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1 // Copyright 2015 The Weave Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "src/states/state_change_queue.h"
6 
7 #include <base/logging.h>
8 
9 namespace weave {
10 
StateChangeQueue(size_t max_queue_size)11 StateChangeQueue::StateChangeQueue(size_t max_queue_size)
12     : max_queue_size_(max_queue_size) {
13   CHECK_GT(max_queue_size_, 0U) << "Max queue size must not be zero";
14 }
15 
NotifyPropertiesUpdated(base::Time timestamp,const base::DictionaryValue & changed_properties)16 bool StateChangeQueue::NotifyPropertiesUpdated(
17     base::Time timestamp,
18     const base::DictionaryValue& changed_properties) {
19   auto& stored_changes = state_changes_[timestamp];
20   // Merge the old property set.
21   if (stored_changes)
22     stored_changes->MergeDictionary(&changed_properties);
23   else
24     stored_changes.reset(changed_properties.DeepCopy());
25 
26   while (state_changes_.size() > max_queue_size_) {
27     // Queue is full.
28     // Merge the two oldest records into one. The merge strategy is:
29     //  - Move non-existent properties from element [old] to [new].
30     //  - If both [old] and [new] specify the same property,
31     //    keep the value of [new].
32     //  - Keep the timestamp of [new].
33     auto element_old = state_changes_.begin();
34     auto element_new = std::next(element_old);
35     // This will skip elements that exist in both [old] and [new].
36     element_old->second->MergeDictionary(element_new->second.get());
37     std::swap(element_old->second, element_new->second);
38     state_changes_.erase(element_old);
39   }
40   return true;
41 }
42 
GetAndClearRecordedStateChanges()43 std::vector<StateChange> StateChangeQueue::GetAndClearRecordedStateChanges() {
44   std::vector<StateChange> changes;
45   changes.reserve(state_changes_.size());
46   for (auto& pair : state_changes_) {
47     changes.push_back(StateChange{pair.first, std::move(pair.second)});
48   }
49   state_changes_.clear();
50   return changes;
51 }
52 
53 }  // namespace weave
54