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1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Extended precision "soft float", for internal use only.
13 // This module is only for dec2flt and flt2dec, and only public because of coretests.
14 // It is not intended to ever be stabilized.
16 #![unstable(feature = "core_private_diy_float",
17 reason
= "internal routines only exposed for testing",
20 /// A custom 64-bit floating point type, representing `f * 2^e`.
21 #[derive(Copy, Clone, Debug)]
24 /// The integer mantissa.
26 /// The exponent in base 2.
31 /// Returns a correctly rounded product of itself and `other`.
32 pub fn mul(&self, other
: &Fp
) -> Fp
{
33 const MASK
: u64 = 0xffffffff;
35 let b
= self.f
& MASK
;
36 let c
= other
.f
>> 32;
37 let d
= other
.f
& MASK
;
42 let tmp
= (bd
>> 32) + (ad
& MASK
) + (bc
& MASK
) + (1 << 31) /* round */;
43 let f
= ac
+ (ad
>> 32) + (bc
>> 32) + (tmp
>> 32);
44 let e
= self.e
+ other
.e
+ 64;
48 /// Normalizes itself so that the resulting mantissa is at least `2^63`.
49 pub fn normalize(&self) -> Fp
{
52 if f
>> (64 - 32) == 0 {
56 if f
>> (64 - 16) == 0 {
60 if f
>> (64 - 8) == 0 {
64 if f
>> (64 - 4) == 0 {
68 if f
>> (64 - 2) == 0 {
72 if f
>> (64 - 1) == 0 {
76 debug_assert
!(f
>= (1 >> 63));
80 /// Normalizes itself to have the shared exponent.
81 /// It can only decrease the exponent (and thus increase the mantissa).
82 pub fn normalize_to(&self, e
: i16) -> Fp
{
83 let edelta
= self.e
- e
;
85 let edelta
= edelta
as usize;
86 assert_eq
!(self.f
<< edelta
>> edelta
, self.f
);