Quellcode-Bibliothek Predictor.cpp Sprache: C

/* vim: set ts=2 sts=2 et sw=2: */
/* 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/. */

#include <algorithm>

#include "Predictor.h"

#include "nsAppDirectoryServiceDefs.h"
#include "nsICacheStorage.h"
#include "nsICachingChannel.h"
#include "nsICancelable.h"
#include "nsIChannel.h"
#include "nsContentUtils.h"
#include "nsIDNSService.h"
#include "mozilla/dom/Document.h"
#include "nsIFile.h"
#include "nsIHttpChannel.h"
#include "nsIInputStream.h"
#include "nsILoadContext.h"
#include "nsILoadContextInfo.h"
#include "nsILoadGroup.h"
#include "nsINetworkPredictorVerifier.h"
#include "nsIObserverService.h"
#include "nsISpeculativeConnect.h"
#include "nsITimer.h"
#include "nsIURI.h"
#include "nsNetUtil.h"
#include "nsServiceManagerUtils.h"
#include "nsStreamUtils.h"
#include "nsString.h"
#include "nsThreadUtils.h"
#include "mozilla/Logging.h"

#include "mozilla/Components.h"
#include "mozilla/OriginAttributes.h"
#include "mozilla/Preferences.h"
#include "mozilla/SchedulerGroup.h"
#include "mozilla/StaticPrefs_network.h"
#include "mozilla/glean/NetwerkMetrics.h"

#include "mozilla/net/NeckoCommon.h"
#include "mozilla/net/NeckoParent.h"

#include "LoadContextInfo.h"
#include "mozilla/ipc/URIUtils.h"
#include "SerializedLoadContext.h"
#include "mozilla/net/NeckoChild.h"

#include "mozilla/dom/ContentParent.h"
#include "mozilla/ClearOnShutdown.h"

#include "CacheControlParser.h"
#include "ReferrerInfo.h"

using namespace mozilla;

namespace mozilla {
namespace net {

Predictor* Predictor::sSelf = nullptr;

static LazyLogModule gPredictorLog("NetworkPredictor");

#define PREDICTOR_LOG(args) \
  MOZ_LOG(gPredictorLog, mozilla::LogLevel::Debug, args)

#define NOW_IN_SECONDS() static_cast<uint32_t>(PR_Now() / PR_USEC_PER_SEC)

// All these time values are in sec
static const uint32_t ONE_DAY = 86400U;
static const uint32_t ONE_WEEK = 7U * ONE_DAY;
static const uint32_t ONE_MONTH = 30U * ONE_DAY;
static const uint32_t ONE_YEAR = 365U * ONE_DAY;

// Version of metadata entries we expect
static const uint32_t METADATA_VERSION = 1;

// Flags available in entries
// FLAG_PREFETCHABLE - we have determined that this item is eligible for
// prefetch
static const uint32_t FLAG_PREFETCHABLE = 1 << 0;

// We save 12 bits in the "flags" section of our metadata for actual flags, the
// rest are to keep track of a rolling count of which loads a resource has been
// used on to determine if we can prefetch that resource or not;
static const uint8_t kRollingLoadOffset = 12;
static const int32_t kMaxPrefetchRollingLoadCount = 20;
static const uint32_t kFlagsMask = ((1 << kRollingLoadOffset) - 1);

// ID Extensions for cache entries
#define PREDICTOR_ORIGIN_EXTENSION "predictor-origin"

// Get the full origin (scheme, host, port) out of a URI (maybe should be part
// of nsIURI instead?)
static nsresult ExtractOrigin(nsIURI* uri, nsIURI** originUri) {
  nsAutoCString s;
  nsresult rv = nsContentUtils::GetWebExposedOriginSerialization(uri, s);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_NewURI(originUri, s);
}

// All URIs we get passed *must* be http or https if they're not null. This
// helps ensure that.
static bool IsNullOrHttp(nsIURI* uri) {
  if (!uri) {
    return true;
  }

  return uri->SchemeIs("http") || uri->SchemeIs("https");
}

// Listener for the speculative DNS requests we'll fire off, which just ignores
// the result (since we're just trying to warm the cache). This also exists to
// reduce round-trips to the main thread, by being something threadsafe the
// Predictor can use.

NS_IMPL_ISUPPORTS(Predictor::DNSListener, nsIDNSListener);

NS_IMETHODIMP
Predictor::DNSListener::OnLookupComplete(nsICancelable* request,
                                         nsIDNSRecord* rec, nsresult status) {
  return NS_OK;
}

// Class to proxy important information from the initial predictor call through
// the cache API and back into the internals of the predictor. We can't use the
// predictor itself, as it may have multiple actions in-flight, and each action
// has different parameters.
NS_IMPL_ISUPPORTS(Predictor::Action, nsICacheEntryOpenCallback);

Predictor::Action::Action(bool fullUri, bool predict, Predictor::Reason reason,
                          nsIURI* targetURI, nsIURI* sourceURI,
                          nsINetworkPredictorVerifier* verifier,
                          Predictor* predictor)
    : mFullUri(fullUri),
      mPredict(predict),
      mTargetURI(targetURI),
      mSourceURI(sourceURI),
      mVerifier(verifier),
      mStackCount(0),
      mPredictor(predictor) {
  mStartTime = TimeStamp::Now();
  if (mPredict) {
    mPredictReason = reason.mPredict;
  } else {
    mLearnReason = reason.mLearn;
  }
}

Predictor::Action::Action(bool fullUri, bool predict, Predictor::Reason reason,
                          nsIURI* targetURI, nsIURI* sourceURI,
                          nsINetworkPredictorVerifier* verifier,
                          Predictor* predictor, uint8_t stackCount)
    : mFullUri(fullUri),
      mPredict(predict),
      mTargetURI(targetURI),
      mSourceURI(sourceURI),
      mVerifier(verifier),
      mStackCount(stackCount),
      mPredictor(predictor) {
  mStartTime = TimeStamp::Now();
  if (mPredict) {
    mPredictReason = reason.mPredict;
  } else {
    mLearnReason = reason.mLearn;
  }
}

NS_IMETHODIMP
Predictor::Action::OnCacheEntryCheck(nsICacheEntry* entry, uint32_t* result) {
  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
  return NS_OK;
}

NS_IMETHODIMP
Predictor::Action::OnCacheEntryAvailable(nsICacheEntry* entry, bool isNew,
                                         nsresult result) {
  MOZ_ASSERT(NS_IsMainThread(), "Got cache entry off main thread!");

  nsAutoCString targetURI, sourceURI;
  if (!mTargetURI) {
    return NS_ERROR_UNEXPECTED;
  }
  mTargetURI->GetAsciiSpec(targetURI);
  if (mSourceURI) {
    mSourceURI->GetAsciiSpec(sourceURI);
  }
  PREDICTOR_LOG(
      ("OnCacheEntryAvailable %p called. entry=%p mFullUri=%d mPredict=%d "
       "mPredictReason=%d mLearnReason=%d mTargetURI=%s "
       "mSourceURI=%s mStackCount=%d isNew=%d result=0x%08" PRIx32,
       this, entry, mFullUri, mPredict, mPredictReason, mLearnReason,
       targetURI.get(), sourceURI.get(), mStackCount, isNew,
       static_cast<uint32_t>(result)));
  if (NS_FAILED(result)) {
    PREDICTOR_LOG(
        ("OnCacheEntryAvailable %p FAILED to get cache entry (0x%08" PRIX32
         "). Aborting.",
         this, static_cast<uint32_t>(result)));
    return NS_OK;
  }
  glean::predictor::wait_time.AccumulateRawDuration(TimeStamp::Now() -
                                                    mStartTime);
  if (mPredict) {
    bool predicted =
        mPredictor->PredictInternal(mPredictReason, entry, isNew, mFullUri,
                                    mTargetURI, mVerifier, mStackCount);
    glean::predictor::predict_work_time.AccumulateRawDuration(TimeStamp::Now() -
                                                              mStartTime);
    if (predicted) {
      glean::predictor::predict_time_to_action.AccumulateRawDuration(
          TimeStamp::Now() - mStartTime);
    } else {
      glean::predictor::predict_time_to_inaction.AccumulateRawDuration(
          TimeStamp::Now() - mStartTime);
    }
  } else {
    mPredictor->LearnInternal(mLearnReason, entry, isNew, mFullUri, mTargetURI,
                              mSourceURI);
    glean::predictor::learn_work_time.AccumulateRawDuration(TimeStamp::Now() -
                                                            mStartTime);
  }

  return NS_OK;
}

NS_IMPL_ISUPPORTS(Predictor, nsINetworkPredictor, nsIObserver,
                  nsISpeculativeConnectionOverrider, nsIInterfaceRequestor,
                  nsICacheEntryMetaDataVisitor, nsINetworkPredictorVerifier)

Predictor::Predictor()

