//! This crate implements a 256-bit unsigned integer type.
//!
//! The implementation tries to follow as closely as possible to primitive
//! integer types, and should implement all the common methods and traits as the
//! primitive integer types.
#![deny(missing_docs)]
#![no_std]
#[cfg(test)]
extern crate alloc;
mod cmp;
mod convert;
mod fmt;
pub mod intrinsics;
mod iter;
mod ops;
mod uint;
pub use self::convert::AsU256;
/// A 256-bit unsigned integer type.
#[derive(Clone, Copy, Default, Eq, Hash, PartialEq)]
#[repr(transparent)]
pub struct U256(pub [u128; 2]);
/// A 256-bit unsigned integer type.
#[allow(non_camel_case_types)]
pub type u256 = U256;
impl U256 {
/// The additive identity for this integer type, i.e. `0`.
pub const ZERO: Self = U256([0; 2]);
/// The multiplicative identity for this integer type, i.e. `1`.
pub const ONE: Self = U256::new(1);
/// Creates a new 256-bit integer value from a primitive `u128` integer.
#[inline]
pub const fn new(value: u128) -> Self {
U256::from_words(0, value)
}
/// Creates a new 256-bit integer value from high and low words.
#[inline]
pub const fn from_words(hi: u128, lo: u128) -> Self {
#[cfg(target_endian = "little")]
{
U256([lo, hi])
}
#[cfg(target_endian = "big")]
{
U256([hi, lo])
}
}
/// Splits a 256-bit integer into high and low words.
#[inline]
pub const fn into_words(self) -> (u128, u128) {
#[cfg(target_endian = "little")]
{
let U256([lo, hi]) = self;
(hi, lo)
}
#[cfg(target_endian = "big")]
{
let U256([hi, lo]) = self;
(hi, lo)
}
}
/// Get the low 128-bit word for this unsigned integer.
#[inline]
pub fn low(&self) -> &u128 {
#[cfg(target_endian = "little")]
{
&self.0[0]
}
#[cfg(target_endian = "big")]
{
&self.0[1]
}
}
/// Get the low 128-bit word for this unsigned integer as a mutable
/// reference.
#[inline]
pub fn low_mut(&mut self) -> &mut u128 {
#[cfg(target_endian = "little")]
{
&mut self.0[0]
}
#[cfg(target_endian = "big")]
{
&mut self.0[1]
}
}
/// Get the high 128-bit word for this unsigned integer.
#[inline]
pub fn high(&self) -> &u128 {
#[cfg(target_endian = "little")]
{
&self.0[1]
}
#[cfg(target_endian = "big")]
{
&self.0[0]
}
}
/// Get the high 128-bit word for this unsigned integer as a mutable
/// reference.
#[inline]
pub fn high_mut(&mut self) -> &mut u128 {
#[cfg(target_endian = "little")]
{
&mut self.0[1]
}
#[cfg(target_endian = "big")]
{
&mut self.0[0]
}
}
/// Cast to a primitive `i8`.
///
/// [`U256`]: struct.U256.html
pub const fn as_i8(self) -> i8 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `i16`.
///
/// [`U256`]: struct.U256.html
pub const fn as_i16(self) -> i16 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `i32`.
///
/// [`U256`]: struct.U256.html
pub const fn as_i32(self) -> i32 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `i64`.
///
/// [`U256`]: struct.U256.html
pub const fn as_i64(self) -> i64 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `i128`.
///
/// [`U256`]: struct.U256.html
pub const fn as_i128(self) -> i128 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `u8`.
///
/// [`U256`]: struct.U256.html
pub const fn as_u8(self) -> u8 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `u16`.
///
/// [`U256`]: struct.U256.html
pub const fn as_u16(self) -> u16 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `u32`.
///
/// [`U256`]: struct.U256.html
pub const fn as_u32(self) -> u32 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `u64`.
///
/// [`U256`]: struct.U256.html
pub const fn as_u64(self) -> u64 {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `u128`.
///
/// [`U256`]: struct.U256.html
pub const fn as_u128(self) -> u128 {
let (_, lo) = self.into_words();
lo
}
/// Cast to a primitive `isize`.
///
/// [`U256`]: struct.U256.html
pub const fn as_isize(self) -> isize {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `usize`.
///
/// [`U256`]: struct.U256.html
pub const fn as_usize(self) -> usize {
let (_, lo) = self.into_words();
lo as _
}
/// Cast to a primitive `f32`.
///
/// [`U256`]: struct.U256.html
pub const fn as_f32(self) -> f32 {
match self.into_words() {
(0, lo) => lo as _,
_ => f32::INFINITY,
}
}
/// Cast to a primitive `f64`.
///
/// [`U256`]: struct.U256.html
pub fn as_f64(self) -> f64 {
// NOTE: Binary representation of 2**128. This is used because `powi` is
// neither `const` nor `no_std`.
const HI: u64 = 0x47f0000000000000;
let (hi, lo) = self.into_words();
(hi as f64) * f64::from_bits(HI) + (lo as f64)
}
}
#[cfg(test)]
mod tests {
use crate::U256;
#[test]
#[allow(clippy::float_cmp)]
fn converts_to_f64() {
assert_eq!(U256::from_words(1, 0).as_f64(), 2.0f64.powi(128))
}
}