| OLD | NEW |
|---|
| (Empty) |
| 1 // Copyright 2013 The Chromium 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 #ifndef CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ | |
| 6 #define CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ | |
| 7 | |
| 8 #include <map> | |
| 9 | |
| 10 #include "base/bind.h" | |
| 11 #include "base/synchronization/lock.h" | |
| 12 #include "content/public/browser/browser_thread.h" | |
| 13 #include "content/public/browser/render_process_host.h" | |
| 14 #include "content/public/browser/render_process_host_observer.h" | |
| 15 | |
| 16 namespace content { | |
| 17 | |
| 18 // RendererDataMemoizingStore is a thread-safe container that retains reference | |
| 19 // counted objects that are associated with one or more render processes. | |
| 20 // Objects are identified by an int and only a single reference to a given | |
| 21 // object is retained. RendererDataMemoizingStore watches for render process | |
| 22 // termination and releases objects that are no longer associated with any | |
| 23 // render process. | |
| 24 // | |
| 25 // TODO(jcampan): Rather than watching for render process termination, we should | |
| 26 // instead be listening to events such as resource cached/ | |
| 27 // removed from cache, and remove the items when we know they | |
| 28 // are not used anymore. | |
| 29 template <typename T> | |
| 30 class RendererDataMemoizingStore : public RenderProcessHostObserver { | |
| 31 public: | |
| 32 RendererDataMemoizingStore() : next_item_id_(1) { | |
| 33 } | |
| 34 | |
| 35 ~RendererDataMemoizingStore() { | |
| 36 DCHECK_EQ(0U, id_to_item_.size()) << "Failed to outlive render processes"; | |
| 37 } | |
| 38 | |
| 39 // Store adds |item| to this collection, associates it with the given render | |
| 40 // process id and returns an opaque identifier for it. If |item| is already | |
| 41 // known, the same identifier will be returned. | |
| 42 int Store(T* item, int process_id) { | |
| 43 DCHECK(item); | |
| 44 base::AutoLock auto_lock(lock_); | |
| 45 | |
| 46 int item_id; | |
| 47 | |
| 48 // Do we already know this item? | |
| 49 typename ReverseItemMap::iterator item_iter = item_to_id_.find(item); | |
| 50 if (item_iter == item_to_id_.end()) { | |
| 51 item_id = next_item_id_++; | |
| 52 // We use 0 as an invalid item_id value. In the unlikely event that | |
| 53 // next_item_id_ wraps around, we reset it to 1. | |
| 54 if (next_item_id_ == 0) | |
| 55 next_item_id_ = 1; | |
| 56 id_to_item_[item_id] = item; | |
| 57 item_to_id_[item] = item_id; | |
| 58 } else { | |
| 59 item_id = item_iter->second; | |
| 60 } | |
| 61 | |
| 62 // Let's update process_id_to_item_id_. | |
| 63 std::pair<IDMap::iterator, IDMap::iterator> process_ids = | |
| 64 process_id_to_item_id_.equal_range(process_id); | |
| 65 bool already_watching_process = (process_ids.first != process_ids.second); | |
| 66 if (std::find_if(process_ids.first, process_ids.second, | |
| 67 MatchSecond<int>(item_id)) == process_ids.second) { | |
| 68 process_id_to_item_id_.insert(std::make_pair(process_id, item_id)); | |
| 69 } | |
| 70 | |
| 71 // And item_id_to_process_id_. | |
| 72 std::pair<IDMap::iterator, IDMap::iterator> item_ids = | |
| 73 item_id_to_process_id_.equal_range(item_id); | |
| 74 if (std::find_if(item_ids.first, item_ids.second, | |
| 75 MatchSecond<int>(process_id)) == item_ids.second) { | |
| 76 item_id_to_process_id_.insert(std::make_pair(item_id, process_id)); | |
| 77 } | |
| 78 | |
| 79 // If we're not doing so already, keep an eye for the process host deletion. | |
| 80 if (!already_watching_process) { | |
| 81 if (BrowserThread::CurrentlyOn(BrowserThread::UI)) { | |
| 82 StartObservingProcess(process_id); | |
| 83 } else { | |
| 84 BrowserThread::PostTask( | |
| 85 BrowserThread::UI, | |
| 86 FROM_HERE, | |
| 87 base::Bind(&RendererDataMemoizingStore::StartObservingProcess, | |
| 88 base::Unretained(this), | |
| 89 process_id)); | |
| 90 } | |
| 91 } | |
| 92 | |
| 93 DCHECK(item_id); | |
| 94 return item_id; | |
| 95 } | |
| 96 | |
| 97 // Retrieve fetches a previously Stored() item, identified by |item_id|. | |
| 98 // If |item_id| is recognized, |item| will be updated and Retrieve() will | |
| 99 // return true, it will otherwise return false. | |
| 100 bool Retrieve(int item_id, scoped_refptr<T>* item) { | |
| 101 base::AutoLock auto_lock(lock_); | |
| 102 | |
| 103 typename ItemMap::iterator iter = id_to_item_.find(item_id); | |
| 104 if (iter == id_to_item_.end()) | |
| 105 return false; | |
| 106 if (item) | |
| 107 *item = iter->second; | |
| 108 return true; | |