{
  MOZ_ASSERT(!sSelf, "multiple Predictor instances!");
  sSelf = this;
}

Predictor::~Predictor() {
  if (mInitialized) Shutdown();

  sSelf = nullptr;
}

// Predictor::nsIObserver

nsresult Predictor::InstallObserver() {
  MOZ_ASSERT(NS_IsMainThread(), "Installing observer off main thread");

  nsresult rv = NS_OK;
  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
  if (!obs) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  rv = obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
  NS_ENSURE_SUCCESS(rv, rv);

  return rv;
}

void Predictor::RemoveObserver() {
  MOZ_ASSERT(NS_IsMainThread(), "Removing observer off main thread");

  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
  if (obs) {
    obs->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
  }
}

NS_IMETHODIMP
Predictor::Observe(nsISupports* subject, const char* topic,
                   const char16_t* data_unicode) {
  nsresult rv = NS_OK;
  MOZ_ASSERT(NS_IsMainThread(),
             "Predictor observing something off main thread!");

  if (!strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, topic)) {
    Shutdown();
  }

  return rv;
}

// Predictor::nsISpeculativeConnectionOverrider

NS_IMETHODIMP
Predictor::GetIgnoreIdle(bool* ignoreIdle) {
  *ignoreIdle = true;
  return NS_OK;
}

NS_IMETHODIMP
Predictor::GetParallelSpeculativeConnectLimit(
    uint32_t* parallelSpeculativeConnectLimit) {
  *parallelSpeculativeConnectLimit = 6;
  return NS_OK;
}

NS_IMETHODIMP
Predictor::GetIsFromPredictor(bool* isFromPredictor) {
  *isFromPredictor = true;
  return NS_OK;
}

NS_IMETHODIMP
Predictor::GetAllow1918(bool* allow1918) {
  *allow1918 = false;
  return NS_OK;
}

// Predictor::nsIInterfaceRequestor

NS_IMETHODIMP
Predictor::GetInterface(const nsIID& iid, void** result) {
  return QueryInterface(iid, result);
}

// Predictor::nsICacheEntryMetaDataVisitor

#define SEEN_META_DATA "predictor::seen"
#define RESOURCE_META_DATA "predictor::resource-count"
#define META_DATA_PREFIX "predictor::"

static bool IsURIMetadataElement(const char* key) {
  return StringBeginsWith(nsDependentCString(key),
                          nsLiteralCString(META_DATA_PREFIX)) &&
         !nsLiteralCString(SEEN_META_DATA).Equals(key) &&
         !nsLiteralCString(RESOURCE_META_DATA).Equals(key);
}

nsresult Predictor::OnMetaDataElement(const char* asciiKey,
                                      const char* asciiValue) {
  MOZ_ASSERT(NS_IsMainThread());

  if (!IsURIMetadataElement(asciiKey)) {
    // This isn't a bit of metadata we care about
    return NS_OK;
  }

  nsCString key, value;
  key.AssignASCII(asciiKey);
  value.AssignASCII(asciiValue);
  mKeysToOperateOn.AppendElement(key);
  mValuesToOperateOn.AppendElement(value);

  return NS_OK;
}

// Predictor::nsINetworkPredictor

nsresult Predictor::Init() {
  MOZ_DIAGNOSTIC_ASSERT(!IsNeckoChild());

  if (!NS_IsMainThread()) {
    MOZ_ASSERT(false, "Predictor::Init called off the main thread!");
    return NS_ERROR_UNEXPECTED;
  }

  nsresult rv = NS_OK;

  rv = InstallObserver();
  NS_ENSURE_SUCCESS(rv, rv);

  mLastStartupTime = mStartupTime = NOW_IN_SECONDS();

  if (!mDNSListener) {
    mDNSListener = new DNSListener();
  }

  mCacheStorageService = mozilla::components::CacheStorage::Service(&rv);
  NS_ENSURE_SUCCESS(rv, rv);

  mSpeculativeService = mozilla::components::IO::Service(&rv);
  NS_ENSURE_SUCCESS(rv, rv);

  rv = NS_NewURI(getter_AddRefs(mStartupURI), "predictor://startup");
  NS_ENSURE_SUCCESS(rv, rv);

  mDnsService = mozilla::components::DNS::Service(&rv);
  NS_ENSURE_SUCCESS(rv, rv);

  mInitialized = true;

  return rv;
}

namespace {
class PredictorLearnRunnable final : public Runnable {
public:
  PredictorLearnRunnable(nsIURI* targetURI, nsIURI* sourceURI,
                         PredictorLearnReason reason,
                         const OriginAttributes& oa)
      : Runnable("PredictorLearnRunnable"),
        mTargetURI(targetURI),
        mSourceURI(sourceURI),
        mReason(reason),
        mOA(oa) {
    MOZ_DIAGNOSTIC_ASSERT(targetURI, "Must have a target URI");
  }

  ~PredictorLearnRunnable() = default;

  NS_IMETHOD Run() override {
    if (!gNeckoChild) {
      // This may have gone away between when this runnable was dispatched and
      // when it actually runs, so let's be safe here, even though we asserted
      // earlier.
      PREDICTOR_LOG(("predictor::learn (async) gNeckoChild went away"));
      return NS_OK;
    }

    PREDICTOR_LOG(("predictor::learn (async) forwarding to parent"));
    gNeckoChild->SendPredLearn(mTargetURI, mSourceURI, mReason, mOA);

    return NS_OK;
  }

private:
  nsCOMPtr<nsIURI> mTargetURI;
  nsCOMPtr<nsIURI> mSourceURI;
  PredictorLearnReason mReason;
  const OriginAttributes mOA;
};

}  // namespace

void Predictor::Shutdown() {
  if (!NS_IsMainThread()) {
    MOZ_ASSERT(false, "Predictor::Shutdown called off the main thread!");
    return;
  }

  RemoveObserver();

  mInitialized = false;
}

nsresult Predictor::Create(const nsIID& aIID, void** aResult) {
  MOZ_ASSERT(NS_IsMainThread());

  nsresult rv;

  RefPtr<Predictor> svc = new Predictor();
  if (IsNeckoChild()) {
    NeckoChild::InitNeckoChild();

    // Child threads only need to be call into the public interface methods
    // so we don't bother with initialization
    return svc->QueryInterface(aIID, aResult);
  }

  rv = svc->Init();
  if (NS_FAILED(rv)) {
    PREDICTOR_LOG(("Failed to initialize predictor, predictor will be a noop"));
  }

  // We treat init failure the same as the service being disabled, since this
  // is all an optimization anyway. No need to freak people out. That's why we
  // gladly continue on QI'ing here.
  rv = svc->QueryInterface(aIID, aResult);

  return rv;
}

NS_IMETHODIMP
Predictor::Predict(nsIURI* targetURI, nsIURI* sourceURI,
                   PredictorPredictReason reason,
                   JS::Handle<JS::Value> originAttributes,
                   nsINetworkPredictorVerifier* verifier, JSContext* aCx) {
  OriginAttributes attrs;

  if (!originAttributes.isObject() || !attrs.Init(aCx, originAttributes)) {
    return NS_ERROR_INVALID_ARG;
  }

  return PredictNative(targetURI, sourceURI, reason, attrs, verifier);
}

// Called from the main thread to initiate predictive actions
NS_IMETHODIMP
Predictor::PredictNative(nsIURI* targetURI, nsIURI* sourceURI,
                         PredictorPredictReason reason,
                         const OriginAttributes& originAttributes,
                         nsINetworkPredictorVerifier* verifier) {
  MOZ_ASSERT(NS_IsMainThread(),
             "Predictor interface methods must be called on the main thread");

  PREDICTOR_LOG(("Predictor::Predict"));

  if (!StaticPrefs::network_predictor_enabled()) {
    PREDICTOR_LOG((" not enabled"));
    return NS_OK;
  }

  if (IsNeckoChild()) {
    if (!gNeckoChild) {
      return NS_ERROR_FAILURE;
    }

    PREDICTOR_LOG((" called on child process"));
    // If two different threads are predicting concurently, this will be
    // overwritten. Thankfully, we only use this in tests, which will
    // overwrite mVerifier perhaps multiple times for each individual test;
    // however, within each test, the multiple predict calls should have the
    // same verifier.
    if (verifier) {
      PREDICTOR_LOG((" was given a verifier"));
      mChildVerifier = verifier;
    }
    PREDICTOR_LOG((" forwarding to parent process"));
    gNeckoChild->SendPredPredict(targetURI, sourceURI, reason, originAttributes,
                                 verifier);
    return NS_OK;
  }

  PREDICTOR_LOG((" called on parent process"));

  if (!mInitialized) {
    PREDICTOR_LOG((" not initialized"));
    return NS_OK;
  }

  if (originAttributes.IsPrivateBrowsing()) {
    // Don't want to do anything in PB mode
    PREDICTOR_LOG((" in PB mode"));
    return NS_OK;
  }

  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
    // Nothing we can do for non-HTTP[S] schemes
    PREDICTOR_LOG((" got non-http[s] URI"));
    return NS_OK;
  }

