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[email protected]8e9d06b2013-11-19 19:05:181// 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"
[email protected]8e9d06b2013-11-19 19:05:1812#include "content/public/browser/browser_thread.h"
[email protected]f68c1462014-04-24 18:17:5313#include "content/public/browser/render_process_host.h"
[email protected]f235aa892013-11-22 23:14:2714#include "content/public/browser/render_process_host_observer.h"
[email protected]8e9d06b2013-11-19 19:05:1815
16namespace 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.
[email protected]f235aa892013-11-22 23:14:2724//
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.
[email protected]8e9d06b2013-11-19 19:05:1829template <typename T>
[email protected]f235aa892013-11-22 23:14:2730class RendererDataMemoizingStore : public RenderProcessHostObserver {
[email protected]8e9d06b2013-11-19 19:05:1831 public:
32 RendererDataMemoizingStore() : next_item_id_(1) {
[email protected]f235aa892013-11-22 23:14:2733 }
34
35 ~RendererDataMemoizingStore() {
36 DCHECK_EQ(0U, id_to_item_.size()) << "Failed to outlive render processes";
[email protected]8e9d06b2013-11-19 19:05:1837 }
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;
[email protected]8e9d06b2013-11-19 19:05:1856 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);
[email protected]f235aa892013-11-22 23:14:2765 bool already_watching_process = (process_ids.first != process_ids.second);
[email protected]8e9d06b2013-11-19 19:05:1866 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
[email protected]f235aa892013-11-22 23:14:2779 // 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
[email protected]9ef0b6a2014-02-27 00:10:0293 DCHECK(item_id);
[email protected]8e9d06b2013-11-19 19:05:1894 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
[email protected]f235aa892013-11-22 23:14:27128 void StartObservingProcess(int process_id) {
129 DCHECK(BrowserThread::CurrentlyOn(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 }
[email protected]8e9d06b2013-11-19 19:05:18138
[email protected]f235aa892013-11-22 23:14:27139 host->AddObserver(this);
[email protected]8e9d06b2013-11-19 19:05:18140 }
141
[email protected]7635eed62013-11-20 08:38:02142 // Remove the item specified by |item_id| from id_to_item_ and item_to_id_.
[email protected]f235aa892013-11-22 23:14:27143 // NOTE: the caller (RemoveRenderProcessItems) must hold lock_.
[email protected]8e9d06b2013-11-19 19:05:18144 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
[email protected]8e9d06b2013-11-19 19:05:18153 id_to_item_.erase(item_iter);
154 }
155
dmichaelc1a49412014-12-18 17:35:42156 void RenderProcessHostDestroyed(RenderProcessHost* host) override {
[email protected]f235aa892013-11-22 23:14:27157 DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
158 RemoveRenderProcessItems(host->GetID());
159 }
160
[email protected]8e9d06b2013-11-19 19:05:18161 // Removes all the items associated with the specified process from the store.
[email protected]f235aa892013-11-22 23:14:27162 void RemoveRenderProcessItems(int process_id) {
[email protected]8e9d06b2013-11-19 19:05:18163 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
[email protected]8e9d06b2013-11-19 19:05:18201 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_