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Optimize 128-bit integer formatting #68

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Merged
dtolnay merged 1 commit into from
Mar 20, 2026
+10 −1
Merged

Optimize 128-bit integer formatting #68

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11 changes: 10 additions & 1 deletion src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -410,7 +410,7 @@ fn enc_16lsd<const OFFSET: usize>(buf: &mut [MaybeUninit<u8>], n: u64) {
let mut remain = n;

// Format per four digits from the lookup table.
for quad_index in (0..4).rev() {
for quad_index in (1..4).rev() {
// pull two pairs
let quad = remain % 1_00_00;
remain /= 1_00_00;
Expand All @@ -426,6 +426,15 @@ fn enc_16lsd<const OFFSET: usize>(buf: &mut [MaybeUninit<u8>], n: u64) {
.write(*DECIMAL_PAIRS.0.get_unchecked(pair2 as usize * 2 + 1));
}
}

// final two pairs
let (pair1, pair2) = divmod100(remain as u32);
unsafe {
buf[OFFSET + 0].write(*DECIMAL_PAIRS.0.get_unchecked(pair1 as usize * 2 + 0));
buf[OFFSET + 1].write(*DECIMAL_PAIRS.0.get_unchecked(pair1 as usize * 2 + 1));
buf[OFFSET + 2].write(*DECIMAL_PAIRS.0.get_unchecked(pair2 as usize * 2 + 0));
buf[OFFSET + 3].write(*DECIMAL_PAIRS.0.get_unchecked(pair2 as usize * 2 + 1));
}
}

// Euclidean division plus remainder with constant 1E16 basically consumes 16
Expand Down