| 109 } | |
| 110 | |
| 111 private: | |
| 112 typedef std::multimap<int, int> IDMap; | |
| 113 typedef std::map<int, scoped_refptr<T> > ItemMap; | |
| 114 typedef std::map<T*, int, typename T::LessThan> ReverseItemMap; | |
| 115 | |
| 116 template <typename M> | |
| 117 struct MatchSecond { | |
| 118 explicit MatchSecond(const M& t) : value(t) {} | |
| 119 | |
| 120 template <typename Pair> | |
| 121 bool operator()(const Pair& p) const { | |
| 122 return (value == p.second); | |
| 123 } | |
| 124 | |
| 125 M value; | |
| 126 }; | |
| 127 | |
| 128 void StartObservingProcess(int process_id) { | |
| 129 DCHECK_CURRENTLY_ON(BrowserThread::UI); | |
| 130 RenderProcessHost* host = RenderProcessHost::FromID(process_id); | |
| 131 if (!host) { | |
| 132 // We lost the race to observe the host before it was destroyed. Since | |
| 133 // this function was called because we're managing objects tied to that | |
| 134 // (now destroyed) RenderProcessHost, let's clean up. | |
| 135 RemoveRenderProcessItems(process_id); | |
| 136 return; | |
| 137 } | |
| 138 | |
| 139 host->AddObserver(this); | |
| 140 } | |
| 141 | |
| 142 // Remove the item specified by |item_id| from id_to_item_ and item_to_id_. | |
| 143 // NOTE: the caller (RemoveRenderProcessItems) must hold lock_. | |
| 144 void RemoveInternal(int item_id) { | |
| 145 typename ItemMap::iterator item_iter = id_to_item_.find(item_id); | |
| 146 DCHECK(item_iter != id_to_item_.end()); | |
| 147 | |
| 148 typename ReverseItemMap::iterator id_iter = | |
| 149 item_to_id_.find(item_iter->second.get()); | |
| 150 DCHECK(id_iter != item_to_id_.end()); | |
| 151 item_to_id_.erase(id_iter); | |
| 152 | |
| 153 id_to_item_.erase(item_iter); | |
| 154 } | |
| 155 | |
| 156 void RenderProcessHostDestroyed(RenderProcessHost* host) override { | |
| 157 DCHECK_CURRENTLY_ON(BrowserThread::UI); | |
| 158 RemoveRenderProcessItems(host->GetID()); | |
| 159 } | |
| 160 | |
| 161 // Removes all the items associated with the specified process from the store. | |
| 162 void RemoveRenderProcessItems(int process_id) { | |
| 163 base::AutoLock auto_lock(lock_); | |
| 164 | |
| 165 // We iterate through all the item ids for that process. | |
| 166 std::pair<IDMap::iterator, IDMap::iterator> process_ids = | |
| 167 process_id_to_item_id_.equal_range(process_id); | |
| 168 for (IDMap::iterator ids_iter = process_ids.first; | |
| 169 ids_iter != process_ids.second; ++ids_iter) { | |
| 170 int item_id = ids_iter->second; | |
| 171 // Find all the processes referring to this item id in | |
| 172 // item_id_to_process_id_, then locate the process being removed within | |
| 173 // that range. | |
| 174 std::pair<IDMap::iterator, IDMap::iterator> item_ids = | |
| 175 item_id_to_process_id_.equal_range(item_id); | |
| 176 IDMap::iterator proc_iter = std::find_if( | |
| 177 item_ids.first, item_ids.second, MatchSecond<int>(process_id)); | |
| 178 DCHECK(proc_iter != item_ids.second); | |
| 179 | |
| 180 // Before removing, determine if no other processes refer to the current | |
| 181 // item id. If |proc_iter| (the current process) is the lower bound of | |
| 182 // processes containing the current item id and if |next_proc_iter| is the | |
| 183 // upper bound (the first process that does not), then only one process, | |
| 184 // the one being removed, refers to the item id. | |
| 185 IDMap::iterator next_proc_iter = proc_iter; | |
| 186 ++next_proc_iter; | |
| 187 bool last_process_for_item_id = | |
| 188 (proc_iter == item_ids.first && next_proc_iter == item_ids.second); | |
| 189 item_id_to_process_id_.erase(proc_iter); | |
| 190 | |
| 191 if (last_process_for_item_id) { | |
| 192 // The current item id is not referenced by any other processes, so | |
| 193 // remove it from id_to_item_ and item_to_id_. | |
| 194 RemoveInternal(item_id); | |
| 195 } | |
| 196 } | |
| 197 if (process_ids.first != process_ids.second) | |
| 198 process_id_to_item_id_.erase(process_ids.first, process_ids.second); | |
| 199 } | |
| 200 | |
| 201 IDMap process_id_to_item_id_; | |
| 202 IDMap item_id_to_process_id_; | |
| 203 ItemMap id_to_item_; | |
| 204 ReverseItemMap item_to_id_; | |
| 205 | |
| 206 int next_item_id_; | |
| 207 | |
| 208 // This lock protects: process_id_to_item_id_, item_id_to_process_id_, | |
| 209 // id_to_item_, and item_to_id_. | |
| 210 base::Lock lock_; | |
| 211 }; | |
| 212 | |
| 213 } // namespace content | |
| 214 | |
| 215 #endif // CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2334813002:
Remove RendererDataMemoizingStore which isn't used anymore after r417444. (Closed)
