use crate::cmp::Ordering;
use crate::fmt::{self, Write};
use crate::hash;
use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr};

use super::display_buffer::DisplayBuffer;

/// Internet 套接字地址，IPv4 或 IPv6。
///
/// Internet 套接字地址包含一个 [IP 地址][IP address]，一个 16 位端口号以及一些可能与版本有关的附加信息。
/// 有关更多详细信息，请参见 [`SocketAddrV4`] 和 [`SocketAddrV6`] 的文档。
///
/// `SocketAddr` 实例的大小可能会因目标操作系统而异。
///
/// [IP address]: IpAddr
///
/// # Examples
///
/// ```
/// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
///
/// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
///
/// assert_eq!("127.0.0.1:8080".parse(), Ok(socket));
/// assert_eq!(socket.port(), 8080);
/// assert_eq!(socket.is_ipv4(), true);
/// ```
///
///
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
#[stable(feature = "rust1", since = "1.0.0")]
pub enum SocketAddr {
    /// IPv4 套接字地址。
    #[stable(feature = "rust1", since = "1.0.0")]
    V4(#[stable(feature = "rust1", since = "1.0.0")] SocketAddrV4),
    /// IPv6 套接字地址。
    #[stable(feature = "rust1", since = "1.0.0")]
    V6(#[stable(feature = "rust1", since = "1.0.0")] SocketAddrV6),
}

/// IPv4 套接字地址。
///
/// IPv4 套接字地址由 [`IPv4` 地址][`IPv4` address] 和一个 16 位端口号组成，如 [IETF RFC 793] 中所述。
///
///
/// 有关同时包含 IPv4 和 IPv6 套接字地址的类型，请参见 [`SocketAddr`]。
///
/// `SocketAddrV4` 结构体的大小可能会因目标操作系统而异。
/// 不要假设此类型与底层系统表示具有相同的内存布局。
///
/// [IETF RFC 793]: https://tools.ietf.org/html/rfc793
/// [`IPv4` address]: Ipv4Addr
///
/// # Examples
///
/// ```
/// use std::net::{Ipv4Addr, SocketAddrV4};
///
/// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
///
/// assert_eq!("127.0.0.1:8080".parse(), Ok(socket));
/// assert_eq!(socket.ip(), &Ipv4Addr::new(127, 0, 0, 1));
/// assert_eq!(socket.port(), 8080);
/// ```
///
#[derive(Copy, Clone, Eq, PartialEq)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct SocketAddrV4 {
    ip: Ipv4Addr,
    port: u16,
}

/// IPv6 套接字地址。
///
/// IPv6 套接字地址由一个 [`IPv6` 地址][`IPv6` address] 和一个 16 位端口号，以及包含流类别、流标签和作用域标识符的字段组成 (更多详细信息，请参见 [IETF RFC 2553，第 3.3 节][IETF RFC 2553, Section 3.3])。
///
///
/// 有关同时包含 IPv4 和 IPv6 套接字地址的类型，请参见 [`SocketAddr`]。
///
/// `SocketAddrV6` 结构体的大小可能会因目标操作系统而异。不要假设此类型与底层系统表示具有相同的内存布局。
///
/// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
/// [`IPv6` address]: Ipv6Addr
///
/// # Examples
///
/// ```
/// use std::net::{Ipv6Addr, SocketAddrV6};
///
/// let socket = SocketAddrV6::new(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
///
/// assert_eq!("[2001:db8::1]:8080".parse(), Ok(socket));
/// assert_eq!(socket.ip(), &Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1));
/// assert_eq!(socket.port(), 8080);
/// ```
///
///
///
#[derive(Copy, Clone, Eq, PartialEq)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct SocketAddrV6 {
    ip: Ipv6Addr,
    port: u16,
    flowinfo: u32,
    scope_id: u32,
}

impl SocketAddr {
    /// 从 [IP 地址][IP address] 和端口号创建一个新的套接字地址。
    ///
    /// [IP address]: IpAddr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[stable(feature = "ip_addr", since = "1.7.0")]
    #[must_use]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn new(ip: IpAddr, port: u16) -> SocketAddr {
        match ip {
            IpAddr::V4(a) => SocketAddr::V4(SocketAddrV4::new(a, port)),
            IpAddr::V6(a) => SocketAddr::V6(SocketAddrV6::new(a, port, 0, 0)),
        }
    }

