encoder.cpp

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2022 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 "ndn-cxx/encoding/encoder.hpp"

#include <boost/endian/conversion.hpp>

namespace ndn {
namespace encoding {

namespace endian = boost::endian;

Encoder::Encoder(size_t totalReserve, size_t reserveFromBack)
  : m_buffer(make_shared<Buffer>(totalReserve))
{
  m_begin = m_end = m_buffer->end() - (reserveFromBack < totalReserve ? reserveFromBack : 0);
}

Encoder::Encoder(const Block& block)
  : m_buffer(const_pointer_cast<Buffer>(block.getBuffer()))
  , m_begin(m_buffer->begin() + (block.begin() - m_buffer->begin()))
  , m_end(m_buffer->begin()   + (block.end()   - m_buffer->begin()))
{
}

void
Encoder::reserveBack(size_t size)
{
  if (m_end + size > m_buffer->end())
    reserve(m_buffer->size() * 2 + size, false);
}

void
Encoder::reserveFront(size_t size)
{
  if (m_buffer->begin() + size > m_begin)
    reserve(m_buffer->size() * 2 + size, true);
}

Block
Encoder::block(bool verifyLength) const
{
  return Block(m_buffer, m_begin, m_end, verifyLength);
}

void
Encoder::reserve(size_t size, bool addInFront)
{
  if (size < m_buffer->size()) {
    size = m_buffer->size();
  }

  if (addInFront) {
    size_t diffEnd = m_buffer->end() - m_end;
    size_t diffBegin = m_buffer->end() - m_begin;

    Buffer* buf = new Buffer(size);
    std::copy_backward(m_buffer->begin(), m_buffer->end(), buf->end());

    m_buffer.reset(buf);

    m_end = m_buffer->end() - diffEnd;
    m_begin = m_buffer->end() - diffBegin;
  }
  else {
    size_t diffEnd = m_end - m_buffer->begin();
    size_t diffBegin = m_begin - m_buffer->begin();

    Buffer* buf = new Buffer(size);
    std::copy(m_buffer->begin(), m_buffer->end(), buf->begin());

    m_buffer.reset(buf);

    m_end = m_buffer->begin() + diffEnd;
    m_begin = m_buffer->begin() + diffBegin;
  }
}

size_t
Encoder::prependBytes(span<const uint8_t> bytes)
{
  return prependRange(bytes.begin(), bytes.end());
}

size_t
Encoder::appendBytes(span<const uint8_t> bytes)
{
  return appendRange(bytes.begin(), bytes.end());
}

size_t
Encoder::prependVarNumber(uint64_t varNumber)
{
  if (varNumber < 253) {
    prependBytes({static_cast<uint8_t>(varNumber)});
    return 1;
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max()) {
    uint16_t value = endian::native_to_big(static_cast<uint16_t>(varNumber));
    prependBytes({reinterpret_cast<const uint8_t*>(&value), 2});
    prependBytes({253});
    return 3;
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max()) {
    uint32_t value = endian::native_to_big(static_cast<uint32_t>(varNumber));
    prependBytes({reinterpret_cast<const uint8_t*>(&value), 4});
    prependBytes({254});
    return 5;
  }
  else {
    uint64_t value = endian::native_to_big(varNumber);
    prependBytes({reinterpret_cast<const uint8_t*>(&value), 8});
    prependBytes({255});
    return 9;
  }
}

size_t
Encoder::appendVarNumber(uint64_t varNumber)
{
  if (varNumber < 253) {
    appendBytes({static_cast<uint8_t>(varNumber)});
    return 1;
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max()) {
    appendBytes({253});
    uint16_t value = endian::native_to_big(static_cast<uint16_t>(varNumber));
    appendBytes({reinterpret_cast<const uint8_t*>(&value), 2});
    return 3;
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max()) {
    appendBytes({254});
    uint32_t value = endian::native_to_big(static_cast<uint32_t>(varNumber));
    appendBytes({reinterpret_cast<const uint8_t*>(&value), 4});
    return 5;
  }
  else {
    appendBytes({255});
    uint64_t value = endian::native_to_big(varNumber);
    appendBytes({reinterpret_cast<const uint8_t*>(&value), 8});
    return 9;
  }
}

size_t
Encoder::prependNonNegativeInteger(uint64_t varNumber)
{
  if (varNumber <= std::numeric_limits<uint8_t>::max()) {
    return prependBytes({static_cast<uint8_t>(varNumber)});
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max()) {
    uint16_t value = endian::native_to_big(static_cast<uint16_t>(varNumber));
    return prependBytes({reinterpret_cast<const uint8_t*>(&value), 2});
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max()) {
    uint32_t value = endian::native_to_big(static_cast<uint32_t>(varNumber));
    return prependBytes({reinterpret_cast<const uint8_t*>(&value), 4});
  }
  else {
    uint64_t value = endian::native_to_big(varNumber);
    return prependBytes({reinterpret_cast<const uint8_t*>(&value), 8});
  }
}

size_t
Encoder::appendNonNegativeInteger(uint64_t varNumber)
{
  if (varNumber <= std::numeric_limits<uint8_t>::max()) {
    return appendBytes({static_cast<uint8_t>(varNumber)});
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max()) {
    uint16_t value = endian::native_to_big(static_cast<uint16_t>(varNumber));
    return appendBytes({reinterpret_cast<const uint8_t*>(&value), 2});
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max()) {
    uint32_t value = endian::native_to_big(static_cast<uint32_t>(varNumber));
    return appendBytes({reinterpret_cast<const uint8_t*>(&value), 4});
  }
  else {
    uint64_t value = endian::native_to_big(varNumber);
    return appendBytes({reinterpret_cast<const uint8_t*>(&value), 8});
  }
}

} // namespace encoding
} // namespace ndn