Add ProxyDecryptor which wraps concrete Decryptor implementations.

webkit/media/crypto/proxy_decryptor.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 WEBKIT_MEDIA_CRYPTO_PROXY_DECRYPTOR_H_
+#define WEBKIT_MEDIA_CRYPTO_PROXY_DECRYPTOR_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "media/base/decryptor.h"
+
+namespace media {
+class DecryptorClient;
+}
+
+namespace webkit_media {
+
+// A decryptor proxy that creates a real decryptor object on demand and
+// forwards decryptor calls to it.
+// TODO(xhwang): Currently we don't support run-time switching among decryptor
+// objects. Fix this when needed.
+class ProxyDecryptor : public media::Decryptor {
+ public:
+  explicit ProxyDecryptor(media::DecryptorClient* client);
+  virtual ~ProxyDecryptor();
+
+  // media::Decryptor implementation.
+  virtual void GenerateKeyRequest(const std::string& key_system,
+                                  const uint8* init_data,
+                                  int init_data_length) OVERRIDE;
+  virtual void AddKey(const std::string& key_system,
+                      const uint8* key,
+                      int key_length,
+                      const uint8* init_data,
+                      int init_data_length,
+                      const std::string& session_id) OVERRIDE;
+  virtual void CancelKeyRequest(const std::string& key_system,
+                                const std::string& session_id) OVERRIDE;
+  virtual scoped_refptr<media::DecoderBuffer> Decrypt(
+      const scoped_refptr<media::DecoderBuffer>& input) OVERRIDE;
+
+ private:
+  media::DecryptorClient* const client_;
+  // Protects the |decryptor_|. The Decryptor interface specifies that the
+  // Decrypt() function will be called on the decoder thread and all other
+  // methods on the renderer thread. The |decryptor_| itself is thread safe
+  // when this rule is obeyed. This lock is solely to prevent the race condition
+  // between setting the |decryptor_| in GenerateKeyRequest() and using it in
+  // Decrypt().
+  base::Lock lock_;
+  scoped_ptr<media::Decryptor> decryptor_;  // Protected by the |lock_|.
+
+  DISALLOW_COPY_AND_ASSIGN(ProxyDecryptor);
+};
+
+}  // namespace webkit_media
+
+#endif  // WEBKIT_MEDIA_CRYPTO_PROXY_DECRYPTOR_H_