Struct swar::Bits2

pub struct Bits2<N>(pub N);

This is used when every 2 bits is a number stored in parallel.

Methods

impl Bits2<u128>

pub fn from_element(e: u128) -> Self

Spread a single value out to each element. Must be able to fit.

use swar::*;

assert_eq!(Bits2::from_element(0b10), Bits2(0xAAAA_AAAA_AAAA_AAAA_AAAA_AAAA_AAAA_AAAA));

pub fn any(self) -> Self

If any bit is set in each element, sets the element to 1, else 0.

use swar::*;

let input = Bits2(0b01101100u128);
let output = Bits2(0b01010100u128);
assert_eq!(input.any(), output);

pub fn union(left: Bits4<u128>, right: Bits4<u128>) -> Self

Takes two inputs that have half-sized elements and compresses them into half the space and puts them in the left and right sides of this.

use swar::*;

let input = Bits2(0xFEED_FACE_CAFE_BEEF_FEED_FACE_CAFE_BEEF);
let (left, right) = input.halve();
let output = Bits2::union(left, right);
assert_eq!(input, output);

pub fn squash(self) -> Bits1<u128>

Squashes half-sized elements into half-sized spaces to the right and fills the left half of the number with zeros.

This is the same as union(0, n).

pub fn count_ones(self) -> u32

pub fn pack_ones(self) -> Bits4<u128>

Sqishes all the bits to the right in each 4-bit segment.

use swar::*;

let input = Bits2(0b11_01_01_00);
let out = Bits4(0b0111_0001);
assert_eq!(input.pack_ones(), out, "got {:08b} expected {:08b}", input.pack_ones().0, out.0);

let input = Bits2(0b11_11_00_00);
let out = Bits4(0b1111_0000);
assert_eq!(input.pack_ones(), out, "got {:08b} expected {:08b}", input.pack_ones().0, out.0);

let input = Bits2(0b01_01_00_01);
let out = Bits4(0b0011_0001);
assert_eq!(input.pack_ones(), out, "got {:08b} expected {:08b}", input.pack_ones().0, out.0);

let input = Bits2(0b11_00_00_11);
let out = Bits4(0b0011_0011);
assert_eq!(input.pack_ones(), out, "got {:08b} expected {:08b}", input.pack_ones().0, out.0);

pub fn sum_weight(self) -> u128

pub fn sum_weight2(self) -> Bits4<u128>

pub fn minhwd(self, other: Self) -> Self

This computes the minimum hamming weight distance from hamming weights.

use swar::*;

// All combinations of inputs 0-2 (hamming weights)
let a = Bits2(0b00_01_10_00_01_10_00_01_10u128);
let b = Bits2(0b00_00_00_01_01_01_10_10_10u128);
// Expected output weights
let e = Bits2(0b00_01_10_01_00_01_10_01_00u128);

assert_eq!(a.minhwd(b), e, "got hamming distances {:b} expected {:b}", a.minhwd(b).0, e.0);

pub fn maxhwd(self, other: Self) -> Self

This computes the maximum hamming weight distance from hamming weights.

use swar::*;

// All combinations of inputs 0-2 (hamming weights)
let a = Bits2(0b00_01_10_00_01_10_00_01_10u128);
let b = Bits2(0b00_00_00_01_01_01_10_10_10u128);
// Expected output weights
let e = Bits2(0b00_01_10_01_10_01_10_01_00u128);

assert_eq!(a.maxhwd(b), e, "got hamming distances {:b} expected {:b}", a.maxhwd(b).0, e.0);

pub fn split(self) -> (Bits4<u128>, Bits4<u128>)

pub fn halve(self) -> (Bits4<u128>, Bits4<u128>)

Takes the left and right sides and spreads them out so that the bits in each element are spread out into twice the amount of space.

use swar::*;

let input = Bits2(0b1101 << 64 | 0b0101u128);
let (left, right) = input.halve();
assert_eq!(left, Bits4(0b0011_0001));
assert_eq!(right, Bits4(0b0001_0001));

Trait Implementations

impl<N: Copy> Copy for Bits2<N>

impl<N: Debug> Debug for Bits2<N>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<N: PartialEq> PartialEq<Bits2<N>> for Bits2<N>

fn eq(&self, other: &Bits2<N>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Bits2<N>) -> bool

This method tests for !=.

impl<N: Eq> Eq for Bits2<N>

impl Add<Bits2<u128>> for Bits2<u128>

Note that you are responsible for dealing with overflow. Try to avoid overflow or use the split() method to add in two halves. You can use split() on the result to get the carry bits.

type Output = Self

The resulting type after applying the + operator.

fn add(self, rhs: Self) -> Self

Performs the + operation.

impl BitAnd<u128> for Bits2<u128>

type Output = Self

The resulting type after applying the & operator.

fn bitand(self, rhs: u128) -> Self

Performs the & operation.

impl Shr<u32> for Bits2<u128>

type Output = Self

The resulting type after applying the >> operator.

fn shr(self, rhs: u32) -> Self

Performs the >> operation.

impl<N: Clone> Clone for Bits2<N>

fn clone(&self) -> Bits2<N>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.