    /// 返回与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
    /// ```
    #[must_use]
    #[stable(feature = "ip_addr", since = "1.7.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn ip(&self) -> IpAddr {
        match *self {
            SocketAddr::V4(ref a) => IpAddr::V4(*a.ip()),
            SocketAddr::V6(ref a) => IpAddr::V6(*a.ip()),
        }
    }

    /// 更改与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let mut socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// socket.set_ip(IpAddr::V4(Ipv4Addr::new(10, 10, 0, 1)));
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(10, 10, 0, 1)));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_ip(&mut self, new_ip: IpAddr) {
        // `match (*self, new_ip)` 会让我们对 self 的副本进行可变，然后把它扔掉。
        match (self, new_ip) {
            (&mut SocketAddr::V4(ref mut a), IpAddr::V4(new_ip)) => a.set_ip(new_ip),
            (&mut SocketAddr::V6(ref mut a), IpAddr::V6(new_ip)) => a.set_ip(new_ip),
            (self_, new_ip) => *self_ = Self::new(new_ip, self_.port()),
        }
    }

    /// 返回与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn port(&self) -> u16 {
        match *self {
            SocketAddr::V4(ref a) => a.port(),
            SocketAddr::V6(ref a) => a.port(),
        }
    }

    /// 更改与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let mut socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// socket.set_port(1025);
    /// assert_eq!(socket.port(), 1025);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_port(&mut self, new_port: u16) {
        match *self {
            SocketAddr::V4(ref mut a) => a.set_port(new_port),
            SocketAddr::V6(ref mut a) => a.set_port(new_port),
        }
    }

    /// 如果此 `SocketAddr` 中的 [IP 地址][IP address] 是 [`IPv4` address]，则返回 [`true`]，否则返回 [`false`]。
    ///
    ///
    /// [IP address]: IpAddr
    /// [`IPv4` address]: IpAddr::V4
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.is_ipv4(), true);
    /// assert_eq!(socket.is_ipv6(), false);
    /// ```
    #[must_use]
    #[stable(feature = "sockaddr_checker", since = "1.16.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn is_ipv4(&self) -> bool {
        matches!(*self, SocketAddr::V4(_))
    }

    /// 如果此 `SocketAddr` 中的 [IP 地址][IP address] 是 [`IPv6` address]，则返回 [`true`]，否则返回 [`false`]。
    ///
    ///
    /// [IP address]: IpAddr
    /// [`IPv6` address]: IpAddr::V6
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv6Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 65535, 0, 1)), 8080);
    /// assert_eq!(socket.is_ipv4(), false);
    /// assert_eq!(socket.is_ipv6(), true);
    /// ```
    #[must_use]
    #[stable(feature = "sockaddr_checker", since = "1.16.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn is_ipv6(&self) -> bool {
        matches!(*self, SocketAddr::V6(_))
    }
}

impl SocketAddrV4 {
    /// 从 [`IPv4` address] 和端口号创建一个新的套接字地址。
    ///
    /// [`IPv4` address]: Ipv4Addr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[must_use]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn new(ip: Ipv4Addr, port: u16) -> SocketAddrV4 {
        SocketAddrV4 { ip, port }
    }

    /// 返回与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// assert_eq!(socket.ip(), &Ipv4Addr::new(127, 0, 0, 1));
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn ip(&self) -> &Ipv4Addr {
        &self.ip
    }

    /// 更改与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let mut socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// socket.set_ip(Ipv4Addr::new(192, 168, 0, 1));
    /// assert_eq!(socket.ip(), &Ipv4Addr::new(192, 168, 0, 1));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_ip(&mut self, new_ip: Ipv4Addr) {
        self.ip = new_ip;
    }

    /// 返回与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn port(&self) -> u16 {
        self.port
    }

