boost::capy::WriteStream

Concept for types that provide awaitable write operations.

Synopsis

Declared in <boost/capy/concept/write_stream.hpp>

template<typename T>
concept WriteStream = requires(T& stream, const_buffer_archetype buffers)
    {
        { stream.write_some(buffers) } ‐> IoAwaitable;
        requires awaitable_decomposes_to<
            decltype(stream.write_some(buffers)),
            system::error_code, std::size_t>;
    };

Description

A type satisfies WriteStream if it provides a write_some member function template that accepts any ConstBufferSequence and is an IoAwaitable whose return value decomposes to (system::error_code, std::size_t).

Syntactic Requirements

`T` must provide a `write_some` member function template accepting any ConstBufferSequence
The return type of `write_some` must satisfy IoAwaitable
The awaitable's result must decompose to `(system::error_code, std::size_t)` via structured bindings

Semantic Requirements

If buffer_size(buffers) > 0, the operation writes one or more bytes of data to the stream from the buffer sequence:

On success: `!ec` is `true`, and `n` is the number of bytes written.
On error: `!!ec` is `true`, and `n` is 0.

If buffer_empty(buffers) is true, the operation completes immediately. !ec is true, and n is 0.

Buffers in the sequence are written completely before proceeding to the next buffer.

Buffer Lifetime

The caller must ensure that the memory referenced by buffers remains valid until the co_await expression returns.

Conforming Signatures

// Templated for any ConstBufferSequence
template<ConstBufferSequence CB>
some_io_awaitable<std::pair<system::error_code, std::size_t>>
write_some(CB const& buffers);

Example

template<WriteStream Stream>
task<void> write_all(Stream& s, char const* buf, std::size_t size)
{
    std::size_t total = 0;
    while (total < size)
    {
        auto [ec, n] = co_await s.write_some(
            const_buffer(buf + total, size - total));
        if (ec)
            co_return;
        total += n;
    }
}

Template Parameters

Name	Description
T	The stream type.