| // 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. |
| |
| #ifndef CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ |
| #define CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ |
| |
| #include <map> |
| |
| #include "base/bind.h" |
| #include "base/synchronization/lock.h" |
| #include "content/public/browser/browser_thread.h" |
| #include "content/public/browser/render_process_host.h" |
| #include "content/public/browser/render_process_host_observer.h" |
| |
| namespace content { |
| |
| // RendererDataMemoizingStore is a thread-safe container that retains reference |
| // counted objects that are associated with one or more render processes. |
| // Objects are identified by an int and only a single reference to a given |
| // object is retained. RendererDataMemoizingStore watches for render process |
| // termination and releases objects that are no longer associated with any |
| // render process. |
| // |
| // TODO(jcampan): Rather than watching for render process termination, we should |
| // instead be listening to events such as resource cached/ |
| // removed from cache, and remove the items when we know they |
| // are not used anymore. |
| template <typename T> |
| class RendererDataMemoizingStore : public RenderProcessHostObserver { |
| public: |
| RendererDataMemoizingStore() : next_item_id_(1) { |
| } |
| |
| ~RendererDataMemoizingStore() { |
| DCHECK_EQ(0U, id_to_item_.size()) << "Failed to outlive render processes"; |
| } |
| |
| // Store adds |item| to this collection, associates it with the given render |
| // process id and returns an opaque identifier for it. If |item| is already |
| // known, the same identifier will be returned. |
| int Store(T* item, int process_id) { |
| DCHECK(item); |
| base::AutoLock auto_lock(lock_); |
| |
| int item_id; |
| |
| // Do we already know this item? |
| typename ReverseItemMap::iterator item_iter = item_to_id_.find(item); |
| if (item_iter == item_to_id_.end()) { |
| item_id = next_item_id_++; |
| // We use 0 as an invalid item_id value. In the unlikely event that |
| // next_item_id_ wraps around, we reset it to 1. |
| if (next_item_id_ == 0) |
| next_item_id_ = 1; |
| id_to_item_[item_id] = item; |
| item_to_id_[item] = item_id; |
| } else { |
| item_id = item_iter->second; |
| } |
| |
| // Let's update process_id_to_item_id_. |
| std::pair<IDMap::iterator, IDMap::iterator> process_ids = |
| process_id_to_item_id_.equal_range(process_id); |
| bool already_watching_process = (process_ids.first != process_ids.second); |
| if (std::find_if(process_ids.first, process_ids.second, |
| MatchSecond<int>(item_id)) == process_ids.second) { |
| process_id_to_item_id_.insert(std::make_pair(process_id, item_id)); |
| } |
| |
| // And item_id_to_process_id_. |
| std::pair<IDMap::iterator, IDMap::iterator> item_ids = |
| item_id_to_process_id_.equal_range(item_id); |
| if (std::find_if(item_ids.first, item_ids.second, |
| MatchSecond<int>(process_id)) == item_ids.second) { |
| item_id_to_process_id_.insert(std::make_pair(item_id, process_id)); |
| } |
| |
| // If we're not doing so already, keep an eye for the process host deletion. |
| if (!already_watching_process) { |
| if (BrowserThread::CurrentlyOn(BrowserThread::UI)) { |
| StartObservingProcess(process_id); |
| } else { |
| BrowserThread::PostTask( |
| BrowserThread::UI, |
| FROM_HERE, |
| base::Bind(&RendererDataMemoizingStore::StartObservingProcess, |
| base::Unretained(this), |
| process_id)); |
| } |
| } |
| |
| DCHECK(item_id); |
| return item_id; |
| } |
| |
| // Retrieve fetches a previously Stored() item, identified by |item_id|. |
| // If |item_id| is recognized, |item| will be updated and Retrieve() will |
| // return true, it will otherwise return false. |
| bool Retrieve(int item_id, scoped_refptr<T>* item) { |
| base::AutoLock auto_lock(lock_); |
| |
| typename ItemMap::iterator iter = id_to_item_.find(item_id); |
| if (iter == id_to_item_.end()) |
