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 <string>
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 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 {
+  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,
+                const std::string& iv,
+                const std::vector<SubsampleEntry>& subsamples);
+
+  // 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 std::string& iv() const { return iv_; }
+  const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; }
+  bool use_cbc() const { return use_cbc_; }
 
  private:
   scoped_array<uint8> key_id_;
   int key_id_size_;
+  std::string iv_;
+  std::vector<SubsampleEntry> subsamples_;
+  // 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_