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 16 namespace 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. 33 class 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
