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Add Ipv6Addr::to_ipv4_mapped #75019

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Aug 12, 2020
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Add Ipv6Addr::to_ipv4_mapped #75019

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40 changes: 40 additions & 0 deletions library/std/src/net/ip.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1488,6 +1488,37 @@ impl Ipv6Addr {
(self.segments()[0] & 0xff00) == 0xff00
}

/// Converts this address to an [IPv4 address] if it's an "IPv4-mapped IPv6 address"
/// defined in [IETF RFC 4291 section 2.5.5.2], otherwise returns [`None`].
///
/// `::ffff:a.b.c.d` becomes `a.b.c.d`.
/// All addresses *not* starting with `::ffff` will return `None`.
///
/// [IPv4 address]: ../../std/net/struct.Ipv4Addr.html
/// [`None`]: ../../std/option/enum.Option.html#variant.None
/// [IETF RFC 4291 section 2.5.5.2]: https://tools.ietf.org/html/rfc4291#section-2.5.5.2
///
/// # Examples
///
/// ```
/// #![feature(ip)]
///
/// use std::net::{Ipv4Addr, Ipv6Addr};
///
/// assert_eq!(Ipv6Addr::new(0xff00, 0, 0, 0, 0, 0, 0, 0).to_ipv4_mapped(), None);
/// assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc00a, 0x2ff).to_ipv4_mapped(),
/// Some(Ipv4Addr::new(192, 10, 2, 255)));
/// assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1).to_ipv4_mapped(), None);
/// ```
pub fn to_ipv4_mapped(&self) -> Option<Ipv4Addr> {
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@tesuji tesuji Aug 2, 2020 •
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Suggested change
pub fn to_ipv4_mapped(&self) -> Option<Ipv4Addr> {
#[unstable(feature = "ipv4_mapped", issue = "none")]
pub fn to_ipv4_mapped(&self) -> Option<Ipv4Addr> {

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thx~

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Do I need to add #![feature(ipv4_mapped)] to the lib.rs?

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Yes, certainly.

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It's done.

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Although there is already an unstable feature named ip, do I still need to add a new unstable feature?

#27709
https://github.com/rust-lang/rust/blob/master/library/std/src/net/ip.rs#L1-L7

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I asked on Zulip and it looks like adding stuff to existing unstable features is fine. So just use the ip feature :)

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Since you requested another review: the unstable attribute is still missing. Please add #[unstable(feature = "ip", issue = "27709")] right above the line containing pub fn.

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Since the following lines have been added at the beginning of this file (ip.rs):

#![unstable(
    feature = "ip",
    reason = "extra functionality has not been \
                                      scrutinized to the level that it should \
                                      be to be stable",
    issue = "27709"
)]

Adding #[unstable(feature = "ip", issue = "27709")] above this fn is unnecessary.

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(It is better to give a permanent link to those code lines in the future).

match self.octets() {
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, a, b, c, d] => {
Some(Ipv4Addr::new(a, b, c, d))
}
_ => None,
}
}

/// Converts this address to an [IPv4 address]. Returns [`None`] if this address is
/// neither IPv4-compatible or IPv4-mapped.
///
Expand Down Expand Up @@ -2084,6 +2115,15 @@ mod tests {
);
}

#[test]
fn ipv6_to_ipv4_mapped() {
assert_eq!(
Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0x1234, 0x5678).to_ipv4_mapped(),
Some(Ipv4Addr::new(0x12, 0x34, 0x56, 0x78))
);
assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0x1234, 0x5678).to_ipv4_mapped(), None);
}

#[test]
fn ipv6_to_ipv4() {
assert_eq!(
Expand Down