  // Ensure we've been given the appropriate arguments for the kind of
  // prediction we're being asked to do
  nsCOMPtr<nsIURI> uriKey = targetURI;
  nsCOMPtr<nsIURI> originKey;
  switch (reason) {
    case nsINetworkPredictor::PREDICT_LINK:
      if (!targetURI || !sourceURI) {
        PREDICTOR_LOG((" link invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      // Link hover is a special case where we can predict without hitting the
      // db, so let's go ahead and fire off that prediction here.
      PredictForLink(targetURI, sourceURI, originAttributes, verifier);
      return NS_OK;
    case nsINetworkPredictor::PREDICT_LOAD:
      if (!targetURI || sourceURI) {
        PREDICTOR_LOG((" load invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      break;
    case nsINetworkPredictor::PREDICT_STARTUP:
      if (targetURI || sourceURI) {
        PREDICTOR_LOG((" startup invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      uriKey = mStartupURI;
      originKey = mStartupURI;
      break;
    default:
      PREDICTOR_LOG((" invalid reason"));
      return NS_ERROR_INVALID_ARG;
  }

  Predictor::Reason argReason{};
  argReason.mPredict = reason;

  // First we open the regular cache entry, to ensure we don't gum up the works
  // waiting on the less-important predictor-only cache entry
  RefPtr<Predictor::Action> uriAction = new Predictor::Action(
      Predictor::Action::IS_FULL_URI, Predictor::Action::DO_PREDICT, argReason,
      uriKey, nullptr, verifier, this);
  nsAutoCString uriKeyStr;
  uriKey->GetAsciiSpec(uriKeyStr);
  PREDICTOR_LOG((" Predict uri=%s reason=%d action=%p", uriKeyStr.get(),
                 reason, uriAction.get()));

  nsCOMPtr<nsICacheStorage> cacheDiskStorage;

  RefPtr<LoadContextInfo> lci = new LoadContextInfo(false, originAttributes);

  nsresult rv = mCacheStorageService->DiskCacheStorage(
      lci, getter_AddRefs(cacheDiskStorage));
  NS_ENSURE_SUCCESS(rv, rv);

  uint32_t openFlags =
      nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY |
      nsICacheStorage::OPEN_PRIORITY | nsICacheStorage::CHECK_MULTITHREADED;
  cacheDiskStorage->AsyncOpenURI(uriKey, ""_ns, openFlags, uriAction);

  // Now we do the origin-only (and therefore predictor-only) entry
  nsCOMPtr<nsIURI> targetOrigin;
  rv = ExtractOrigin(uriKey, getter_AddRefs(targetOrigin));
  NS_ENSURE_SUCCESS(rv, rv);
  if (!originKey) {
    originKey = targetOrigin;
  }

  RefPtr<Predictor::Action> originAction = new Predictor::Action(
      Predictor::Action::IS_ORIGIN, Predictor::Action::DO_PREDICT, argReason,
      targetOrigin, nullptr, verifier, this);
  nsAutoCString originKeyStr;
  originKey->GetAsciiSpec(originKeyStr);
  PREDICTOR_LOG((" Predict origin=%s reason=%d action=%p",
                 originKeyStr.get(), reason, originAction.get()));
  openFlags = nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY |
              nsICacheStorage::CHECK_MULTITHREADED;
  cacheDiskStorage->AsyncOpenURI(originKey,
                                 nsLiteralCString(PREDICTOR_ORIGIN_EXTENSION),
                                 openFlags, originAction);

  PREDICTOR_LOG((" predict returning"));
  return NS_OK;
}

bool Predictor::PredictInternal(PredictorPredictReason reason,
                                nsICacheEntry* entry, bool isNew, bool fullUri,
                                nsIURI* targetURI,
                                nsINetworkPredictorVerifier* verifier,
                                uint8_t stackCount) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::PredictInternal"));
  bool rv = false;

  nsCOMPtr<nsILoadContextInfo> lci;
  entry->GetLoadContextInfo(getter_AddRefs(lci));

  if (!lci) {
    return rv;
  }

  if (reason == nsINetworkPredictor::PREDICT_LOAD) {
    MaybeLearnForStartup(targetURI, fullUri, *lci->OriginAttributesPtr());
  }

  if (isNew) {
    // nothing else we can do here
    PREDICTOR_LOG((" new entry"));
    return rv;
  }

  switch (reason) {
    case nsINetworkPredictor::PREDICT_LOAD:
      rv = PredictForPageload(entry, targetURI, stackCount, fullUri, verifier);
      break;
    case nsINetworkPredictor::PREDICT_STARTUP:
      rv = PredictForStartup(entry, fullUri, verifier);
      break;
    default:
      PREDICTOR_LOG((" invalid reason"));
      MOZ_ASSERT(false, "Got unexpected value for prediction reason");
  }

  return rv;
}

void Predictor::PredictForLink(nsIURI* targetURI, nsIURI* sourceURI,
                               const OriginAttributes& originAttributes,
                               nsINetworkPredictorVerifier* verifier) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::PredictForLink"));
  if (!mSpeculativeService) {
    PREDICTOR_LOG((" missing speculative service"));
    return;
  }

  if (!StaticPrefs::network_predictor_enable_hover_on_ssl()) {
    if (sourceURI->SchemeIs("https")) {
      // We don't want to predict from an HTTPS page, to avoid info leakage
      PREDICTOR_LOG((" Not predicting for link hover - on an SSL page"));
      return;
    }
  }

  nsCOMPtr<nsIPrincipal> principal =
      BasePrincipal::CreateContentPrincipal(targetURI, originAttributes);

  mSpeculativeService->SpeculativeConnect(targetURI, principal, nullptr, false);
  if (verifier) {
    PREDICTOR_LOG((" sending verification"));
    verifier->OnPredictPreconnect(targetURI);
  }
}

// This is the driver for prediction based on a new pageload.
static const uint8_t MAX_PAGELOAD_DEPTH = 10;
bool Predictor::PredictForPageload(nsICacheEntry* entry, nsIURI* targetURI,
                                   uint8_t stackCount, bool fullUri,
                                   nsINetworkPredictorVerifier* verifier) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::PredictForPageload"));

  if (stackCount > MAX_PAGELOAD_DEPTH) {
    PREDICTOR_LOG((" exceeded recursion depth!"));
    return false;
  }

  uint32_t lastLoad;
  nsresult rv = entry->GetLastFetched(&lastLoad);
  NS_ENSURE_SUCCESS(rv, false);

  int32_t globalDegradation = CalculateGlobalDegradation(lastLoad);
  PREDICTOR_LOG((" globalDegradation = %d", globalDegradation));

  uint32_t loadCount;
  rv = entry->GetFetchCount(&loadCount);
  NS_ENSURE_SUCCESS(rv, false);

  nsCOMPtr<nsILoadContextInfo> lci;

  rv = entry->GetLoadContextInfo(getter_AddRefs(lci));
  NS_ENSURE_SUCCESS(rv, false);

  nsCOMPtr<nsIURI> redirectURI;
  if (WouldRedirect(entry, loadCount, lastLoad, globalDegradation,
                    getter_AddRefs(redirectURI))) {
    mPreconnects.AppendElement(redirectURI);
    Predictor::Reason reason{};
    reason.mPredict = nsINetworkPredictor::PREDICT_LOAD;
    RefPtr<Predictor::Action> redirectAction = new Predictor::Action(
        Predictor::Action::IS_FULL_URI, Predictor::Action::DO_PREDICT, reason,
        redirectURI, nullptr, verifier, this, stackCount + 1);
    nsAutoCString redirectUriString;
    redirectURI->GetAsciiSpec(redirectUriString);

    nsCOMPtr<nsICacheStorage> cacheDiskStorage;

    rv = mCacheStorageService->DiskCacheStorage(
        lci, getter_AddRefs(cacheDiskStorage));
    NS_ENSURE_SUCCESS(rv, false);

    PREDICTOR_LOG((" Predict redirect uri=%s action=%p",
                   redirectUriString.get(), redirectAction.get()));
    uint32_t openFlags =
        nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY |
        nsICacheStorage::OPEN_PRIORITY | nsICacheStorage::CHECK_MULTITHREADED;
    cacheDiskStorage->AsyncOpenURI(redirectURI, ""_ns, openFlags,
                                   redirectAction);
    return RunPredictions(nullptr, *lci->OriginAttributesPtr(), verifier);
  }

  CalculatePredictions(entry, targetURI, lastLoad, loadCount, globalDegradation,
                       fullUri);

  return RunPredictions(targetURI, *lci->OriginAttributesPtr(), verifier);
}

// This is the driver for predicting at browser startup time based on pages that
// have previously been loaded close to startup.
bool Predictor::PredictForStartup(nsICacheEntry* entry, bool fullUri,
                                  nsINetworkPredictorVerifier* verifier) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::PredictForStartup"));

  nsCOMPtr<nsILoadContextInfo> lci;

  nsresult rv = entry->GetLoadContextInfo(getter_AddRefs(lci));
  NS_ENSURE_SUCCESS(rv, false);

  int32_t globalDegradation = CalculateGlobalDegradation(mLastStartupTime);
  CalculatePredictions(entry, nullptr, mLastStartupTime, mStartupCount,
                       globalDegradation, fullUri);
  return RunPredictions(nullptr, *lci->OriginAttributesPtr(), verifier);
}

