Modularize Compact Language Detector 2 (CLD2) data sources

components/translate/content/browser/browser_cld_data_provider.h

+// Copyright 2014 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 COMPONENTS_TRANSLATE_CONTENT_BROWSER_BROWSER_CLD_DATA_PROVIDER_H_
+#define COMPONENTS_TRANSLATE_CONTENT_BROWSER_BROWSER_CLD_DATA_PROVIDER_H_
+
+#include "ipc/ipc_listener.h"
+
+namespace IPC {
+class Message;
+}
+
+namespace content {
+class RenderViewHost;
+}
+
+namespace translate {
+
+// Browser-side interface responsible for providing CLD data.
+// The implementation must be paired with a renderer-side implementation of
+// the RendererCldDataProvider class:
+//
+//   components/translate/content/renderer/renderer_cld_data_provider.h
+//
+// ... and the glue between them is typically a pair of request/response IPC
+// messages using the CldDataProviderMsgStart IPCMessageStart enumerated
+// constant from ipc_message_start.h
+class BrowserCldDataProvider : public IPC::Listener {
+ public:
+  virtual ~BrowserCldDataProvider() {}
+
+  // IPC::Listener implementation:
+  // If the specified message is a request for CLD data, invokes
+  // OnCldDataRequest() and returns true. In all other cases, this method does
+  // nothing. This method is defined as virtual in order to force the
+  // implementation to define the specific IPC message(s) that it handles.
+  virtual bool OnMessageReceived(const IPC::Message&) = 0;
+
+  // Called when the browser process receives an appropriate message in
+  // OnMessageReceived, above. The implementation should attempt to locate
+  // the CLD data, cache any metadata required for accessing that data, and
+  // ultimately trigger a response by invoking SendCldDataResponse.
+  //
+  // The renderer process may poll for data, in which case this method may be
+  // repeatedly invoked. The implementation must be safe to call any number
+  // of times.
+  virtual void OnCldDataRequest() = 0;
+
+  // Invoked when OnCldDataRequest, above, results in a successful lookup or
+  // the data is already cached and ready to respond to. The implementation
+  // should take whatever action is appropriate for responding to the paired
+  // RendererCldDataProvider, typically by sending an IPC response.
+  virtual void SendCldDataResponse() = 0;
+};
+
+// Static factory function defined by the implementation that produces a new
+// provider for the specified render view host.
+BrowserCldDataProvider* CreateBrowserCldDataProviderFor(
+    content::RenderViewHost*);
+
+}  // namespace translate
+
+#endif  // COMPONENTS_TRANSLATE_CONTENT_BROWSER_BROWSER_CLD_DATAP_PROVIDER_H_