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

Change-Id: I11d5c8921abcf04411aac38382dc285269f553ef
Refs: #3009
diff --git a/src/security/transform/base64-decode.hpp b/src/security/transform/base64-decode.hpp
new file mode 100644
index 0000000..cfd5876
--- /dev/null
+++ b/src/security/transform/base64-decode.hpp
@@ -0,0 +1,89 @@
+/* -*- 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.
+ */
+
+#ifndef NDN_CXX_SECURITY_TRANSFORM_BASE64_DECODE_HPP
+#define NDN_CXX_SECURITY_TRANSFORM_BASE64_DECODE_HPP
+
+#include "transform-base.hpp"
+
+namespace ndn {
+namespace security {
+namespace transform {
+
+/**
+ * @brief The module to perform Base64 decoding transformation.
+ */
+class Base64Decode : public Transform
+{
+public:
+  /**
+   * @brief Create a base64 decoding module
+   *
+   * @p expectNewlineEvery64Bytes if true, expect newline after every 64 bytes, otherwise expect
+   *                              all input to be in a single line. Output is undefined if input
+   *                              does not conform to the requirement.
+   */
+  explicit
+  Base64Decode(bool expectNewlineEvery64Bytes = true);
+
+private:
+
+  /**
+   * @brief Read partial transformation results into output buffer and write them into next module.
+   */
+  virtual void
+  preTransform() final;
+
+  /**
+   * @brief Decode data @p buf in base64 format
+   *
+   * @return number of bytes that have been accepted by the converter
+   */
+  virtual size_t
+  convert(const uint8_t* buf, size_t size) final;
+
+  /**
+   * @brief Finalize base64 decoding
+   *
+   * This method with read all decoding results from the converter and write them into next module.
+   */
+  virtual void
+  finalize() final;
+
+  /**
+   * @brief Try to fill partial decoding result into output buffer.
+   */
+  void
+  fillOutputBuffer();
+
+private:
+  class Impl;
+  unique_ptr<Impl> m_impl;
+};
+
+unique_ptr<Transform>
+base64Decode(bool expectNewlineEvery64Bytes = true);
+
+} // namespace transform
+} // namespace security
+} // namespace ndn
+
+#endif // NDN_CXX_SECURITY_TRANSFORM_BASE64_DECODE_HPP