/Lib/include/boost/asio/buffered_read_stream.hpp

//

// buffered_read_stream.hpp

// ~~~~~~~~~~~~~~~~~~~~~~~~

//

// Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com)

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//



#ifndef BOOST_ASIO_BUFFERED_READ_STREAM_HPP

#define BOOST_ASIO_BUFFERED_READ_STREAM_HPP



#if defined(_MSC_VER) && (_MSC_VER >= 1200)

# pragma once

#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)



#include <boost/asio/detail/push_options.hpp>



#include <boost/asio/detail/push_options.hpp>

#include <cstddef>

#include <cstring>

#include <boost/config.hpp>

#include <boost/type_traits.hpp>

#include <boost/asio/detail/pop_options.hpp>



#include <boost/asio/buffered_read_stream_fwd.hpp>

#include <boost/asio/buffer.hpp>

#include <boost/asio/error.hpp>

#include <boost/asio/io_service.hpp>

#include <boost/asio/detail/bind_handler.hpp>

#include <boost/asio/detail/buffer_resize_guard.hpp>

#include <boost/asio/detail/buffered_stream_storage.hpp>

#include <boost/asio/detail/noncopyable.hpp>



namespace boost {

namespace asio {



/// Adds buffering to the read-related operations of a stream.

/**

 * The buffered_read_stream class template can be used to add buffering to the

 * synchronous and asynchronous read operations of a stream.

 *

 * @par Thread Safety

 * @e Distinct @e objects: Safe.@n

 * @e Shared @e objects: Unsafe.

 *

 * @par Concepts:

 * AsyncReadStream, AsyncWriteStream, Stream, Sync_Read_Stream, SyncWriteStream.

 */

template <typename Stream>

class buffered_read_stream

  : private noncopyable

{

public:

  /// The type of the next layer.

  typedef typename boost::remove_reference<Stream>::type next_layer_type;



  /// The type of the lowest layer.

  typedef typename next_layer_type::lowest_layer_type lowest_layer_type;



#if defined(GENERATING_DOCUMENTATION)

  /// The default buffer size.

  static const std::size_t default_buffer_size = implementation_defined;

#else

  BOOST_STATIC_CONSTANT(std::size_t, default_buffer_size = 1024);

#endif



  /// Construct, passing the specified argument to initialise the next layer.

  template <typename Arg>

  explicit buffered_read_stream(Arg& a)

    : next_layer_(a),

      storage_(default_buffer_size)

  {

  }



  /// Construct, passing the specified argument to initialise the next layer.

  template <typename Arg>

  buffered_read_stream(Arg& a, std::size_t buffer_size)

    : next_layer_(a),

      storage_(buffer_size)

  {

  }



  /// Get a reference to the next layer.

  next_layer_type& next_layer()

  {

    return next_layer_;

  }



  /// Get a reference to the lowest layer.

  lowest_layer_type& lowest_layer()

  {

    return next_layer_.lowest_layer();

  }



  /// (Deprecated: use get_io_service().) Get the io_service associated with

  /// the object.

  boost::asio::io_service& io_service()

  {

    return next_layer_.get_io_service();

  }



  /// Get the io_service associated with the object.

  boost::asio::io_service& get_io_service()

  {

    return next_layer_.get_io_service();

  }



  /// Close the stream.

  void close()

  {

    next_layer_.close();

  }



  /// Close the stream.

  boost::system::error_code close(boost::system::error_code& ec)

  {

    return next_layer_.close(ec);

  }



  /// Write the given data to the stream. Returns the number of bytes written.

  /// Throws an exception on failure.

  template <typename ConstBufferSequence>

  std::size_t write_some(const ConstBufferSequence& buffers)

  {

    return next_layer_.write_some(buffers);

  }



  /// Write the given data to the stream. Returns the number of bytes written,

  /// or 0 if an error occurred.

  template <typename ConstBufferSequence>

  std::size_t write_some(const ConstBufferSequence& buffers,

      boost::system::error_code& ec)

  {

    return next_layer_.write_some(buffers, ec);

  }



  /// Start an asynchronous write. The data being written must be valid for the

  /// lifetime of the asynchronous operation.

  template <typename ConstBufferSequence, typename WriteHandler>

  void async_write_some(const ConstBufferSequence& buffers,

      WriteHandler handler)

