Refactoring of chrome speech recognition architecture (CL1.3)

content/browser/speech/speech_recognition_engine.h

Index: content/browser/speech/speech_recognition_engine.h
diff --git a/content/browser/speech/speech_recognition_engine.h b/content/browser/speech/speech_recognition_engine.h
new file mode 100644
index 0000000000000000000000000000000000000000..3a2f0c28a2ce1d98e2ec452b8874b2b228f9dd1d
--- /dev/null
+++ b/content/browser/speech/speech_recognition_engine.h
@@ -0,0 +1,88 @@
+// 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 CONTENT_BROWSER_SPEECH_SPEECH_RECOGNITION_ENGINE_H_
+#define CONTENT_BROWSER_SPEECH_SPEECH_RECOGNITION_ENGINE_H_
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "content/public/common/speech_recognition_result.h"
+
+namespace content {
+struct SpeechRecognitionResult;
+struct SpeechRecognitionError;
+}
+
+namespace speech {
+
+class AudioChunk;
+
+// This interface models the basic contract that a speech recognition engine,
+// either working locally or relying on a remote web-service, must obey.
+// The expected call sequence for exported methods is:
+// SpeechRecognitionBegins       Mandatory at beginning of SR.
+//   PushSpeechAudio             For every audio chunk pushed.
+//   SpeechAudioStreamComplete   Finalize the audio stream (if no errors).
+// SpeechRecognitionEnds         Mandatory at end of SR (even on errors).
+class SpeechRecognitionEngine {
+ public:
+  // Interface for receiving callbacks from this object.
+  class Delegate {
+   public:
+    virtual void OnSpeechEngineResult(
+        const content::SpeechRecognitionResult& result) = 0;
+    virtual void OnSpeechEngineError(
+        const content::SpeechRecognitionError& error) = 0;
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  virtual ~SpeechRecognitionEngine() {}
+
+  // Notify the engine that we started the recognition, so it can prepare for
+  // the upcoming PushSpeechAudio() calls.
+  virtual void SpeechRecognitionBegins() = 0;
+
+  // Notify the engine that we have ended (either gracefully or aborting) the
+  // recognition, so it can cleanup.
+  virtual void SpeechRecognitionEnds() = 0;
+
+  // Push a chunk of uncompressed audio data, where the chunk length agrees with
+  // DesiredAudioChunkDurationMs(), and bytes_per_sample agrees to the engine
+  // configuration.
+  virtual void PushSpeechAudio(const AudioChunk& data) = 0;
+
+  // Notifies the engine that audio capture has completed and no more chunks
+  // will be pushed. The engine can finalize the recognition in order to provide
+  // a final result.
+  virtual void SpeechAudioStreamComplete() = 0;
+
+  // Checks wheter recognition of pushed audio data is pending.
+  virtual bool IsRecognitionPending() const = 0;
+
+  // Retrieves the desired duration, in milliseconds, of pushed AudioChunk(s).
+  virtual int DesiredAudioChunkDurationMs() const = 0;
+
+  // set_delegate detached from constructor for lazy dependency injection.
+  void set_delegate(Delegate* delegate) {delegate_ = delegate;}
+
+ protected:
+   Delegate* sr_delegate() const {return delegate_;}

[hans, 2012/03/16 11:12:56]

should this just be called delegate() ?

nit: spaces around the statement in {}

[Primiano Tucci (use gerrit), 2012/03/16 15:03:42]

Hmm I named it so because there was a name clash into GoogleSSFERemoteEngine
that implemented also URLFetcherDelegate. But now it seems to be gone (probably
URLFetcherDelegate has changed in the meanwhile).

+
+ private:
+   Delegate* delegate_;
+};
+
+// This typedef is to workaround the issue with certain versions of
+// Visual Studio where it gets confused between multiple Delegate
+// classes and gives a C2500 error. (I saw this error on the try bots -
+// the workaround was not needed for my machine).
+typedef SpeechRecognitionEngine::Delegate SpeechRecognitionEngineDelegate;
+
+}  // namespace speech
+
+#endif  // CONTENT_BROWSER_SPEECH_SPEECH_RECOGNITION_ENGINE_H_