OEMCrypto v16.1

Merge of http://go/wvgerrit/93404

This CL updates the Widevine CDM to support OEMCrypto v16.1

Test: Tested in 16.2 CL
Bug: 141247171
Change-Id: I69bd993500f6fb63bf6010c8b0250dc7acc3d71b

libwvdrmengine/cdm/util/src/string_conversions.cpp

@@ -87,10 +87,12 @@ std::string a2bs_hex(const std::string& byte) {
 }
 
 std::string b2a_hex(const std::vector<uint8_t>& byte) {
-  return HexEncode(&byte[0], byte.size());
+  if (byte.empty()) return "";
+  return HexEncode(byte.data(), byte.size());
 }
 
 std::string b2a_hex(const std::string& byte) {
+  if (byte.empty()) return "";
   return HexEncode(reinterpret_cast<const uint8_t*>(byte.data()),
                    byte.length());
 }
@@ -251,7 +253,7 @@ std::vector<uint8_t> Base64SafeDecode(const std::string& b64_input) {
 
 std::string HexEncode(const uint8_t* in_buffer, unsigned int size) {
   static const char kHexChars[] = "0123456789ABCDEF";
-
+  if (size == 0) return "";
   // Each input byte creates two output hex characters.
   std::string out_buffer(size * 2, '\0');
 
@@ -298,4 +300,14 @@ std::string BytesToString(const uint8_t* bytes, unsigned size) {
   return std::string(char_bytes, char_bytes + size);
 }
 
+// Encode unsigned integer into a big endian formatted string
+std::string EncodeUint32(unsigned int u) {
+  std::string s;
+  s.append(1, (u >> 24) & 0xFF);
+  s.append(1, (u >> 16) & 0xFF);
+  s.append(1, (u >> 8) & 0xFF);
+  s.append(1, (u >> 0) & 0xFF);
+  return s;
+}
+
 }  // namespace wvcdm