ||
         passesAccessControlCheck(securityOrigin);
}

void Resource::setIntegrityDisposition(
    ResourceIntegrityDisposition disposition) {
  DCHECK_NE(disposition, ResourceIntegrityDisposition::NotChecked);
  DCHECK(m_type == Resource::Script || m_type == Resource::CSSStyleSheet);
  m_integrityDisposition = disposition;
}

bool Resource::mustRefetchDueToIntegrityMetadata(
    const FetchRequest& request) const {
  if (request.integrityMetadata().isEmpty())
    return false;

  return !IntegrityMetadata::setsEqual(m_integrityMetadata,
                                       request.integrityMetadata());
}

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

double Resource::currentAge() const {
  return blink::currentAge(response(), m_responseTimestamp);
}

static double freshnessLifetime(const ResourceResponse& response,
                                double responseTimestamp) {
#if !OS(ANDROID)
  // On desktop, local files should be reloaded in case they change.
  if (response.url().isLocalFile())
    return 0;
#endif

  // Cache other non-http / non-filesystem resources liberally.
  if (!response.url().protocolIsInHTTPFamily() &&
      !response.url().protocolIs("filesystem"))
    return std::numeric_limits<double>::max();

  // RFC2616 13.2.4
  double maxAgeValue = response.cacheControlMaxAge();
  if (std::isfinite(maxAgeValue))
    return maxAgeValue;
  double expiresValue = response.expires();
  double dateValue = response.date();
  double creationTime =
      std::isfinite(dateValue) ? dateValue : responseTimestamp;
  if (std::isfinite(expiresValue))
    return expiresValue - creationTime;
  double lastModifiedValue = response.lastModified();
  if (std::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;
}

double Resource::freshnessLifetime() const {
  return blink::freshnessLifetime(response(), m_responseTimestamp);
}

static bool canUseResponse(const ResourceResponse& response,
                           double responseTimestamp) {
  if (response.isNull())
    return false;

  // FIXME: Why isn't must-revalidate considered a reason we can't use the
  // response?
  if (response.cacheControlContainsNoCache() ||
      response.cacheControlContainsNoStore())
    return false;

  if (response.httpStatusCode() == 303) {
    // Must not be cached.
    return false;
  }

  if (response.httpStatusCode() == 302 || response.httpStatusCode() == 307) {
    // Default to not cacheable unless explicitly allowed.
    bool hasMaxAge = std::isfinite(response.cacheControlMaxAge());
    bool hasExpires = std::isfinite(response.expires());
    // TODO: consider catching Cache-Control "private" and "public" here.
    if (!hasMaxAge && !hasExpires)
      return false;
  }

  return currentAge(response, responseTimestamp) <=
         freshnessLifetime(response, responseTimestamp);
}

const ResourceRequest& Resource::lastResourceRequest() const {
  if (!m_redirectChain.size())
    return resourceRequest();
  return m_redirectChain.back().m_request;
}

void Resource::setRevalidatingRequest(const ResourceRequest& request) {
  SECURITY_CHECK(m_redirectChain.isEmpty());
  DCHECK(!request.isNull());
  CHECK(!m_isRevalidationStartForbidden);
  m_isRevalidating = true;
  m_resourceRequest = request;
  m_status = ResourceStatus::NotStarted;
}

bool Resource::willFollowRedirect(const ResourceRequest& newRequest,
                                  const ResourceResponse& redirectResponse) {
  if (m_isRevalidating)
    revalidationFailed();
  m_redirectChain.push_back(RedirectPair(newRequest, redirectResponse));
  return true;
}

void Resource::setResponse(const ResourceResponse& response) {
  m_response = response;
  if (this->response().wasFetchedViaServiceWorker()) {
    m_cacheHandler = ServiceWorkerResponseCachedMetadataHandler::create(
        this, m_fetcherSecurityOrigin.get());
  }
}

void Resource::responseReceived(const ResourceResponse& response,
                                std::unique_ptr<WebDataConsumerHandle>) {
  m_responseTimestamp = currentTime();
  if (m_preloadDiscoveryTime) {
    int timeSinceDiscovery = static_cast<int>(
        1000 * (monotonicallyIncreasingTime() - m_preloadDiscoveryTime));
    DEFINE_STATIC_LOCAL(CustomCountHistogram,
                        preloadDiscoveryToFirstByteHistogram,
                        ("PreloadScanner.TTFB", 0, 10000, 50));
    preloadDiscoveryToFirstByteHistogram.count(timeSinceDiscovery);
  }

  if (m_isRevalidating) {
    if (response.httpStatusCode() == 304) {
      revalidationSucceeded(response);
      return;
    }
    revalidationFailed();
  }
  setResponse(response);
  String encoding = response.textEncodingName();
  if (!encoding.isNull())
    setEncoding(encoding);
}

void Resource::setSerializedCachedMetadata(const char* data, size_t size) {
  DCHECK(!m_isRevalidating);
  DCHECK(!response().isNull());
  if (m_cacheHandler)
    m_cacheHandler->setSerializedCachedMetadata(data, size);
}

