Switch to PacketNumberQueue interval iteration and avoid allocations in new ACK frame generation. G…

net/quic/quic_sent_entropy_manager.cc

 // Copyright 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/quic_sent_entropy_manager.h"
 
 #include "base/logging.h"
 #include "net/base/linked_hash_map.h"
+#include "net/quic/quic_flags.h"
 
 using std::make_pair;
 using std::max;
 using std::min;
 
 namespace net {
 
 QuicSentEntropyManager::QuicSentEntropyManager() : map_offset_(1) {}
 
 QuicSentEntropyManager::~QuicSentEntropyManager() {}
@@ skipping 54 matching lines @@
   }
   if (!missing_packets.Empty() &&
       missing_packets.Min() < GetSmallestPacketWithEntropy()) {
     return false;
   }
   // First the entropy for largest_observed packet number should be updated.
   UpdateCumulativeEntropy(largest_observed, &last_valid_entropy_);
 
   // Now XOR out all the missing entropies.
   QuicPacketEntropyHash expected_entropy_hash = last_valid_entropy_.entropy;
-  for (QuicPacketNumber packet : missing_packets) {
-    expected_entropy_hash ^= GetPacketEntropy(packet);
+  if (FLAGS_quic_use_packet_number_queue_intervals) {
+    for (auto itr = missing_packets.begin_intervals();
+         itr != missing_packets.end_intervals(); ++itr) {
+      const auto& interval = *itr;
+      for (QuicPacketNumber packet_number = interval.min();
+           packet_number < interval.max(); ++packet_number) {
+        expected_entropy_hash ^= GetPacketEntropy(packet_number);
+      }
+    }
+  } else {
+    for (QuicPacketNumber packet : missing_packets) {
+      expected_entropy_hash ^= GetPacketEntropy(packet);
+    }
   }
   DLOG_IF(WARNING, entropy_hash != expected_entropy_hash)
       << "Invalid entropy hash: " << static_cast<int>(entropy_hash)
       << " expected entropy hash: " << static_cast<int>(expected_entropy_hash);
   return entropy_hash == expected_entropy_hash;
 }
 
 void QuicSentEntropyManager::ClearEntropyBefore(
     QuicPacketNumber packet_number) {
   // Don't discard entropy before updating the cumulative entropy used to
   // calculate EntropyHash and IsValidEntropy.
   if (last_cumulative_entropy_.packet_number < packet_number) {
     UpdateCumulativeEntropy(packet_number, &last_cumulative_entropy_);
   }
   if (last_valid_entropy_.packet_number < packet_number) {
     UpdateCumulativeEntropy(packet_number, &last_valid_entropy_);
   }
   while (map_offset_ < packet_number) {
     packets_entropy_.pop_front();
     ++map_offset_;
   }
   DVLOG(2) << "Cleared entropy before: " << packet_number;
 }
 
 }  // namespace net