// This calculates how much to degrade our confidence in our data based on
// the last time this top-level resource was loaded. This "global degradation"
// applies to *all* subresources we have associated with the top-level
// resource. This will be in addition to any reduction in confidence we have
// associated with a particular subresource.
int32_t Predictor::CalculateGlobalDegradation(uint32_t lastLoad) {
  MOZ_ASSERT(NS_IsMainThread());

  int32_t globalDegradation;
  uint32_t delta = NOW_IN_SECONDS() - lastLoad;
  if (delta < ONE_DAY) {
    globalDegradation = StaticPrefs::network_predictor_page_degradation_day();
  } else if (delta < ONE_WEEK) {
    globalDegradation = StaticPrefs::network_predictor_page_degradation_week();
  } else if (delta < ONE_MONTH) {
    globalDegradation = StaticPrefs::network_predictor_page_degradation_month();
  } else if (delta < ONE_YEAR) {
    globalDegradation = StaticPrefs::network_predictor_page_degradation_year();
  } else {
    globalDegradation = StaticPrefs::network_predictor_page_degradation_max();
  }

  glean::predictor::global_degradation.AccumulateSingleSample(
      globalDegradation);
  return globalDegradation;
}

// This calculates our overall confidence that a particular subresource will be
// loaded as part of a top-level load.
// @param hitCount - the number of times we have loaded this subresource as part
//                   of this top-level load
// @param hitsPossible - the number of times we have performed this top-level
//                       load
// @param lastHit - the timestamp of the last time we loaded this subresource as
//                  part of this top-level load
// @param lastPossible - the timestamp of the last time we performed this
//                       top-level load
// @param globalDegradation - the degradation for this top-level load as
//                            determined by CalculateGlobalDegradation
int32_t Predictor::CalculateConfidence(uint32_t hitCount, uint32_t hitsPossible,
                                       uint32_t lastHit, uint32_t lastPossible,
                                       int32_t globalDegradation) {
  MOZ_ASSERT(NS_IsMainThread());

  uint32_t predictionsCalculated = 1;

  if (!hitsPossible) {
    glean::predictor::predictions_calculated.AccumulateSingleSample(
        predictionsCalculated);
    return 0;
  }

  int32_t baseConfidence = (hitCount * 100) / hitsPossible;
  int32_t maxConfidence = 100;
  int32_t confidenceDegradation = 0;

  if (lastHit < lastPossible) {
    // We didn't load this subresource the last time this top-level load was
    // performed, so let's not bother preconnecting (at the very least).
    maxConfidence =
        StaticPrefs::network_predictor_preconnect_min_confidence() - 1;

    // Now calculate how much we want to degrade our confidence based on how
    // long it's been between the last time we did this top-level load and the
    // last time this top-level load included this subresource.
    PRTime delta = lastPossible - lastHit;
    if (delta == 0) {
      confidenceDegradation = 0;
    } else if (delta < ONE_DAY) {
      confidenceDegradation =
          StaticPrefs::network_predictor_subresource_degradation_day();
    } else if (delta < ONE_WEEK) {
      confidenceDegradation =
          StaticPrefs::network_predictor_subresource_degradation_week();
    } else if (delta < ONE_MONTH) {
      confidenceDegradation =
          StaticPrefs::network_predictor_subresource_degradation_month();
    } else if (delta < ONE_YEAR) {
      confidenceDegradation =
          StaticPrefs::network_predictor_subresource_degradation_year();
    } else {
      confidenceDegradation =
          StaticPrefs::network_predictor_subresource_degradation_max();
      maxConfidence = 0;
    }
  }

  // Calculate our confidence and clamp it to between 0 and maxConfidence
  // (<= 100)
  int32_t confidence =
      baseConfidence - confidenceDegradation - globalDegradation;
  confidence = std::max(confidence, 0);
  confidence = std::min(confidence, maxConfidence);

  glean::predictor::base_confidence.AccumulateSingleSample(baseConfidence);
  glean::predictor::subresource_degradation.AccumulateSingleSample(
      confidenceDegradation);
  glean::predictor::confidence.AccumulateSingleSample(confidence);
  glean::predictor::predictions_calculated.AccumulateSingleSample(
      predictionsCalculated);
  return confidence;
}

static void MakeMetadataEntry(const uint32_t hitCount, const uint32_t lastHit,
                              const uint32_t flags, nsCString& newValue) {
  newValue.Truncate();
  newValue.AppendInt(METADATA_VERSION);
  newValue.Append(',');
  newValue.AppendInt(hitCount);
  newValue.Append(',');
  newValue.AppendInt(lastHit);
  newValue.Append(',');
  newValue.AppendInt(flags);
}

// On every page load, the rolling window gets shifted by one bit, leaving the
// lowest bit at 0, to indicate that the subresource in question has not been
// seen on the most recent page load. If, at some point later during the page
// load, the subresource is seen again, we will then set the lowest bit to 1.
// This is how we keep track of how many of the last n pageloads (for n <= 20) a
// particular subresource has been seen. The rolling window is kept in the upper
// 20 bits of the flags element of the metadata. This saves 12 bits for regular
// old flags.
void Predictor::UpdateRollingLoadCount(nsICacheEntry* entry,
                                       const uint32_t flags, const char* key,
                                       const uint32_t hitCount,
                                       const uint32_t lastHit) {
  // Extract just the rolling load count from the flags, shift it to clear the
  // lowest bit, and put the new value with the existing flags.
  uint32_t rollingLoadCount = flags & ~kFlagsMask;
  rollingLoadCount <<= 1;
  uint32_t newFlags = (flags & kFlagsMask) | rollingLoadCount;

  // Finally, update the metadata on the cache entry.
  nsAutoCString newValue;
  MakeMetadataEntry(hitCount, lastHit, newFlags, newValue);
  entry->SetMetaDataElement(key, newValue.BeginReading());
}

uint32_t Predictor::ClampedPrefetchRollingLoadCount() {
  int32_t n = StaticPrefs::network_predictor_prefetch_rolling_load_count();
  if (n < 0) {
    return 0;
  }
  if (n > kMaxPrefetchRollingLoadCount) {
    return kMaxPrefetchRollingLoadCount;
  }
  return n;
}

void Predictor::CalculatePredictions(nsICacheEntry* entry, nsIURI* referrer,
                                     uint32_t lastLoad, uint32_t loadCount,
                                     int32_t globalDegradation, bool fullUri) {
  MOZ_ASSERT(NS_IsMainThread());

  // Since the visitor gets called under a cache lock, all we do there is get
  // copies of the keys/values we care about, and then do the real work here
  entry->VisitMetaData(this);
  nsTArray<nsCString> keysToOperateOn = std::move(mKeysToOperateOn),
                      valuesToOperateOn = std::move(mValuesToOperateOn);

  MOZ_ASSERT(keysToOperateOn.Length() == valuesToOperateOn.Length());
  for (size_t i = 0; i < keysToOperateOn.Length(); ++i) {
    const char* key = keysToOperateOn[i].BeginReading();
    const char* value = valuesToOperateOn[i].BeginReading();

    nsCString uri;
    uint32_t hitCount, lastHit, flags;
    if (!ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags)) {
      // This failed, get rid of it so we don't waste space
      entry->SetMetaDataElement(key, nullptr);
      continue;
    }

    int32_t confidence = CalculateConfidence(hitCount, loadCount, lastHit,
                                             lastLoad, globalDegradation);
    if (fullUri) {
      UpdateRollingLoadCount(entry, flags, key, hitCount, lastHit);
    }
    PREDICTOR_LOG(("CalculatePredictions key=%s value=%s confidence=%d", key,
                   value, confidence));
    PrefetchIgnoreReason reason = PREFETCH_OK;
    if (!fullUri) {
      // Not full URI - don't prefetch! No sense in it!
      PREDICTOR_LOG((" forcing non-cacheability - not full URI"));
      if (flags & FLAG_PREFETCHABLE) {
        // This only applies if we had somehow otherwise marked this
        // prefetchable.
        reason = NOT_FULL_URI;
      }
      flags &= ~FLAG_PREFETCHABLE;
    } else if (!referrer) {
      // No referrer means we can't prefetch, so pretend it's non-cacheable,
      // no matter what.
      PREDICTOR_LOG((" forcing non-cacheability - no referrer"));
      if (flags & FLAG_PREFETCHABLE) {
        // This only applies if we had somehow otherwise marked this
        // prefetchable.
        reason = NO_REFERRER;
      }
      flags &= ~FLAG_PREFETCHABLE;
    } else {
      uint32_t expectedRollingLoadCount =
          (1 << ClampedPrefetchRollingLoadCount()) - 1;
      expectedRollingLoadCount <<= kRollingLoadOffset;
      if ((flags & expectedRollingLoadCount) != expectedRollingLoadCount) {
        PREDICTOR_LOG((" forcing non-cacheability - missed a load"));
        if (flags & FLAG_PREFETCHABLE) {
          // This only applies if we had somehow otherwise marked this
          // prefetchable.
          reason = MISSED_A_LOAD;
        }
        flags &= ~FLAG_PREFETCHABLE;
      }
    }

