Implement a traffic policer in the simulator

net/quic/test_tools/simulator/traffic_policer.h

Index: net/quic/test_tools/simulator/traffic_policer.h
diff --git a/net/quic/test_tools/simulator/traffic_policer.h b/net/quic/test_tools/simulator/traffic_policer.h
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+// Copyright (c) 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_QUIC_TEST_TOOLS_SIMULATOR_TRAFFIC_POLICER_H_
+#define NET_QUIC_TEST_TOOLS_SIMULATOR_TRAFFIC_POLICER_H_
+
+#include <unordered_map>
+
+#include "net/quic/test_tools/simulator/port.h"
+
+namespace net {
+namespace simulator {
+
+// Traffic policer uses a token bucket to limit the bandwidth of the traffic
+// passing through.  It wraps around an input port and exposes an output port.
+// Only the traffic from input to the output is policed, so in case when
+// bidirectional policing is desired, two policers have to be used.  The flows
+// are hashed by the source only.
+class TrafficPolicer : public Actor, public ConstrainedPortInterface {
+ public:
+  TrafficPolicer(Simulator* simulator,
+                 std::string name,
+                 QuicByteCount initial_bucket_size,
+                 QuicByteCount max_bucket_size,
+                 QuicBandwidth target_bandwidth,
+                 Endpoint* input);
+  ~TrafficPolicer() override;
+
+  Endpoint* input() { return input_; }
+  Endpoint* output() { return &output_; }
+
+  void AcceptPacket(std::unique_ptr<Packet> packet) override;
+  QuicTime::Delta TimeUntilAvailable() override;
+
+  void Act() override;
+
+ private:
+  class Output : public Endpoint {
+   public:
+    explicit Output(TrafficPolicer* policer);
+    ~Output() override;
+
+    UnconstrainedPortInterface* GetRxPort() override;
+    void SetTxPort(ConstrainedPortInterface* port) override;
+    void Act() override;
+
+   private:
+    TrafficPolicer* policer_;
+  };
+
+  // Refill the token buckets with all the tokens that have been granted since
+  // |last_refill_time_|.
+  void Refill();
+
+  QuicByteCount initial_bucket_size_;
+  QuicByteCount max_bucket_size_;
+  QuicBandwidth target_bandwidth_;
+
+  // The time at which the token buckets were last refilled.
+  QuicTime last_refill_time_;
+
+  ConstrainedPortInterface* output_tx_port_;
+
+  Endpoint* input_;
+  Output output_;
+
+  // Maps each destination to the number of tokens it has left.
+  std::unordered_map<std::string, QuicByteCount> token_buckets_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrafficPolicer);
+};
+
+}  // namespace simulator
+}  // namespace net
+
+#endif  // NET_QUIC_TEST_TOOLS_SIMULATOR_TRAFFIC_POLICER_H_