1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 //! Functions for computing canonical and compatible decompositions for Unicode characters.
12 use std::char;
13 use std::ops::FnMut;
14 use lookups::{canonical_fully_decomposed, composition_table, compatibility_fully_decomposed};
15
16 /// Compute canonical Unicode decomposition for character.
17 /// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
18 /// for more information.
19 #[inline]
decompose_canonical<F>(c: char, emit_char: F) where F: FnMut(char)20 pub fn decompose_canonical<F>(c: char, emit_char: F) where F: FnMut(char) {
21 decompose(c, canonical_fully_decomposed, emit_char)
22 }
23
24 /// Compute canonical or compatible Unicode decomposition for character.
25 /// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
26 /// for more information.
27 #[inline]
decompose_compatible<F: FnMut(char)>(c: char, emit_char: F)28 pub fn decompose_compatible<F: FnMut(char)>(c: char, emit_char: F) {
29 let decompose_char = |c| compatibility_fully_decomposed(c)
30 .or_else(|| canonical_fully_decomposed(c));
31 decompose(c, decompose_char, emit_char)
32 }
33
34 #[inline]
decompose<D, F>(c: char, decompose_char: D, mut emit_char: F) where D: Fn(char) -> Option<&'static [char]>, F: FnMut(char)35 fn decompose<D, F>(c: char, decompose_char: D, mut emit_char: F)
36 where D: Fn(char) -> Option<&'static [char]>, F: FnMut(char)
37 {
38 // 7-bit ASCII never decomposes
39 if c <= '\x7f' {
40 emit_char(c);
41 return;
42 }
43
44 // Perform decomposition for Hangul
45 if is_hangul_syllable(c) {
46 decompose_hangul(c, emit_char);
47 return;
48 }
49
50 if let Some(decomposed) = decompose_char(c) {
51 for &d in decomposed {
52 emit_char(d);
53 }
54 return;
55 }
56
57 // Finally bottom out.
58 emit_char(c);
59 }
60
61 /// Compose two characters into a single character, if possible.
62 /// See [Unicode Standard Annex #15](http://www.unicode.org/reports/tr15/)
63 /// for more information.
compose(a: char, b: char) -> Option<char>64 pub fn compose(a: char, b: char) -> Option<char> {
65 compose_hangul(a, b).or_else(|| composition_table(a, b))
66 }
67
68 // Constants from Unicode 9.0.0 Section 3.12 Conjoining Jamo Behavior
69 // http://www.unicode.org/versions/Unicode9.0.0/ch03.pdf#M9.32468.Heading.310.Combining.Jamo.Behavior
70 const S_BASE: u32 = 0xAC00;
71 const L_BASE: u32 = 0x1100;
72 const V_BASE: u32 = 0x1161;
73 const T_BASE: u32 = 0x11A7;
74 const L_COUNT: u32 = 19;
75 const V_COUNT: u32 = 21;
76 const T_COUNT: u32 = 28;
77 const N_COUNT: u32 = (V_COUNT * T_COUNT);
78 const S_COUNT: u32 = (L_COUNT * N_COUNT);
79
80 const S_LAST: u32 = S_BASE + S_COUNT - 1;
81 const L_LAST: u32 = L_BASE + L_COUNT - 1;
82 const V_LAST: u32 = V_BASE + V_COUNT - 1;
83 const T_LAST: u32 = T_BASE + T_COUNT - 1;
84
85 // Composition only occurs for `TPart`s in `U+11A8 ... U+11C2`,
86 // i.e. `T_BASE + 1 ... T_LAST`.
87 const T_FIRST: u32 = T_BASE + 1;
88
is_hangul_syllable(c: char) -> bool89 pub(crate) fn is_hangul_syllable(c: char) -> bool {
90 (c as u32) >= S_BASE && (c as u32) < (S_BASE + S_COUNT)
91 }
92
93 // Decompose a precomposed Hangul syllable
94 #[allow(unsafe_code)]
95 #[inline(always)]
decompose_hangul<F>(s: char, mut emit_char: F) where F: FnMut(char)96 fn decompose_hangul<F>(s: char, mut emit_char: F) where F: FnMut(char) {
97 let s_index = s as u32 - S_BASE;
98 let l_index = s_index / N_COUNT;
99 unsafe {
100 emit_char(char::from_u32_unchecked(L_BASE + l_index));
101
102 let v_index = (s_index % N_COUNT) / T_COUNT;
103 emit_char(char::from_u32_unchecked(V_BASE + v_index));
104
105 let t_index = s_index % T_COUNT;
106 if t_index > 0 {
107 emit_char(char::from_u32_unchecked(T_BASE + t_index));
108 }
109 }
110 }
111
112 #[inline]
hangul_decomposition_length(s: char) -> usize113 pub(crate) fn hangul_decomposition_length(s: char) -> usize {
114 let si = s as u32 - S_BASE;
115 let ti = si % T_COUNT;
116 if ti > 0 { 3 } else { 2 }
117 }
118
119 // Compose a pair of Hangul Jamo
120 #[allow(unsafe_code)]
121 #[inline(always)]
122 #[allow(ellipsis_inclusive_range_patterns)]
compose_hangul(a: char, b: char) -> Option<char>123 fn compose_hangul(a: char, b: char) -> Option<char> {
124 let (a, b) = (a as u32, b as u32);
125 match (a, b) {
126 // Compose a leading consonant and a vowel together into an LV_Syllable
127 (L_BASE ... L_LAST, V_BASE ... V_LAST) => {
128 let l_index = a - L_BASE;
129 let v_index = b - V_BASE;
130 let lv_index = l_index * N_COUNT + v_index * T_COUNT;
131 let s = S_BASE + lv_index;
132 Some(unsafe {char::from_u32_unchecked(s)})
133 },
134 // Compose an LV_Syllable and a trailing consonant into an LVT_Syllable
135 (S_BASE ... S_LAST, T_FIRST ... T_LAST) if (a - S_BASE) % T_COUNT == 0 => {
136 Some(unsafe {char::from_u32_unchecked(a + (b - T_BASE))})
137 },
138 _ => None,
139 }
140 }
141
142 #[cfg(test)]
143 mod tests {
144 use super::compose_hangul;
145
146 // Regression test from a bugfix where we were composing an LV_Syllable with
147 // T_BASE directly. (We should only compose an LV_Syllable with a character
148 // in the range `T_BASE + 1 ... T_LAST`.)
149 #[test]
test_hangul_composition()150 fn test_hangul_composition() {
151 assert_eq!(compose_hangul('\u{c8e0}', '\u{11a7}'), None);
152 }
153 }
154