darkbio-wire 0.5.0

// wire-rs: encrypted protocol between Ark and host
// Copyright 2026 Dark Bio AG. All rights reserved.

//! Standard byte I/O with separate read and write deadlines. Transport chooses
//! an absolute deadline. The adapter limits how long its I/O can block and keeps
//! the stream reusable after a timeout.

use std::io;
use std::time::Instant;

/// A standard byte reader whose blocking operations honor an absolute deadline.
///
/// An idle read returns `TimedOut` when its deadline expires, without consuming
/// bytes. Transport retries early timeouts and interruptions within the same
/// deadline. Reads that consume bytes must report them through the standard
/// [`io::Read`] contract. Timeouts leave the adapter open and reusable.
///
/// The actual I/O must honor the deadline. Checking the clock before a call that
/// can block indefinitely is insufficient. With no deadline, reads wait for data
/// or shutdown. The stream's shutdown operation must release blocked reads.
pub trait Read: io::Read {
    /// Installs the deadline for subsequent reads until replaced; `None` clears
    /// it. Returns promptly, transfers no bytes and leaves the write deadline
    /// unchanged.
    /// Reads attempted after expiration must not wait. Adapters may return
    /// immediately available bytes, EOF or an empty read, or report `TimedOut`.
    /// Transport enforces its own deadline before calling the adapter. If this
    /// setter fails, transport returns the error without attempting a read.
    fn set_read_deadline(&mut self, deadline: Option<Instant>) -> io::Result<()>;
}

impl<T: Read + ?Sized> Read for &mut T {
    fn set_read_deadline(&mut self, deadline: Option<Instant>) -> io::Result<()> {
        (**self).set_read_deadline(deadline)
    }
}

impl<T: Read + ?Sized> Read for Box<T> {
    fn set_read_deadline(&mut self, deadline: Option<Instant>) -> io::Result<()> {
        (**self).set_read_deadline(deadline)
    }
}

/// A standard byte writer whose writes and flushes honor an absolute deadline.
///
/// The installed deadline covers partial writes and flush. Progress does not
/// restart it. Expiration returns `TimedOut` and leaves the adapter open and
/// reusable. Each write reports accepted bytes through the standard [`io::Write`]
/// contract. A frame can therefore fail after earlier writes accepted a prefix.
/// Successful output does not guarantee that the peer received or processed it.
///
/// Pending transfers must remain ordered before subsequent output or be cancelled
/// before that output begins. An abandoned operation must never append bytes out
/// of order after a later call starts writing. The adapter must bound actual I/O.
pub trait Write: io::Write {
    /// Installs the deadline for subsequent writes and flushes until replaced.
    /// Returns promptly, transfers no bytes and leaves the read deadline unchanged.
    /// Operations attempted after expiration return `TimedOut`. If this setter
    /// fails, transport returns the error without attempting a write or flush.
    fn set_write_deadline(&mut self, deadline: Instant) -> io::Result<()>;
}

impl<T: Write + ?Sized> Write for &mut T {
    fn set_write_deadline(&mut self, deadline: Instant) -> io::Result<()> {
        (**self).set_write_deadline(deadline)
    }
}

impl<T: Write + ?Sized> Write for Box<T> {
    fn set_write_deadline(&mut self, deadline: Instant) -> io::Result<()> {
        (**self).set_write_deadline(deadline)
    }
}

/// Refuses work whose absolute I/O deadline has already elapsed.
pub(super) fn check_deadline(deadline: Instant) -> io::Result<()> {
    if Instant::now() >= deadline {
        Err(io::Error::new(
            io::ErrorKind::TimedOut,
            "I/O deadline expired",
        ))
    } else {
        Ok(())
    }
}