Add ContentDecryptionModule interface.

This interface should be implemented by any CDM (ContentDecryptionModule) that needs to be hosted by the CDMWrapper. This version only supports Decrypt(). DecryptAndDecode() support will be added in the future.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/10823299

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@152056 0039d316-1c4b-4281-b951-d872f2087c98

webkit/media/crypto/ppapi/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_
+
+#if defined(_MSC_VER)
+typedef unsigned char uint8_t;
+typedef unsigned int uint32_t;
+typedef __int64 int64_t;
+#else
+#include <stdint.h>
+#endif
+
+namespace cdm {
+class ContentDecryptionModule;
+}
+
+extern "C" {
+cdm::ContentDecryptionModule* CreateCdmInstance();
+void DestroyCdmInstance(cdm::ContentDecryptionModule* instance);
+const char* GetCdmVersion();
+}
+
+namespace cdm {
+
+// An input buffer can be split into several continuous subsamples.
+// A SubsampleEntry specifies the number of clear and cipher bytes in each
+// subsample. For example, the following buffer has three subsamples:
+//
+// |<----- subsample1 ----->|<----- subsample2 ----->|<----- subsample3 ----->|
+// |   clear1   |  cipher1  |  clear2  |   cipher2   | clear3 |    cipher3    |
+//
+// For decryption, all of the cipher bytes in a buffer should be concatenated
+// (in the subsample order) into a single logical stream. The clear bytes should
+// not be considered as part of decryption.
+//
+// Stream to decrypt:   |  cipher1  |   cipher2   |    cipher3    |
+// Decrypted stream:    | decrypted1|  decrypted2 |   decrypted3  |
+//
+// After decryption, the decrypted bytes should be copied over the position
+// of the corresponding cipher bytes in the original buffer to form the output
+// buffer. Following the above example, the decrypted buffer should be:
+//
+// |<----- subsample1 ----->|<----- subsample2 ----->|<----- subsample3 ----->|
+// |   clear1   | decrypted1|  clear2  |  decrypted2 | clear3 |   decrypted3  |
+//
+// TODO(xhwang): Add checks to make sure these structs have fixed layout.
+struct SubsampleEntry {
+  uint32_t clear_bytes;
+  uint32_t cipher_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_size;  // Size (in bytes) of |iv|.
+
+  uint8_t* checksum;
+  uint32_t checksum_size;  // Size (in bytes) of the |checksum|.
+
+  struct SubsampleEntry* subsamples;
+  uint32_t num_subsamples;  // Number of subsamples in |subsamples|.
+
+  int64_t timestamp;  // Presentation timestamp in microseconds.
+};
+
+struct OutputBuffer {
+  uint8_t* data;  // Pointer to the beginning of the output data.
+  uint32_t data_size;  // Size (in bytes) of |data|.
+
+  int64_t timestamp;  // Presentation timestamp in microseconds.
+};
+
+class ContentDecryptionModule {
+ public:
+  enum Status {
+    kSuccess = 0,
+    kErrorUnknown,
+    kErrorNoKey
+  };
+
+  // Generates a |key_request| as well as a |session_id| given the |init_data|.
+  // The CDM may also extract a |default_url|.
+  // Returns kSuccess if the key request was successfully generated,
+  // in which case the callee should have allocated memory for the output
+  // parameters (e.g |session_id|) and passed the ownership to the caller.
+  // Returns kErrorUnknown otherwise, in which case the output
+  // parameters should not be used by the caller.
+  //
+  // TODO(xhwang): It's not safe to pass the ownership of the dynamically
+  // allocated memory over library boundaries. Fix it after related PPAPI change
+  // and sample CDM are landed.
+  virtual Status GenerateKeyRequest(const uint8_t* init_data,
+                                    int init_data_size,
+                                    char** session_id,
+                                    int* session_id_size,
+                                    uint8_t** key_request,
+                                    int* key_request_size,
+                                    char** default_url,
+                                    int* default_url_size) = 0;
+
+  // Adds the |key| to the CDM to be associated with |key_id|.
+  // Returns kSuccess if the key was successfully added.
+  // Returns kErrorUnknown otherwise.
+  virtual Status AddKey(const char* session_id,
+                        int session_id_size,
+                        const uint8_t* key,
+                        int key_size,
+                        const uint8_t* key_id,
+                        int key_id_size) = 0;
+
+  // Cancels any pending key request made to the CDM for |session_id|.
+  // Returns kSuccess if all pending key requests for |session_id| were
+  // successfully canceled or there was no key request to be canceled.
+  // Returns kErrorUnknown otherwise.
+  virtual Status CancelKeyRequest(const char* session_id,
+                                  int session_id_size) = 0;
+
+  // Decrypts the |encrypted_buffer|.
+  // Returns kSuccess if decryption succeeded, in which case the callee
+  // should have filled the |decrypted_buffer| and passed the ownership of
+  // |data| in |decrypted_buffer| to the caller.
+  // Returns kErrorNoKey if the CDM did not have the necessary decryption key
+  // to decrypt.
+  // Returns kErrorUnknown if any other error happened.
+  // In these two cases, |decrypted_buffer| should not be used by the caller.
+  //
+  // TODO(xhwang): It's not safe to pass the ownership of the dynamically
+  // allocated memory over library boundaries. Fix it after related PPAPI change
+  // and sample CDM are landed.
+  virtual Status Decrypt(const char* session_id,
+                         int session_id_size,
+                         const InputBuffer& encrypted_buffer,
+                         OutputBuffer* decrypted_buffer) = 0;
+
+  virtual ~ContentDecryptionModule() {};
+};
+
+}  // namespace cdm
+
+#endif  // WEBKIT_MEDIA_CRYPTO_CONTENT_DECRYPTION_MODULE_H_