CachedMetadataHandler* Resource::cacheHandler() {
  return m_cacheHandler.get();
}

String Resource::reasonNotDeletable() const {
  StringBuilder builder;
  if (hasClientsOrObservers()) {
    builder.append("hasClients(");
    builder.appendNumber(m_clients.size());
    if (!m_clientsAwaitingCallback.isEmpty()) {
      builder.append(", AwaitingCallback=");
      builder.appendNumber(m_clientsAwaitingCallback.size());
    }
    if (!m_finishedClients.isEmpty()) {
      builder.append(", Finished=");
      builder.appendNumber(m_finishedClients.size());
    }
    builder.append(')');
  }
  if (m_loader) {
    if (!builder.isEmpty())
      builder.append(' ');
    builder.append("m_loader");
  }
  if (m_preloadCount) {
    if (!builder.isEmpty())
      builder.append(' ');
    builder.append("m_preloadCount(");
    builder.appendNumber(m_preloadCount);
    builder.append(')');
  }
  if (memoryCache()->contains(this)) {
    if (!builder.isEmpty())
      builder.append(' ');
    builder.append("in_memory_cache");
  }
  return builder.toString();
}

void Resource::didAddClient(ResourceClient* c) {
  if (isLoaded()) {
    c->notifyFinished(this);
    if (m_clients.contains(c)) {
      m_finishedClients.insert(c);
      m_clients.erase(c);
    }
  }
}

static bool typeNeedsSynchronousCacheHit(Resource::Type type) {
  // Some resources types default to return data synchronously. For most of
  // these, it's because there are layout tests that expect data to return
  // synchronously in case of cache hit. In the case of fonts, there was a
  // performance regression.
  // FIXME: Get to the point where we don't need to special-case sync/async
  // behavior for different resource types.
  if (type == Resource::Image)
    return true;
  if (type == Resource::CSSStyleSheet)
    return true;
  if (type == Resource::Script)
    return true;
  if (type == Resource::Font)
    return true;
  return false;
}

void Resource::willAddClientOrObserver(PreloadReferencePolicy policy) {
  if (policy == MarkAsReferenced && m_preloadResult == PreloadNotReferenced) {
    if (isLoaded())
      m_preloadResult = PreloadReferencedWhileComplete;
    else if (isLoading())
      m_preloadResult = PreloadReferencedWhileLoading;
    else
      m_preloadResult = PreloadReferenced;

    if (m_preloadDiscoveryTime) {
      int timeSinceDiscovery = static_cast<int>(
          1000 * (monotonicallyIncreasingTime() - m_preloadDiscoveryTime));
      DEFINE_STATIC_LOCAL(CustomCountHistogram, preloadDiscoveryHistogram,
                          ("PreloadScanner.ReferenceTime", 0, 10000, 50));
      preloadDiscoveryHistogram.count(timeSinceDiscovery);
    }
  }
  if (!hasClientsOrObservers()) {
    m_isAlive = true;
  }
}

void Resource::addClient(ResourceClient* client,
                         PreloadReferencePolicy policy) {
  CHECK(!m_isAddRemoveClientProhibited);

  willAddClientOrObserver(policy);

  if (m_isRevalidating) {
    m_clients.insert(client);
    return;
  }

  // If an error has occurred or we have existing data to send to the new client
  // and the resource type supprts it, send it asynchronously.
  if ((errorOccurred() || !response().isNull()) &&
      !typeNeedsSynchronousCacheHit(getType()) && !m_needsSynchronousCacheHit) {
    m_clientsAwaitingCallback.insert(client);
    ResourceCallback::callbackHandler().schedule(this);
    return;
  }

  m_clients.insert(client);
  didAddClient(client);
  return;
}

void Resource::removeClient(ResourceClient* client) {
  CHECK(!m_isAddRemoveClientProhibited);

  // This code may be called in a pre-finalizer, where weak members in the
  // HashCountedSet are already swept out.