    /// 更改与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let mut socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// socket.set_port(4242);
    /// assert_eq!(socket.port(), 4242);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_port(&mut self, new_port: u16) {
        self.port = new_port;
    }
}

impl SocketAddrV6 {
    /// 从 [`IPv6` address]，16 位端口号以及 `flowinfo` 和 `scope_id` 字段创建新的套接字地址。
    ///
    /// 有关 `flowinfo` 和 `scope_id` 参数的含义和布局的更多信息，请参见 [IETF RFC 2553，第 3.3 节][IETF RFC 2553, Section 3.3]。
    ///
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    /// [`IPv6` address]: Ipv6Addr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// ```
    ///
    #[stable(feature = "rust1", since = "1.0.0")]
    #[must_use]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn new(ip: Ipv6Addr, port: u16, flowinfo: u32, scope_id: u32) -> SocketAddrV6 {
        SocketAddrV6 { ip, port, flowinfo, scope_id }
    }

    /// 返回与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// assert_eq!(socket.ip(), &Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1));
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn ip(&self) -> &Ipv6Addr {
        &self.ip
    }

    /// 更改与此套接字地址关联的 IP 地址。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// socket.set_ip(Ipv6Addr::new(76, 45, 0, 0, 0, 0, 0, 0));
    /// assert_eq!(socket.ip(), &Ipv6Addr::new(76, 45, 0, 0, 0, 0, 0, 0));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_ip(&mut self, new_ip: Ipv6Addr) {
        self.ip = new_ip;
    }

    /// 返回与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn port(&self) -> u16 {
        self.port
    }

    /// 更改与此套接字地址关联的端口号。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// socket.set_port(4242);
    /// assert_eq!(socket.port(), 4242);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_port(&mut self, new_port: u16) {
        self.port = new_port;
    }

    /// 返回与此地址关联的流信息。
    ///
    /// 该信息对应于 [IETF RFC 2553，第 3.3 节][IETF RFC 2553, Section 3.3] 中指定的 C 的 `netinet/in.h` 中的 `sin6_flowinfo` 字段。
    /// 它结合了关于流标签和流量类别的信息，分别在 [IETF RFC 2460]，[第 6 节][Section 6] 和 [第 7 节][Section 7] 中指定。
    ///
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    /// [IETF RFC 2460]: https://tools.ietf.org/html/rfc2460
    /// [Section 6]: https://tools.ietf.org/html/rfc2460#section-6
    /// [Section 7]: https://tools.ietf.org/html/rfc2460#section-7
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 10, 0);
    /// assert_eq!(socket.flowinfo(), 10);
    /// ```
    ///
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn flowinfo(&self) -> u32 {
        self.flowinfo
    }

    /// 更改与此套接字地址关联的流信息。
    ///
    /// 有关更多详细信息，请参见 [`SocketAddrV6::flowinfo`] 的文档。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 10, 0);
    /// socket.set_flowinfo(56);
    /// assert_eq!(socket.flowinfo(), 56);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_flowinfo(&mut self, new_flowinfo: u32) {
        self.flowinfo = new_flowinfo;
    }

    /// 返回与此地址关联的作用域 ID。
    ///
    /// 该信息对应于 [IETF RFC 2553，第 3.3 节][IETF RFC 2553, Section 3.3] 中指定的 C 的 `netinet/in.h` 中的 `sin6_scope_id` 字段。
    ///
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 78);
    /// assert_eq!(socket.scope_id(), 78);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_stable(feature = "const_socketaddr", since = "1.69.0")]
    #[inline]
    pub const fn scope_id(&self) -> u32 {
        self.scope_id
    }

    /// 更改与此套接字地址关联的作用域 ID。
    ///
    /// 有关更多详细信息，请参见 [`SocketAddrV6::scope_id`] 的文档。
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 78);
    /// socket.set_scope_id(42);
    /// assert_eq!(socket.scope_id(), 42);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    #[inline]
    pub fn set_scope_id(&mut self, new_scope_id: u32) {
        self.scope_id = new_scope_id;
    }
}

#[stable(feature = "ip_from_ip", since = "1.16.0")]
impl From<SocketAddrV4> for SocketAddr {
    /// 将 [`SocketAddrV4`] 转换为 [`SocketAddr::V4`]。
    #[inline]
    fn from(sock4: SocketAddrV4) -> SocketAddr {
        SocketAddr::V4(sock4)
    }
}

