Reduce the complexity of WebSocketThrottle's wakeup code

net/websockets/websocket_throttle.cc

 // Copyright (c) 2012 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/websockets/websocket_throttle.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
+#include <utility>
 
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "net/base/io_buffer.h"
 #include "net/socket_stream/socket_stream.h"
 #include "net/websockets/websocket_job.h"
 
 namespace net {
 
+namespace {
+
+const size_t kMaxWebSocketJobsThrottled = 1024;
+
+}  // namespace
+
 WebSocketThrottle::WebSocketThrottle() {
 }
 
 WebSocketThrottle::~WebSocketThrottle() {
   DCHECK(queue_.empty());
   DCHECK(addr_map_.empty());
 }
 
 // static
 WebSocketThrottle* WebSocketThrottle::GetInstance() {
   return Singleton<WebSocketThrottle>::get();
 }
 
-void WebSocketThrottle::PutInQueue(WebSocketJob* job) {
+bool WebSocketThrottle::PutInQueue(WebSocketJob* job) {
+  if (queue_.size() >= kMaxWebSocketJobsThrottled)
+    return false;
+
   queue_.push_back(job);
   const AddressList& address_list = job->address_list();
   std::set<IPEndPoint> address_set;
   for (AddressList::const_iterator addr_iter = address_list.begin();
        addr_iter != address_list.end();
        ++addr_iter) {
     const IPEndPoint& address = *addr_iter;
     // If |address| is already processed, don't do it again.
     if (!address_set.insert(address).second)
       continue;
 
     ConnectingAddressMap::iterator iter = addr_map_.find(address);
     if (iter == addr_map_.end()) {
-      ConnectingQueue* queue = new ConnectingQueue();
-      queue->push_back(job);
-      addr_map_[address] = queue;
+      ConnectingAddressMap::iterator new_queue =
+          addr_map_.insert(make_pair(address, ConnectingQueue())).first;
+      new_queue->second.push_back(job);
     } else {
-      iter->second->push_back(job);
+      DCHECK(!iter->second.empty());
+      iter->second.push_back(job);
       job->SetWaiting();
       DVLOG(1) << "Waiting on " << address.ToString();
     }
   }
+
+  return true;
 }
 
 void WebSocketThrottle::RemoveFromQueue(WebSocketJob* job) {
   ConnectingQueue::iterator queue_iter =
       std::find(queue_.begin(), queue_.end(), job);
   if (queue_iter == queue_.end())
     return;
   queue_.erase(queue_iter);
-  const AddressList& address_list = job->address_list();
+
+  std::set<WebSocketJob*> wakeup_candidates;
+
+  const AddressList& resolved_address_list = job->address_list();
   std::set<IPEndPoint> address_set;
-  for (AddressList::const_iterator addr_iter = address_list.begin();
-       addr_iter != address_list.end();
+  for (AddressList::const_iterator addr_iter = resolved_address_list.begin();
+       addr_iter != resolved_address_list.end();
        ++addr_iter) {
     const IPEndPoint& address = *addr_iter;
     // If |address| is already processed, don't do it again.
     if (!address_set.insert(address).second)
       continue;
 
     ConnectingAddressMap::iterator map_iter = addr_map_.find(address);
     DCHECK(map_iter != addr_map_.end());
 
-    ConnectingQueue* queue = map_iter->second;
-    // Job may not be front of queue if the socket is closed while waiting.
-    ConnectingQueue::iterator address_queue_iter =
-        std::find(queue->begin(), queue->end(), job);
-    if (address_queue_iter != queue->end())
-      queue->erase(address_queue_iter);
-    if (queue->empty()) {
-      delete queue;
+    ConnectingQueue& per_address_queue = map_iter->second;
+    DCHECK(!per_address_queue.empty());
+    // Job may not be front of the queue if the socket is closed while waiting.
+    ConnectingQueue::iterator per_address_queue_iter =
+        std::find(per_address_queue.begin(), per_address_queue.end(), job);
+    bool was_front = false;
+    if (per_address_queue_iter != per_address_queue.end()) {
+      was_front = (per_address_queue_iter == per_address_queue.begin());
+      per_address_queue.erase(per_address_queue_iter);
+    }
+    if (per_address_queue.empty()) {
       addr_map_.erase(map_iter);
+    } else if (was_front) {
+      // The new front is a wake-up candidate.
+      wakeup_candidates.insert(per_address_queue.front());
     }
   }
+
+  WakeupSocketIfNecessary(wakeup_candidates);
 }
 
-void WebSocketThrottle::WakeupSocketIfNecessary() {
-  for (ConnectingQueue::iterator iter = queue_.begin();
-       iter != queue_.end();
+void WebSocketThrottle::WakeupSocketIfNecessary(
+    const std::set<WebSocketJob*>& wakeup_candidates) {
+  for (std::set<WebSocketJob*>::const_iterator iter = wakeup_candidates.begin();
+       iter != wakeup_candidates.end();
        ++iter) {
     WebSocketJob* job = *iter;
     if (!job->IsWaiting())
       continue;
 
     bool should_wakeup = true;
-    const AddressList& address_list = job->address_list();
-    for (AddressList::const_iterator addr_iter = address_list.begin();
-         addr_iter != address_list.end();
+    const AddressList& resolved_address_list = job->address_list();
+    for (AddressList::const_iterator addr_iter = resolved_address_list.begin();
+         addr_iter != resolved_address_list.end();
          ++addr_iter) {
       const IPEndPoint& address = *addr_iter;
       ConnectingAddressMap::iterator map_iter = addr_map_.find(address);
       DCHECK(map_iter != addr_map_.end());
-      ConnectingQueue* queue = map_iter->second;
-      if (job != queue->front()) {
+      const ConnectingQueue& per_address_queue = map_iter->second;
+      if (job != per_address_queue.front()) {
         should_wakeup = false;
         break;
       }
     }
     if (should_wakeup)
       job->Wakeup();
   }
 }
 
 }  // namespace net