tor-browser

The Tor Browser
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MemoryPressureObserver.cpp (2275B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      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/. */
      6 
      7 #include "MemoryPressureObserver.h"
      8 
      9 #include "mozilla/Services.h"
     10 #include "nsCOMPtr.h"
     11 #include "nsDependentString.h"
     12 #include "nsIObserverService.h"
     13 #include "nsLiteralString.h"
     14 
     15 namespace mozilla {
     16 namespace layers {
     17 
     18 MemoryPressureObserver::MemoryPressureObserver(
     19    MemoryPressureListener* aListener)
     20    : mListener(aListener) {}
     21 
     22 MemoryPressureObserver::~MemoryPressureObserver() {
     23  // If this assertion is hit we probably forgot to unregister the observer.
     24  MOZ_ASSERT(!mListener);
     25 }
     26 
     27 already_AddRefed<MemoryPressureObserver> MemoryPressureObserver::Create(
     28    MemoryPressureListener* aListener) {
     29  nsCOMPtr<nsIObserverService> service = services::GetObserverService();
     30 
     31  if (!service) {
     32    return nullptr;
     33  }
     34 
     35  RefPtr<MemoryPressureObserver> observer =
     36      new MemoryPressureObserver(aListener);
     37 
     38  bool useWeakRef = false;
     39  service->AddObserver(observer, "memory-pressure", useWeakRef);
     40 
     41  return observer.forget();
     42 }
     43 
     44 void MemoryPressureObserver::Unregister() {
     45  if (!mListener) {
     46    return;
     47  }
     48 
     49  nsCOMPtr<nsIObserverService> service = services::GetObserverService();
     50  if (service) {
     51    service->RemoveObserver(this, "memory-pressure");
     52  }
     53 
     54  mListener = nullptr;
     55 }
     56 
     57 NS_IMETHODIMP
     58 MemoryPressureObserver::Observe(nsISupports* aSubject, const char* aTopic,
     59                                const char16_t* aData) {
     60  if (mListener && strcmp(aTopic, "memory-pressure") == 0) {
     61    MemoryPressureReason reason = MemoryPressureReason::LOW_MEMORY;
     62    auto reason_string = nsDependentString(aData);
     63    if (StringBeginsWith(reason_string, u"low-memory-ongoing"_ns)) {
     64      reason = MemoryPressureReason::LOW_MEMORY_ONGOING;
     65    } else if (StringBeginsWith(reason_string, u"heap-minimize"_ns)) {
     66      reason = MemoryPressureReason::HEAP_MINIMIZE;
     67    }
     68    mListener->OnMemoryPressure(reason);
     69  }
     70 
     71  return NS_OK;
     72 }
     73 
     74 NS_IMPL_ISUPPORTS(MemoryPressureObserver, nsIObserver)
     75 
     76 }  // namespace layers
     77 }  // namespace mozilla