Auto merge of #49418 - frewsxcv:frewsxcv-network-order, r=TimNN

Clarify network byte order conversions for integer / IP address conversions.

Opened primarily to address https://github.com/rust-lang/rust/issues/48819.

Also added a few other conversion docs/examples.

src/libstd/net/ip.rs

@@ -778,7 +778,16 @@ fn from_inner(addr: c::in_addr) -> Ipv4Addr {
 
 #[stable(feature = "ip_u32", since = "1.1.0")]
 impl From<Ipv4Addr> for u32 {
-    /// It performs the conversion in network order (big-endian).
+    /// Convert an `Ipv4Addr` into a host byte order `u32`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::Ipv4Addr;
+    ///
+    /// let addr = Ipv4Addr::new(13, 12, 11, 10);
+    /// assert_eq!(0x0d0c0b0au32, u32::from(addr));
+    /// ```
     fn from(ip: Ipv4Addr) -> u32 {
         let ip = ip.octets();
         ((ip[0] as u32) << 24) + ((ip[1] as u32) << 16) + ((ip[2] as u32) << 8) + (ip[3] as u32)
@@ -787,7 +796,16 @@ fn from(ip: Ipv4Addr) -> u32 {
 
 #[stable(feature = "ip_u32", since = "1.1.0")]
 impl From<u32> for Ipv4Addr {
-    /// It performs the conversion in network order (big-endian).
+    /// Convert a host byte order `u32` into an `Ipv4Addr`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::Ipv4Addr;
+    ///
+    /// let addr = Ipv4Addr::from(0x0d0c0b0au32);
+    /// assert_eq!(Ipv4Addr::new(13, 12, 11, 10), addr);
+    /// ```
     fn from(ip: u32) -> Ipv4Addr {
         Ipv4Addr::new((ip >> 24) as u8, (ip >> 16) as u8, (ip >> 8) as u8, ip as u8)
     }
@@ -795,6 +813,14 @@ fn from(ip: u32) -> Ipv4Addr {
 
 #[stable(feature = "from_slice_v4", since = "1.9.0")]
 impl From<[u8; 4]> for Ipv4Addr {
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::Ipv4Addr;
+    ///
+    /// let addr = Ipv4Addr::from([13u8, 12u8, 11u8, 10u8]);
+    /// assert_eq!(Ipv4Addr::new(13, 12, 11, 10), addr);
+    /// ```
     fn from(octets: [u8; 4]) -> Ipv4Addr {
         Ipv4Addr::new(octets[0], octets[1], octets[2], octets[3])
     }
@@ -802,6 +828,16 @@ fn from(ip: u32) -> Ipv4Addr {
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
 impl From<[u8; 4]> for IpAddr {
+    /// Create an `IpAddr::V4` from a four element byte array.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::{IpAddr, Ipv4Addr};
+    ///
+    /// let addr = IpAddr::from([13u8, 12u8, 11u8, 10u8]);
+    /// assert_eq!(IpAddr::V4(Ipv4Addr::new(13, 12, 11, 10)), addr);
+    /// ```
     fn from(octets: [u8; 4]) -> IpAddr {
         IpAddr::V4(Ipv4Addr::from(octets))
     }
@@ -1395,6 +1431,27 @@ fn from(ip: u128) -> Ipv6Addr {
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
 impl From<[u8; 16]> for IpAddr {
+    /// Create an `IpAddr::V6` from a sixteen element byte array.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::{IpAddr, Ipv6Addr};
+    ///
+    /// let addr = IpAddr::from([
+    ///     25u8, 24u8, 23u8, 22u8, 21u8, 20u8, 19u8, 18u8,
+    ///     17u8, 16u8, 15u8, 14u8, 13u8, 12u8, 11u8, 10u8,
+    /// ]);
+    /// assert_eq!(
+    ///     IpAddr::V6(Ipv6Addr::new(
+    ///         0x1918, 0x1716,
+    ///         0x1514, 0x1312,
+    ///         0x1110, 0x0f0e,
+    ///         0x0d0c, 0x0b0a
+    ///     )),
+    ///     addr
+    /// );
+    /// ```
     fn from(octets: [u8; 16]) -> IpAddr {
         IpAddr::V6(Ipv6Addr::from(octets))
     }
@@ -1402,6 +1459,27 @@ fn from(ip: u128) -> Ipv6Addr {
 
 #[stable(feature = "ip_from_slice", since = "1.17.0")]
 impl From<[u16; 8]> for IpAddr {
+    /// Create an `IpAddr::V6` from an eight element 16-bit array.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::net::{IpAddr, Ipv6Addr};
+    ///
+    /// let addr = IpAddr::from([
+    ///     525u16, 524u16, 523u16, 522u16,
+    ///     521u16, 520u16, 519u16, 518u16,
+    /// ]);
+    /// assert_eq!(
+    ///     IpAddr::V6(Ipv6Addr::new(
+    ///         0x20d, 0x20c,
+    ///         0x20b, 0x20a,
+    ///         0x209, 0x208,
+    ///         0x207, 0x206
+    ///     )),
+    ///     addr
+    /// );
+    /// ```
     fn from(segments: [u16; 8]) -> IpAddr {
         IpAddr::V6(Ipv6Addr::from(segments))
     }