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Merge pull request #1178 from iex-rs/tiny-bit-faster-hex

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Optimize Unicode decoding by 1% 🤡
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David Tolnay 2024-08-19 10:28:01 -07:00 committed by GitHub
commit 50c4328e21
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1 changed files with 10 additions and 8 deletions
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18
src/read.rs
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@ -1055,15 +1055,17 @@ static HEX0: [i16; 256] = build_hex_table(0);
static HEX1: [i16; 256] = build_hex_table(4);
fn decode_four_hex_digits(a: u8, b: u8, c: u8, d: u8) -> Option<u16> {
let a = HEX1[a as usize];
let b = HEX0[b as usize];
let c = HEX1[c as usize];
let d = HEX0[d as usize];
let a = HEX1[a as usize] as i32;
let b = HEX0[b as usize] as i32;
let c = HEX1[c as usize] as i32;
let d = HEX0[d as usize] as i32;
let codepoint = ((a | b) << 8) | c | d;
// A single sign bit check.
if (a | b | c | d) < 0 {
return None;
if codepoint >= 0 {
Some(codepoint as u16)
} else {
None
}
Some((((a | b) << 8) | c | d) as u16)
}