Move WV CAS Descriptor Generator to the media_cas_packager_sdk.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=219162536

media_cas_packager_sdk/public/wv_cas_ca_descriptor.h

@@ -0,0 +1,75 @@
+////////////////////////////////////////////////////////////////////////////////
+// Copyright 2018 Google LLC.
+//
+// This software is licensed under the terms defined in the Widevine Master
+// License Agreement. For a copy of this agreement, please contact
+// widevine-licensing@google.com.
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef MEDIA_CAS_PACKAGER_SDK_PUBLIC_WV_CAS_CA_DESCRIPTOR_H_
+#define MEDIA_CAS_PACKAGER_SDK_PUBLIC_WV_CAS_CA_DESCRIPTOR_H_
+
+#include <stddef.h>
+#include <string>
+
+#include "media_cas_packager_sdk/public/wv_cas_status.h"
+
+namespace widevine {
+namespace cas {
+
+// Simple CA Descriptor generator for Widevine CAS.
+//
+// The CA descriptor format is defined in ISO/IEC 13818-1:2015 (table 2-59):
+//   CA_descriptor() {
+//     descriptor_tag            8    uimsbf
+//     descriptor_length         8    uimsbf
+//     CA_system_id             16    uimsbf
+//     reserved                  3    bslbf
+//     CA_PID                   13    uimsbf
+//     for (i = 0; i < N; i++) {
+//       private_data_byte          uimsbf
+//     }
+//   }
+//
+// Class is not thread safe.
+class WvCasCaDescriptor {
+ public:
+  WvCasCaDescriptor() = default;
+  WvCasCaDescriptor(const WvCasCaDescriptor&) = delete;
+  WvCasCaDescriptor& operator=(const WvCasCaDescriptor&) = delete;
+  virtual ~WvCasCaDescriptor() = default;
+
+  // Generate a CA descriptor for the ECM stream for an encrypted program
+  // stream.
+  //
+  // Args:
+  // |ca_pid| the 13-bit PID of the ECMs
+  // |provider| provider name, put in private data for client to construct pssh
+  // |content_id| content ID, put in private data for client to construct pssh
+  // |serialized_ca_desc| a std::string object to receive the encoded descriptor.
+  //
+  // Notes:
+  // The descriptor generated by this call may be inserted into a CA Table
+  // section (for an EMM stream) or into a TS Program Map Table section (for an
+  // ECM stream). The descriptor will be 6 bytes plus any bytes added as
+  // (user-defined) private data.
+  virtual WvCasStatus GenerateCaDescriptor(uint16_t ca_pid,
+                                           const std::string& provider,
+                                           const std::string& content_id,
+                                           std::string* serialized_ca_desc) const;
+
+  // Return the base size (before private data is added) of the CA
+  // descriptor. The user can call this to plan the layout of the Table section
+  // where the descriptor will be added.
+  virtual size_t CaDescriptorBaseSize() const;
+
+ protected:
+  // Protected visibility to support unit testing.
+  virtual std::string GeneratePrivateData(const std::string& provider,
+                                     const std::string& content_id) const;
+};
+
+}  // namespace cas
+}  // namespace widevine
+
+#endif  // MEDIA_CAS_PACKAGER_SDK_PUBLIC_WV_CAS_CA_DESCRIPTOR_H_