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// Copyright © 2024 Mikhail Hogrefe
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::natural::arithmetic::shr::limbs_slice_shr_in_place;
use crate::natural::Natural;
use crate::platform::Limb;
use alloc::vec::Vec;
use itertools::Itertools;
use malachite_base::num::arithmetic::traits::Parity;
use malachite_base::num::basic::integers::PrimitiveInt;
use malachite_base::num::basic::traits::Zero;
use malachite_base::num::conversion::traits::{ExactFrom, WrappingFrom};
use malachite_base::num::logic::traits::{BitAccess, BitConvertible};
impl BitConvertible for Natural {
/// Returns a [`Vec`] containing the bits of a [`Natural`] in ascending order: least- to
/// most-significant.
///
/// If the number is 0, the [`Vec`] is empty; otherwise, it ends with `true`.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.significant_bits()`.
///
/// # Examples
/// ```
/// use malachite_base::num::logic::traits::BitConvertible;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::natural::Natural;
///
/// assert!(Natural::ZERO.to_bits_asc().is_empty());
/// // 105 = 1101001b
/// assert_eq!(
/// Natural::from(105u32).to_bits_asc(),
/// &[true, false, false, true, false, true, true]
/// );
/// ```
fn to_bits_asc(&self) -> Vec<bool> {
let mut bits = Vec::new();
if *self == 0 {
return bits;
}
let limbs = self.limbs();
let last_index = usize::exact_from(self.limb_count()) - 1;
let mut last = limbs[last_index];
for limb in limbs.take(last_index) {
for i in 0..Limb::WIDTH {
bits.push(limb.get_bit(i));
}
}
while last != 0 {
bits.push(last.odd());
last >>= 1;
}
bits
}
/// Returns a [`Vec`] containing the bits of a [`Natural`] in descending order: most- to
/// least-significant.
///
/// If the number is 0, the [`Vec`] is empty; otherwise, it begins with `true`.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `self.significant_bits()`.
///
/// # Examples
/// ```
/// use malachite_base::num::logic::traits::BitConvertible;
/// use malachite_base::num::basic::traits::Zero;
/// use malachite_nz::natural::Natural;
///
/// assert!(Natural::ZERO.to_bits_desc().is_empty());
/// // 105 = 1101001b
/// assert_eq!(
/// Natural::from(105u32).to_bits_desc(),
/// &[true, true, false, true, false, false, true]
/// );
/// ```
fn to_bits_desc(&self) -> Vec<bool> {
let mut bits = self.to_bits_asc();
bits.reverse();
bits
}
/// Converts an iterator of bits into a [`Natural`]. The bits should be in ascending order
/// (least- to most-significant).
///
/// $$
/// f((b_i)_ {i=0}^{k-1}) = \sum_{i=0}^{k-1}2^i \[b_i\],
/// $$
/// where braces denote the Iverson bracket, which converts a bit to 0 or 1.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.count()`.
///
/// # Examples
/// ```
/// use malachite_base::num::logic::traits::BitConvertible;
/// use malachite_nz::natural::Natural;
/// use core::iter::empty;
///
/// assert_eq!(Natural::from_bits_asc(empty()), 0);
/// // 105 = 1101001b
/// assert_eq!(
/// Natural::from_bits_asc([true, false, false, true, false, true, true].iter().cloned()),
/// 105
/// );
/// ```
fn from_bits_asc<I: Iterator<Item = bool>>(xs: I) -> Natural {
Natural::from_owned_limbs_asc(
xs.chunks(usize::wrapping_from(Limb::WIDTH))
.into_iter()
.map(Limb::from_bits_asc)
.collect(),
)
}
/// Converts an iterator of bits into a [`Natural`]. The bits should be in descending order
/// (most- to least-significant).
///
/// $$
/// f((b_i)_ {i=0}^{k-1}) = \sum_{i=0}^{k-1}2^{k-i-1} \[b_i\],
/// $$
/// where braces denote the Iverson bracket, which converts a bit to 0 or 1.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `xs.count()`.
///
/// # Examples
/// ```
/// use malachite_base::num::logic::traits::BitConvertible;
/// use malachite_nz::natural::Natural;
/// use core::iter::empty;
///
/// assert_eq!(Natural::from_bits_desc(empty()), 0);
/// // 105 = 1101001b
/// assert_eq!(
/// Natural::from_bits_desc([true, true, false, true, false, false, true].iter().cloned()),
/// 105
/// );
/// ```
fn from_bits_desc<I: Iterator<Item = bool>>(xs: I) -> Natural {
let mut out = Vec::new();
let mut last_width = 0;
for chunk in &xs.chunks(usize::exact_from(Limb::WIDTH)) {
let mut x = 0;
let mut i = 0;
for bit in chunk {
x <<= 1;
if bit {
x |= 1;
}
i += 1;
}
last_width = i;
out.push(x);
}
match out.len() {
0 => Natural::ZERO,
1 => Natural::from(out[0]),
_ => {
out.reverse();
if last_width != Limb::WIDTH {
let out_0 = out[0];
out[0] = 0;
limbs_slice_shr_in_place(&mut out, Limb::WIDTH - last_width);
out[0] |= out_0;
}
Natural::from_owned_limbs_asc(out)
}
}
}
}