Add ContentDecryptionModule interface.

webkit/media/crypto/content_decryption_module.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_CONTENT_DECRYPTION_MODULE_H_
+#define WEBKIT_MEDIA_CRYPTO_CONTENT_DECRYPTION_MODULE_H_
+
+#include <stdint.h>

[ddorwin, 2012/08/13 23:28:20]

This may fail MSVC 2008. See
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/zFzvBFptJj4/dis....

[xhwang, 2012/08/14 16:26:07]

Summary of the discussion:
- stdint types are available for VC10 and VC11 on Windows.
- stdint types are recommended by Google's C++ style guide.
- chrome is going to move towards stdint types and will probably add a stdint.h
file for pre-VC9(VS2008) versions.

Added typedef for Windows.

+
+class ContentDecryptionModule;
+
+extern ContentDecryptionModule* CdmCreateInstance(const void* config_data,
+                                                  uint32_t config_data_size);
+extern const char* CdmGetVersion();
+
+enum CdmStatus {
+  kCdmStatusSuccess = 0,

[ddorwin, 2012/08/13 23:28:20]

"Though the Google C++ Style Guide says to use kConstantNaming for enums, Chrome
still uses MACRO_STYLE naming for enums for consistency with our existing code."

[xhwang, 2012/08/14 16:26:07]

We are already using kConstantNaming at least in media code, see:
http://codereview.chromium.org/10855051/diff/5002/media/base/message_loop_fac...

+  kCdmStatusErrorUnknown = 1,
+  kCdmStatusErrorClient = 2,
+  kCdmStatusErrorService = 3,
+  kCdmStatusErrorOutput = 4,
+  kCdmStatusErrorHardwareChange = 5,
+  kCdmStatusErrorDomain = 6
+};
+
+// The Common Encryption spec supports subsample encryption, where portions

[ddorwin, 2012/08/13 23:28:20]

The ISO...

But, I think we should just define this as how Subsample Encryption is done and
not lead in with comments about ISO.

[xhwang, 2012/08/14 16:26:07]

Updated comment with examples and w/o mentioning ISO.

+// 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 {
+  uint32_t clear_bytes;
+  uint32_t cypher_bytes;
+};
+
+struct InputBuffer {
+  uint8_t* data;  // Pointer to the beginning of the input data.
+  uint32_t data_size;  // Size (in bytes) of |data|.
+  uint32_t data_offset;  // Number of bytes to be discarded before decryption.
+  uint8_t* key_id;  // Key ID to identify the decryption key.
+  uint32_t key_id_size;  // Size (in bytes) of |key_id|.
+  uint8_t* iv;  // Initialization vector.
+  uint32_t iv_len;  // Size (in bytes) of |iv|.
+  uint8_t* checksum;  // Pointer to the beginning of the checksum.
+  uint32_t checksum_size;  // Size (in bytes) of the |checksum|.
+  // Subsamples as specified in ISO common encryption.

[ddorwin, 2012/08/13 23:28:20]

Same. No need for a comment really since it's already a type.

[xhwang, 2012/08/14 16:26:07]

Done.

+  struct SubsampleEntry* subsamples;
+  uint32_t num_subsamples;  // Number of subsamples in |subsamples|.
+  int64_t timestamp;  // Presentation timestamp in milliseconds.

[ddorwin, 2012/08/13 23:28:20]

Any idea what the CDM does with this value and the next?

Do we even need them in the plugin (caller of this interface) if we are already
saving a request ID in the browser?

[xhwang, 2012/08/14 16:26:07]

We need timestamp to track buffers since buffer can go out of decoding order.

+  int64_t duration;  // Duration in milliseconds.
+};
+
+struct OutputBuffer {
+  uint8_t* data;  // Pointer to the beginning of the output data.

[ddorwin, 2012/08/13 23:28:20]

This assumes the caller is allocating the output buffer. Fine for the very short
term if you want to pre-allocate a large enough buffer. However, we need a TODO
to fix the memory allocation.

[xhwang, 2012/08/14 16:26:07]

In Decrypt(), the OutputBuffer is passed in as "OutputBuffer* decrypted_buffer".
So the caller allocates the OutputBuffer but leave the data as NULL, the callee
(the CDM) will set the data, data_size, etc. So it's still the callee who
allocates the memory.

[ddorwin, 2012/08/14 22:52:11]

Probably worth commenting this somewhere. Decrypt() I guess. I assume those are
the places you'll be adding comments after the first round of reviews.

[xhwang, 2012/08/15 01:18:26]

Done.

+  uint32_t data_size;  // Size (in bytes) of |data|.
+  int64_t timestamp;  // Presentation timestamp in milliseconds.
+  int64_t duration;  // Duration in milliseconds.
+};
+
+class ContentDecryptionModule {
+ public:
+  virtual CdmStatus GenerateKeyRequest(const uint8_t* init_data,
+                                       uint32_t init_data_size,
+                                       char** session_id,
+                                       uint32_t* session_id_size,
+                                       uint8_t** key_request,
+                                       uint32_t* key_request_size) = 0;
+
+  virtual CdmStatus AddKey(const char* session_id,
+                           uint32_t session_id_size,
+                           const uint8_t* init_data,

[ddorwin, 2012/08/13 23:28:20]

key, not init_data.
EME supports init_data today, but we don't need to support it here and the next
version won't.

[xhwang, 2012/08/14 16:26:07]

Done.

+                           uint32_t init_data_size) = 0;
+
+  virtual CdmStatus CancelKeyRequest(const char* session_id,
+                                     uint32_t session_id_size) = 0;
+
+  virtual CdmStatus Decrypt(const char* session_id,
+                            uint32_t session_id_size,
+                            const InputBuffer &encrypted_buffer,
+                            OutputBuffer* decrypted_buffer) = 0;

[ddorwin, 2012/08/13 23:28:20]

space after &

+
+  virtual ~ContentDecryptionModule() {};
+};
+
+#endif  // WEBKIT_MEDIA_CRYPTO_CONTENT_DECRYPTION_MODULE_H_