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feat(simd-split-at-semicolon): Semicolon index calculation using SIMD (~= 10%) #21

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feat(simd-split-at-semicolon): Semicolon index calculation using SIMD (~= 10%) #21

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18 changes: 11 additions & 7 deletions src/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -288,12 +288,17 @@ fn update_stats(stats: &mut HashMap<StrVec, Stat, FastHasherBuilder>, station: &

// SAFETY: buffer must contain a semicolon in the last min(8, buffer.len()) bytes
unsafe fn split_at_semicolon(buffer: &[u8]) -> (&[u8], &[u8]) {
let mut pos = buffer.len() - 4;
const SPLAT: Simd<u8, LANES> = Simd::splat(b';');
const LANES: usize = 4;

unsafe {
// SAFETY: readme promises there will be a semicolon
while *buffer.get_unchecked(pos) != b';' {
pos -= 1;
}
let start = buffer.len() - 7;
let end = buffer.len() - 4;
let bytes = Simd::<u8, LANES>::from_slice(&buffer[start..=end]);

// SAFETY: Readme promises there will be a semicolon
let pos = start + bytes.simd_eq(SPLAT).first_set().unwrap_unchecked();

let (before, after) = buffer.split_at_unchecked(pos + 1);
(&before[..before.len() - 1], after)
}
Expand All @@ -314,8 +319,7 @@ pub fn find_newline(mut buffer: &[u8]) -> Option<usize> {
buffer = rest;
}

let bytes = Simd::<u8, LANES>::load_or_default(buffer);
bytes.simd_eq(SPLAT).first_set().map(|set| set + i)
buffer.iter().position(|&b| b == b'\n').map(|pos| pos + i)
}

#[inline]
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