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
21use core::ptr;
22
23#[cfg_attr(feature = "no-panic", inline)]
24pub fn div5(x: u64) -> u64 {
25    x / 5
26}
27
28#[cfg_attr(feature = "no-panic", inline)]
29pub fn div10(x: u64) -> u64 {
30    x / 10
31}
32
33#[cfg_attr(feature = "no-panic", inline)]
34pub fn div100(x: u64) -> u64 {
35    x / 100
36}
37
38#[cfg_attr(feature = "no-panic", inline)]
39pub(crate) fn pow5_factor(mut value: u64) -> u32 {
40    const M_INV_5: u64 = 14757395258967641293; // 5 * m_inv_5 = 1 (mod 2^64)
41    const N_DIV_5: u64 = 3689348814741910323; // #{ n | n = 0 (mod 2^64) } = 2^64 / 5
42    let mut count = 0u32;
43    loop {
44        debug_assert!(value != 0);
45        value = value.wrapping_mul(M_INV_5);
46        if value > N_DIV_5 {
47            break;
48        }
49        count += 1;
50    }
51    count
52}
53
54// Returns true if value is divisible by 5^p.
55#[cfg_attr(feature = "no-panic", inline)]
56pub fn multiple_of_power_of_5(value: u64, p: u32) -> bool {
57    // I tried a case distinction on p, but there was no performance difference.
58    pow5_factor(value) >= p
59}
60
61// Returns true if value is divisible by 2^p.
62#[cfg_attr(feature = "no-panic", inline)]
63pub fn multiple_of_power_of_2(value: u64, p: u32) -> bool {
64    debug_assert!(value != 0);
65    debug_assert!(p < 64);
66    // __builtin_ctzll doesn't appear to be faster here.
67    (value & ((1u64 << p) - 1)) == 0
68}
69
70#[cfg_attr(feature = "no-panic", inline)]
71pub fn mul_shift_64(m: u64, mul: &(u64, u64), j: u32) -> u64 {
72    let b0 = m as u128 * mul.0 as u128;
73    let b2 = m as u128 * mul.1 as u128;
74    (((b0 >> 64) + b2) >> (j - 64)) as u64
75}
76
77#[cfg_attr(feature = "no-panic", inline)]
78pub unsafe fn mul_shift_all_64(
79    m: u64,
80    mul: &(u64, u64),
81    j: u32,
82    vp: *mut u64,
83    vm: *mut u64,
84    mm_shift: u32,
85) -> u64 {
86    ptr::write(vp, mul_shift_64(4 * m + 2, mul, j));
87    ptr::write(vm, mul_shift_64(4 * m - 1 - mm_shift as u64, mul, j));
88    mul_shift_64(4 * m, mul, j)
89}
ryu/d2s_intrinsics.rs

ryu/
d2s_intrinsics.rs
