core/num/
diy_float.rs

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1//! Extended precision "soft float", for internal use only.
2
3// This module is only for dec2flt and flt2dec, and only public because of coretests.
4// It is not intended to ever be stabilized.
5#![doc(hidden)]
6#![unstable(
7    feature = "core_private_diy_float",
8    reason = "internal routines only exposed for testing",
9    issue = "none"
10)]
11
12/// A custom 64-bit floating point type, representing `f * 2^e`.
13#[derive(Copy, Clone, Debug)]
14#[doc(hidden)]
15pub struct Fp {
16    /// The integer mantissa.
17    pub f: u64,
18    /// The exponent in base 2.
19    pub e: i16,
20}
21
22impl Fp {
23    /// Returns a correctly rounded product of itself and `other`.
24    pub fn mul(self, other: Self) -> Self {
25        let (lo, hi) = self.f.widening_mul(other.f);
26        let f = hi + (lo >> 63) /* round */;
27        let e = self.e + other.e + 64;
28        Self { f, e }
29    }
30
31    /// Normalizes itself so that the resulting mantissa is at least `2^63`.
32    pub fn normalize(self) -> Self {
33        let lz = self.f.leading_zeros();
34        let f = self.f << lz;
35        let e = self.e - lz as i16;
36        debug_assert!(f >= (1 << 63));
37        Self { f, e }
38    }
39
40    /// Normalizes itself to have the shared exponent.
41    /// It can only decrease the exponent (and thus increase the mantissa).
42    pub fn normalize_to(self, e: i16) -> Self {
43        let edelta = self.e - e;
44        assert!(edelta >= 0);
45        let edelta = edelta as usize;
46        assert_eq!(self.f << edelta >> edelta, self.f);
47        Self { f: self.f << edelta, e }
48    }
49}
core/num/diy_float.rs

core/num/
diy_float.rs
