Add Common Encryption support to BMFF, including subsample decryption.

media/base/decrypt_config.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 MEDIA_BASE_DECRYPT_CONFIG_H_
 #define MEDIA_BASE_DECRYPT_CONFIG_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
+struct SubsampleEntry {
+  int clear_bytes;
+  int cypher_bytes;
+};
+
 // Contains all information that a decryptor needs to decrypt.
 class MEDIA_EXPORT DecryptConfig {
  public:
-  explicit DecryptConfig(const uint8* key_id, int key_id_size);
+  DecryptConfig(const uint8* key_id, int key_id_size,

[ddorwin, 2012/06/26 06:09:19]

Do we really need two constructors - there is a lot of duplication in the .cc
file. Could WebM just specify 0,0 for the other values?

[fgalligan1, 2012/06/27 00:28:36]

For WebM we will also be adding the HMAC parameters.

[strobe_, 2012/06/27 02:01:21]

Done.

+                const uint8* iv, int iv_size);
+  DecryptConfig(const uint8* key_id, int key_id_size,
+                const uint8* iv, int iv_size,
+                const SubsampleEntry* subsamples, int subsample_count);
+
+  // TODO(strobe): This constructor implicitly sets CBC mode and uses a default
+  // IV, to preserve compatibility with an early implementation. It should be
+  // removed, along with CBC mode and the default IV, when
+  // https://chromiumcodereview.appspot.com/10535029 lands.
+  DecryptConfig(const uint8* key_id, int key_id_size);
+
   ~DecryptConfig();
 
   const uint8* key_id() const { return key_id_.get(); }
   int key_id_size() const { return key_id_size_; }
+  const uint8* iv() const { return iv_.get(); }
+  int iv_size() const { return iv_size_; }
+  const SubsampleEntry* subsamples() const { return subsamples_.get(); }

[ddorwin, 2012/06/26 06:09:19]

Any reason not to return and store these as a vector?

[strobe_, 2012/06/27 02:01:21]

Done.

+  int subsample_count() const { return subsample_count_; }
+  bool use_cbc() const { return use_cbc_; }
+
+  SubsampleEntry* mutable_subsamples() { return subsamples_.get(); }

[ddorwin, 2012/06/26 06:09:19]

I'm wondering why this is necessary.

[strobe_, 2012/06/27 02:01:21]

Addressed in later comments. Can either:
- Allow updating via SetSubsamples()
- Allow mutation of contents through interface
- Create a new DecryptConfig() with modified parameters
- Retain current mutable_subsamples() method

 
  private:
   scoped_array<uint8> key_id_;
   int key_id_size_;
+  scoped_array<uint8> iv_;
+  int iv_size_;
+  scoped_array<SubsampleEntry> subsamples_;
+  int subsample_count_;
+  // TODO(strobe): Remove when CBC is no longer used.
+  bool use_cbc_;
 
   DISALLOW_COPY_AND_ASSIGN(DecryptConfig);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECRYPT_CONFIG_H_