  if (m_finishedClients.contains(client))
    m_finishedClients.erase(client);
  else if (m_clientsAwaitingCallback.contains(client))
    m_clientsAwaitingCallback.erase(client);
  else
    m_clients.erase(client);

  if (m_clientsAwaitingCallback.isEmpty())
    ResourceCallback::callbackHandler().cancel(this);

  didRemoveClientOrObserver();
}

void Resource::didRemoveClientOrObserver() {
  if (!hasClientsOrObservers() && m_isAlive) {
    m_isAlive = false;
    allClientsAndObserversRemoved();

    // RFC2616 14.9.2:
    // "no-store: ... MUST make a best-effort attempt to remove the information
    // from volatile storage as promptly as possible"
    // "... History buffers MAY store such responses as part of their normal
    // operation."
    // We allow non-secure content to be reused in history, but we do not allow
    // secure content to be reused.
    if (hasCacheControlNoStoreHeader() && url().protocolIs("https"))
      memoryCache()->remove(this);
  }
}

void Resource::allClientsAndObserversRemoved() {
  if (!m_loader)
    return;
  if (!m_cancelTimer.isActive())
    m_cancelTimer.startOneShot(0, BLINK_FROM_HERE);
}

void Resource::cancelTimerFired(TimerBase* timer) {
  DCHECK_EQ(timer, &m_cancelTimer);
  if (!hasClientsOrObservers() && m_loader)
    m_loader->cancel();
}

void Resource::setDecodedSize(size_t decodedSize) {
  if (decodedSize == m_decodedSize)
    return;
  size_t oldSize = size();
  m_decodedSize = decodedSize;
  memoryCache()->update(this, oldSize, size());
}

void Resource::setEncodedSize(size_t encodedSize) {
  if (encodedSize == m_encodedSize && encodedSize == m_encodedSizeMemoryUsage)
    return;
  size_t oldSize = size();
  m_encodedSize = encodedSize;
  m_encodedSizeMemoryUsage = encodedSize;
  memoryCache()->update(this, oldSize, size());
}

void Resource::finishPendingClients() {
  // We're going to notify clients one by one. It is simple if the client does
  // nothing. However there are a couple other things that can happen.
  //
  // 1. Clients can be added during the loop. Make sure they are not processed.
  // 2. Clients can be removed during the loop. Make sure they are always
  //    available to be removed. Also don't call removed clients or add them
  //    back.
  //
  // Handle case (1) by saving a list of clients to notify. A separate list also
  // ensure a client is either in m_clients or m_clientsAwaitingCallback.
  HeapVector<Member<ResourceClient>> clientsToNotify;
  copyToVector(m_clientsAwaitingCallback, clientsToNotify);

  for (const auto& client : clientsToNotify) {
    // Handle case (2) to skip removed clients.
    if (!m_clientsAwaitingCallback.erase(client))
      continue;
    m_clients.insert(client);

    // When revalidation starts after waiting clients are scheduled and
    // before they are added here. In such cases, we just add the clients
    // to |m_clients| without didAddClient(), as in Resource::addClient().
    if (!m_isRevalidating)
      didAddClient(client);
  }

  // It is still possible for the above loop to finish a new client
  // synchronously. If there's no client waiting we should deschedule.
  bool scheduled = ResourceCallback::callbackHandler().isScheduled(this);
  if (scheduled && m_clientsAwaitingCallback.isEmpty())
    ResourceCallback::callbackHandler().cancel(this);

  // Prevent the case when there are clients waiting but no callback scheduled.
  DCHECK(m_clientsAwaitingCallback.isEmpty() || scheduled);
}

void Resource::prune() {
  destroyDecodedDataIfPossible();
}

void Resource::onPurgeMemory() {
  prune();
  if (!m_cacheHandler)
    return;
  m_cacheHandler->clearCachedMetadata(CachedMetadataHandler::CacheLocally);
}

void Resource::onMemoryDump(WebMemoryDumpLevelOfDetail levelOfDetail,
                            WebProcessMemoryDump* memoryDump) const {
  static const size_t kMaxURLReportLength = 128;
  static const int kMaxResourceClientToShowInMemoryInfra = 10;

  const String dumpName = getMemoryDumpName();
  WebMemoryAllocatorDump* dump =
      memoryDump->createMemoryAllocatorDump(dumpName);
  dump->addScalar("encoded_size", "bytes", m_encodedSizeMemoryUsage);
  if (hasClientsOrObservers())
    dump->addScalar("live_size", "bytes", m_encodedSizeMemoryUsage);
  else
    dump->addScalar("dead_size", "bytes", m_encodedSizeMemoryUsage);

  if (m_data)
    m_data->onMemoryDump(dumpName, memoryDump);

  if (levelOfDetail == WebMemoryDumpLevelOfDetail::Detailed) {
    String urlToReport = url().getString();
    if (urlToReport.length() > kMaxURLReportLength) {
      urlToReport.truncate(kMaxURLReportLength);
      urlToReport = urlToReport + "...";
    }
    dump->addString("url", "", urlToReport);

    dump->addString("reason_not_deletable", "", reasonNotDeletable());

