// 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;

// Returns (lo, hi).

#[cfg(not(integer128))]

#[cfg_attr(feature = "no-panic", inline)]

pub fn umul128(a: u64, b: u64) -> (u64, u64) {

    let a_lo = a as u32;

    let a_hi = (a >> 32) as u32;

    let b_lo = b as u32;

    let b_hi = (b >> 32) as u32;

    let b00 = a_lo as u64 * b_lo as u64;

    let b01 = a_lo as u64 * b_hi as u64;

    let b10 = a_hi as u64 * b_lo as u64;

    let b11 = a_hi as u64 * b_hi as u64;

    let b00_lo = b00 as u32;

    let b00_hi = (b00 >> 32) as u32;

    let mid1 = b10 + b00_hi as u64;

    let mid1_lo = mid1 as u32;

    let mid1_hi = (mid1 >> 32) as u32;

    let mid2 = b01 + mid1_lo as u64;

    let mid2_lo = mid2 as u32;

    let mid2_hi = (mid2 >> 32) as u32;

    let p_hi = b11 + mid1_hi as u64 + mid2_hi as u64;

    let p_lo = ((mid2_lo as u64) << 32) | b00_lo as u64;

    (p_lo, p_hi)

}

#[cfg(not(integer128))]

#[cfg_attr(feature = "no-panic", inline)]

pub fn shiftright128(lo: u64, hi: u64, dist: u32) -> u64 {

    // We don't need to handle the case dist >= 64 here (see above).

    debug_assert!(dist > 0);

    debug_assert!(dist < 64);

    (hi << (64 - dist)) | (lo >> dist)

}

#[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(integer128)]

#[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(integer128)]

#[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)

}

#[cfg(not(integer128))]

#[cfg_attr(feature = "no-panic", inline)]

pub unsafe fn mul_shift_all_64(

    mut m: u64,

    mul: &(u64, u64),

    j: u32,

    vp: *mut u64,

    vm: *mut u64,

    mm_shift: u32,

) -> u64 {

    m <<= 1;

    // m is maximum 55 bits

    let (lo, tmp) = umul128(m, mul.0);

    let (mut mid, mut hi) = umul128(m, mul.1);

    mid = mid.wrapping_add(tmp);

    hi = hi.wrapping_add((mid < tmp) as u64); // overflow into hi

    let lo2 = lo.wrapping_add(mul.0);

    let mid2 = mid.wrapping_add(mul.1).wrapping_add((lo2 < lo) as u64);

    let hi2 = hi.wrapping_add((mid2 < mid) as u64);

    ptr::write(vp, shiftright128(mid2, hi2, j - 64 - 1));

    if mm_shift == 1 {

        let lo3 = lo.wrapping_sub(mul.0);

        let mid3 = mid.wrapping_sub(mul.1).wrapping_sub((lo3 > lo) as u64);

        let hi3 = hi.wrapping_sub((mid3 > mid) as u64);

        ptr::write(vm, shiftright128(mid3, hi3, j - 64 - 1));

    } else {

        let lo3 = lo + lo;

        let mid3 = mid.wrapping_add(mid).wrapping_add((lo3 < lo) as u64);

        let hi3 = hi.wrapping_add(hi).wrapping_add((mid3 < mid) as u64);

        let lo4 = lo3.wrapping_sub(mul.0);

        let mid4 = mid3.wrapping_sub(mul.1).wrapping_sub((lo4 > lo3) as u64);

        let hi4 = hi3.wrapping_sub((mid4 > mid3) as u64);

        ptr::write(vm, shiftright128(mid4, hi4, j - 64));

    }

    shiftright128(mid, hi, j - 64 - 1)

}