    PREDICTOR_LOG((" setting up prediction"));
    SetupPrediction(confidence, flags, uri, reason);
  }
}

// (Maybe) adds a predictive action to the prediction runner, based on our
// calculated confidence for the subresource in question.
void Predictor::SetupPrediction(int32_t confidence, uint32_t flags,
                                const nsCString& uri,
                                PrefetchIgnoreReason earlyReason) {
  MOZ_ASSERT(NS_IsMainThread());

  nsresult rv = NS_OK;
  PREDICTOR_LOG(
      ("SetupPrediction enable-prefetch=%d prefetch-min-confidence=%d "
       "preconnect-min-confidence=%d preresolve-min-confidence=%d "
       "flags=%d confidence=%d uri=%s",
       StaticPrefs::network_predictor_enable_prefetch(),
       StaticPrefs::network_predictor_prefetch_min_confidence(),
       StaticPrefs::network_predictor_preconnect_min_confidence(),
       StaticPrefs::network_predictor_preresolve_min_confidence(), flags,
       confidence, uri.get()));

  bool prefetchOk = !!(flags & FLAG_PREFETCHABLE);
  PrefetchIgnoreReason reason = earlyReason;
  if (prefetchOk && !StaticPrefs::network_predictor_enable_prefetch()) {
    prefetchOk = false;
    reason = PREFETCH_DISABLED;
  } else if (prefetchOk && !ClampedPrefetchRollingLoadCount() &&
             confidence <
                 StaticPrefs::network_predictor_prefetch_min_confidence()) {
    prefetchOk = false;
    if (!ClampedPrefetchRollingLoadCount()) {
      reason = PREFETCH_DISABLED_VIA_COUNT;
    } else {
      reason = CONFIDENCE_TOO_LOW;
    }
  }

  // prefetchOk == false and reason == PREFETCH_OK indicates that the reason
  // we aren't prefetching this item is because it was marked un-prefetchable in
  // our metadata. We already have separate telemetry on that decision, so we
  // aren't going to accumulate more here. Right now we only care about why
  // something we had marked prefetchable isn't being prefetched.
  if (!prefetchOk && reason != PREFETCH_OK) {
    glean::predictor::prefetch_ignore_reason.AccumulateSingleSample(reason);
  }

  if (prefetchOk) {
    nsCOMPtr<nsIURI> prefetchURI;
    rv = NS_NewURI(getter_AddRefs(prefetchURI), uri);
    if (NS_SUCCEEDED(rv)) {
      mPrefetches.AppendElement(prefetchURI);
    }
  } else if (confidence >=
             StaticPrefs::network_predictor_preconnect_min_confidence()) {
    nsCOMPtr<nsIURI> preconnectURI;
    rv = NS_NewURI(getter_AddRefs(preconnectURI), uri);
    if (NS_SUCCEEDED(rv)) {
      mPreconnects.AppendElement(preconnectURI);
    }
  } else if (confidence >=
             StaticPrefs::network_predictor_preresolve_min_confidence()) {
    nsCOMPtr<nsIURI> preresolveURI;
    rv = NS_NewURI(getter_AddRefs(preresolveURI), uri);
    if (NS_SUCCEEDED(rv)) {
      mPreresolves.AppendElement(preresolveURI);
    }
  }

  if (NS_FAILED(rv)) {
    PREDICTOR_LOG(
        (" NS_NewURI returned 0x%" PRIx32, static_cast<uint32_t>(rv)));
  }
}

nsresult Predictor::Prefetch(nsIURI* uri, nsIURI* referrer,
                             const OriginAttributes& originAttributes,
                             nsINetworkPredictorVerifier* verifier) {
  nsAutoCString strUri, strReferrer;
  uri->GetAsciiSpec(strUri);
  referrer->GetAsciiSpec(strReferrer);
  PREDICTOR_LOG(("Predictor::Prefetch uri=%s referrer=%s verifier=%p",
                 strUri.get(), strReferrer.get(), verifier));
  nsCOMPtr<nsIChannel> channel;
  nsresult rv = NS_NewChannel(
      getter_AddRefs(channel), uri, nsContentUtils::GetSystemPrincipal(),
      nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
      nsIContentPolicy::TYPE_OTHER, nullptr, /* nsICookieJarSettings */
      nullptr,                               /* aPerformanceStorage */
      nullptr,                               /* aLoadGroup */
      nullptr,                               /* aCallbacks */
      nsIRequest::LOAD_BACKGROUND);

  if (NS_FAILED(rv)) {
    PREDICTOR_LOG(
        (" NS_NewChannel failed rv=0x%" PRIX32, static_cast<uint32_t>(rv)));
    return rv;
  }

  nsCOMPtr<nsILoadInfo> loadInfo = channel->LoadInfo();
  rv = loadInfo->SetOriginAttributes(originAttributes);

  if (NS_FAILED(rv)) {
    PREDICTOR_LOG(
        (" Set originAttributes into loadInfo failed rv=0x%" PRIX32,
         static_cast<uint32_t>(rv)));
    return rv;
  }

  nsCOMPtr<nsIHttpChannel> httpChannel;
  httpChannel = do_QueryInterface(channel);
  if (!httpChannel) {
    PREDICTOR_LOG((" Could not get HTTP Channel from new channel!"));
    return NS_ERROR_UNEXPECTED;
  }

  nsCOMPtr<nsIReferrerInfo> referrerInfo = new dom::ReferrerInfo(referrer);
  rv = httpChannel->SetReferrerInfoWithoutClone(referrerInfo);
  NS_ENSURE_SUCCESS(rv, rv);
  // XXX - set a header here to indicate this is a prefetch?

  nsCOMPtr<nsIStreamListener> listener =
      new PrefetchListener(verifier, uri, this);
  PREDICTOR_LOG((" calling AsyncOpen listener=%p channel=%p", listener.get(),
                 channel.get()));
  rv = channel->AsyncOpen(listener);
  if (NS_FAILED(rv)) {
    PREDICTOR_LOG(
        (" AsyncOpen failed rv=0x%" PRIX32, static_cast<uint32_t>(rv)));
  }

  return rv;
}

// Runs predictions that have been set up.
bool Predictor::RunPredictions(nsIURI* referrer,
                               const OriginAttributes& originAttributes,
                               nsINetworkPredictorVerifier* verifier) {
  MOZ_ASSERT(NS_IsMainThread(), "Running prediction off main thread");

  PREDICTOR_LOG(("Predictor::RunPredictions"));

  bool predicted = false;
  uint32_t len, i;

  nsTArray<nsCOMPtr<nsIURI>> prefetches = std::move(mPrefetches),
                             preconnects = std::move(mPreconnects),
                             preresolves = std::move(mPreresolves);

  uint32_t totalPredictions = 0;
  uint32_t totalPrefetches = 0;
  uint32_t totalPreconnects = 0;
  uint32_t totalPreresolves = 0;

  len = prefetches.Length();
  for (i = 0; i < len; ++i) {
    PREDICTOR_LOG((" doing prefetch"));
    nsCOMPtr<nsIURI> uri = prefetches[i];
    if (NS_SUCCEEDED(Prefetch(uri, referrer, originAttributes, verifier))) {
      ++totalPredictions;
      ++totalPrefetches;
      predicted = true;
    }
  }

  len = preconnects.Length();
  for (i = 0; i < len; ++i) {
    PREDICTOR_LOG((" doing preconnect"));
    nsCOMPtr<nsIURI> uri = preconnects[i];
    ++totalPredictions;
    ++totalPreconnects;
    nsCOMPtr<nsIPrincipal> principal =
        BasePrincipal::CreateContentPrincipal(uri, originAttributes);
    mSpeculativeService->SpeculativeConnect(uri, principal, this, false);
    predicted = true;
    if (verifier) {
      PREDICTOR_LOG((" sending preconnect verification"));
      verifier->OnPredictPreconnect(uri);
    }
  }

  len = preresolves.Length();
  for (i = 0; i < len; ++i) {
    nsCOMPtr<nsIURI> uri = preresolves[i];
    ++totalPredictions;
    ++totalPreresolves;
    nsAutoCString hostname;
    uri->GetAsciiHost(hostname);
    PREDICTOR_LOG((" doing preresolve %s", hostname.get()));
    nsCOMPtr<nsICancelable> tmpCancelable;
    mDnsService->AsyncResolveNative(
        hostname, nsIDNSService::RESOLVE_TYPE_DEFAULT,
        (nsIDNSService::RESOLVE_PRIORITY_MEDIUM |
         nsIDNSService::RESOLVE_SPECULATE),
        nullptr, mDNSListener, nullptr, originAttributes,
        getter_AddRefs(tmpCancelable));

