// 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)]

pub(crate) fn pow5_factor(mut value: u64) -> u32 {

    const M_INV_5: u64 = 14757395258967641293; // 5 * m_inv_5 = 1 (mod 2^64)

    const N_DIV_5: u64 = 3689348814741910323; // #{ n | n = 0 (mod 2^64) } = 2^64 / 5

    let mut count = 0u32;

    loop {

        debug_assert!(value != 0);

        value = value.wrapping_mul(M_INV_5);

        if value > N_DIV_5 {

            break;

        }

        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)

}