[/
    Copyright (c) 2013-2016 Vinnie Falco (vinnie dot falco at gmail 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:Reader Reader]

Parser implementations will construct the corresponding `reader` object
during the parse. This customization point allows the Body to determine
the strategy for storing incoming message body data.

In this table:

* `X` denotes a type meeting the requirements of [*`Reader`].

* `a` denotes a value of type `X`.

* `p` is any pointer.

* `n` is a value convertible to `std::size_t`.

* `ec` is a value of type `error_code&`.

* `m` denotes a value of type `message const&` where
    `std::is_same<decltype(m.body), Body::value_type>:value == true`


[table Reader requirements
[[operation] [type] [semantics, pre/post-conditions]]
[
    [`X a(m);`]
    []
    [
        `a` is constructible from `m`. The lifetime of `m` is
        guaranteed to end no earlier than after `a` is destroyed.
    ]
]
[
    [`a.write(p, n, ec)`]
    [`void`]
    [
        Deserializes the input sequence into the body.
        If `ec` is set, the deserialization is aborted and the error
        is returned to the caller.
    ]
]
]

[note Definitions for required `Reader` member functions should be declared
inline so the generated code becomes part of the implementation. ]

[endsect]