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#![doc = include_str!("../README.md")]
#![feature(unicode_internals)]
use core::unicode::conversions;
use std::mem;
#[inline]
fn contains_nonascii(v: usize) -> bool {
const NONASCII_MASK: usize = 0x8080808080808080;
(NONASCII_MASK & v) != 0
}
#[inline]
unsafe fn is_ascii_funsafe<const N: usize>(b: *const u8) -> bool {
let mut count = 0;
for j in 0..N {
let chunk = b.cast::<usize>().add(j).read_unaligned();
count += contains_nonascii(chunk) as usize;
}
count == 0
}
#[inline]
unsafe fn convert_while_ascii(
b: &[u8],
out: &mut [mem::MaybeUninit<u8>],
f: fn(&u8) -> u8,
) -> usize {
debug_assert!(out.len() >= b.len());
const USIZE_SIZE: usize = mem::size_of::<usize>();
const MAGIC_UNROLL: usize = 16;
let mut i = 0;
while i + USIZE_SIZE * MAGIC_UNROLL <= b.len() {
let c = b.get_unchecked(i..);
let o = out.get_unchecked_mut(i..);
if !is_ascii_funsafe::<MAGIC_UNROLL>(c.as_ptr()) {
return i;
}
for j in 0..USIZE_SIZE * MAGIC_UNROLL {
let out = o.get_unchecked_mut(j);
out.write(f(c.get_unchecked(j)));
}
i += USIZE_SIZE * MAGIC_UNROLL;
}
i
}
pub fn to_lowercase(s: &str) -> String {
let mut out = Vec::<u8>::with_capacity(s.len());
let b = s.as_bytes();
unsafe {
let n = convert_while_ascii(b, out.spare_capacity_mut(), u8::to_ascii_lowercase);
out.set_len(n);
}
let rest = unsafe { s.get_unchecked(out.len()..) };
let mut to = unsafe { String::from_utf8_unchecked(out) };
for (i, c) in rest.char_indices() {
if c == 'Σ' {
map_uppercase_sigma(s, i, &mut to)
} else {
match conversions::to_lower(c) {
[a, '\0', _] => to.push(a),
[a, b, '\0'] => {
to.push(a);
to.push(b);
}
[a, b, c] => {
to.push(a);
to.push(b);
to.push(c);
}
}
}
}
fn map_uppercase_sigma(from: &str, i: usize, out: &mut String) {
debug_assert!('Σ'.len_utf8() == 2);
let is_word_final = case_ignoreable_then_cased(from[..i].chars().rev())
&& !case_ignoreable_then_cased(from[i + 2..].chars());
out.push_str(if is_word_final { "ς" } else { "σ" });
}
fn case_ignoreable_then_cased<I: Iterator<Item = char>>(mut iter: I) -> bool {
use core::unicode::{Case_Ignorable, Cased};
match iter.find(|&c| !Case_Ignorable(c)) {
Some(c) => Cased(c),
None => false,
}
}
to
}
pub fn to_uppercase(s: &str) -> String {
let mut out = Vec::<u8>::with_capacity(s.len());
let b = s.as_bytes();
unsafe {
let n = convert_while_ascii(b, out.spare_capacity_mut(), u8::to_ascii_uppercase);
out.set_len(n);
}
let rest = unsafe { s.get_unchecked(out.len()..) };
let mut to = unsafe { String::from_utf8_unchecked(out) };
for c in rest.chars() {
match conversions::to_upper(c) {
[a, '\0', _] => to.push(a),
[a, b, '\0'] => {
to.push(a);
to.push(b);
}
[a, b, c] => {
to.push(a);
to.push(b);
to.push(c);
}
}
}
to
}
pub fn is_ascii(b: &[u8]) -> bool {
const USIZE_SIZE: usize = mem::size_of::<usize>();
const MAGIC_UNROLL: usize = 16;
if b.len() < USIZE_SIZE {
return b.iter().all(u8::is_ascii);
}
unsafe {
let mut i = 0;
while i + USIZE_SIZE * MAGIC_UNROLL <= b.len() {
if !is_ascii_funsafe::<MAGIC_UNROLL>(b.as_ptr().add(i)) {
return false;
}
i += USIZE_SIZE * MAGIC_UNROLL;
}
while i + USIZE_SIZE < b.len() {
if !is_ascii_funsafe::<1>(b.as_ptr().add(i)) {
return false;
}
i += USIZE_SIZE;
}
let i = b.len() - USIZE_SIZE;
is_ascii_funsafe::<1>(b.as_ptr().add(i))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn lowercase() {
assert_eq!(to_lowercase(""), "");
assert_eq!(to_lowercase("AÉDžaé "), "aédžaé ");
assert_eq!(to_lowercase("ΑΣ"), "ας");
assert_eq!(to_lowercase("Α'Σ"), "α'ς");
assert_eq!(to_lowercase("Α''Σ"), "α''ς");
assert_eq!(to_lowercase("ΑΣ Α"), "ας α");
assert_eq!(to_lowercase("Α'Σ Α"), "α'ς α");
assert_eq!(to_lowercase("Α''Σ Α"), "α''ς α");
assert_eq!(to_lowercase("ΑΣ' Α"), "ας' α");
assert_eq!(to_lowercase("ΑΣ'' Α"), "ας'' α");
assert_eq!(to_lowercase("Α'Σ' Α"), "α'ς' α");
assert_eq!(to_lowercase("Α''Σ'' Α"), "α''ς'' α");
assert_eq!(to_lowercase("Α Σ"), "α σ");
assert_eq!(to_lowercase("Α 'Σ"), "α 'σ");
assert_eq!(to_lowercase("Α ''Σ"), "α ''σ");
assert_eq!(to_lowercase("Σ"), "σ");
assert_eq!(to_lowercase("'Σ"), "'σ");
assert_eq!(to_lowercase("''Σ"), "''σ");
assert_eq!(to_lowercase("ΑΣΑ"), "ασα");
assert_eq!(to_lowercase("ΑΣ'Α"), "ασ'α");
assert_eq!(to_lowercase("ΑΣ''Α"), "ασ''α");
}
#[test]
fn long() {
let mut upper = str::repeat("A", 128);
let mut lower = str::repeat("a", 128);
assert_eq!(to_lowercase(&upper), lower);
assert_eq!(to_uppercase(&lower), upper);
upper.push('Σ');
lower.push('σ');
assert_eq!(to_lowercase(&upper), lower);
assert_eq!(to_uppercase(&lower), upper);
}
#[test]
fn case_conv_long() {
let upper = str::repeat("A", 512);
let lower = str::repeat("a", 512);
assert_eq!(to_lowercase(&upper), lower);
assert_eq!(to_uppercase(&lower), upper);
}
#[test]
fn case_conv_long_unicode() {
let upper = str::repeat("É", 512);
let lower = str::repeat("é", 512);
assert_eq!(to_lowercase(&upper), lower);
assert_eq!(to_uppercase(&lower), upper);
}
#[test]
fn uppercase() {
assert_eq!(to_uppercase(""), "");
assert_eq!(to_uppercase("aéDžßfiᾀ"), "AÉDŽSSFIἈΙ");
}
}