util: Add stateful digest
Change-Id: I6ed564dc9146d180cec2848a73ec9e8e8f10d921
Refs: #1934
diff --git a/src/util/digest.hpp b/src/util/digest.hpp
new file mode 100644
index 0000000..39ff811
--- /dev/null
+++ b/src/util/digest.hpp
@@ -0,0 +1,191 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2014 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_UTIL_DIGEST_HPP
+#define NDN_UTIL_DIGEST_HPP
+
+#include "../encoding/buffer.hpp"
+#include "../encoding/block.hpp"
+#include "../security/cryptopp.hpp"
+#include "concepts.hpp"
+
+namespace ndn {
+namespace util {
+
+/**
+ * @brief provides a digest calculation
+ *
+ * Take SHA256 as an example:
+ *
+ * Digest<CryptoPP::SHA256> digest;
+ * digest.update(buf1, size1);
+ * digest.update(buf2, size2);
+ * ...
+ * ConstBufferPtr result = digest.computeDigest();
+ *
+ * @sa http://redmine.named-data.net/issues/1934
+ */
+template<typename Hash>
+class Digest
+{
+public:
+ BOOST_CONCEPT_ASSERT((Hashable<Hash>));
+
+ typedef Hash HashFunction;
+
+ class Error : public std::runtime_error
+ {
+ public:
+ explicit
+ Error(const std::string& what)
+ : std::runtime_error(what)
+ {
+ }
+ };
+
+ Digest();
+
+ /**
+ * @brief Discard the current state and start a new digest.
+ */
+ void
+ reset();
+
+ /**
+ * @brief Check if digest is empty.
+ *
+ * An empty digest means nothing has been taken into calculation.
+ */
+ bool
+ empty() const
+ {
+ return !m_isInProcess;
+ }
+
+ /**
+ * @brief Obtain the digest
+ *
+ * Note this digest is finalized once this method is invoked.
+ */
+ ConstBufferPtr
+ computeDigest();
+
+ /**
+ * @brief Check if supplied digest equal to this digest
+ *
+ * Note that this method will invoke computeDigest().
+ * Once this method is invoked, both this digest and the supplied digest are finalized.
+ */
+ bool
+ operator==(Digest<Hash>& digest);
+
+ /**
+ * @brief Check if supplied digest is not equal to this digest
+ *
+ * Note that this method will invoke computeDigest().
+ * Once this method is invoked, both this digest and the supplied digest are finalized.
+ */
+ bool
+ operator!=(Digest<Hash>& digest)
+ {
+ return !(*this == digest);
+ }
+
+ /**
+ * @brief Add existing digest to digest calculation
+ * @param src digest to combine with
+ *
+ * The result of this combination is hash (hash (...))
+ * Note that this method will invoke computeDigest().
+ * Once this method is invoked, the supplied digest is fixed.
+ */
+ Digest<Hash>&
+ operator<<(Digest<Hash>& src);
+
+ /**
+ * @brief Add string to digest calculation
+ * @param str string to put into digest
+ */
+ Digest<Hash>&
+ operator<<(const std::string& str);
+
+ /**
+ * @brief Add block to digest calculation
+ * @param block to put into digest
+ */
+ Digest<Hash>&
+ operator<<(const Block& block);
+
+ /**
+ * @brief Add uint64_t value to digest calculation
+ * @param value uint64_t value to put into digest
+ */
+ Digest<Hash>&
+ operator<<(uint64_t value);
+
+ /**
+ * @brief Add a buffer to digest calculation
+ *
+ * Update the state of the digest if it is not finalized
+ * and mark the digest as InProcess.
+ *
+ * @param buffer the input buffer
+ * @param size the size of the input buffer.
+ * @throws Error if the digest has been finalized.
+ */
+ void
+ update(const uint8_t* buffer, size_t size);
+
+ /**
+ * @brief Compute one-time digest
+ * @param buffer the input buffer
+ * @param size the size of the input buffer.
+ * @return digest computed according to the HashAlgorithm
+ */
+ static ConstBufferPtr
+ computeDigest(const uint8_t* buffer, size_t size);
+
+
+private:
+ /**
+ * @brief Finalize digest.
+ *
+ * All subsequent calls to "operator<<" will throw an exception
+ */
+ void
+ finalize();
+
+private:
+ Hash m_hash;
+ BufferPtr m_buffer;
+ bool m_isInProcess;
+ bool m_isFinalized;
+};
+
+/**
+ * @brief A digest using SHA256 as the hash function.
+ */
+typedef Digest<CryptoPP::SHA256> Sha256;
+
+} // namespace util
+} // namespace ndn
+
+#endif // NDN_UTIL_DIGEST_HPP