    // Fetch HTTPS RR if needed.
    if (StaticPrefs::network_dns_upgrade_with_https_rr() ||
        StaticPrefs::network_dns_use_https_rr_as_altsvc()) {
      mDnsService->AsyncResolveNative(
          hostname, nsIDNSService::RESOLVE_TYPE_HTTPSSVC,
          (nsIDNSService::RESOLVE_PRIORITY_MEDIUM |
           nsIDNSService::RESOLVE_SPECULATE),
          nullptr, mDNSListener, nullptr, originAttributes,
          getter_AddRefs(tmpCancelable));
    }

    predicted = true;
    if (verifier) {
      PREDICTOR_LOG((" sending preresolve verification"));
      verifier->OnPredictDNS(uri);
    }
  }

  glean::predictor::total_predictions.AccumulateSingleSample(totalPredictions);
  glean::predictor::total_prefetches.AccumulateSingleSample(totalPrefetches);
  glean::predictor::total_preconnects.AccumulateSingleSample(totalPreconnects);
  glean::predictor::total_preresolves.AccumulateSingleSample(totalPreresolves);

  return predicted;
}

// Find out if a top-level page is likely to redirect.
bool Predictor::WouldRedirect(nsICacheEntry* entry, uint32_t loadCount,
                              uint32_t lastLoad, int32_t globalDegradation,
                              nsIURI** redirectURI) {
  // TODO - not doing redirects for first go around
  MOZ_ASSERT(NS_IsMainThread());

  return false;
}

NS_IMETHODIMP
Predictor::Learn(nsIURI* targetURI, nsIURI* sourceURI,
                 PredictorLearnReason reason,
                 JS::Handle<JS::Value> originAttributes, JSContext* aCx) {
  OriginAttributes attrs;

  if (!originAttributes.isObject() || !attrs.Init(aCx, originAttributes)) {
    return NS_ERROR_INVALID_ARG;
  }

  return LearnNative(targetURI, sourceURI, reason, attrs);
}

// Called from the main thread to update the database
NS_IMETHODIMP
Predictor::LearnNative(nsIURI* targetURI, nsIURI* sourceURI,
                       PredictorLearnReason reason,
                       const OriginAttributes& originAttributes) {
  MOZ_ASSERT(NS_IsMainThread(),
             "Predictor interface methods must be called on the main thread");

  PREDICTOR_LOG(("Predictor::Learn"));

  if (!StaticPrefs::network_predictor_enabled()) {
    PREDICTOR_LOG((" not enabled"));
    return NS_OK;
  }

  if (IsNeckoChild()) {
    if (!gNeckoChild) {
      return NS_ERROR_FAILURE;
    }

    PREDICTOR_LOG((" called on child process"));

    RefPtr<PredictorLearnRunnable> runnable = new PredictorLearnRunnable(
        targetURI, sourceURI, reason, originAttributes);
    SchedulerGroup::Dispatch(runnable.forget());
    return NS_OK;
  }

  PREDICTOR_LOG((" called on parent process"));

  if (!mInitialized) {
    PREDICTOR_LOG((" not initialized"));
    return NS_OK;
  }

  if (originAttributes.IsPrivateBrowsing()) {
    // Don't want to do anything in PB mode
    PREDICTOR_LOG((" in PB mode"));
    return NS_OK;
  }

  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
    PREDICTOR_LOG((" got non-HTTP[S] URI"));
    return NS_ERROR_INVALID_ARG;
  }

  nsCOMPtr<nsIURI> targetOrigin;
  nsCOMPtr<nsIURI> sourceOrigin;
  nsCOMPtr<nsIURI> uriKey;
  nsCOMPtr<nsIURI> originKey;
  nsresult rv;

  switch (reason) {
    case nsINetworkPredictor::LEARN_LOAD_TOPLEVEL:
      if (!targetURI || sourceURI) {
        PREDICTOR_LOG((" load toplevel invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin));
      NS_ENSURE_SUCCESS(rv, rv);
      uriKey = targetURI;
      originKey = targetOrigin;
      break;
    case nsINetworkPredictor::LEARN_STARTUP:
      if (!targetURI || sourceURI) {
        PREDICTOR_LOG((" startup invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin));
      NS_ENSURE_SUCCESS(rv, rv);
      uriKey = mStartupURI;
      originKey = mStartupURI;
      break;
    case nsINetworkPredictor::LEARN_LOAD_REDIRECT:
    case nsINetworkPredictor::LEARN_LOAD_SUBRESOURCE:
      if (!targetURI || !sourceURI) {
        PREDICTOR_LOG((" redirect/subresource invalid URI state"));
        return NS_ERROR_INVALID_ARG;
      }
      rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin));
      NS_ENSURE_SUCCESS(rv, rv);
      rv = ExtractOrigin(sourceURI, getter_AddRefs(sourceOrigin));
      NS_ENSURE_SUCCESS(rv, rv);
      uriKey = sourceURI;
      originKey = sourceOrigin;
      break;
    default:
      PREDICTOR_LOG((" invalid reason"));
      return NS_ERROR_INVALID_ARG;
  }

  uint32_t learnAttempts = 1;
  Predictor::Reason argReason{};
  argReason.mLearn = reason;

  // We always open the full uri (general cache) entry first, so we don't gum up
  // the works waiting on predictor-only entries to open
  RefPtr<Predictor::Action> uriAction = new Predictor::Action(
      Predictor::Action::IS_FULL_URI, Predictor::Action::DO_LEARN, argReason,
      targetURI, sourceURI, nullptr, this);
  nsAutoCString uriKeyStr, targetUriStr, sourceUriStr;
  uriKey->GetAsciiSpec(uriKeyStr);
  targetURI->GetAsciiSpec(targetUriStr);
  if (sourceURI) {
    sourceURI->GetAsciiSpec(sourceUriStr);
  }
  PREDICTOR_LOG(
      (" Learn uriKey=%s targetURI=%s sourceURI=%s reason=%d "
       "action=%p",
       uriKeyStr.get(), targetUriStr.get(), sourceUriStr.get(), reason,
       uriAction.get()));

  nsCOMPtr<nsICacheStorage> cacheDiskStorage;

  RefPtr<LoadContextInfo> lci = new LoadContextInfo(false, originAttributes);

  rv = mCacheStorageService->DiskCacheStorage(lci,
                                              getter_AddRefs(cacheDiskStorage));
  NS_ENSURE_SUCCESS(rv, rv);

  // For learning full URI things, we *always* open readonly and secretly, as we
  // rely on actual pageloads to update the entry's metadata for us.
  uint32_t uriOpenFlags = nsICacheStorage::OPEN_READONLY |
                          nsICacheStorage::OPEN_SECRETLY |
                          nsICacheStorage::CHECK_MULTITHREADED;
  if (reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL) {
    // Learning for toplevel we want to open the full uri entry priority, since
    // it's likely this entry will be used soon anyway, and we want this to be
    // opened ASAP.
    uriOpenFlags |= nsICacheStorage::OPEN_PRIORITY;
  }
  cacheDiskStorage->AsyncOpenURI(uriKey, ""_ns, uriOpenFlags, uriAction);

  // Now we open the origin-only (and therefore predictor-only) entry
  RefPtr<Predictor::Action> originAction = new Predictor::Action(
      Predictor::Action::IS_ORIGIN, Predictor::Action::DO_LEARN, argReason,
      targetOrigin, sourceOrigin, nullptr, this);
  nsAutoCString originKeyStr, targetOriginStr, sourceOriginStr;
  originKey->GetAsciiSpec(originKeyStr);
  targetOrigin->GetAsciiSpec(targetOriginStr);
  if (sourceOrigin) {
    sourceOrigin->GetAsciiSpec(sourceOriginStr);
  }
  PREDICTOR_LOG(
      (" Learn originKey=%s targetOrigin=%s sourceOrigin=%s reason=%d "
       "action=%p",
       originKeyStr.get(), targetOriginStr.get(), sourceOriginStr.get(), reason,
       originAction.get()));
  uint32_t originOpenFlags;
  if (reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL) {
    // This is the only case when we want to update the 'last used' metadata on
    // the cache entry we're getting. This only applies to predictor-specific
    // entries.
    originOpenFlags =
        nsICacheStorage::OPEN_NORMALLY | nsICacheStorage::CHECK_MULTITHREADED;
  } else {
    originOpenFlags = nsICacheStorage::OPEN_READONLY |
                      nsICacheStorage::OPEN_SECRETLY |
                      nsICacheStorage::CHECK_MULTITHREADED;
  }
  cacheDiskStorage->AsyncOpenURI(originKey,
                                 nsLiteralCString(PREDICTOR_ORIGIN_EXTENSION),
                                 originOpenFlags, originAction);

  glean::predictor::learn_attempts.AccumulateSingleSample(learnAttempts);
  PREDICTOR_LOG(("Predictor::Learn returning"));
  return NS_OK;
}

void Predictor::LearnInternal(PredictorLearnReason reason, nsICacheEntry* entry,
                              bool isNew, bool fullUri, nsIURI* targetURI,
                              nsIURI* sourceURI) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::LearnInternal"));

  nsCString junk;
  if (!fullUri && reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL &&
      NS_FAILED(
          entry->GetMetaDataElement(SEEN_META_DATA, getter_Copies(junk)))) {
    // This is an origin-only entry that we haven't seen before. Let's mark it
    // as seen.
    PREDICTOR_LOG((" marking new origin entry as seen"));
    nsresult rv = entry->SetMetaDataElement(SEEN_META_DATA, "1");
    if (NS_FAILED(rv)) {
      PREDICTOR_LOG((" failed to mark origin entry seen"));
      return;
    }

