328 lines
10 KiB
Rust
328 lines
10 KiB
Rust
// Copyright 2013 The rust-url developers.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Punycode ([RFC 3492](http://tools.ietf.org/html/rfc3492)) implementation.
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//!
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//! Since Punycode fundamentally works on unicode code points,
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//! `encode` and `decode` take and return slices and vectors of `char`.
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//! `encode_str` and `decode_to_string` provide convenience wrappers
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//! that convert from and to Rust’s UTF-8 based `str` and `String` types.
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use alloc::{string::String, vec::Vec};
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use core::char;
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use core::u32;
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// Bootstring parameters for Punycode
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static BASE: u32 = 36;
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static T_MIN: u32 = 1;
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static T_MAX: u32 = 26;
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static SKEW: u32 = 38;
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static DAMP: u32 = 700;
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static INITIAL_BIAS: u32 = 72;
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static INITIAL_N: u32 = 0x80;
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static DELIMITER: char = '-';
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#[inline]
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fn adapt(mut delta: u32, num_points: u32, first_time: bool) -> u32 {
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delta /= if first_time { DAMP } else { 2 };
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delta += delta / num_points;
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let mut k = 0;
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while delta > ((BASE - T_MIN) * T_MAX) / 2 {
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delta /= BASE - T_MIN;
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k += BASE;
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}
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k + (((BASE - T_MIN + 1) * delta) / (delta + SKEW))
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}
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/// Convert Punycode to an Unicode `String`.
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///
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/// This is a convenience wrapper around `decode`.
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#[inline]
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pub fn decode_to_string(input: &str) -> Option<String> {
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decode(input).map(|chars| chars.into_iter().collect())
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}
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/// Convert Punycode to Unicode.
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///
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/// Return None on malformed input or overflow.
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/// Overflow can only happen on inputs that take more than
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/// 63 encoded bytes, the DNS limit on domain name labels.
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pub fn decode(input: &str) -> Option<Vec<char>> {
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Some(Decoder::default().decode(input).ok()?.collect())
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}
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#[derive(Default)]
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pub(crate) struct Decoder {
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insertions: Vec<(usize, char)>,
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}
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impl Decoder {
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/// Split the input iterator and return a Vec with insertions of encoded characters
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pub(crate) fn decode<'a>(&'a mut self, input: &'a str) -> Result<Decode<'a>, ()> {
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self.insertions.clear();
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// Handle "basic" (ASCII) code points.
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// They are encoded as-is before the last delimiter, if any.
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let (base, input) = match input.rfind(DELIMITER) {
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None => ("", input),
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Some(position) => (
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&input[..position],
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if position > 0 {
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&input[position + 1..]
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} else {
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input
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},
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),
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};
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if !base.is_ascii() {
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return Err(());
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}
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let base_len = base.len();
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let mut length = base_len as u32;
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let mut code_point = INITIAL_N;
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let mut bias = INITIAL_BIAS;
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let mut i = 0;
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let mut iter = input.bytes();
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loop {
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let previous_i = i;
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let mut weight = 1;
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let mut k = BASE;
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let mut byte = match iter.next() {
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None => break,
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Some(byte) => byte,
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};
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// Decode a generalized variable-length integer into delta,
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// which gets added to i.
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loop {
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let digit = match byte {
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byte @ b'0'..=b'9' => byte - b'0' + 26,
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byte @ b'A'..=b'Z' => byte - b'A',
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byte @ b'a'..=b'z' => byte - b'a',
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_ => return Err(()),
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} as u32;
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if digit > (u32::MAX - i) / weight {
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return Err(()); // Overflow
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}
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i += digit * weight;
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let t = if k <= bias {
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T_MIN
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} else if k >= bias + T_MAX {
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T_MAX
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} else {
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k - bias
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};
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if digit < t {
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break;
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}
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if weight > u32::MAX / (BASE - t) {
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return Err(()); // Overflow
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}
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weight *= BASE - t;
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k += BASE;
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byte = match iter.next() {
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None => return Err(()), // End of input before the end of this delta
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Some(byte) => byte,
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};
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}
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bias = adapt(i - previous_i, length + 1, previous_i == 0);
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if i / (length + 1) > u32::MAX - code_point {
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return Err(()); // Overflow
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}
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// i was supposed to wrap around from length+1 to 0,
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// incrementing code_point each time.