  {

    next_layer_.async_write_some(buffers, handler);

  }



  /// Fill the buffer with some data. Returns the number of bytes placed in the

  /// buffer as a result of the operation. Throws an exception on failure.

  std::size_t fill()

  {

    detail::buffer_resize_guard<detail::buffered_stream_storage>

      resize_guard(storage_);

    std::size_t previous_size = storage_.size();

    storage_.resize(storage_.capacity());

    storage_.resize(previous_size + next_layer_.read_some(buffer(

            storage_.data() + previous_size,

            storage_.size() - previous_size)));

    resize_guard.commit();

    return storage_.size() - previous_size;

  }



  /// Fill the buffer with some data. Returns the number of bytes placed in the

  /// buffer as a result of the operation, or 0 if an error occurred.

  std::size_t fill(boost::system::error_code& ec)

  {

    detail::buffer_resize_guard<detail::buffered_stream_storage>

      resize_guard(storage_);

    std::size_t previous_size = storage_.size();

    storage_.resize(storage_.capacity());

    storage_.resize(previous_size + next_layer_.read_some(buffer(

            storage_.data() + previous_size,

            storage_.size() - previous_size),

          ec));

    resize_guard.commit();

    return storage_.size() - previous_size;

  }



  template <typename ReadHandler>

  class fill_handler

  {

  public:

    fill_handler(boost::asio::io_service& io_service,

        detail::buffered_stream_storage& storage,

        std::size_t previous_size, ReadHandler handler)

      : io_service_(io_service),

        storage_(storage),

        previous_size_(previous_size),

        handler_(handler)

    {

    }



    void operator()(const boost::system::error_code& ec,

        std::size_t bytes_transferred)

    {

      storage_.resize(previous_size_ + bytes_transferred);

      io_service_.dispatch(detail::bind_handler(

            handler_, ec, bytes_transferred));

    }



  private:

    boost::asio::io_service& io_service_;

    detail::buffered_stream_storage& storage_;

    std::size_t previous_size_;

    ReadHandler handler_;

  };



  /// Start an asynchronous fill.

  template <typename ReadHandler>

  void async_fill(ReadHandler handler)

  {

    std::size_t previous_size = storage_.size();

    storage_.resize(storage_.capacity());

    next_layer_.async_read_some(

        buffer(

          storage_.data() + previous_size,

          storage_.size() - previous_size),

        fill_handler<ReadHandler>(get_io_service(),

          storage_, previous_size, handler));

  }



  /// Read some data from the stream. Returns the number of bytes read. Throws

  /// an exception on failure.

  template <typename MutableBufferSequence>

  std::size_t read_some(const MutableBufferSequence& buffers)

  {

    if (storage_.empty())

      fill();

    return copy(buffers);

  }



  /// Read some data from the stream. Returns the number of bytes read or 0 if

  /// an error occurred.

  template <typename MutableBufferSequence>

  std::size_t read_some(const MutableBufferSequence& buffers,

      boost::system::error_code& ec)

  {

    ec = boost::system::error_code();

    if (storage_.empty() && !fill(ec))

      return 0;

    return copy(buffers);

  }



  template <typename MutableBufferSequence, typename ReadHandler>

  class read_some_handler

  {

  public:

    read_some_handler(boost::asio::io_service& io_service,

        detail::buffered_stream_storage& storage,

        const MutableBufferSequence& buffers, ReadHandler handler)

      : io_service_(io_service),

        storage_(storage),

        buffers_(buffers),

        handler_(handler)

    {

    }



    void operator()(const boost::system::error_code& ec, std::size_t)

    {

      if (ec || storage_.empty())

      {

        std::size_t length = 0;

        io_service_.dispatch(detail::bind_handler(handler_, ec, length));

      }

      else

      {

        using namespace std; // For memcpy.



        std::size_t bytes_avail = storage_.size();

        std::size_t bytes_copied = 0;



        typename MutableBufferSequence::const_iterator iter = buffers_.begin();

        typename MutableBufferSequence::const_iterator end = buffers_.end();

        for (; iter != end && bytes_avail > 0; ++iter)

        {

          std::size_t max_length = buffer_size(*iter);

          std::size_t length = (max_length < bytes_avail)

