1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224
// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Functions for computing canonical and compatible decompositions for Unicode characters.
use crate::lookups::{
canonical_fully_decomposed, cjk_compat_variants_fully_decomposed,
compatibility_fully_decomposed, composition_table,
};
use core::char;
/// Compute canonical Unicode decomposition for character.
/// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
/// for more information.
#[inline]
pub fn decompose_canonical<F>(c: char, emit_char: F)
where
F: FnMut(char),
{
decompose(c, canonical_fully_decomposed, emit_char)
}
/// Compute canonical or compatible Unicode decomposition for character.
/// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
/// for more information.
#[inline]
pub fn decompose_compatible<F: FnMut(char)>(c: char, emit_char: F) {
let decompose_char =
|c| compatibility_fully_decomposed(c).or_else(|| canonical_fully_decomposed(c));
decompose(c, decompose_char, emit_char)
}
/// Compute standard-variation decomposition for character.
///
/// [Standardized Variation Sequences] are used instead of the standard canonical
/// decompositions, notably for CJK codepoints with singleton canonical decompositions,
/// to avoid losing information. See the
/// [Unicode Variation Sequence FAQ](http://unicode.org/faq/vs.html) and the
/// "Other Enhancements" section of the
/// [Unicode 6.3 Release Summary](https://www.unicode.org/versions/Unicode6.3.0/#Summary)
/// for more information.
#[inline]
pub fn decompose_cjk_compat_variants<F>(c: char, mut emit_char: F)
where
F: FnMut(char),
{
// 7-bit ASCII never decomposes
if c <= '\x7f' {
emit_char(c);
return;
}
// Don't perform decomposition for Hangul
if let Some(decomposed) = cjk_compat_variants_fully_decomposed(c) {
for &d in decomposed {
emit_char(d);
}
return;
}
// Finally bottom out.
emit_char(c);
}
#[inline]
#[allow(unsafe_code)]
fn decompose<D, F>(c: char, decompose_char: D, mut emit_char: F)
where
D: Fn(char) -> Option<&'static [char]>,
F: FnMut(char),
{
// 7-bit ASCII never decomposes
if c <= '\x7f' {
emit_char(c);
return;
}
// Perform decomposition for Hangul
if is_hangul_syllable(c) {
// Safety: Hangul Syllables invariant checked by is_hangul_syllable above
unsafe {
decompose_hangul(c, emit_char);
}
return;
}
if let Some(decomposed) = decompose_char(c) {
for &d in decomposed {
emit_char(d);
}
return;
}
// Finally bottom out.
emit_char(c);
}
/// Compose two characters into a single character, if possible.
/// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
/// for more information.
pub fn compose(a: char, b: char) -> Option<char> {
compose_hangul(a, b).or_else(|| composition_table(a, b))
}
// Constants from Unicode 9.0.0 Section 3.12 Conjoining Jamo Behavior
// http://www.unicode.org/versions/Unicode9.0.0/ch03.pdf#M9.32468.Heading.310.Combining.Jamo.Behavior
const S_BASE: u32 = 0xAC00;
const L_BASE: u32 = 0x1100;
const V_BASE: u32 = 0x1161;
const T_BASE: u32 = 0x11A7;
const L_COUNT: u32 = 19;
const V_COUNT: u32 = 21;
const T_COUNT: u32 = 28;
const N_COUNT: u32 = V_COUNT * T_COUNT;
const S_COUNT: u32 = L_COUNT * N_COUNT;
const S_LAST: u32 = S_BASE + S_COUNT - 1;
const L_LAST: u32 = L_BASE + L_COUNT - 1;
const V_LAST: u32 = V_BASE + V_COUNT - 1;
const T_LAST: u32 = T_BASE + T_COUNT - 1;
// Composition only occurs for `TPart`s in `U+11A8 ..= U+11C2`,
// i.e. `T_BASE + 1 ..= T_LAST`.
