trale 0.3.0

Trale is a minimalistic Rust async executor using io_uring for efficient, correct task execution.
Documentation 
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//! Asynchronous writes.
//!
//! The `write` module provides functionality for performing asynchronous writes
//! to non-blocking file descriptors (FDs). It allows tasks to attempt writing
//! data to an FD without blocking the executor, enabling efficient handling of
//! I/O operations in an async environment.
//!
//! Various futures within trale implement the `AsyncWrite` trait, and those
//! that do will allow you to await a call to [AsyncWrite::write].
use std::{
    future::Future,
    io,
    os::fd::{AsFd, AsRawFd},
    pin::Pin,
    task::{Context, Poll},
};

use io_uring::{opcode, types};

use crate::reactor::ReactorIo;

/// Asynchronous writes.
///
/// All futures in trale that can be written to will implement this type. You
/// can call the [AsyncWrite::write] function to obtain a future which will
/// complete once the requested write has finished (successfully or not).
pub trait AsyncWrite {
    /// Return a future that, when `.await`ed will block until the write has
    /// been successful or not. When successful, the number of bytes that were
    /// written is returned. Note that this might be *less* than the number of
    /// bytes in `buf`.
    fn write(&mut self, buf: &[u8]) -> impl Future<Output = io::Result<usize>>;
}

pub(crate) struct AsyncWriter<'a, T: AsFd + Unpin> {
    pub(crate) fd: T,
    pub(crate) io: ReactorIo,
    pub(crate) buf: &'a [u8],
    pub(crate) seekable: bool,
}

impl<T: AsFd + Unpin> Future for AsyncWriter<'_, T> {
    type Output = io::Result<usize>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = unsafe { self.get_unchecked_mut() };

        this.io
            .submit_or_get_result(|| {
                (
                    opcode::Write::new(
                        types::Fd(this.fd.as_fd().as_raw_fd()),
                        this.buf.as_ptr(),
                        this.buf.len() as _,
                    )
                    .offset(if this.seekable { u64::MAX } else { 0 })
                    .build(),
                    cx.waker().clone(),
                )
            })
            .map(|x| x.map(|x| x as _))
    }
}