src/encoding/encoding-buffer.hpp

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
/*
 * Copyright (c) 2013, Regents of the University of California
 *
 * BSD license, See the LICENSE file for more information
 *
 * Author: Wentao Shang <wentao@cs.ucla.edu>
 */

#ifndef NDN_ENCODING_BUFFER_HPP
#define NDN_ENCODING_BUFFER_HPP

#include "../common.hpp"

#include <list>
#include <exception>
#include <algorithm>

#include "buffer.hpp"
#include "tlv.hpp"

#include <boost/lexical_cast.hpp>

namespace ndn {

/**
 * @brief Class representing wire element of the NDN packet
 */
class EncodingBuffer
{
public:
  /// @brief Error that can be thrown from the block
  struct Error : public std::runtime_error { Error(const std::string &what) : std::runtime_error(what) {} };

  enum
    {
      DefaultBufferSize = 8800,
      BufferReservedSize = 400
    };
  
  /**
   * @brief Default constructor to create a fix-sized EncodingBuffer
   */
  EncodingBuffer ()
    : m_buffer (new Buffer ((size_t) DefaultBufferSize))
  {
    m_begin = m_end = m_buffer->end () - BufferReservedSize;
  }

  /**
   * @brief Constructor to create a EncodingBuffer with user-specified size
   */
  EncodingBuffer (size_t size)
    : m_buffer (new Buffer (size))
  {
    if (size <= BufferReservedSize)
      m_begin = m_end = m_buffer->end ();
    else
      m_begin = m_end = m_buffer->end () - BufferReservedSize;
  }

  inline size_t
  size () const;

  inline size_t
  capacity () const;

  inline uint8_t*
  buf ();

  inline const uint8_t*
  buf () const;

  inline void
  resize (size_t sz, bool addInFront);

  inline Buffer::iterator
  begin ();

  inline Buffer::iterator
  end ();

  inline Buffer::const_iterator
  begin () const;

  inline Buffer::const_iterator
  end () const;

  inline size_t
  prependByte (uint8_t val);

  inline size_t
  prependByteArray (const uint8_t *arr, size_t len);

  inline size_t
  prependBuffer (const Buffer& arr);

  inline size_t
  prependNonNegativeInteger (uint64_t varNumber);

  inline size_t
  prependVarNumber (uint64_t varNumber);

  inline size_t
  appendByte (uint8_t val);

  inline size_t
  appendByteArray (const uint8_t *arr, size_t len);

  inline size_t
  appendBuffer (const Buffer& arr);

  inline size_t
  appendNonNegativeInteger (uint64_t varNumber);

  inline size_t
  appendVarNumber (uint64_t varNumber);

private:
  BufferPtr m_buffer;

  // invariant: m_begin always points to the position of last-written byte (if prepending data)
  Buffer::iterator m_begin;
  // invariant: m_end always points to the position of next unwritten byte (if appending data)
  Buffer::iterator m_end;
};

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

inline size_t
EncodingBuffer::size () const
{
  return m_end - m_begin;
}

inline size_t
EncodingBuffer::capacity () const
{
  return m_buffer->size ();
}

inline uint8_t*
EncodingBuffer::buf ()
{
  return &(*m_begin);
}

inline const uint8_t*
EncodingBuffer::buf () const
{
  return &(*m_begin);
}
  
inline void
EncodingBuffer::resize (size_t sz, bool addInFront)
{
  if (addInFront)
    {
      size_t diff_end = m_buffer->end () - m_end;
      size_t diff_begin = m_buffer->end () - m_begin;

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

      m_buffer.reset (buf);

      m_end = m_buffer->end () - diff_end;
      m_begin = m_buffer->end () - diff_begin;
    }
  else
    {
      size_t diff_end = m_end - m_buffer->begin ();
      size_t diff_begin = m_begin - m_buffer->begin ();

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

      m_buffer.reset (buf);

      m_end = m_buffer->begin () + diff_end;
      m_begin = m_buffer->begin () + diff_begin;      
    }
}

inline Buffer::iterator
EncodingBuffer::begin ()
{
  return m_begin;
}

inline Buffer::iterator
EncodingBuffer::end ()
{
  return m_end;
}

inline Buffer::const_iterator
EncodingBuffer::begin () const
{
  return m_begin;
}

inline Buffer::const_iterator
EncodingBuffer::end () const
{
  return m_end;
}


//////////////////////////////////////////////////////////
// Prepend to the back of the buffer. Resize if needed. //
//////////////////////////////////////////////////////////

inline size_t
EncodingBuffer::prependByte (uint8_t val)
{
  if (m_begin == m_buffer->begin ())
    resize (m_buffer->size () * 2, true);

  m_begin--;
  *m_begin = val;
  return 1;
}

inline size_t
EncodingBuffer::prependByteArray (const uint8_t *arr, size_t len)
{
  if ((m_buffer->begin () + len) > m_begin)
    resize (m_buffer->size () * 2 + len, true);