    // Need to ensure someone else can get to the entry if necessary
    entry->MetaDataReady();
    return;
  }

  switch (reason) {
    case nsINetworkPredictor::LEARN_LOAD_TOPLEVEL:
      // This case only exists to be used during tests - code outside the
      // predictor tests should NEVER call Learn with LEARN_LOAD_TOPLEVEL.
      // The predictor xpcshell test needs this branch, however, because we
      // have no real page loads in xpcshell, and this is how we fake it up
      // so that all the work that normally happens behind the scenes in a
      // page load can be done for testing purposes.
      if (fullUri && StaticPrefs::network_predictor_doing_tests()) {
        PREDICTOR_LOG(
            (" WARNING - updating rolling load count. "
             "If you see this outside tests, you did it wrong"));

        // Since the visitor gets called under a cache lock, all we do there is
        // get copies of the keys/values we care about, and then do the real
        // work here
        entry->VisitMetaData(this);
        nsTArray<nsCString> keysToOperateOn = std::move(mKeysToOperateOn),
                            valuesToOperateOn = std::move(mValuesToOperateOn);

        MOZ_ASSERT(keysToOperateOn.Length() == valuesToOperateOn.Length());
        for (size_t i = 0; i < keysToOperateOn.Length(); ++i) {
          const char* key = keysToOperateOn[i].BeginReading();
          const char* value = valuesToOperateOn[i].BeginReading();

          nsCString uri;
          uint32_t hitCount, lastHit, flags;
          if (!ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags)) {
            // This failed, get rid of it so we don't waste space
            entry->SetMetaDataElement(key, nullptr);
            continue;
          }
          UpdateRollingLoadCount(entry, flags, key, hitCount, lastHit);
        }
      } else {
        PREDICTOR_LOG((" nothing to do for toplevel"));
      }
      break;
    case nsINetworkPredictor::LEARN_LOAD_REDIRECT:
      if (fullUri) {
        LearnForRedirect(entry, targetURI);
      }
      break;
    case nsINetworkPredictor::LEARN_LOAD_SUBRESOURCE:
      LearnForSubresource(entry, targetURI);
      break;
    case nsINetworkPredictor::LEARN_STARTUP:
      LearnForStartup(entry, targetURI);
      break;
    default:
      PREDICTOR_LOG((" unexpected reason value"));
      MOZ_ASSERT(false, "Got unexpected value for learn reason!");
  }
}

NS_IMPL_ISUPPORTS(Predictor::SpaceCleaner, nsICacheEntryMetaDataVisitor)

NS_IMETHODIMP
Predictor::SpaceCleaner::OnMetaDataElement(const char* key, const char* value) {
  MOZ_ASSERT(NS_IsMainThread());

  if (!IsURIMetadataElement(key)) {
    // This isn't a bit of metadata we care about
    return NS_OK;
  }

  nsCString uri;
  uint32_t hitCount, lastHit, flags;
  bool ok =
      mPredictor->ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags);

  if (!ok) {
    // Couldn't parse this one, just get rid of it
    nsCString nsKey;
    nsKey.AssignASCII(key);
    mLongKeysToDelete.AppendElement(nsKey);
    return NS_OK;
  }

  uint32_t uriLength = uri.Length();
  if (uriLength > StaticPrefs::network_predictor_max_uri_length()) {
    // Default to getting rid of URIs that are too long and were put in before
    // we had our limit on URI length, in order to free up some space.
    nsCString nsKey;
    nsKey.AssignASCII(key);
    mLongKeysToDelete.AppendElement(nsKey);
    return NS_OK;
  }

  if (!mLRUKeyToDelete || lastHit < mLRUStamp) {
    mLRUKeyToDelete = key;
    mLRUStamp = lastHit;
  }

  return NS_OK;
}

void Predictor::SpaceCleaner::Finalize(nsICacheEntry* entry) {
  MOZ_ASSERT(NS_IsMainThread());

  if (mLRUKeyToDelete) {
    entry->SetMetaDataElement(mLRUKeyToDelete, nullptr);
  }

  for (size_t i = 0; i < mLongKeysToDelete.Length(); ++i) {
    entry->SetMetaDataElement(mLongKeysToDelete[i].BeginReading(), nullptr);
  }
}

// Called when a subresource has been hit from a top-level load. Uses the two
// helper functions above to update the database appropriately.
void Predictor::LearnForSubresource(nsICacheEntry* entry, nsIURI* targetURI) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(("Predictor::LearnForSubresource"));

  uint32_t lastLoad;
  nsresult rv = entry->GetLastFetched(&lastLoad);
  NS_ENSURE_SUCCESS_VOID(rv);

  uint32_t loadCount;
  rv = entry->GetFetchCount(&loadCount);
  NS_ENSURE_SUCCESS_VOID(rv);

  nsCString key;
  key.AssignLiteral(META_DATA_PREFIX);
  nsCString uri;
  targetURI->GetAsciiSpec(uri);
  key.Append(uri);
  if (uri.Length() > StaticPrefs::network_predictor_max_uri_length()) {
    // We do this to conserve space/prevent OOMs
    PREDICTOR_LOG((" uri too long!"));
    entry->SetMetaDataElement(key.BeginReading(), nullptr);
    return;
  }

  nsCString value;
  rv = entry->GetMetaDataElement(key.BeginReading(), getter_Copies(value));

  uint32_t hitCount, lastHit, flags;
  bool isNewResource =
      (NS_FAILED(rv) ||
       !ParseMetaDataEntry(key.BeginReading(), value.BeginReading(), uri,
                           hitCount, lastHit, flags));

  int32_t resourceCount = 0;
  if (isNewResource) {
    // This is a new addition
    PREDICTOR_LOG((" new resource"));
    nsCString s;
    rv = entry->GetMetaDataElement(RESOURCE_META_DATA, getter_Copies(s));
    if (NS_SUCCEEDED(rv)) {
      resourceCount = atoi(s.BeginReading());
    }
    if (resourceCount >=
        StaticPrefs::network_predictor_max_resources_per_entry()) {
      RefPtr<Predictor::SpaceCleaner> cleaner =
          new Predictor::SpaceCleaner(this);
      entry->VisitMetaData(cleaner);
      cleaner->Finalize(entry);
    } else {
      ++resourceCount;
    }
    nsAutoCString count;
    count.AppendInt(resourceCount);
    rv = entry->SetMetaDataElement(RESOURCE_META_DATA, count.BeginReading());
    if (NS_FAILED(rv)) {
      PREDICTOR_LOG((" failed to update resource count"));
      return;
    }
    hitCount = 1;
    flags = 0;
  } else {
    PREDICTOR_LOG((" existing resource"));
    hitCount = std::min(hitCount + 1, loadCount);
  }

  // Update the rolling load count to mark this sub-resource as seen on the
  // most-recent pageload so it can be eligible for prefetch (assuming all
  // the other stars align).
  flags |= (1 << kRollingLoadOffset);

  nsCString newValue;
  MakeMetadataEntry(hitCount, lastLoad, flags, newValue);
  rv = entry->SetMetaDataElement(key.BeginReading(), newValue.BeginReading());
  PREDICTOR_LOG(
      (" SetMetaDataElement -> 0x%08" PRIX32, static_cast<uint32_t>(rv)));
  if (NS_FAILED(rv) && isNewResource) {
    // Roll back the increment to the resource count we made above.
    PREDICTOR_LOG((" rolling back resource count update"));
    --resourceCount;
    if (resourceCount == 0) {
      entry->SetMetaDataElement(RESOURCE_META_DATA, nullptr);
    } else {
      nsAutoCString count;
      count.AppendInt(resourceCount);
      entry->SetMetaDataElement(RESOURCE_META_DATA, count.BeginReading());
    }
  }
}

// This is called when a top-level loaded ended up redirecting to a different
// URI so we can keep track of that fact.
void Predictor::LearnForRedirect(nsICacheEntry* entry, nsIURI* targetURI) {
  MOZ_ASSERT(NS_IsMainThread());

  // TODO - not doing redirects for first go around
  PREDICTOR_LOG(("Predictor::LearnForRedirect"));
}

// This will add a page to our list of startup pages if it's being loaded
// before our startup window has expired.
void Predictor::MaybeLearnForStartup(nsIURI* uri, bool fullUri,
                                     const OriginAttributes& originAttributes) {
  MOZ_ASSERT(NS_IsMainThread());

  // TODO - not doing startup for first go around
  PREDICTOR_LOG(("Predictor::MaybeLearnForStartup"));
}

// Add information about a top-level load to our list of startup pages
void Predictor::LearnForStartup(nsICacheEntry* entry, nsIURI* targetURI) {
  MOZ_ASSERT(NS_IsMainThread());

