[/
/ Copyright (c) 2003-2025 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:CompletionCondition Completion condition requirements]
A ['completion condition] is a function object that is used with the algorithms
[link asio.reference.read `read`], [link asio.reference.async_read
`async_read`], [link asio.reference.write `write`], and [link
asio.reference.async_write `async_write`] to determine when the algorithm has
completed transferring data.
A type `X` meets the `CompletionCondition` requirements if it satisfies the
requirements of `Destructible` (C++Std [destructible]) and
`MoveConstructible` (C++Std [moveconstructible]), as well as the additional
requirements listed below.
In the table below, `x` denotes a value of type `X`, `ec` denotes a (possibly
const) value of type `error_code`, and `n` denotes a (possibly const) value of
type `size_t`.
[table CompletionCondition requirements
[[expression] [return type] [assertion/note[br]pre/post-condition]]
[
[`x(ec, n)`]
[`size_t`]
[
Let `n` be the total number of bytes transferred by the read or write
algorithm so far.[br]
[br]
Returns the maximum number of bytes to be transferred on the next
`read_some`, `async_read_some`, `write_some`, or `async_write_some`
operation performed by the algorithm. Returns `0` to indicate that the
algorithm is complete.
]
]
]
[endsect]