            ? max_length : bytes_avail;

          memcpy(buffer_cast<void*>(*iter),

              storage_.data() + bytes_copied, length);

          bytes_copied += length;

          bytes_avail -= length;

        }



        storage_.consume(bytes_copied);

        io_service_.dispatch(detail::bind_handler(handler_, ec, bytes_copied));

      }

    }



  private:

    boost::asio::io_service& io_service_;

    detail::buffered_stream_storage& storage_;

    MutableBufferSequence buffers_;

    ReadHandler handler_;

  };



  /// Start an asynchronous read. The buffer into which the data will be read

  /// must be valid for the lifetime of the asynchronous operation.

  template <typename MutableBufferSequence, typename ReadHandler>

  void async_read_some(const MutableBufferSequence& buffers,

      ReadHandler handler)

  {

    if (storage_.empty())

    {

      async_fill(read_some_handler<MutableBufferSequence, ReadHandler>(

            get_io_service(), storage_, buffers, handler));

    }

    else

    {

      std::size_t length = copy(buffers);

      get_io_service().post(detail::bind_handler(

            handler, boost::system::error_code(), length));

    }

  }



  /// Peek at the incoming data on the stream. Returns the number of bytes read.

  /// Throws an exception on failure.

  template <typename MutableBufferSequence>

  std::size_t peek(const MutableBufferSequence& buffers)

  {

    if (storage_.empty())

      fill();

    return peek_copy(buffers);

  }



  /// Peek at the incoming data on the stream. Returns the number of bytes read,

  /// or 0 if an error occurred.

  template <typename MutableBufferSequence>

  std::size_t peek(const MutableBufferSequence& buffers,

      boost::system::error_code& ec)

  {

    ec = boost::system::error_code();

    if (storage_.empty() && !fill(ec))

      return 0;

    return peek_copy(buffers);

  }



  /// Determine the amount of data that may be read without blocking.

  std::size_t in_avail()

  {

    return storage_.size();

  }



  /// Determine the amount of data that may be read without blocking.

  std::size_t in_avail(boost::system::error_code& ec)

  {

    ec = boost::system::error_code();

    return storage_.size();

  }



private:

  /// Copy data out of the internal buffer to the specified target buffer.

  /// Returns the number of bytes copied.

  template <typename MutableBufferSequence>

  std::size_t copy(const MutableBufferSequence& buffers)

  {

    using namespace std; // For memcpy.



    std::size_t bytes_avail = storage_.size();

    std::size_t bytes_copied = 0;



    typename MutableBufferSequence::const_iterator iter = buffers.begin();

    typename MutableBufferSequence::const_iterator end = buffers.end();

    for (; iter != end && bytes_avail > 0; ++iter)

    {

      std::size_t max_length = buffer_size(*iter);

      std::size_t length = (max_length < bytes_avail)

        ? max_length : bytes_avail;

      memcpy(buffer_cast<void*>(*iter), storage_.data() + bytes_copied, length);

      bytes_copied += length;

      bytes_avail -= length;

    }



    storage_.consume(bytes_copied);

    return bytes_copied;

  }



  /// Copy data from the internal buffer to the specified target buffer, without

  /// removing the data from the internal buffer. Returns the number of bytes

  /// copied.

  template <typename MutableBufferSequence>

  std::size_t peek_copy(const MutableBufferSequence& buffers)

  {

    using namespace std; // For memcpy.



    std::size_t bytes_avail = storage_.size();

    std::size_t bytes_copied = 0;



    typename MutableBufferSequence::const_iterator iter = buffers.begin();

    typename MutableBufferSequence::const_iterator end = buffers.end();

    for (; iter != end && bytes_avail > 0; ++iter)

    {

      std::size_t max_length = buffer_size(*iter);

      std::size_t length = (max_length < bytes_avail)

        ? max_length : bytes_avail;

      memcpy(buffer_cast<void*>(*iter), storage_.data() + bytes_copied, length);

      bytes_copied += length;

      bytes_avail -= length;

    }



    return bytes_copied;

  }



  /// The next layer.

  Stream next_layer_;



  // The data in the buffer.

  detail::buffered_stream_storage storage_;

};



} // namespace asio

} // namespace boost



#include <boost/asio/detail/pop_options.hpp>



#endif // BOOST_ASIO_BUFFERED_READ_STREAM_HPP