security: Add base64 and hex encoding/decoding support in transformation

Change-Id: I11d5c8921abcf04411aac38382dc285269f553ef
Refs: #3009
diff --git a/src/security/transform/hex-encode.cpp b/src/security/transform/hex-encode.cpp
new file mode 100644
index 0000000..6d54f0e
--- /dev/null
+++ b/src/security/transform/hex-encode.cpp
@@ -0,0 +1,76 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2016 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#include "hex-encode.hpp"
+
+namespace ndn {
+namespace security {
+namespace transform {
+
+static const char H2CL[16] = {
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+};
+
+static const char H2CU[16] = {
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
+};
+
+HexEncode::HexEncode(bool useUpperCase)
+  : m_useUpperCase(useUpperCase)
+{
+}
+
+size_t
+HexEncode::convert(const uint8_t* data, size_t dataLen)
+{
+  setOutputBuffer(toHex(data, dataLen));
+  return dataLen;
+}
+
+unique_ptr<Transform::OBuffer>
+HexEncode::toHex(const uint8_t* data, size_t dataLen)
+{
+  const char* encodePad = (m_useUpperCase) ? H2CU : H2CL;
+
+  auto encoded = make_unique<OBuffer>(dataLen * 2);
+  uint8_t* buf = &encoded->front();
+  for (size_t i = 0; i < dataLen; i++) {
+    buf[0] = encodePad[((data[i] >> 4) & 0x0F)];
+    buf++;
+    buf[0] = encodePad[(data[i] & 0x0F)];
+    buf++;
+  }
+  return encoded;
+}
+
+
+
+unique_ptr<Transform>
+hexEncode(bool useUpperCase)
+{
+  return make_unique<HexEncode>(useUpperCase);
+}
+
+} // namespace transform
+} // namespace security
+} // namespace ndn