The Tor Browser: content/media/MediaShutdownManager.cpp@44a2da4a2ab2

Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

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

     3 /* This Source Code Form is subject to the terms of the Mozilla Public

     4  * License, v. 2.0. If a copy of the MPL was not distributed with this

     5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     7 #include "MediaShutdownManager.h"

     8 #include "nsContentUtils.h"

     9 #include "mozilla/StaticPtr.h"

    10 #include "MediaDecoder.h"

    11 #include "SharedThreadPool.h"

    12 #include "prlog.h"

    14 namespace mozilla {

    16 #ifdef PR_LOGGING

    17 extern PRLogModuleInfo* gMediaDecoderLog;

    18 #define DECODER_LOG(type, msg) PR_LOG(gMediaDecoderLog, type, msg)

    19 #else

    20 #define DECODER_LOG(type, msg)

    21 #endif

    23 NS_IMPL_ISUPPORTS(MediaShutdownManager, nsIObserver)

    25 MediaShutdownManager::MediaShutdownManager()

    26   : mIsObservingShutdown(false),

    27     mIsDoingXPCOMShutDown(false)

    28 {

    29   MOZ_ASSERT(NS_IsMainThread());

    30   MOZ_COUNT_CTOR(MediaShutdownManager);

    31 }

    33 MediaShutdownManager::~MediaShutdownManager()

    34 {

    35   MOZ_ASSERT(NS_IsMainThread());

    36   MOZ_COUNT_DTOR(MediaShutdownManager);

    37 }

    39 // Note that we don't use ClearOnShutdown() on this StaticRefPtr, as that

    40 // may interfere with our shutdown listener.

    41 StaticRefPtr<MediaShutdownManager> MediaShutdownManager::sInstance;

    43 MediaShutdownManager&

    44 MediaShutdownManager::Instance()

    45 {

    46   MOZ_ASSERT(NS_IsMainThread());

    47   if (!sInstance) {

    48     sInstance = new MediaShutdownManager();

    49   }

    50   return *sInstance;

    51 }

    53 void

    54 MediaShutdownManager::EnsureCorrectShutdownObserverState()

    55 {

    56   MOZ_ASSERT(!mIsDoingXPCOMShutDown);

    57   bool needShutdownObserver = mDecoders.Count() > 0;

    58   if (needShutdownObserver != mIsObservingShutdown) {

    59     mIsObservingShutdown = needShutdownObserver;

    60     if (mIsObservingShutdown) {

    61       nsContentUtils::RegisterShutdownObserver(this);

    62     } else {

    63       nsContentUtils::UnregisterShutdownObserver(this);

    64       // Clear our singleton reference. This will probably delete

    65       // this instance, so don't deref |this| clearing sInstance.

    66       sInstance = nullptr;

    67     }

    68   }

    69 }

    71 void

    72 MediaShutdownManager::Register(MediaDecoder* aDecoder)

    73 {

    74   MOZ_ASSERT(NS_IsMainThread());

    75   // Don't call Register() after you've Unregistered() all the decoders,

    76   // that's not going to work.

    77   MOZ_ASSERT(!mDecoders.Contains(aDecoder));

    78   mDecoders.PutEntry(aDecoder);

    79   MOZ_ASSERT(mDecoders.Contains(aDecoder));

    80   MOZ_ASSERT(mDecoders.Count() > 0);

    81   EnsureCorrectShutdownObserverState();

    82 }

    84 void

    85 MediaShutdownManager::Unregister(MediaDecoder* aDecoder)

    86 {

    87   MOZ_ASSERT(NS_IsMainThread());

    88   MOZ_ASSERT(mDecoders.Contains(aDecoder));

    89   if (!mIsDoingXPCOMShutDown) {

    90     mDecoders.RemoveEntry(aDecoder);

    91     EnsureCorrectShutdownObserverState();

    92   }

    93 }

    95 NS_IMETHODIMP

    96 MediaShutdownManager::Observe(nsISupports *aSubjet,

    97                               const char *aTopic,

    98                               const char16_t *someData)

    99 {

   100   MOZ_ASSERT(NS_IsMainThread());

   101   if (strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {

   102     Shutdown();

   103   }

   104   return NS_OK;

   105 }

   107 static PLDHashOperator

   108 ShutdownMediaDecoder(nsRefPtrHashKey<MediaDecoder>* aEntry, void*)

   109 {

   110   aEntry->GetKey()->Shutdown();

   111   return PL_DHASH_REMOVE;

   112 }

   114 void

   115 MediaShutdownManager::Shutdown()

   116 {

   117   MOZ_ASSERT(NS_IsMainThread());

   118   MOZ_ASSERT(sInstance);

   120   DECODER_LOG(PR_LOG_DEBUG, ("MediaShutdownManager::Shutdown() start..."));

   122   // Mark that we're shutting down, so that Unregister(*) calls don't remove

   123   // hashtable entries. If Unregsiter(*) was to remove from the hash table,

   124   // the iterations over the hashtables below would be disrupted.

   125   mIsDoingXPCOMShutDown = true;

   127   // Iterate over the decoders and shut them down, and remove them from the

   128   // hashtable.

   129   mDecoders.EnumerateEntries(ShutdownMediaDecoder, nullptr);

   131   // Ensure all media shared thread pools are shutdown. This joins with all

   132   // threads in the state machine thread pool, the decoder thread pool, and

   133   // any others.

   134   SharedThreadPool::SpinUntilShutdown();

   136   // Remove the MediaShutdownManager instance from the shutdown observer

   137   // list.

   138   nsContentUtils::UnregisterShutdownObserver(this);

   140   // Clear the singleton instance. The only remaining reference should be the

   141   // reference that the observer service used to call us with. The

   142   // MediaShutdownManager will be deleted once the observer service cleans

   143   // up after it finishes its notifications.

   144   sInstance = nullptr;

   146   DECODER_LOG(PR_LOG_DEBUG, ("MediaShutdownManager::Shutdown() end."));

   147 }

   149 } // namespace mozilla

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