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use ad hoc parser for small integers

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this results in about a 3% speed up for small integer and float parsing
This commit is contained in:
ConnorSkees 2020-05-26 23:38:24 -04:00
parent 0bc6445ebf
commit e9ffaa579e
1 changed files with 13 additions and 2 deletions
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15
src/value/parse.rs
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@ -431,6 +431,17 @@ fn single_value<I: Iterator<Item = Token>>(
}) })
} }
/// Parse numbers from strings *known* to contain
/// only the characters 0-9
fn parse_i64(s: String) -> i64 {
let mut output = 0i64;
for b in s.as_bytes() {
output *= 10;
output += i64::from(b - b'0');
}
output
}
impl Value { impl Value {
pub fn from_tokens<I: Iterator<Item = Token>>( pub fn from_tokens<I: Iterator<Item = Token>>(
toks: &mut PeekMoreIterator<I>, toks: &mut PeekMoreIterator<I>,
@ -735,7 +746,7 @@ impl Value {
let n = if val.dec_len == 0 { let n = if val.dec_len == 0 {
if val.num.len() <= 18 && val.times_ten.is_empty() { if val.num.len() <= 18 && val.times_ten.is_empty() {
let n = Rational64::new_raw(val.num.parse::<i64>().unwrap(), 1); let n = Rational64::new_raw(parse_i64(val.num), 1);
return Some(Ok(IntermediateValue::Value(Value::Dimension( return Some(Ok(IntermediateValue::Value(Value::Dimension(
Number::new_machine(n), Number::new_machine(n),
unit, unit,
@ -746,7 +757,7 @@ impl Value {
} else { } else {
if val.num.len() <= 18 && val.times_ten.is_empty() { if val.num.len() <= 18 && val.times_ten.is_empty() {
let n = let n =
Rational64::new(val.num.parse::<i64>().unwrap(), pow(10, val.dec_len)); Rational64::new(parse_i64(val.num), pow(10, val.dec_len));
return Some(Ok(IntermediateValue::Value(Value::Dimension( return Some(Ok(IntermediateValue::Value(Value::Dimension(
Number::new_machine(n), Number::new_machine(n),
unit, unit,