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    // Translated from C to Rust. The original C code can be found at
    // https://github.com/ulfjack/ryu and carries the following license:
    //
    // Copyright 2018 Ulf Adams
    //
    // The contents of this file may be used under the terms of the Apache License,
    // Version 2.0.
    //
    //    (See accompanying file LICENSE-Apache or copy at
    //     http://www.apache.org/licenses/LICENSE-2.0)
    //
    // Alternatively, the contents of this file may be used under the terms of
    // the Boost Software License, Version 1.0.
    //    (See accompanying file LICENSE-Boost or copy at
    //     https://www.boost.org/LICENSE_1_0.txt)
    //
    // Unless required by applicable law or agreed to in writing, this software
    // is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    // KIND, either express or implied.

    use core::ptr;

    #[cfg_attr(feature = "no-panic", inline)]
    pub fn div5(x: u64) -> u64 {
        x / 5
    }

    #[cfg_attr(feature = "no-panic", inline)]
    pub fn div10(x: u64) -> u64 {
        x / 10
    }

    #[cfg_attr(feature = "no-panic", inline)]
    pub fn div100(x: u64) -> u64 {
        x / 100
    }

    #[cfg_attr(feature = "no-panic", inline)]
    fn pow5_factor(mut value: u64) -> u32 {
        let mut count = 0u32;
        loop {
            debug_assert!(value != 0);
            let q = div5(value);
            let r = (value as u32).wrapping_sub(5u32.wrapping_mul(q as u32));
            if r != 0 {
                break;
            }
            value = q;
            count += 1;
        }
        count
    }

    // Returns true if value is divisible by 5^p.
    #[cfg_attr(feature = "no-panic", inline)]
    pub fn multiple_of_power_of_5(value: u64, p: u32) -> bool {
        // I tried a case distinction on p, but there was no performance difference.
        pow5_factor(value) >= p
    }

    // Returns true if value is divisible by 2^p.
    #[cfg_attr(feature = "no-panic", inline)]
    pub fn multiple_of_power_of_2(value: u64, p: u32) -> bool {
        debug_assert!(value != 0);
        debug_assert!(p < 64);
        // __builtin_ctzll doesn't appear to be faster here.
        (value & ((1u64 << p) - 1)) == 0
    }

    #[cfg_attr(feature = "no-panic", inline)]
    pub fn mul_shift_64(m: u64, mul: &(u64, u64), j: u32) -> u64 {
        let b0 = m as u128 * mul.0 as u128;
        let b2 = m as u128 * mul.1 as u128;
        (((b0 >> 64) + b2) >> (j - 64)) as u64
    }

    #[cfg_attr(feature = "no-panic", inline)]
    pub unsafe fn mul_shift_all_64(
        m: u64,
        mul: &(u64, u64),
        j: u32,
        vp: *mut u64,
        vm: *mut u64,
        mm_shift: u32,
    ) -> u64 {
        ptr::write(vp, mul_shift_64(4 * m + 2, mul, j));
        ptr::write(vm, mul_shift_64(4 * m - 1 - mm_shift as u64, mul, j));
        mul_shift_64(4 * m, mul, j)
    }