Implementation of network level throttler.

net/base/network_stream_throttler.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/base/network_stream_throttler.h"
+
+namespace net {
+
+namespace {
+
+class NetworkStreamThrottlerImpl : public NetworkStreamThrottler {
+ public:
+  class ThrottleImpl : public NetworkStreamThrottler::Throttle {
+   public:
+    ~ThrottleImpl() override;
+
+    // Throttle
+    bool IsThrottled() const override { return throttled_; }
+    void SetPriority(RequestPriority priority) override;
+
+   private:
+    friend NetworkStreamThrottlerImpl;
+
+    using QueuePointer = PriorityQueue<ThrottleImpl*>::Pointer;
+
+    // Caller must arrange that |*delegate| and |*throttler| outlives
+    // the ThrottleImpl class.
+    ThrottleImpl(bool throttled,
+                 RequestPriority priority,
+                 Delegate* delegate,
+                 NetworkStreamThrottlerImpl* throttler);
+
+    QueuePointer queue_pointer() const { return queue_pointer_; }
+    void set_queue_pointer(const QueuePointer& pointer) {
+      queue_pointer_ = pointer;
+    }
+
+    // Note that this call calls the delegate, and hence
+    // may result in re-entrant calls into the throtter or
+    // ThrottleImpl.  The throttler should not rely on
+    // any state other than its own existence being persistent
+    // across this call.
+    void NotifyUnthrottled();
+
+    bool throttled_;
+    Delegate* const delegate_;
+    PriorityQueue<ThrottleImpl*>::Pointer queue_pointer_;
+
+    NetworkStreamThrottlerImpl* const throttler_;
+
+    DISALLOW_COPY_AND_ASSIGN(ThrottleImpl);
+  };
+
+  NetworkStreamThrottlerImpl();
+  ~NetworkStreamThrottlerImpl() override;
+
+  std::unique_ptr<Throttle> CreateThrottle(Delegate* delegate,
+                                           RequestPriority priority,
+                                           bool ignore_limits) override;
+
+ private:
+  void OnStreamPriorityChanged(ThrottleImpl* throttle,
+                               RequestPriority new_priority);
+  void OnStreamDestroyed(ThrottleImpl* throttle);
+
+  PriorityQueue<ThrottleImpl*> priority_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(NetworkStreamThrottlerImpl);
+};
+
+// Currently this is a null implementation that does no throttling;
+// all entries are created in the unthrottled state, and no throttle state
+// change notifications are transmitted.
+
+NetworkStreamThrottlerImpl::ThrottleImpl::~ThrottleImpl() {
+  if (throttler_)
+    throttler_->OnStreamDestroyed(this);
+}
+
+void NetworkStreamThrottlerImpl::ThrottleImpl::SetPriority(
+    RequestPriority priority) {
+  if (throttler_)
+    throttler_->OnStreamPriorityChanged(this, priority);
+}
+
+NetworkStreamThrottlerImpl::ThrottleImpl::ThrottleImpl(
+    bool throttled,
+    RequestPriority priority,
+    NetworkStreamThrottler::Delegate* delegate,
+    NetworkStreamThrottlerImpl* throttler)
+    : throttled_(throttled), delegate_(delegate), throttler_(throttler) {}
+
+void NetworkStreamThrottlerImpl::ThrottleImpl::NotifyUnthrottled() {
+  throttled_ = false;
+  // TODO(rdsmith): Figure out if/how this needs to be made asynchronous.
+  if (delegate_)
+    delegate_->OnThrottleStateChanged();
+}
+
+NetworkStreamThrottlerImpl::NetworkStreamThrottlerImpl()
+    : priority_queue_(MAXIMUM_PRIORITY + 1) {}
+
+NetworkStreamThrottlerImpl::~NetworkStreamThrottlerImpl() {}
+
+std::unique_ptr<NetworkStreamThrottler::Throttle>
+NetworkStreamThrottlerImpl::CreateThrottle(
+    NetworkStreamThrottler::Delegate* delegate,
+    RequestPriority priority,
+    bool ignore_limits) {
+  std::unique_ptr<NetworkStreamThrottlerImpl::ThrottleImpl> stream(
+      new ThrottleImpl(false, priority, delegate, this));
+
+  stream->set_queue_pointer(priority_queue_.Insert(stream.get(), priority));
+
+  return std::move(stream);
+}
+
+void NetworkStreamThrottlerImpl::OnStreamPriorityChanged(
+    NetworkStreamThrottlerImpl::ThrottleImpl* stream,
+    RequestPriority new_priority) {
+  priority_queue_.Erase(stream->queue_pointer());
+  stream->set_queue_pointer(priority_queue_.Insert(stream, new_priority));
+}
+
+void NetworkStreamThrottlerImpl::OnStreamDestroyed(ThrottleImpl* stream) {
+  priority_queue_.Erase(stream->queue_pointer());
+}
+
+}  // namespace
+
+// static
+std::unique_ptr<NetworkStreamThrottler>
+NetworkStreamThrottler::CreateThrottler() {
+  return std::unique_ptr<NetworkStreamThrottler>(
+      new NetworkStreamThrottlerImpl);
+}
+
+}  // namespace net