[/
 / Copyright (c) 2003-2016 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)
 /]

[section:DynamicBufferSequence Dynamic buffer sequence requirements]

A dynamic buffer sequence encapsulates memory storage that may be automatically
resized as required, where the memory is divided into an input sequence
followed by an output sequence. These memory regions are internal to the
dynamic buffer sequence, but direct access to the elements is provided to
permit them to be efficiently used with I/O operations, such as the `send` or
`receive` operations of a socket. Data written to the output sequence of a
dynamic buffer sequence object is appended to the input sequence of the same
object.

A dynamic buffer sequence type `X` shall satisfy the requirements of
`MoveConstructible` (C++ Std, [moveconstructible]) types in addition to those
listed below.

In the table below, `X` denotes a dynamic buffer sequence class, `x` denotes a
value of type `X&`, `x1` denotes values of type `const X&`, and `n` denotes a
value of type `size_t`, and `u` denotes an identifier.

[table DynamicBufferSequence requirements
  [[expression] [type] [assertion/note\npre/post-conditions]]
  [
    [`X::const_buffers_type`]
    [type meeting [link asio.reference.ConstBufferSequence ConstBufferSequence]
     requirements.]
    [This type represents the memory associated with the input sequence.]
  ]
  [
    [`X::mutable_buffers_type`]
    [type meeting [link asio.reference.MutableBufferSequence MutableBufferSequence]
     requirements.]
    [This type represents the memory associated with the output sequence.]
  ]
  [
    [`x1.size()`]
    [`size_t`]
    [Returns the size, in bytes, of the input sequence.]
  ]
  [
    [`x1.max_size()`]
    [`size_t`]
    [Returns the permitted maximum of the sum of the sizes of the input
     sequence and output sequence.]
  ]
  [
    [`x1.capacity()`]
    [`size_t`]
    [Returns the maximum sum of the sizes of the input sequence and output
     sequence that the dynamic buffer sequence can hold without requiring
     reallocation.]
  ]
  [
    [`x1.data()`]
    [`X::const_buffers_type`]
    [Returns a constant buffer sequence `u` that represents the memory
     associated with the input sequence, and where `buffer_size(u) == size()`.]
  ]
  [
    [`x.prepare(n)`]
    [`X::mutable_buffers_type`]
    [Requires: `size() + n <= max_size()`.\n
     \n
     Returns a mutable buffer sequence `u` representing the output sequence, and
     where `buffer_size(u) == n`. The dynamic buffer sequence reallocates
     memory as required. All constant or mutable buffer sequences previously
     obtained using `data()` or `prepare()` are invalidated.\n
     \n
     Throws: `length_error` if `size() + n > max_size()`.]
  ]
  [
    [`x.commit(n)`]
    []
    [Appends `n` bytes from the start of the output sequence to the end of the
     input sequence. The remainder of the output sequence is discarded. If `n`
     is greater than the size of the output sequence, the entire output sequence
     is appended to the input sequence. All constant or mutable buffer sequences
     previously obtained using `data()` or `prepare()` are invalidated.]
  ]
  [
    [`x.consume(n)`]
    []
    [Removes `n` bytes from beginning of the input sequence. If `n` is greater
     than the size of the input sequence, the entire input sequence is removed.
     All constant or mutable buffer sequences previously obtained using `data()`
     or `prepare()` are invalidated.]
  ]
]

[endsect]