use crate::digit_table::DIGIT_TABLE;

use core::ptr;

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

pub unsafe fn write_mantissa_long(mut output: u64, mut result: *mut u8) {

    if (output >> 32) != 0 {

        // One expensive 64-bit division.

        let mut output2 = (output - 100_000_000 * (output / 100_000_000)) as u32;

        output /= 100_000_000;

        let c = output2 % 10_000;

        output2 /= 10_000;

        let d = output2 % 10_000;

        let c0 = (c % 100) << 1;

        let c1 = (c / 100) << 1;

        let d0 = (d % 100) << 1;

        let d1 = (d / 100) << 1;

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c0 as isize), result.sub(2), 2);

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c1 as isize), result.sub(4), 2);

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(d0 as isize), result.sub(6), 2);

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(d1 as isize), result.sub(8), 2);

        result = result.sub(8);

    }

    write_mantissa(output as u32, result);

}

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

pub unsafe fn write_mantissa(mut output: u32, mut result: *mut u8) {

    while output >= 10_000 {

        let c = output - 10_000 * (output / 10_000);

        output /= 10_000;

        let c0 = (c % 100) << 1;

        let c1 = (c / 100) << 1;

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c0 as isize), result.sub(2), 2);

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c1 as isize), result.sub(4), 2);

        result = result.sub(4);

    }

    if output >= 100 {

        let c = (output % 100) << 1;

        output /= 100;

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c as isize), result.sub(2), 2);

        result = result.sub(2);

    }

    if output >= 10 {

        let c = output << 1;

        ptr::copy_nonoverlapping(DIGIT_TABLE.as_ptr().offset(c as isize), result.sub(2), 2);

    } else {

        *result.sub(1) = b'0' + output as u8;

    }

}