#[stable(feature = "ip_from_ip", since = "1.16.0")]
impl From<SocketAddrV6> for SocketAddr {
    /// 将 [`SocketAddrV6`] 转换为 [`SocketAddr::V6`]。
    #[inline]
    fn from(sock6: SocketAddrV6) -> SocketAddr {
        SocketAddr::V6(sock6)
    }
}

#[stable(feature = "addr_from_into_ip", since = "1.17.0")]
impl<I: Into<IpAddr>> From<(I, u16)> for SocketAddr {
    /// 将元组结构体 (Into <[`IpAddr`]>，`u16`) 转换为 [`SocketAddr`]。
    ///
    /// 此转换为 [`IpAddr::V4`] 创建 [`SocketAddr::V4`]，并为 [`IpAddr::V6`] 创建 [`SocketAddr::V6`]。
    ///
    ///
    /// `u16` 被视为新创建的 [`SocketAddr`] 的端口。
    fn from(pieces: (I, u16)) -> SocketAddr {
        SocketAddr::new(pieces.0.into(), pieces.1)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddr {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match *self {
            SocketAddr::V4(ref a) => a.fmt(f),
            SocketAddr::V6(ref a) => a.fmt(f),
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddr {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddrV4 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // 如果没有对齐要求，直接将 socket 地址写入 `f`。
        // 否则，将其写入本地缓冲区，然后使用 `f.pad`。
        if f.precision().is_none() && f.width().is_none() {
            write!(f, "{}:{}", self.ip(), self.port())
        } else {
            const LONGEST_IPV4_SOCKET_ADDR: &str = "255.255.255.255:65536";

            let mut buf = DisplayBuffer::<{ LONGEST_IPV4_SOCKET_ADDR.len() }>::new();
            // 缓冲区足够长，可以容纳最长的 IPv4 套接字地址，所以这永远不会失败。
            write!(buf, "{}:{}", self.ip(), self.port()).unwrap();

            f.pad(buf.as_str())
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddrV4 {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddrV6 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // 如果没有对齐要求，直接将 socket 地址写入 `f`。
        // 否则，将其写入本地缓冲区，然后使用 `f.pad`。
        if f.precision().is_none() && f.width().is_none() {
            match self.scope_id() {
                0 => write!(f, "[{}]:{}", self.ip(), self.port()),
                scope_id => write!(f, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
            }
        } else {
            const LONGEST_IPV6_SOCKET_ADDR: &str =
                "[ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%4294967296]:65536";

            let mut buf = DisplayBuffer::<{ LONGEST_IPV6_SOCKET_ADDR.len() }>::new();
            match self.scope_id() {
                0 => write!(buf, "[{}]:{}", self.ip(), self.port()),
                scope_id => write!(buf, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
            }
            // 缓冲区足够长，可以容纳最长的 IPv6 套接字地址，所以这永远不会失败。
            .unwrap();

            f.pad(buf.as_str())
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddrV6 {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl PartialOrd for SocketAddrV4 {
    #[inline]
    fn partial_cmp(&self, other: &SocketAddrV4) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl PartialOrd for SocketAddrV6 {
    #[inline]
    fn partial_cmp(&self, other: &SocketAddrV6) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl Ord for SocketAddrV4 {
    #[inline]
    fn cmp(&self, other: &SocketAddrV4) -> Ordering {
        self.ip().cmp(other.ip()).then(self.port().cmp(&other.port()))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl Ord for SocketAddrV6 {
    #[inline]
    fn cmp(&self, other: &SocketAddrV6) -> Ordering {
        self.ip().cmp(other.ip()).then(self.port().cmp(&other.port()))
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl hash::Hash for SocketAddrV4 {
    fn hash<H: hash::Hasher>(&self, s: &mut H) {
        (self.port, self.ip).hash(s)
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl hash::Hash for SocketAddrV6 {
    fn hash<H: hash::Hasher>(&self, s: &mut H) {
        (self.port, &self.ip, self.flowinfo, self.scope_id).hash(s)
    }
}