//! Networking primitives for TCP/UDP communication.
//!
//! This module provides networking functionality for the Transmission Control and User
//! Datagram Protocols, as well as types for IP and socket addresses.
//!
//! # Organization
//!
//! * [`TcpListener`] and [`TcpStream`] provide functionality for communication over TCP
//! * [`UdpSocket`] provides functionality for communication over UDP
//! * [`IpAddr`] represents IP addresses of either IPv4 or IPv6; [`Ipv4Addr`] and
//!   [`Ipv6Addr`] are respectively IPv4 and IPv6 addresses
//! * [`SocketAddr`] represents socket addresses of either IPv4 or IPv6; [`SocketAddrV4`]
//!   and [`SocketAddrV6`] are respectively IPv4 and IPv6 socket addresses
//! * [`ToSocketAddrs`] is a trait that is used for generic address resolution when interacting
//!   with networking objects like [`TcpListener`], [`TcpStream`] or [`UdpSocket`]
//! * Other types are return or parameter types for various methods in this module
//!
//! Rust disables inheritance of socket objects to child processes by default when possible.  For
//! example, through the use of the `CLOEXEC` flag in UNIX systems or the `HANDLE_FLAG_INHERIT`
//! flag on Windows.

use crate::std::io::{self, ErrorKind};

pub use self::ip_addr::{IpAddr, Ipv4Addr, Ipv6Addr, Ipv6MulticastScope};
pub use self::socket_addr::{SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs};
pub use self::tcp::IntoIncoming;
pub use self::tcp::{Incoming, TcpListener, TcpStream};
pub use self::udp::UdpSocket;
pub use core::net::AddrParseError;

mod ip_addr;
mod socket_addr;
mod tcp;
#[cfg(test)]
pub(crate) mod test;
mod udp;

/// Possible values which can be passed to the [`TcpStream::shutdown`] method.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Shutdown {
    /// The reading portion of the [`TcpStream`] should be shut down.
    ///
    /// All currently blocked and future [reads] will return <code>[Ok]\(0)</code>.
    ///
    /// [reads]: crate::std::io::Read "io::Read"
    Read,
    /// The writing portion of the [`TcpStream`] should be shut down.
    ///
    /// All currently blocked and future [writes] will return an error.
    ///
    /// [writes]: crate::std::io::Write "io::Write"
    Write,
    /// Both the reading and the writing portions of the [`TcpStream`] should be shut down.
    ///
    /// See [`Shutdown::Read`] and [`Shutdown::Write`] for more information.
    Both,
}

fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
where
    F: FnMut(io::Result<&SocketAddr>) -> io::Result<T>,
{
    let addrs = match addr.to_socket_addrs() {
        Ok(addrs) => addrs,
        Err(e) => return f(Err(e)),
    };
    let mut last_err = None;
    for addr in addrs {
        match f(Ok(&addr)) {
            Ok(l) => return Ok(l),
            Err(e) => last_err = Some(e),
        }
    }
    Err(last_err.unwrap_or_else(|| {
        io::const_io_error!(
            ErrorKind::InvalidInput,
            "could not resolve to any addresses"
        )
    }))
}