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code_point += i / (length + 1);
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i %= length + 1;
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let c = match char::from_u32(code_point) {
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Some(c) => c,
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None => return Err(()),
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};
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// Move earlier insertions farther out in the string
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for (idx, _) in &mut self.insertions {
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if *idx >= i as usize {
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*idx += 1;
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}
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}
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self.insertions.push((i as usize, c));
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length += 1;
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i += 1;
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}
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self.insertions.sort_by_key(|(i, _)| *i);
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Ok(Decode {
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base: base.chars(),
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insertions: &self.insertions,
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inserted: 0,
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position: 0,
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len: base_len + self.insertions.len(),
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})
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}
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}
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pub(crate) struct Decode<'a> {
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base: core::str::Chars<'a>,
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pub(crate) insertions: &'a [(usize, char)],
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inserted: usize,
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position: usize,
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len: usize,
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}
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impl<'a> Iterator for Decode<'a> {
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type Item = char;
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fn next(&mut self) -> Option<Self::Item> {
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loop {
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match self.insertions.get(self.inserted) {
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Some((pos, c)) if *pos == self.position => {
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self.inserted += 1;
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self.position += 1;
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return Some(*c);
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}
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_ => {}
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}
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if let Some(c) = self.base.next() {
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self.position += 1;
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return Some(c);
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} else if self.inserted >= self.insertions.len() {
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return None;
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}
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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let len = self.len - self.position;
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(len, Some(len))
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}
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}
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impl<'a> ExactSizeIterator for Decode<'a> {
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fn len(&self) -> usize {
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self.len - self.position
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}
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}
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/// Convert an Unicode `str` to Punycode.
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///
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/// This is a convenience wrapper around `encode`.
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#[inline]
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pub fn encode_str(input: &str) -> Option<String> {
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if input.len() > u32::MAX as usize {
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return None;
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}
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let mut buf = String::with_capacity(input.len());
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encode_into(input.chars(), &mut buf).ok().map(|()| buf)
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}
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/// Convert Unicode to Punycode.
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///
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/// Return None on overflow, which can only happen on inputs that would take more than
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/// 63 encoded bytes, the DNS limit on domain name labels.
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pub fn encode(input: &[char]) -> Option<String> {
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if input.len() > u32::MAX as usize {
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return None;
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}
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let mut buf = String::with_capacity(input.len());
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encode_into(input.iter().copied(), &mut buf)
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.ok()
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.map(|()| buf)
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}
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pub(crate) fn encode_into<I>(input: I, output: &mut String) -> Result<(), ()>
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where
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I: Iterator<Item = char> + Clone,
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{
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// Handle "basic" (ASCII) code points. They are encoded as-is.
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let (mut input_length, mut basic_length) = (0u32, 0);
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for c in input.clone() {
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input_length = input_length.checked_add(1).ok_or(())?;
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if c.is_ascii() {
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output.push(c);
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basic_length += 1;
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}
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}
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if basic_length > 0 {
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output.push('-')
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}
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let mut code_point = INITIAL_N;
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let mut delta = 0;
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let mut bias = INITIAL_BIAS;
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let mut processed = basic_length;
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while processed < input_length {
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// All code points < code_point have been handled already.
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// Find the next larger one.
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let min_code_point = input
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.clone()
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.map(|c| c as u32)
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.filter(|&c| c >= code_point)
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.min()
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.unwrap();
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if min_code_point - code_point > (u32::MAX - delta) / (processed + 1) {
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return Err(()); // Overflow
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}
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// Increase delta to advance the decoder’s <code_point,i> state to <min_code_point,0>
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delta += (min_code_point - code_point) * (processed + 1);
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code_point = min_code_point;
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for c in input.clone() {
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let c = c as u32;
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if c < code_point {
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delta = delta.checked_add(1).ok_or(())?;
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}
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if c == code_point {
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// Represent delta as a generalized variable-length integer:
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let mut q = delta;
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let mut k = BASE;
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loop {
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let t = if k <= bias {
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T_MIN
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} else if k >= bias + T_MAX {
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T_MAX
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} else {
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k - bias
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};
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if q < t {
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break;
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}
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let value = t + ((q - t) % (BASE - t));
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output.push(value_to_digit(value));
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q = (q - t) / (BASE - t);
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k += BASE;
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}
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output.push(value_to_digit(q));
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bias = adapt(delta, processed + 1, processed == basic_length);
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delta = 0;
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processed += 1;
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}
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}
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delta += 1;
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code_point += 1;
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}
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Ok(())
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}
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#[inline]
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fn value_to_digit(value: u32) -> char {
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match value {
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0..=25 => (value as u8 + b'a') as char, // a..z
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26..=35 => (value as u8 - 26 + b'0') as char, // 0..9
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_ => panic!(),
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}
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}
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#[test]
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#[ignore = "slow"]
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#[cfg(target_pointer_width = "64")]
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fn huge_encode() {
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let mut buf = String::new();
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assert!(encode_into(std::iter::repeat('ß').take(u32::MAX as usize + 1), &mut buf).is_err());
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assert_eq!(buf.len(), 0);
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}
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