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// Copyright 2012-2014 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 core::cmp::{Equal, Less, Greater};
use core::option::{Option, Some, None};
use core::slice::ImmutableSlice;
use tables::normalization::{canonical_table, compatibility_table, composition_table};
fn bsearch_table<T>(c: char, r: &'static [(char, &'static [T])]) -> Option<&'static [T]> {
match r.bsearch(|&(val, _)| {
if c == val { Equal }
else if val < c { Less }
else { Greater }
}) {
Some(idx) => {
let (_, result) = r[idx];
Some(result)
}
None => None
}
}
/// Compute canonical Unicode decomposition for character
pub fn decompose_canonical(c: char, i: |char|) { d(c, i, false); }
/// Compute canonical or compatible Unicode decomposition for character
pub fn decompose_compatible(c: char, i: |char|) { d(c, i, true); }
fn d(c: char, i: |char|, k: bool) {
// 7-bit ASCII never decomposes
if c <= '\x7f' { i(c); return; }
// Perform decomposition for Hangul
if (c as u32) >= S_BASE && (c as u32) < (S_BASE + S_COUNT) {
decompose_hangul(c, i);
return;
}
// First check the canonical decompositions
match bsearch_table(c, canonical_table) {
Some(canon) => {
for x in canon.iter() {
d(*x, |b| i(b), k);
}
return;
}
None => ()
}
// Bottom out if we're not doing compat.
if !k { i(c); return; }
// Then check the compatibility decompositions
match bsearch_table(c, compatibility_table) {
Some(compat) => {
for x in compat.iter() {
d(*x, |b| i(b), k);
}
return;
}
None => ()
}
// Finally bottom out.
i(c);
}
pub fn compose(a: char, b: char) -> Option<char> {
compose_hangul(a, b).or_else(|| {
match bsearch_table(a, composition_table) {
None => None,
Some(candidates) => {
match candidates.bsearch(|&(val, _)| {
if b == val { Equal }
else if val < b { Less }
else { Greater }
}) {
Some(idx) => {
let (_, result) = candidates[idx];
Some(result)
}
None => None
}
}
}
})
}
// Constants from Unicode 6.3.0 Section 3.12 Conjoining Jamo Behavior
static S_BASE: u32 = 0xAC00;
static L_BASE: u32 = 0x1100;
static V_BASE: u32 = 0x1161;
static T_BASE: u32 = 0x11A7;
static L_COUNT: u32 = 19;
static V_COUNT: u32 = 21;
static T_COUNT: u32 = 28;
static N_COUNT: u32 = (V_COUNT * T_COUNT);
static S_COUNT: u32 = (L_COUNT * N_COUNT);
// Decompose a precomposed Hangul syllable
#[inline(always)]
fn decompose_hangul(s: char, f: |char|) {
use core::mem::transmute;
let si = s as u32 - S_BASE;
let li = si / N_COUNT;
unsafe {
f(transmute(L_BASE + li));
let vi = (si % N_COUNT) / T_COUNT;
f(transmute(V_BASE + vi));
let ti = si % T_COUNT;
if ti > 0 {
f(transmute(T_BASE + ti));
}
}
}
// Compose a pair of Hangul Jamo
#[inline(always)]
fn compose_hangul(a: char, b: char) -> Option<char> {
use core::mem::transmute;
let l = a as u32;
let v = b as u32;
// Compose an LPart and a VPart
if L_BASE <= l && l < (L_BASE + L_COUNT) && V_BASE <= v && v < (V_BASE + V_COUNT) {
let r = S_BASE + (l - L_BASE) * N_COUNT + (v - V_BASE) * T_COUNT;
return unsafe { Some(transmute(r)) };
}
// Compose an LVPart and a TPart
if S_BASE <= l && l <= (S_BASE+S_COUNT-T_COUNT) && T_BASE <= v && v < (T_BASE+T_COUNT) {
let r = l + (v - T_BASE);
return unsafe { Some(transmute(r)) };
}
None
}
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