    Vector<String> clientNames;
    ResourceClientWalker<ResourceClient> walker(m_clients);
    while (ResourceClient* client = walker.next())
      clientNames.push_back(client->debugName());
    ResourceClientWalker<ResourceClient> walker2(m_clientsAwaitingCallback);
    while (ResourceClient* client = walker2.next())
      clientNames.push_back("(awaiting) " + client->debugName());
    ResourceClientWalker<ResourceClient> walker3(m_finishedClients);
    while (ResourceClient* client = walker3.next())
      clientNames.push_back("(finished) " + client->debugName());
    std::sort(clientNames.begin(), clientNames.end(),
              WTF::codePointCompareLessThan);

    StringBuilder builder;
    for (size_t i = 0;
         i < clientNames.size() && i < kMaxResourceClientToShowInMemoryInfra;
         ++i) {
      if (i > 0)
        builder.append(" / ");
      builder.append(clientNames[i]);
    }
    if (clientNames.size() > kMaxResourceClientToShowInMemoryInfra) {
      builder.append(" / and ");
      builder.appendNumber(clientNames.size() -
                           kMaxResourceClientToShowInMemoryInfra);
      builder.append(" more");
    }
    dump->addString("ResourceClient", "", builder.toString());
  }

  const String overheadName = dumpName + "/metadata";
  WebMemoryAllocatorDump* overheadDump =
      memoryDump->createMemoryAllocatorDump(overheadName);
  overheadDump->addScalar("size", "bytes", overheadSize());
  memoryDump->addSuballocation(
      overheadDump->guid(), String(WTF::Partitions::kAllocatedObjectPoolName));
}

String Resource::getMemoryDumpName() const {
  return String::format(
      "web_cache/%s_resources/%ld",
      resourceTypeToString(getType(), options().initiatorInfo.name),
      m_identifier);
}

void Resource::setCachePolicyBypassingCache() {
  m_resourceRequest.setCachePolicy(WebCachePolicy::BypassingCache);
}

void Resource::setPreviewsStateNoTransform() {
  m_resourceRequest.setPreviewsState(WebURLRequest::PreviewsNoTransform);
}

void Resource::clearRangeRequestHeader() {
  m_resourceRequest.clearHTTPHeaderField("range");
}

void Resource::revalidationSucceeded(
    const ResourceResponse& validatingResponse) {
  SECURITY_CHECK(m_redirectChain.isEmpty());
  SECURITY_CHECK(equalIgnoringFragmentIdentifier(validatingResponse.url(),
                                                 response().url()));
  m_response.setResourceLoadTiming(validatingResponse.resourceLoadTiming());

  // RFC2616 10.3.5
  // Update cached headers from the 304 response
  const HTTPHeaderMap& newHeaders = validatingResponse.httpHeaderFields();
  for (const auto& header : newHeaders) {
    // Entity headers should not be sent by servers when generating a 304
    // response; misconfigured servers send them anyway. We shouldn't allow such
    // headers to update the original request. We'll base this on the list
    // defined by RFC2616 7.1, with a few additions for extension headers we
    // care about.
    if (!shouldUpdateHeaderAfterRevalidation(header.key))
      continue;
    m_response.setHTTPHeaderField(header.key, header.value);
  }

  m_isRevalidating = false;
}

void Resource::revalidationFailed() {
  SECURITY_CHECK(m_redirectChain.isEmpty());
  clearData();
  m_cacheHandler.clear();
  destroyDecodedDataForFailedRevalidation();
  m_isRevalidating = false;
}

bool Resource::canReuseRedirectChain() const {
  for (auto& redirect : m_redirectChain) {
    if (!canUseResponse(redirect.m_redirectResponse, m_responseTimestamp))
      return false;
    if (redirect.m_request.cacheControlContainsNoCache() ||
        redirect.m_request.cacheControlContainsNoStore())
      return false;
  }
  return true;
}

bool Resource::hasCacheControlNoStoreHeader() const {
  return response().cacheControlContainsNoStore() ||
         resourceRequest().cacheControlContainsNoStore();
}

bool Resource::mustReloadDueToVaryHeader(
    const ResourceRequest& newRequest) const {
  const AtomicString& vary = response().httpHeaderField(HTTPNames::Vary);
  if (vary.isNull())
    return false;
  if (vary == "*")
    return true;

