Load CMA backend from shared library

chromecast/public/media/decrypt_config.h

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.

[gunsch, 2015/07/27 17:14:49]

remove (c)

[halliwell, 2015/07/28 02:19:36]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROMECAST_PUBLIC_MEDIA_DECRYPT_CONFIG_H_
+#define CHROMECAST_PUBLIC_MEDIA_DECRYPT_CONFIG_H_
+
+#include <stdint.h>
+#include <string>
+#include <vector>
+
+namespace chromecast {
+namespace media {
+
+// The Common Encryption spec provides for subsample encryption, where portions
+// of a sample are set in cleartext. A SubsampleEntry specifies the number of
+// clear and encrypted bytes in each subsample. For decryption, all of the
+// encrypted bytes in a sample should be considered a single logical stream,
+// regardless of how they are divided into subsamples, and the clear bytes
+// should not be considered as part of decryption. This is logically equivalent
+// to concatenating all 'cypher_bytes' portions of subsamples, decrypting that
+// result, and then copying each byte from the decrypted block over the
+// position of the corresponding encrypted byte.
+struct SubsampleEntry {
+  SubsampleEntry() : clear_bytes(0), cypher_bytes(0) {}

[gunsch, 2015/07/27 17:14:49]

Do we need both ctors, or in practice do we only use one? (I realize this is a
copy from media/base/).

[halliwell, 2015/07/28 02:19:36]

we need both - obviously we only use the uint32_t, uint32_t version to copy the
data across, but since it's in a std::vector, a no-arg ctor is required.

+  SubsampleEntry(uint32_t clear_bytes, uint32_t cypher_bytes)
+      : clear_bytes(clear_bytes), cypher_bytes(cypher_bytes) {}
+  uint32_t clear_bytes;
+  uint32_t cypher_bytes;
+};
+
+// Contains all information that a decryptor needs to decrypt a media sample.
+class DecryptConfig {
+ public:
+  virtual ~DecryptConfig() {}
+
+  virtual const std::string& key_id() const = 0;

[gunsch, 2015/07/27 17:14:49]

I'm a little wary of providing references here rather than copies, but will only
cast_shell be providing implementations of DecryptConfig to the backend and not
the other way around? Might be OK in that case.

[byungchul, 2015/07/27 18:22:23]

Make it as a simple struct?

[halliwell, 2015/07/28 02:19:36]

correct, it's us implementing this, not vendors.  We're just wrapping the
media::DecryptConfig API.

+  virtual const std::string& iv() const = 0;
+  virtual const std::vector<SubsampleEntry>& subsamples() const = 0;
+};
+
+}  // namespace media
+}  // namespace chromecast
+
+#endif  // CHROMECAST_PUBLIC_MEDIA_DECRYPT_CONFIG_H_