  // These actually do the same set of work, just on different entries, so we
  // can pass through to get the real work done here
  PREDICTOR_LOG(("Predictor::LearnForStartup"));
  LearnForSubresource(entry, targetURI);
}

bool Predictor::ParseMetaDataEntry(const char* key, const char* value,
                                   nsCString& uri, uint32_t& hitCount,
                                   uint32_t& lastHit, uint32_t& flags) {
  MOZ_ASSERT(NS_IsMainThread());

  PREDICTOR_LOG(
      ("Predictor::ParseMetaDataEntry key=%s value=%s", key ? key : "", value));

  const char* comma = strchr(value, ',');
  if (!comma) {
    PREDICTOR_LOG((" could not find first comma"));
    return false;
  }

  uint32_t version = static_cast<uint32_t>(atoi(value));
  PREDICTOR_LOG((" version -> %u", version));

  if (version != METADATA_VERSION) {
    PREDICTOR_LOG(
        (" metadata version mismatch %u != %u", version, METADATA_VERSION));
    return false;
  }

  value = comma + 1;
  comma = strchr(value, ',');
  if (!comma) {
    PREDICTOR_LOG((" could not find second comma"));
    return false;
  }

  hitCount = static_cast<uint32_t>(atoi(value));
  PREDICTOR_LOG((" hitCount -> %u", hitCount));

  value = comma + 1;
  comma = strchr(value, ',');
  if (!comma) {
    PREDICTOR_LOG((" could not find third comma"));
    return false;
  }

  lastHit = static_cast<uint32_t>(atoi(value));
  PREDICTOR_LOG((" lastHit -> %u", lastHit));

  value = comma + 1;
  flags = static_cast<uint32_t>(atoi(value));
  PREDICTOR_LOG((" flags -> %u", flags));

  if (key) {
    const char* uriStart = key + (sizeof(META_DATA_PREFIX) - 1);
    uri.AssignASCII(uriStart);
    PREDICTOR_LOG((" uri -> %s", uriStart));
  } else {
    uri.Truncate();
  }

  return true;
}

NS_IMETHODIMP
Predictor::Reset() {
  MOZ_ASSERT(NS_IsMainThread(),
             "Predictor interface methods must be called on the main thread");

  PREDICTOR_LOG(("Predictor::Reset"));

  if (!StaticPrefs::network_predictor_enabled()) {
    PREDICTOR_LOG((" not enabled"));
    return NS_OK;
  }

  if (IsNeckoChild()) {
    if (!gNeckoChild) {
      return NS_ERROR_FAILURE;
    }

    PREDICTOR_LOG((" forwarding to parent process"));
    gNeckoChild->SendPredReset();
    return NS_OK;
  }

  PREDICTOR_LOG((" called on parent process"));

  if (!mInitialized) {
    PREDICTOR_LOG((" not initialized"));
    return NS_OK;
  }

  RefPtr<Predictor::Resetter> reset = new Predictor::Resetter(this);
  PREDICTOR_LOG((" created a resetter"));
  mCacheStorageService->AsyncVisitAllStorages(reset, true);
  PREDICTOR_LOG((" Cache async launched, returning now"));

  return NS_OK;
}

NS_IMPL_ISUPPORTS(Predictor::Resetter, nsICacheEntryOpenCallback,
                  nsICacheEntryMetaDataVisitor, nsICacheStorageVisitor);

Predictor::Resetter::Resetter(Predictor* predictor)
    : mEntriesToVisit(0), mPredictor(predictor) {}

NS_IMETHODIMP
Predictor::Resetter::OnCacheEntryCheck(nsICacheEntry* entry, uint32_t* result) {
  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
  return NS_OK;
}

NS_IMETHODIMP
Predictor::Resetter::OnCacheEntryAvailable(nsICacheEntry* entry, bool isNew,
                                           nsresult result) {
  MOZ_ASSERT(NS_IsMainThread());

  if (NS_FAILED(result)) {
    // This can happen when we've tried to open an entry that doesn't exist for
    // some non-reset operation, and then get reset shortly thereafter (as
    // happens in some of our tests).
    --mEntriesToVisit;
    if (!mEntriesToVisit) {
      Complete();
    }
    return NS_OK;
  }

  entry->VisitMetaData(this);
  nsTArray<nsCString> keysToDelete = std::move(mKeysToDelete);

  for (size_t i = 0; i < keysToDelete.Length(); ++i) {
    const char* key = keysToDelete[i].BeginReading();
    entry->SetMetaDataElement(key, nullptr);
  }

  --mEntriesToVisit;
  if (!mEntriesToVisit) {
    Complete();
  }

  return NS_OK;
}

NS_IMETHODIMP
Predictor::Resetter::OnMetaDataElement(const char* asciiKey,
                                       const char* asciiValue) {
  MOZ_ASSERT(NS_IsMainThread());

  if (!StringBeginsWith(nsDependentCString(asciiKey),
                        nsLiteralCString(META_DATA_PREFIX))) {
    // Not a metadata entry we care about, carry on
    return NS_OK;
  }

  nsCString key;
  key.AssignASCII(asciiKey);
  mKeysToDelete.AppendElement(key);

  return NS_OK;
}

NS_IMETHODIMP
Predictor::Resetter::OnCacheStorageInfo(uint32_t entryCount,
                                        uint64_t consumption, uint64_t capacity,
                                        nsIFile* diskDirectory) {
  MOZ_ASSERT(NS_IsMainThread());

  return NS_OK;
}

NS_IMETHODIMP
Predictor::Resetter::OnCacheEntryInfo(nsIURI* uri, const nsACString& idEnhance,
                                      int64_t dataSize, int64_t altDataSize,
                                      uint32_t fetchCount,
                                      uint32_t lastModifiedTime,
                                      uint32_t expirationTime, bool aPinned,
                                      nsILoadContextInfo* aInfo) {
  MOZ_ASSERT(NS_IsMainThread());

  nsresult rv;

  // The predictor will only ever touch entries with no idEnhance ("") or an
  // idEnhance of PREDICTOR_ORIGIN_EXTENSION, so we filter out any entries that
  // don't match that to avoid doing extra work.
  if (idEnhance.EqualsLiteral(PREDICTOR_ORIGIN_EXTENSION)) {
    // This is an entry we own, so we can just doom it entirely
    nsCOMPtr<nsICacheStorage> cacheDiskStorage;

    rv = mPredictor->mCacheStorageService->DiskCacheStorage(
        aInfo, getter_AddRefs(cacheDiskStorage));

    NS_ENSURE_SUCCESS(rv, rv);
    cacheDiskStorage->AsyncDoomURI(uri, idEnhance, nullptr);
  } else if (idEnhance.IsEmpty()) {
    // This is an entry we don't own, so we have to be a little more careful and
    // just get rid of our own metadata entries. Append it to an array of things
    // to operate on and then do the operations later so we don't end up calling
    // Complete() multiple times/too soon.
    ++mEntriesToVisit;
    mURIsToVisit.AppendElement(uri);
    mInfosToVisit.AppendElement(aInfo);
  }

  return NS_OK;
}

NS_IMETHODIMP
Predictor::Resetter::OnCacheEntryVisitCompleted() {
  MOZ_ASSERT(NS_IsMainThread());

  nsresult rv;

  nsTArray<nsCOMPtr<nsIURI>> urisToVisit = std::move(mURIsToVisit);

  MOZ_ASSERT(mEntriesToVisit == urisToVisit.Length());

  nsTArray<nsCOMPtr<nsILoadContextInfo>> infosToVisit =
      std::move(mInfosToVisit);

  MOZ_ASSERT(mEntriesToVisit == infosToVisit.Length());

  if (!mEntriesToVisit) {
    Complete();
    return NS_OK;
  }

  uint32_t entriesToVisit = urisToVisit.Length();
  for (uint32_t i = 0; i < entriesToVisit; ++i) {
    nsCString u;
    nsCOMPtr<nsICacheStorage> cacheDiskStorage;

    rv = mPredictor->mCacheStorageService->DiskCacheStorage(
        infosToVisit[i], getter_AddRefs(cacheDiskStorage));
    NS_ENSURE_SUCCESS(rv, rv);

    urisToVisit[i]->GetAsciiSpec(u);
    rv = cacheDiskStorage->AsyncOpenURI(
        urisToVisit[i], ""_ns,
        nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY |
            nsICacheStorage::CHECK_MULTITHREADED,
        this);
    if (NS_FAILED(rv)) {
      mEntriesToVisit--;
      if (!mEntriesToVisit) {
        Complete();
        return NS_OK;
      }
    }
  }

  return NS_OK;
}

void Predictor::Resetter::Complete() {
  MOZ_ASSERT(NS_IsMainThread());

  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
  if (!obs) {
    PREDICTOR_LOG(("COULD NOT GET OBSERVER SERVICE!"));
    return;
  }

--> --------------------

--> maximum size reached

--> --------------------

quality97%

¤ Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.0.39Bemerkung: (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.