Refactoring the SysInfoProvider.

chrome/browser/chromeos/syslogs/syslogs_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_SYSLOGS_SYSLOGS_FETCHER_H_
+#define CHROME_BROWSER_CHROMEOS_SYSLOGS_SYSLOGS_FETCHER_H_
+
+#include <string>
+#include <map>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+
+namespace chromeos {
+
+typedef std::map<std::string, std::string> SysLogsResponse;
+typedef base::Callback<void(SysLogsResponse*)> SysLogsFetcherCallback;
+
+// The SysLogsInterface provides a interface for the data sources that the
+// SysLogsFetcher class uses to fetch logs and other information.
+class SysLogsInterface {
+ public:
+  // Fetches data and passes it by to the callback
+  virtual void Fetch(const SysLogsFetcherCallback& request) = 0;
+  virtual ~SysLogsInterface() {}
+};
+
+typedef std::vector<SysLogsInterface*> SysLogsDataSources;
+
+// The SysLogsFetcher receives a list of data sources which must be classes that
+// implement the SysLogsInterface. It's Fetch function receives as a parameter
+// a callback that takes only one parameter SysLogsResponse that is a map of
+// keys and values.
+// Each data source also returns a SysLogsResponse. If two data sources return
+// the same key, the last one will replace the previous one.
+// Each data source gets deleted after all of them are called, the
+// SysLogsFetcher deletes itself after calling the callback it received.
+// The class runs on the UI thread.
+//
+// EXAMPLE:
+// class Example {
+//   public:
+//      ProcessLogs(chrome::SysLogsResponse) {
+//        //do something with the logs
+//      }
+//      GetLogs() {
+//        chrome::SysLogsFetcher* fetcher =
+//          chrome::SysLogsFetcherFactory::GetInstance()->CreateFetcher();
+//        fetcher->Fetch(base::Bind(&Example::ProcessLogs,this));
+//      }
+class SysLogsFetcher {
+ public:
+  explicit SysLogsFetcher(SysLogsDataSources backends);
+  ~SysLogsFetcher() {}
+
+  void Fetch(const SysLogsFetcherCallback& request);
+
+ 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 request_ callback. After this it
+  // deletes itself.
+  void AddData(SysLogsResponse* data);
+
+  SysLogsDataSources data_sources_;
+  SysLogsFetcherCallback request_;
+
+  SysLogsResponse* response_; // The actual response data.
+  size_t responses_;          // The number of callbacks it should get.
+
+  base::WeakPtrFactory<SysLogsFetcher> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SysLogsFetcher);
+};
+
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_SYSLOGS_SYSLOGS_FETCHER_H_
+