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perf: speed up high-precision parsing #21

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Merged
tisonkun merged 3 commits into from
Aug 9, 2026
Merged

perf: speed up high-precision parsing #21

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4830087
perf: speed up high-precision parsing
Colerar Jul 29, 2026
a1dc6ea
fix: preserve malformed parse errors
tisonkun Aug 9, 2026
794c7f3
Merge branch 'main' into high-prec-parse-perf
tisonkun Aug 9, 2026
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37 changes: 20 additions & 17 deletions bsize/src/parse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -125,16 +125,15 @@ fn parse_size(mut src: &[u8]) -> Result<u64, ParseError> {
match b {
b'0'..=b'9' => {
saw_digit = true;
if fraction_start.is_none() {
integer = integer
.checked_mul(10)
.and_then(|v| v.checked_add(u64::from(b - b'0')))
.ok_or(ParseError::Overflow)?;
}
integer = integer
.checked_mul(10)
.and_then(|v| v.checked_add(u64::from(b - b'0')))
.ok_or(ParseError::Overflow)?;
}
b'_' => {}
b'.' if saw_digit && fraction_start.is_none() => {
b'.' if saw_digit => {
fraction_start = Some(index + 1);
break;
}
_ => return Err(ParseError::Malformed),
}
Expand All @@ -144,9 +143,7 @@ fn parse_size(mut src: &[u8]) -> Result<u64, ParseError> {
return Err(ParseError::Empty);
}

let mut bytes = integer
.checked_mul(multiplier)
.ok_or(ParseError::Overflow)?;
let integer_bytes = integer.checked_mul(multiplier);

if let Some(start) = fraction_start {
// Multiply the fraction by the unit multiplier from right to left in base 10.
Expand All @@ -156,20 +153,25 @@ fn parse_size(mut src: &[u8]) -> Result<u64, ParseError> {
let mut carry = 0u64;
let mut rounding_digit = 0u64;
for b in src[start..].iter().copied().rev() {
if b == b'_' {
continue;
match b {
b'0'..=b'9' => {
let product = u64::from(b - b'0') * multiplier + carry;
rounding_digit = product % 10;
carry = product / 10;
}
b'_' => {}
_ => return Err(ParseError::Malformed),
}

let product = u64::from(b - b'0') * multiplier + carry;
rounding_digit = product % 10;
carry = product / 10;
}

let mut bytes = integer_bytes.ok_or(ParseError::Overflow)?;
let fraction = carry + u64::from(rounding_digit >= 5);
bytes = bytes.checked_add(fraction).ok_or(ParseError::Overflow)?;

return Ok(bytes);
}

Ok(bytes)
integer_bytes.ok_or(ParseError::Overflow)
}

#[cfg(test)]
Expand Down Expand Up @@ -277,6 +279,7 @@ mod tests {
"1 000 B",
"1.3 42.0 B",
"1.3 ... B",
"19.aE",
"IB",
"iB",
"1iB",
Expand Down