Quelle nsCategoryCache.h Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 nsCategoryCache_h_
#define nsCategoryCache_h_

#include "mozilla/Attributes.h"

#include "nsIObserver.h"

#include "nsServiceManagerUtils.h"

#include "nsCOMArray.h"
#include "nsInterfaceHashtable.h"

#include "nsXPCOM.h"
#include "MainThreadUtils.h"

class nsCategoryObserver final : public nsIObserver {
  ~nsCategoryObserver();

public:
  explicit nsCategoryObserver(const nsACString& aCategory);

  void ListenerDied();
  void SetListener(void(aCallback)(void*), void* aClosure);
  nsInterfaceHashtable<nsCStringHashKey, nsISupports>& GetHash() {
    return mHash;
  }

  NS_DECL_ISUPPORTS
  NS_DECL_NSIOBSERVER
private:
  void RemoveObservers();

  nsInterfaceHashtable<nsCStringHashKey, nsISupports> mHash;
  nsCString mCategory;
  void (*mCallback)(void*);
  void* mClosure;
  bool mObserversRemoved;
};

/**
* This is a helper class that caches services that are registered in a certain
* category. The intended usage is that a service stores a variable of type
* nsCategoryCache<nsIFoo> in a member variable, where nsIFoo is the interface
* that these services should implement. The constructor of this class should
* then get the name of the category.
*/
template <class T>
class nsCategoryCache final {
public:
  explicit nsCategoryCache(const char* aCategory) : mCategoryName(aCategory) {
    MOZ_ASSERT(NS_IsMainThread());
  }
  ~nsCategoryCache() {
    MOZ_ASSERT(NS_IsMainThread());
    if (mObserver) {
      mObserver->ListenerDied();
    }
  }

  void GetEntries(nsCOMArray<T>& aResult) {
    MOZ_ASSERT(NS_IsMainThread());
    LazyInit();

    AddEntries(aResult);
  }

  /**
   * This function returns an nsCOMArray of interface pointers to the cached
   * category enries for the requested category.  This was added in order to be
   * used in call sites where the overhead of excessive allocations can be
   * unacceptable.  See bug 1360971 for an example.
   */
  const nsCOMArray<T>& GetCachedEntries() {
    MOZ_ASSERT(NS_IsMainThread());
    LazyInit();

    if (mCachedEntries.IsEmpty()) {
      AddEntries(mCachedEntries);
    }
    return mCachedEntries;
  }

private:
  void LazyInit() {
    // Lazy initialization, so that services in this category can't
    // cause reentrant getService (bug 386376)
    if (!mObserver) {
      mObserver = new nsCategoryObserver(mCategoryName);
      mObserver->SetListener(nsCategoryCache<T>::OnCategoryChanged, this);
    }
  }

  void AddEntries(nsCOMArray<T>& aResult) {
    for (nsISupports* entry : mObserver->GetHash().Values()) {
      nsCOMPtr<T> service = do_QueryInterface(entry);
      if (service) {
        aResult.AppendElement(service.forget());
      }
    }
  }

  static void OnCategoryChanged(void* aClosure) {
    MOZ_ASSERT(NS_IsMainThread());
    auto self = static_cast<nsCategoryCache<T>*>(aClosure);
    self->mCachedEntries.Clear();
  }

private:
  // Not to be implemented
  nsCategoryCache(const nsCategoryCache<T>&);

  nsCString mCategoryName;
  RefPtr<nsCategoryObserver> mObserver;
  nsCOMArray<T> mCachedEntries;
};

#endif

quality96%

¤ Dauer der Verarbeitung: 0.2 Sekunden (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.