nsEffectiveTLDService.h

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/* 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/. */

#ifndef EffectiveTLDService_h

#define EffectiveTLDService_h

#include "MainThreadUtils.h"

#include "mozilla/Dafsa.h"

#include "mozilla/MruCache.h"

#include "mozilla/StaticPtr.h"

#include "nsHashKeys.h"

#include "nsIEffectiveTLDService.h"

#include "nsString.h"

class nsIIDNService;

class nsEffectiveTLDService final : public nsIEffectiveTLDService {

 public:

  // The `nsEffectiveTLDService` is allocated in a static singleton.

  // We'll use a fake reference count for the type.

  NS_IMETHOD_(MozExternalRefCountType) AddRef() override { return 2; }

  NS_IMETHOD_(MozExternalRefCountType) Release() override { return 1; }

  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;

  using HasThreadSafeRefCnt = std::true_type;

  NS_DECL_NSIEFFECTIVETLDSERVICE

  static already_AddRefed<nsIEffectiveTLDService> GetXPCOMSingleton();

 private:

  constexpr explicit nsEffectiveTLDService(mozilla::Dafsa::Graph aGraph)

      : mGraph(aGraph) {}

  nsresult GetBaseDomainInternal(nsCString& aHostname, int32_t aAdditionalParts,

                                 bool aOnlyKnownPublicSuffix,

                                 nsACString& aBaseDomain);

  static nsEffectiveTLDService sSingleton;

  // The DAFSA provides a compact encoding of the rather large eTLD list.

  const mozilla::Dafsa mGraph;

  // Note that the cache entries here can record entries that were cached

  // successfully or unsuccessfully.  mResult must be checked before using an

  // entry.  If it's a success error code, the cache entry is valid and can be

  // used.

  struct TLDCacheEntry {

    nsCString mHost;

    nsCString mBaseDomain;

    nsresult mResult;

};

  // We use a small most recently used cache to compensate for DAFSA lookups

  // being slightly slower than a binary search on a larger table of strings.

//

  // We first check the cache for a matching result and avoid a DAFSA lookup

  // if a match is found. Otherwise we lookup the domain in the DAFSA and then

  // cache the result. During standard browsing the same domains are repeatedly

  // fed into |GetBaseDomainInternal| so this ends up being an effective

  // mitigation getting about a 99% hit rate with four tabs open.

  struct TldCache

      : public mozilla::MruCache<nsACString, TLDCacheEntry, TldCache> {

    static bool IsEmpty(const TLDCacheEntry& aVal) {

      return aVal.mHost.IsEmpty();

    static mozilla::HashNumber Hash(const nsACString& aKey) {

      return mozilla::HashString(aKey);

    static bool Match(const nsACString& aKey, const TLDCacheEntry& aVal) {

      return aKey == aVal.mHost;

};

  // Only accessed on the main thread.

  mozilla::StaticAutoPtr<TldCache> mMruTable

      MOZ_GUARDED_BY(mozilla::sMainThreadCapability);

};

#endif  // EffectiveTLDService_h