Refactoring the SysInfoProvider.

chrome/browser/chromeos/system_logs/system_logs_fetcher.h

+// Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SYSTEM_LOGS_FETCHER_H_
+#define CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SYSTEM_LOGS_FETCHER_H_
+
+#include <map>
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/scoped_vector.h"
+#include "base/memory/weak_ptr.h"
+
+namespace chromeos {
+
+typedef std::map<std::string, std::string> SystemLogsResponse;
+
+// Callback that the data sources use to return data.
+typedef base::Callback<void(SystemLogsResponse* response)>
+    SysLogsSourceCallback;
+
+// Callback that the SystemLogsFetcher uses to return data.
+typedef base::Callback<void(scoped_ptr<SystemLogsResponse> response)>
+    SysLogsFetcherCallback;
+
+// The SystemLogsSource provides a interface for the data sources that
+// the SystemLogsFetcher class uses to fetch logs and other
+// information.
+class SystemLogsSource {
+ public:
+  // Fetches data and passes it by to the callback
+  virtual void Fetch(const SysLogsSourceCallback& callback) = 0;
+  virtual ~SystemLogsSource() {}
+};
+
+// The SystemLogsFetcher creates a list of data sources which must be
+// classes that implement the SystemLogsSource. It's Fetch function
+// receives as a parameter a callback that takes only one parameter
+// SystemLogsResponse that is a map of keys and values.
+// Each data source also returns a SystemLogsResponse. If two data sources
+// return the same key, only the first one will be stored.
+// The class runs on the UI thread.
+//
+// EXAMPLE:
+// class Example {
+//  public:
+//   void ProcessLogs(SystemLogsResponse* response) {
+//      //do something with the logs
+//   }
+//   void GetLogs() {
+//     SystemLogsFetcher* fetcher = new SystemLogsFetcher();
+//     fetcher->Fetch(base::Bind(&Example::ProcessLogs, this));
+//   }
+class SystemLogsFetcher {
+ public:
+  SystemLogsFetcher();
+  ~SystemLogsFetcher();
+
+  void Fetch(const SysLogsFetcherCallback& callback);
+
+ private:
+  // Callback passed to all the data sources. It merges the |data| it recieves
+  // into response_. When all the data sources have responded, it deletes their
+  // objects and returns the response to the callback_. After this it
+  // deletes this instance of the object.
+  void AddResponse(SystemLogsResponse* response);
+
+  ScopedVector<SystemLogsSource> data_sources_;
+  SysLogsFetcherCallback callback_;
+
+  scoped_ptr<SystemLogsResponse> response_;  // The actual response data.
+  size_t num_pending_requests_;   // The number of callbacks it should get.
+
+  base::WeakPtrFactory<SystemLogsFetcher> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemLogsFetcher);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SYSTEM_LOGS_FETCHER_H_
+