1 files changed, 78 insertions, 0 deletions
diff --git a/chromium/net/quic/congestion_control/available_channel_estimator.cc b/chromium/net/quic/congestion_control/available_channel_estimator.cc
new file mode 100644
index 00000000000..ef091abce43
--- /dev/null
+++ b/chromium/net/quic/congestion_control/available_channel_estimator.cc
@@ -0,0 +1,78 @@
+// Copyright (c) 2013 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/quic/congestion_control/available_channel_estimator.h"
+
+static const int kNumberOfSamples = 9;
+
+namespace net {
+
+AvailableChannelEstimator::AvailableChannelEstimator(
+    QuicPacketSequenceNumber sequence_number,
+    QuicTime first_send_time,
+    QuicTime first_receive_time)
+    : first_sequence_number_(sequence_number),
+      first_send_time_(first_send_time),
+      first_receive_time_(first_receive_time),
+      last_incorporated_sequence_number_(sequence_number),
+      last_time_sent_(QuicTime::Zero()),
+      last_receive_time_(QuicTime::Zero()),
+      number_of_sequence_numbers_(0),
+      received_bytes_(0) {
+}
+
+void AvailableChannelEstimator::OnIncomingFeedback(
+    QuicPacketSequenceNumber sequence_number,
+    QuicByteCount packet_size,
+    QuicTime sent_time,
+    QuicTime receive_time) {
+  if (sequence_number <= first_sequence_number_) {
+    // Ignore pre-probe feedback.
+    return;
+  }
+  if (sequence_number <= last_incorporated_sequence_number_) {
+    // Ignore old feedback; will remove duplicates.
+    return;
+  }
+  // Remember the highest received sequence number.
+  last_incorporated_sequence_number_ = sequence_number;
+  if (number_of_sequence_numbers_ < kNumberOfSamples) {
+    // We don't care how many sequence numbers we have after we pass
+    // kNumberOfSamples.
+    number_of_sequence_numbers_++;
+  }
+  last_receive_time_ = receive_time;
+  last_time_sent_ = sent_time;
+  received_bytes_ += packet_size;
+  // TODO(pwestin): the variance here should give us information about accuracy.
+}
+
+AvailableChannelEstimateState
+    AvailableChannelEstimator::GetAvailableChannelEstimate(
+        QuicBandwidth* bandwidth) const {
+  if (number_of_sequence_numbers_ < 2) {
+    return kAvailableChannelEstimateUnknown;
+  }
+  QuicTime::Delta send_delta = last_time_sent_.Subtract(first_send_time_);
+  QuicTime::Delta receive_delta =
+      last_receive_time_.Subtract(first_receive_time_);
+
+  // TODO(pwestin): room for improvement here. Keeping it simple for now.
+  *bandwidth = QuicBandwidth::FromBytesAndTimeDelta(received_bytes_,
+                                                    receive_delta);
+
+  QuicTime::Delta diff = receive_delta.Subtract(send_delta);
+  QuicTime::Delta ten_percent_of_send_time =
+      QuicTime::Delta::FromMicroseconds(send_delta.ToMicroseconds() / 10);
+
+  if (diff < ten_percent_of_send_time) {
+    return kAvailableChannelEstimateSenderLimited;
+  }
+  if (number_of_sequence_numbers_ < kNumberOfSamples) {
+    return kAvailableChannelEstimateUncertain;
+  }
+  return kAvailableChannelEstimateGood;
+}
+
+}  // namespace net