fn fmt()

in sgx_tstd/src/net/ip_addr.rs [1681:1762]
71 lines of code
15 McCabe index (conditional complexity)

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // If there are no alignment requirements, write the IP address directly to `f`.
        // Otherwise, write it to a local buffer and then use `f.pad`.
        if f.precision().is_none() && f.width().is_none() {
            let segments = self.segments();

            // Special case for :: and ::1; otherwise they get written with the
            // IPv4 formatter
            if self.is_unspecified() {
                f.write_str("::")
            } else if self.is_loopback() {
                f.write_str("::1")
            } else if let Some(ipv4) = self.to_ipv4() {
                match segments[5] {
                    // IPv4 Compatible address
                    0 => write!(f, "::{}", ipv4),
                    // IPv4 Mapped address
                    0xffff => write!(f, "::ffff:{}", ipv4),
                    _ => unreachable!(),
                }
            } else {
                #[derive(Copy, Clone, Default)]
                struct Span {
                    start: usize,
                    len: usize,
                }

                // Find the inner 0 span
                let zeroes = {
                    let mut longest = Span::default();
                    let mut current = Span::default();

                    for (i, &segment) in segments.iter().enumerate() {
                        if segment == 0 {
                            if current.len == 0 {
                                current.start = i;
                            }

                            current.len += 1;

                            if current.len > longest.len {
                                longest = current;
                            }
                        } else {
                            current = Span::default();
                        }
                    }

                    longest
                };

                /// Write a colon-separated part of the address
                #[inline]
                fn fmt_subslice(f: &mut fmt::Formatter<'_>, chunk: &[u16]) -> fmt::Result {
                    if let Some((first, tail)) = chunk.split_first() {
                        write!(f, "{:x}", first)?;
                        for segment in tail {
                            f.write_char(':')?;
                            write!(f, "{:x}", segment)?;
                        }
                    }
                    Ok(())
                }

                if zeroes.len > 1 {
                    fmt_subslice(f, &segments[..zeroes.start])?;
                    f.write_str("::")?;
                    fmt_subslice(f, &segments[zeroes.start + zeroes.len..])
                } else {
                    fmt_subslice(f, &segments)
                }
            }
        } else {
            const LONGEST_IPV6_ADDR: &str = "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff";

            let mut buf = DisplayBuffer::<{ LONGEST_IPV6_ADDR.len() }>::new();
            // Buffer is long enough for the longest possible IPv6 address, so this should never fail.
            write!(buf, "{}", self).unwrap();

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