Implementation of network level throttler.

net/base/network_stream_throttler.h

+// 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.
+
+#ifndef NET_BASE_NETWORK_STREAM_THROTTLER_H_
+#define NET_BASE_NETWORK_STREAM_THROTTLER_H_
+
+#include "base/memory/weak_ptr.h"
+#include "net/base/priority_queue.h"
+#include "net/base/request_priority.h"
+
+namespace net {
+
+class NetworkStreamThrottler {
+ public:
+  // Abstract base class other classes can inherit from to get
+  // notifications from throttle state changes.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Called whenever the throttle state of this stream has changed.
+    // The new state can be determined through Throttle::throttled().
+    virtual void OnThrottleStateChanged() = 0;
+  };
+
+  // Concrete class owned by external stream representations that
+  // routes notifications.
+  class Throttle {
+   public:
+    ~Throttle();
+
+    bool throttled() { return throttled_; }
+
+    // The caller must make sure that |*delegate| outlives this
+    // object.
+    void set_delegate(Delegate* delegate) { delegate_ = delegate; }
+
+    // Note that this may result in a possibly reentrant call to
+    // |Delegate::OnThrottleStateChanged|.
+    void SetPriority(RequestPriority priority);
+
+   private:
+    friend NetworkStreamThrottler;
+
+    using QueuePointer = PriorityQueue<Throttle*>::Pointer;
+
+    Throttle(bool throttled,
+             RequestPriority priority,
+             base::WeakPtr<NetworkStreamThrottler> throttler);
+
+    void NotifyThrottleStateChanged(bool new_throttle_state);
+    QueuePointer queue_pointer() { return queue_pointer_; }
+    void set_queue_pointer(const QueuePointer& pointer) {
+      queue_pointer_ = pointer;
+    }
+
+    bool throttled_;
+    RequestPriority priority_;
+    Delegate* delegate_;
+    PriorityQueue<Throttle*>::Pointer queue_pointer_;
+
+    base::WeakPtr<NetworkStreamThrottler> throttler_;
+
+    DISALLOW_COPY_AND_ASSIGN(Throttle);
+  };
+
+  NetworkStreamThrottler();
+  ~NetworkStreamThrottler();
+
+  scoped_ptr<Throttle> CreateThrottle(RequestPriority priority);
+
+ private:
+  void OnStreamPriorityChanged(Throttle* throttle,
+                               RequestPriority old_priority,
+                               RequestPriority new_priority);
+  void OnStreamDestroyed(Throttle* throttle);
+
+  PriorityQueue<Throttle*> priority_queue_;
+  base::WeakPtrFactory<NetworkStreamThrottler> factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(NetworkStreamThrottler);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_NETWORK_STREAM_THROTTLER_H_