  m_begin -= len;
  std::copy (arr, arr + len, m_begin);
  return len;
}

inline size_t
EncodingBuffer::prependBuffer (const Buffer& arr)
{
  if ((m_buffer->begin () + arr.size ()) > m_begin)
    resize (m_buffer->size () * 2 + arr.size (), true);

  m_begin -= arr.size ();
  std::copy (arr.begin (), arr.end (), m_begin);
  return arr.size ();
}

inline size_t
EncodingBuffer::prependNonNegativeInteger (uint64_t varNumber)
{
  if (varNumber < 253) {
    return prependByte (static_cast<uint8_t> (varNumber));
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max ()) {
    uint16_t value = htobe16 (static_cast<uint16_t> (varNumber));
    return prependByteArray (reinterpret_cast<const uint8_t*> (&value), 2);
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max ()) {
    uint32_t value = htobe32 (static_cast<uint32_t> (varNumber));
    return prependByteArray (reinterpret_cast<const uint8_t*> (&value), 4);
  }
  else {
    uint64_t value = htobe64 (varNumber);
    return prependByteArray (reinterpret_cast<const uint8_t*> (&value), 8);
  }
}

inline size_t
EncodingBuffer::prependVarNumber (uint64_t varNumber)
{
  if (varNumber < 253) {
    prependByte (static_cast<uint8_t> (varNumber));
    return 1;
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max ()) {
    uint16_t value = htobe16 (static_cast<uint16_t> (varNumber));
    prependByteArray (reinterpret_cast<const uint8_t*> (&value), 2);
    prependByte (253);
    return 3;
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max ()) {
    uint32_t value = htobe32 (static_cast<uint32_t> (varNumber));
    prependByteArray (reinterpret_cast<const uint8_t*> (&value), 4);
    prependByte (254);
    return 5;
  }
  else {
    uint64_t value = htobe64 (varNumber);
    prependByteArray (reinterpret_cast<const uint8_t*> (&value), 8);
    prependByte (255);
    return 9;
  }
}

/////////////////////////////////////////////////////////
// Append to the back of the buffer. Resize if needed. //
/////////////////////////////////////////////////////////

inline size_t
EncodingBuffer::appendByte (uint8_t val)
{
  if (m_end == m_buffer->end ())
    resize (m_buffer->size () * 2, false);

  *m_end = val;
  m_end++;
  return 1;
}

inline size_t
EncodingBuffer::appendByteArray (const uint8_t *arr, size_t len)
{
  if ((m_end + len) > m_buffer->end ())
    resize (m_buffer->size () * 2 + len, false);

  std::copy (arr, arr + len, m_end);
  m_end += len;
  return len;
}

inline size_t
EncodingBuffer::appendBuffer (const Buffer& arr)
{
  if ((m_end + arr.size ()) > m_buffer->end ())
    resize (m_buffer->size () * 2 + arr.size (), false);

  std::copy (arr.begin (), arr.end (), m_end);
  m_end -= arr.size ();
  return arr.size ();
}

inline size_t
EncodingBuffer::appendNonNegativeInteger (uint64_t varNumber)
{
  if (varNumber < 253) {
    return appendByte (static_cast<uint8_t> (varNumber));
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max ()) {
    uint16_t value = htobe16 (static_cast<uint16_t> (varNumber));
    return appendByteArray (reinterpret_cast<const uint8_t*> (&value), 2);
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max ()) {
    uint32_t value = htobe32 (static_cast<uint32_t> (varNumber));
    return appendByteArray (reinterpret_cast<const uint8_t*> (&value), 4);
  }
  else {
    uint64_t value = htobe64 (varNumber);
    return appendByteArray (reinterpret_cast<const uint8_t*> (&value), 8);
  }
}

inline size_t
EncodingBuffer::appendVarNumber (uint64_t varNumber)
{
  if (varNumber < 253) {
    appendByte (static_cast<uint8_t> (varNumber));
    return 1;
  }
  else if (varNumber <= std::numeric_limits<uint16_t>::max ()) {
    appendByte (253);
    uint16_t value = htobe16 (static_cast<uint16_t> (varNumber));
    appendByteArray (reinterpret_cast<const uint8_t*> (&value), 2);
    return 3;
  }
  else if (varNumber <= std::numeric_limits<uint32_t>::max ()) {
    appendByte (254);
    uint32_t value = htobe32 (static_cast<uint32_t> (varNumber));
    appendByteArray (reinterpret_cast<const uint8_t*> (&value), 4);
    return 5;
  }
  else {
    appendByte (255);
    uint64_t value = htobe64 (varNumber);
    appendByteArray (reinterpret_cast<const uint8_t*> (&value), 8);
    return 9;
  }
}

} // ndn

#endif // NDN_ENCODING_BUFFER_HPP