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 CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_ 6#define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_ 7 8#include <queue> 9 10#include "base/bind.h" 11#include "base/callback.h" 12#include "base/memory/ref_counted.h" 13#include "base/threading/sequenced_worker_pool.h" 14#include "content/public/browser/browser_thread.h" 15 16namespace extensions { 17 18// An abstract base class for all kinds of system information providers. Each 19// kind of SystemInfoProvider is a single shared instance. It is created if 20// needed, and destroyed at exit time. This is done via LazyInstance and 21// scoped_refptr. 22// 23// The SystemInfoProvider is designed to query system information on the worker 24// pool. It also maintains a queue of callbacks on the UI thread which are 25// waiting for the completion of querying operation. Once the query operation 26// is completed, all pending callbacks in the queue get called on the UI 27// thread. In this way, it avoids frequent querying operation in case of lots 28// of query requests, e.g. calling systemInfo.cpu.get repeatedly in an 29// extension process. 30// 31// Each kind of SystemInfoProvider should satisfy an API query in a subclass on 32// the blocking pool. 33class SystemInfoProvider 34 : public base::RefCountedThreadSafe<SystemInfoProvider> { 35 public: 36 // Callback type for completing to get information. The argument indicates 37 // whether its contents are valid, for example, no error occurs in querying 38 // the information. 39 typedef base::Callback<void(bool)> QueryInfoCompletionCallback; 40 typedef std::queue<QueryInfoCompletionCallback> CallbackQueue; 41 42 SystemInfoProvider(); 43 44 // Override to do any prepare work on UI thread before |QueryInfo()| gets 45 // called. 46 virtual void PrepareQueryOnUIThread(); 47 48 // The parameter |do_query_info_callback| is query info task which is posted 49 // to SystemInfoProvider sequenced worker pool. 50 // 51 // You can do any initial things of *InfoProvider before start to query info. 52 // While overriding this method, |do_query_info_callback| *must* be called 53 // directly or indirectly. 54 // 55 // Sample usage please refer to StorageInfoProvider. 56 virtual void InitializeProvider(const base::Closure& do_query_info_callback); 57 58 // Start to query the system information. Should be called on UI thread. 59 // The |callback| will get called once the query is completed. 60 // 61 // If the parameter |callback| itself calls StartQueryInfo(callback2), 62 // callback2 will be called immediately rather than triggering another call to 63 // the system. 64 void StartQueryInfo(const QueryInfoCompletionCallback& callback); 65 66 protected: 67 virtual ~SystemInfoProvider(); 68 69 private: 70 friend class base::RefCountedThreadSafe<SystemInfoProvider>; 71 72 // Interface to query the system information synchronously. 73 // Return true if no error occurs. 74 // Should be called in the blocking pool. 75 virtual bool QueryInfo() = 0; 76 77 // Called on UI thread. The |success| parameter means whether it succeeds 78 // to get the information. 79 void OnQueryCompleted(bool success); 80 81 void StartQueryInfoPostInitialization(); 82 83 // The queue of callbacks waiting for the info querying completion. It is 84 // maintained on the UI thread. 85 CallbackQueue callbacks_; 86 87 // Indicates if it is waiting for the querying completion. 88 bool is_waiting_for_completion_; 89 90 // Sequenced worker pool to make the operation of querying information get 91 // executed in order. 92 scoped_refptr<base::SequencedTaskRunner> worker_pool_; 93 94 DISALLOW_COPY_AND_ASSIGN(SystemInfoProvider); 95}; 96 97} // namespace extensions 98 99#endif // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_ 100