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}
50