gecko-dev/xpcom/components/nsCategoryCache.cpp

/* -*- 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/. */

#include "nsIObserverService.h"
#include "mozilla/Services.h"
#include "mozilla/SimpleEnumerator.h"
#include "nsISupportsPrimitives.h"
#include "nsIStringEnumerator.h"

#include "nsXPCOMCID.h"

#include "nsCategoryCache.h"

using mozilla::SimpleEnumerator;

nsCategoryObserver::nsCategoryObserver(const nsACString& aCategory)
  : mCategory(aCategory)
  , mCallback(nullptr)
  , mClosure(nullptr)
  , mObserversRemoved(false)
{
  MOZ_ASSERT(NS_IsMainThread());
  // First, enumerate the currently existing entries
  nsCOMPtr<nsICategoryManager> catMan =
    do_GetService(NS_CATEGORYMANAGER_CONTRACTID);
  if (!catMan) {
    return;
  }

  nsCOMPtr<nsISimpleEnumerator> enumerator;
  nsresult rv = catMan->EnumerateCategory(aCategory,
                                          getter_AddRefs(enumerator));
  if (NS_FAILED(rv)) {
    return;
  }

  for (auto& categoryEntry : SimpleEnumerator<nsICategoryEntry>(enumerator)) {
    nsAutoCString entryValue;
    categoryEntry->GetValue(entryValue);

    if (nsCOMPtr<nsISupports> service = do_GetService(entryValue.get())) {
      nsAutoCString entryName;
      categoryEntry->GetEntry(entryName);

      mHash.Put(entryName, service);
    }
  }

  // Now, listen for changes
  nsCOMPtr<nsIObserverService> serv =
    mozilla::services::GetObserverService();
  if (serv) {
    serv->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
    serv->AddObserver(this, NS_XPCOM_CATEGORY_ENTRY_ADDED_OBSERVER_ID, false);
    serv->AddObserver(this, NS_XPCOM_CATEGORY_ENTRY_REMOVED_OBSERVER_ID, false);
    serv->AddObserver(this, NS_XPCOM_CATEGORY_CLEARED_OBSERVER_ID, false);
  }
}

nsCategoryObserver::~nsCategoryObserver() = default;

NS_IMPL_ISUPPORTS(nsCategoryObserver, nsIObserver)

void
nsCategoryObserver::ListenerDied()
{
  MOZ_ASSERT(NS_IsMainThread());
  RemoveObservers();
  mCallback = nullptr;
  mClosure = nullptr;
}

void
nsCategoryObserver::SetListener(void(aCallback)(void*), void* aClosure)
{
  MOZ_ASSERT(NS_IsMainThread());
  mCallback = aCallback;
  mClosure = aClosure;
}

void
nsCategoryObserver::RemoveObservers()
{
  MOZ_ASSERT(NS_IsMainThread());

  if (mObserversRemoved) {
    return;
  }

  if (mCallback) {
    mCallback(mClosure);
  }

  mObserversRemoved = true;
  nsCOMPtr<nsIObserverService> obsSvc =
    mozilla::services::GetObserverService();
  if (obsSvc) {
    obsSvc->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
    obsSvc->RemoveObserver(this, NS_XPCOM_CATEGORY_ENTRY_ADDED_OBSERVER_ID);
    obsSvc->RemoveObserver(this, NS_XPCOM_CATEGORY_ENTRY_REMOVED_OBSERVER_ID);
    obsSvc->RemoveObserver(this, NS_XPCOM_CATEGORY_CLEARED_OBSERVER_ID);
  }
}

NS_IMETHODIMP
nsCategoryObserver::Observe(nsISupports* aSubject, const char* aTopic,
                            const char16_t* aData)
{
  MOZ_ASSERT(NS_IsMainThread());

  if (strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
    mHash.Clear();
    RemoveObservers();

    return NS_OK;
  }

  if (!aData ||
      !nsDependentString(aData).Equals(NS_ConvertASCIItoUTF16(mCategory))) {
    return NS_OK;
  }

  nsAutoCString str;
  nsCOMPtr<nsISupportsCString> strWrapper(do_QueryInterface(aSubject));
  if (strWrapper) {
    strWrapper->GetData(str);
  }

  if (strcmp(aTopic, NS_XPCOM_CATEGORY_ENTRY_ADDED_OBSERVER_ID) == 0) {
    // We may get an add notification even when we already have an entry. This
    // is due to the notification happening asynchronously, so if the entry gets
    // added and an nsCategoryObserver gets instantiated before events get
    // processed, we'd get the notification for an existing entry.
    // Do nothing in that case.
    if (mHash.GetWeak(str)) {
      return NS_OK;
    }

    nsCOMPtr<nsICategoryManager> catMan =
      do_GetService(NS_CATEGORYMANAGER_CONTRACTID);
    if (!catMan) {
      return NS_OK;
    }

    nsCString entryValue;
    catMan->GetCategoryEntry(mCategory, str, entryValue);

    nsCOMPtr<nsISupports> service = do_GetService(entryValue.get());

    if (service) {
      mHash.Put(str, service);
    }
    if (mCallback) {
      mCallback(mClosure);
    }
  } else if (strcmp(aTopic, NS_XPCOM_CATEGORY_ENTRY_REMOVED_OBSERVER_ID) == 0) {
    mHash.Remove(str);
    if (mCallback) {
      mCallback(mClosure);
    }
  } else if (strcmp(aTopic, NS_XPCOM_CATEGORY_CLEARED_OBSERVER_ID) == 0) {
    mHash.Clear();
    if (mCallback) {
      mCallback(mClosure);
    }
  }
  return NS_OK;
}