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// Adapted from https://github.com/Alexhuszagh/rust-lexical.
use super::algorithm::*;
use super::bhcomp::*;
use super::digit::*;
use super::exponent::*;
use super::num::*;
// PARSERS
// -------
/// Parse float for which the entire integer and fraction parts fit into a 64
/// bit mantissa.
pub fn parse_concise_float<F>(mantissa: u64, mant_exp: i32) -> F
where
F: Float,
{
if let Some(float) = fast_path(mantissa, mant_exp) {
return float;
}
// Moderate path (use an extended 80-bit representation).
let truncated = false;
let (fp, valid) = moderate_path::<F>(mantissa, mant_exp, truncated);
if valid {
return fp.into_float::<F>();
}
let b = fp.into_downward_float::<F>();
if b.is_special() {
// We have a non-finite number, we get to leave early.
return b;
}
// Slow path, fast path didn't work.
let mut buffer = itoa::Buffer::new();
let integer = buffer.format(mantissa).as_bytes();
let fraction = &[];
bhcomp(b, integer, fraction, mant_exp)
}
/// Parse float from extracted float components.
///
/// * `integer` - Slice containing the integer digits.
/// * `fraction` - Slice containing the fraction digits.
/// * `exponent` - Parsed, 32-bit exponent.
///
/// Precondition: The integer must not have leading zeros.
pub fn parse_truncated_float<F>(integer: &[u8], mut fraction: &[u8], exponent: i32) -> F
where
F: Float,
{
// Trim trailing zeroes from the fraction part.
while fraction.last() == Some(&b'0') {
fraction = &fraction[..fraction.len() - 1];
}
// Calculate the number of truncated digits.
let mut truncated = 0;
let mut mantissa: u64 = 0;
let mut iter = integer.iter().chain(fraction);
for &c in &mut iter {
mantissa = match add_digit(mantissa, to_digit(c).unwrap()) {
Some(v) => v,
None => {
truncated = 1 + iter.count();
break;
}
};
}
let mant_exp = mantissa_exponent(exponent, fraction.len(), truncated);
let is_truncated = true;
fallback_path(
integer,
fraction,
mantissa,
exponent,
mant_exp,
is_truncated,
)
}
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