ryu/
d2s_intrinsics.rs

1// Translated from C to Rust. The original C code can be found at
2// https://github.com/ulfjack/ryu and carries the following license:
3//
4// Copyright 2018 Ulf Adams
5//
6// The contents of this file may be used under the terms of the Apache License,
7// Version 2.0.
8//
9//    (See accompanying file LICENSE-Apache or copy at
10//     http://www.apache.org/licenses/LICENSE-2.0)
11//
12// Alternatively, the contents of this file may be used under the terms of
13// the Boost Software License, Version 1.0.
14//    (See accompanying file LICENSE-Boost or copy at
15//     https://www.boost.org/LICENSE_1_0.txt)
16//
17// Unless required by applicable law or agreed to in writing, this software
18// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
19// KIND, either express or implied.
20
21// Returns (lo, hi).
22#[cfg(not(integer128))]
23#[cfg_attr(feature = "no-panic", inline)]
24pub fn umul128(a: u64, b: u64) -> (u64, u64) {
25    let a_lo = a as u32;
26    let a_hi = (a >> 32) as u32;
27    let b_lo = b as u32;
28    let b_hi = (b >> 32) as u32;
29
30    let b00 = a_lo as u64 * b_lo as u64;
31    let b01 = a_lo as u64 * b_hi as u64;
32    let b10 = a_hi as u64 * b_lo as u64;
33    let b11 = a_hi as u64 * b_hi as u64;
34
35    let b00_lo = b00 as u32;
36    let b00_hi = (b00 >> 32) as u32;
37
38    let mid1 = b10 + b00_hi as u64;
39    let mid1_lo = mid1 as u32;
40    let mid1_hi = (mid1 >> 32) as u32;
41
42    let mid2 = b01 + mid1_lo as u64;
43    let mid2_lo = mid2 as u32;
44    let mid2_hi = (mid2 >> 32) as u32;
45
46    let p_hi = b11 + mid1_hi as u64 + mid2_hi as u64;
47    let p_lo = ((mid2_lo as u64) << 32) | b00_lo as u64;
48
49    (p_lo, p_hi)
50}
51
52#[cfg(not(integer128))]
53#[cfg_attr(feature = "no-panic", inline)]
54pub fn shiftright128(lo: u64, hi: u64, dist: u32) -> u64 {
55    // We don't need to handle the case dist >= 64 here (see above).
56    debug_assert!(dist > 0);
57    debug_assert!(dist < 64);
58    (hi << (64 - dist)) | (lo >> dist)
59}
60
61#[cfg_attr(feature = "no-panic", inline)]
62pub fn div5(x: u64) -> u64 {
63    x / 5
64}
65
66#[cfg_attr(feature = "no-panic", inline)]
67pub fn div10(x: u64) -> u64 {
68    x / 10
69}
70
71#[cfg_attr(feature = "no-panic", inline)]
72pub fn div100(x: u64) -> u64 {
73    x / 100
74}
75
76#[cfg_attr(feature = "no-panic", inline)]
77fn pow5_factor(mut value: u64) -> u32 {
78    let mut count = 0u32;
79    loop {
80        debug_assert!(value != 0);
81        let q = div5(value);
82        let r = (value as u32).wrapping_sub(5u32.wrapping_mul(q as u32));
83        if r != 0 {
84            break;
85        }
86        value = q;
87        count += 1;
88    }
89    count
90}
91
92// Returns true if value is divisible by 5^p.
93#[cfg_attr(feature = "no-panic", inline)]
94pub fn multiple_of_power_of_5(value: u64, p: u32) -> bool {
95    // I tried a case distinction on p, but there was no performance difference.
96    pow5_factor(value) >= p
97}
98
99// Returns true if value is divisible by 2^p.
100#[cfg_attr(feature = "no-panic", inline)]
101pub fn multiple_of_power_of_2(value: u64, p: u32) -> bool {
102    debug_assert!(value != 0);
103    // return __builtin_ctzll(value) >= p;
104    (value & ((1u64 << p) - 1)) == 0
105}
ryu/d2s_intrinsics.rs

ryu/
d2s_intrinsics.rs
