ncurses non-blocking I/O with Boost.Asio
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README.md

ncurses-poll

1. Introduction

This repository contains a simple header, ncurses-poll.hpp. With it, you can perform non-blocking I/O in your ncurses application.

2. Features

2.1 Multiple instances

Each instance of ncurses_poll wraps an ncurses SCREEN*. Multiple instances can be handled simultaneously in one thread.

Note that there's no need to call set_term() because this is done by the header before callbacks are invoked.

2.2 Boost.Asio and coroutines

Asynchronous I/O is achieved using Boost.Asio. Thus, other libraries(e.g. Beast) which uses Boost.Asio can be easily integrated into your ncurses applications.

Boost.Asio's stackless coroutine is also supported for cleaner and human-friendlier code.

3. Documentation

3.1 Event loop

An ncurses_poll instance must run within a Boost.Asio event loop (aka io_context). A const reference to an io_context instance should be passed to the constructor.

3.2 Session

The ncurses_poll class template requires a parameter Session, which is the type of session. The session may contain username, permission, or other data concerning a specific connection.

Session must be a class with a constructor which accepts a pointer to this ncurses_poll<session> class.

To get pointer to current session instance of an ncurses_poll instance, call session() method.

3.2 Async read/write

A read/write operation may block, so we need to determine whether the stream is readable/writable before performing I/O.

The on_readable and on_writable methods accept a single parameter, the const reference to a callback function. Once the stream is readable/writable, the given callback will be invoked.

The callback function should be of the following type:

using callback =
    std::function<void(const boost::system::error_code&, ncurses_poll*)>;
  • The first argument of callback is the error code, upon success it yields zero, otherwise it is set to the corresponding errno. You should always handle error_code before performing I/O.
  • The second argument is the pointer to the ncurses_poll instance.

3.3 Using coroutines

Boost.Asio's stackless coroutine requires a boost::asio::coroutine instance. You can simply use the coro property of ncurses_poll. For example, in a callback function:

if (!ec) reenter(poll->coro) for (;;) {
    yield poll->on_writable(cb);
    // ...
}

3.4 Other operations

To get corresponding io_context instance, call get_io_context() method.

To get SCREEN pointer to current ncurses instance, call screen() method.

3.5 See also