| return false; |
| if (item) |
| *item = iter->second; |
| return true; |
| } |
| |
| private: |
| typedef std::multimap<int, int> IDMap; |
| typedef std::map<int, scoped_refptr<T> > ItemMap; |
| typedef std::map<T*, int, typename T::LessThan> ReverseItemMap; |
| |
| template <typename M> |
| struct MatchSecond { |
| explicit MatchSecond(const M& t) : value(t) {} |
| |
| template <typename Pair> |
| bool operator()(const Pair& p) const { |
| return (value == p.second); |
| } |
| |
| M value; |
| }; |
| |
| void StartObservingProcess(int process_id) { |
| DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI)); |
| RenderProcessHost* host = RenderProcessHost::FromID(process_id); |
| if (!host) { |
| // We lost the race to observe the host before it was destroyed. Since |
| // this function was called because we're managing objects tied to that |
| // (now destroyed) RenderProcessHost, let's clean up. |
| RemoveRenderProcessItems(process_id); |
| return; |
| } |
| |
| host->AddObserver(this); |
| } |
| |
| // Remove the item specified by |item_id| from id_to_item_ and item_to_id_. |
| // NOTE: the caller (RemoveRenderProcessItems) must hold lock_. |
| void RemoveInternal(int item_id) { |
| typename ItemMap::iterator item_iter = id_to_item_.find(item_id); |
| DCHECK(item_iter != id_to_item_.end()); |
| |
| typename ReverseItemMap::iterator id_iter = |
| item_to_id_.find(item_iter->second.get()); |
| DCHECK(id_iter != item_to_id_.end()); |
| item_to_id_.erase(id_iter); |
| |
| id_to_item_.erase(item_iter); |
| } |
| |
| void RenderProcessHostDestroyed(RenderProcessHost* host) { |
| DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI)); |
| RemoveRenderProcessItems(host->GetID()); |
| } |
| |
| // Removes all the items associated with the specified process from the store. |
| void RemoveRenderProcessItems(int process_id) { |
| base::AutoLock auto_lock(lock_); |
| |
| // We iterate through all the item ids for that process. |
| std::pair<IDMap::iterator, IDMap::iterator> process_ids = |
| process_id_to_item_id_.equal_range(process_id); |
| for (IDMap::iterator ids_iter = process_ids.first; |
| ids_iter != process_ids.second; ++ids_iter) { |
| int item_id = ids_iter->second; |
| // Find all the processes referring to this item id in |
| // item_id_to_process_id_, then locate the process being removed within |
| // that range. |
| std::pair<IDMap::iterator, IDMap::iterator> item_ids = |
| item_id_to_process_id_.equal_range(item_id); |
| IDMap::iterator proc_iter = std::find_if( |
| item_ids.first, item_ids.second, MatchSecond<int>(process_id)); |
| DCHECK(proc_iter != item_ids.second); |
| |
| // Before removing, determine if no other processes refer to the current |
| // item id. If |proc_iter| (the current process) is the lower bound of |
| // processes containing the current item id and if |next_proc_iter| is the |
| // upper bound (the first process that does not), then only one process, |
| // the one being removed, refers to the item id. |
| IDMap::iterator next_proc_iter = proc_iter; |
| ++next_proc_iter; |
| bool last_process_for_item_id = |
| (proc_iter == item_ids.first && next_proc_iter == item_ids.second); |
| item_id_to_process_id_.erase(proc_iter); |
| |
| if (last_process_for_item_id) { |
| // The current item id is not referenced by any other processes, so |
| // remove it from id_to_item_ and item_to_id_. |
| RemoveInternal(item_id); |
| } |
| } |
| if (process_ids.first != process_ids.second) |
| process_id_to_item_id_.erase(process_ids.first, process_ids.second); |
| } |
| |
| IDMap process_id_to_item_id_; |
| IDMap item_id_to_process_id_; |
| ItemMap id_to_item_; |
| ReverseItemMap item_to_id_; |
| |
| int next_item_id_; |
| |
| // This lock protects: process_id_to_item_id_, item_id_to_process_id_, |
| // id_to_item_, and item_to_id_. |
| base::Lock lock_; |
| }; |
| |
| } // namespace content |
| |
| #endif // CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_ |