  CommaDelimitedHeaderSet varyHeaders;
  parseCommaDelimitedHeader(vary, varyHeaders);
  for (const String& header : varyHeaders) {
    AtomicString atomicHeader(header);
    if (resourceRequest().httpHeaderField(atomicHeader) !=
        newRequest.httpHeaderField(atomicHeader)) {
      return true;
    }
  }
  return false;
}

bool Resource::mustRevalidateDueToCacheHeaders() const {
  return !canUseResponse(response(), m_responseTimestamp) ||
         resourceRequest().cacheControlContainsNoCache() ||
         resourceRequest().cacheControlContainsNoStore();
}

bool Resource::canUseCacheValidator() const {
  if (isLoading() || errorOccurred())
    return false;

  if (hasCacheControlNoStoreHeader())
    return false;

  // Do not revalidate Resource with redirects. https://crbug.com/613971
  if (!redirectChain().isEmpty())
    return false;

  return response().hasCacheValidatorFields() ||
         resourceRequest().hasCacheValidatorFields();
}

size_t Resource::calculateOverheadSize() const {
  static const int kAverageClientsHashMapSize = 384;
  return sizeof(Resource) + response().memoryUsage() +
         kAverageClientsHashMapSize +
         resourceRequest().url().getString().length() * 2;
}

void Resource::didChangePriority(ResourceLoadPriority loadPriority,
                                 int intraPriorityValue) {
  m_resourceRequest.setPriority(loadPriority, intraPriorityValue);
  if (m_loader)
    m_loader->didChangePriority(loadPriority, intraPriorityValue);
}

// TODO(toyoshim): Consider to generate automatically. https://crbug.com/675515.
static const char* initiatorTypeNameToString(
    const AtomicString& initiatorTypeName) {
  if (initiatorTypeName == FetchInitiatorTypeNames::css)
    return "CSS resource";
  if (initiatorTypeName == FetchInitiatorTypeNames::document)
    return "Document";
  if (initiatorTypeName == FetchInitiatorTypeNames::icon)
    return "Icon";
  if (initiatorTypeName == FetchInitiatorTypeNames::internal)
    return "Internal resource";
  if (initiatorTypeName == FetchInitiatorTypeNames::link)
    return "Link element resource";
  if (initiatorTypeName == FetchInitiatorTypeNames::processinginstruction)
    return "Processing instruction";
  if (initiatorTypeName == FetchInitiatorTypeNames::texttrack)
    return "Text track";
  if (initiatorTypeName == FetchInitiatorTypeNames::xml)
    return "XML resource";
  if (initiatorTypeName == FetchInitiatorTypeNames::xmlhttprequest)
    return "XMLHttpRequest";

  static_assert(
      FetchInitiatorTypeNames::FetchInitiatorTypeNamesCount == 12,
      "New FetchInitiatorTypeNames should be handled correctly here.");

  return "Resource";
}

const char* Resource::resourceTypeToString(
    Type type,
    const AtomicString& fetchInitiatorName) {
  switch (type) {
    case Resource::MainResource:
      return "Main resource";
    case Resource::Image:
      return "Image";
    case Resource::CSSStyleSheet:
      return "CSS stylesheet";
    case Resource::Script:
      return "Script";
    case Resource::Font:
      return "Font";
    case Resource::Raw:
      return initiatorTypeNameToString(fetchInitiatorName);
    case Resource::SVGDocument:
      return "SVG document";
    case Resource::XSLStyleSheet:
      return "XSL stylesheet";
    case Resource::LinkPrefetch:
      return "Link prefetch resource";
    case Resource::TextTrack:
      return "Text track";
    case Resource::ImportResource:
      return "Imported resource";
    case Resource::Media:
      return "Media";
    case Resource::Manifest:
      return "Manifest";
    case Resource::Mock:
      return "Mock";
  }
  NOTREACHED();
  return initiatorTypeNameToString(fetchInitiatorName);
}

bool Resource::shouldBlockLoadEvent() const {
  return !m_linkPreload && isLoadEventBlockingResourceType();
}

bool Resource::isLoadEventBlockingResourceType() const {
  switch (m_type) {
    case Resource::MainResource:
    case Resource::Image:
    case Resource::CSSStyleSheet:
    case Resource::Script:
    case Resource::Font:
    case Resource::SVGDocument:
    case Resource::XSLStyleSheet:
    case Resource::ImportResource:
      return true;
    case Resource::Raw:
    case Resource::LinkPrefetch:
    case Resource::TextTrack:
    case Resource::Media:
    case Resource::Manifest:
    case Resource::Mock:
      return false;
  }
  NOTREACHED();
  return false;
}

}  // namespace blink