const T_FIRST: u32 = T_BASE + 1;
// Safety-usable invariant: This ensures that c is a valid Hangul Syllable character (U+AC00..U+D7AF)
pub(crate) fn is_hangul_syllable(c: char) -> bool {
// Safety: This checks the range 0xAC00 (S_BASE) to 0xD7A4 (S_BASE + S_COUNT), upholding the safety-usable invariant
(c as u32) >= S_BASE && (c as u32) < (S_BASE + S_COUNT)
}
// Decompose a precomposed Hangul syllable
// Safety: `s` MUST be a valid Hangul Syllable character, between U+AC00..U+D7AF
#[allow(unsafe_code, unused_unsafe)]
#[inline(always)]
unsafe fn decompose_hangul<F>(s: char, mut emit_char: F)
where
F: FnMut(char),
{
// This will be at most 0x2baf, the size of the Hangul Syllables block
let s_index = s as u32 - S_BASE;
// This will be at most 0x2baf / (21 * 28), 19
let l_index = s_index / N_COUNT;
unsafe {
// Safety: L_BASE (0x1100) plus at most 19 is still going to be in range for a valid Unicode code point in the BMP (< 0xD800)
emit_char(char::from_u32_unchecked(L_BASE + l_index));
// Safety: This will be at most (N_COUNT - 1) / T_COUNT = (V*T - 1) / T, which gives us an upper bound of V_COUNT = 21
let v_index = (s_index % N_COUNT) / T_COUNT;
// Safety: V_BASE (0x1161) plus at most 21 is still going to be in range for a valid Unicode code point in the BMP (< 0xD800)
emit_char(char::from_u32_unchecked(V_BASE + v_index));
// Safety: This will be at most T_COUNT - 1 (27)
let t_index = s_index % T_COUNT;
if t_index > 0 {
// Safety: T_BASE (0x11A7) plus at most 27 is still going to be in range for a valid Unicode code point in the BMP (< 0xD800)
emit_char(char::from_u32_unchecked(T_BASE + t_index));
}
}
}
#[inline]
pub(crate) fn hangul_decomposition_length(s: char) -> usize {
let si = s as u32 - S_BASE;
let ti = si % T_COUNT;
if ti > 0 {
3
} else {
2
}
}
// Compose a pair of Hangul Jamo
#[allow(unsafe_code)]
#[inline(always)]
#[allow(ellipsis_inclusive_range_patterns)]
fn compose_hangul(a: char, b: char) -> Option<char> {
let (a, b) = (a as u32, b as u32);
match (a, b) {
// Compose a leading consonant and a vowel together into an LV_Syllable
(L_BASE..=L_LAST, V_BASE..=V_LAST) => {
// Safety: based on the above bounds, l_index will be less than or equal to L_COUNT (19)
// and v_index will be <= V_COUNT (21)
let l_index = a - L_BASE;
let v_index = b - V_BASE;
// Safety: This will be <= 19 * (20 * 21) + (21 * 20), which is 8400.
let lv_index = l_index * N_COUNT + v_index * T_COUNT;
// Safety: This is between 0xAC00 and 0xCCD0, which are in range for Hangul Syllables (U+AC00..U+D7AF) and also in range
// for BMP unicode
let s = S_BASE + lv_index;
// Safety: We've verified this is in-range
Some(unsafe { char::from_u32_unchecked(s) })
}
// Compose an LV_Syllable and a trailing consonant into an LVT_Syllable
(S_BASE..=S_LAST, T_FIRST..=T_LAST) if (a - S_BASE) % T_COUNT == 0 => {
// Safety: a is between 0xAC00 and (0xAC00 + 19 * 21 * 28). b - T_BASE is between 0 and 19.
// Adding a number 0 to 19 to a number that is at largest 0xD7A4 will not go out of bounds to 0xD800 (where the
// surrogates start), so this is safe.
Some(unsafe { char::from_u32_unchecked(a + (b - T_BASE)) })
}
_ => None,
}
}
#[cfg(test)]
mod tests {
use super::compose_hangul;
// Regression test from a bugfix where we were composing an LV_Syllable with
// T_BASE directly. (We should only compose an LV_Syllable with a character
// in the range `T_BASE + 1 ..= T_LAST`.)
#[test]
fn test_hangul_composition() {
assert_eq!(compose_hangul('\u{c8e0}', '\u{11a7}'), None);
}
}