ruint/
lib.rs

1#![doc = include_str!("../README.md")]
2#![doc(issue_tracker_base_url = "https://github.com/recmo/uint/issues/")]
3#![warn(
4    clippy::all,
5    clippy::pedantic,
6    clippy::nursery,
7    clippy::missing_inline_in_public_items,
8    clippy::std_instead_of_alloc,
9    clippy::std_instead_of_core,
10    missing_docs,
11    unreachable_pub
12)]
13#![allow(
14    clippy::doc_markdown, // Unfortunately many false positives on Latex.
15    clippy::inline_always,
16    clippy::module_name_repetitions,
17    clippy::redundant_pub_crate,
18    clippy::unreadable_literal,
19    clippy::let_unit_value,
20    clippy::option_if_let_else,
21    clippy::cast_sign_loss,
22    clippy::cast_lossless,
23)]
24#![cfg_attr(test, allow(clippy::wildcard_imports, clippy::cognitive_complexity))]
25#![cfg_attr(not(test), warn(unused_crate_dependencies))]
26#![cfg_attr(not(feature = "std"), no_std)]
27// Unstable features
28#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
29#![cfg_attr(feature = "nightly", feature(core_intrinsics))]
30#![cfg_attr(feature = "nightly", allow(internal_features))]
31#![cfg_attr(
32    feature = "generic_const_exprs",
33    feature(generic_const_exprs),
34    allow(incomplete_features)
35)]
36
37#[cfg(feature = "alloc")]
38#[allow(unused_imports)]
39// `unused_imports` triggers on macro_use, which is required by some support
40// modules.
41#[macro_use]
42extern crate alloc;
43
44#[macro_use]
45mod macros;
46
47mod add;
48pub mod algorithms;
49pub mod aliases;
50mod base_convert;
51mod bit_arr;
52mod bits;
53mod bytes;
54mod cmp;
55mod const_for;
56mod div;
57mod fmt;
58mod from;
59mod gcd;
60mod log;
61mod modular;
62mod mul;
63mod pow;
64mod root;
65mod special;
66mod string;
67mod utils;
68
69pub mod support;
70
71#[doc(inline)]
72pub use bit_arr::Bits;
73
74#[doc(inline)]
75pub use self::{
76    base_convert::BaseConvertError,
77    bytes::nbytes,
78    from::{FromUintError, ToFieldError, ToUintError, UintTryFrom, UintTryTo},
79    string::ParseError,
80};
81
82// For documentation purposes we expose the macro directly, otherwise it is
83// wrapped in ./macros.rs.
84#[cfg(doc)]
85#[doc(inline)]
86pub use ruint_macro::uint;
87
88/// Extra features that are nightly only.
89#[cfg(feature = "generic_const_exprs")]
90pub mod nightly {
91    /// Alias for `Uint` specified only by bit size.
92    ///
93    /// Compared to [`crate::Uint`] it compile-time computes the required number
94    /// of limbs. Unfortunately this requires the nightly feature
95    /// `generic_const_exprs`.
96    ///
97    /// # References
98    /// * [Working group](https://rust-lang.github.io/project-const-generics/)
99    ///   const generics working group.
100    /// * [RFC2000](https://rust-lang.github.io/rfcs/2000-const-generics.html)
101    ///   const generics.
102    /// * [#60551](https://github.com/rust-lang/rust/issues/60551) associated
103    ///   constants in const generics.
104    /// * [#76560](https://github.com/rust-lang/rust/issues/76560) tracking
105    ///   issue for `generic_const_exprs`.
106    /// * [Rust blog](https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html)
107    ///   2021-09-06 Splitting const generics.
108    pub type Uint<const BITS: usize> = crate::Uint<BITS, { crate::nlimbs(BITS) }>;
109
110    /// Alias for `Bits` specified only by bit size.
111    ///
112    /// See [`Uint`] for more information.
113    pub type Bits<const BITS: usize> = crate::Bits<BITS, { crate::nlimbs(BITS) }>;
114}
115
116// FEATURE: (BLOCKED) Many functions could be made `const` if a number of
117// features land. This requires
118// #![feature(const_mut_refs)]
119// #![feature(const_float_classify)]
120// #![feature(const_fn_floating_point_arithmetic)]
121// #![feature(const_float_bits_conv)]
122// and more.
123
124/// The ring of numbers modulo $2^{\mathtt{BITS}}$.
125///
126/// [`Uint`] implements nearly all traits and methods from the `std` unsigned
127/// integer types, including most nightly only ones.
128///
129/// # Notable differences from `std` uint types.
130///
131/// * The operators `+`, `-`, `*`, etc. using wrapping math by default. The std
132///   operators panic on overflow in debug, and are undefined in release, see
133///   [reference][std-overflow].
134/// * The [`Uint::checked_shl`], [`Uint::overflowing_shl`], etc return overflow
135///   when non-zero bits are shifted out. In std they return overflow when the
136///   shift amount is greater than the bit size.
137/// * Some methods like [`u64::div_euclid`] and [`u64::rem_euclid`] are left out
138///   because they are meaningless or redundant for unsigned integers. Std has
139///   them for compatibility with their signed integers.
140/// * Many functions that are `const` in std are not in [`Uint`].
141/// * [`Uint::to_le_bytes`] and [`Uint::to_be_bytes`] require the output size to
142///   be provided as a const-generic argument. They will runtime panic if the
143///   provided size is incorrect.
144/// * [`Uint::widening_mul`] takes as argument an [`Uint`] of arbitrary size and
145///   returns a result that is sized to fit the product without overflow (i.e.
146///   the sum of the bit sizes of self and the argument). The std version
147///   requires same-sized arguments and returns a pair of lower and higher bits.
148///
149/// [std-overflow]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#overflow
150#[derive(Clone, Copy, Eq, PartialEq, Hash)]
151#[repr(transparent)]
152pub struct Uint<const BITS: usize, const LIMBS: usize> {
153    limbs: [u64; LIMBS],
154}
155
156impl<const BITS: usize, const LIMBS: usize> Uint<BITS, LIMBS> {
157    /// The size of this integer type in 64-bit limbs.
158    pub const LIMBS: usize = {
159        let limbs = nlimbs(BITS);
160        assert!(
161            LIMBS == limbs,
162            "Can not construct Uint<BITS, LIMBS> with incorrect LIMBS"
163        );
164        limbs
165    };
166
167    /// Bit mask for the last limb.
168    pub const MASK: u64 = mask(BITS);
169
170    /// The size of this integer type in bits.
171    pub const BITS: usize = BITS;
172
173    /// The value zero. This is the only value that exists in all [`Uint`]
174    /// types.
175    pub const ZERO: Self = Self::from_limbs([0; LIMBS]);
176
177    /// The smallest value that can be represented by this integer type.
178    /// Synonym for [`Self::ZERO`].
179    pub const MIN: Self = Self::ZERO;
180
181    /// The largest value that can be represented by this integer type,
182    /// $2^{\mathtt{BITS}} − 1$.
183    pub const MAX: Self = {
184        let mut limbs = [u64::MAX; LIMBS];
185        if BITS > 0 {
186            limbs[LIMBS - 1] &= Self::MASK;
187        }
188        Self::from_limbs(limbs)
189    };
190
191    /// View the array of limbs.
192    #[inline(always)]
193    #[must_use]
194    pub const fn as_limbs(&self) -> &[u64; LIMBS] {
195        &self.limbs
196    }
197
198    /// Access the array of limbs.
199    ///
200    /// # Safety
201    ///
202    /// This function is unsafe because it allows setting a bit outside the bit
203    /// size if the bit-size is not limb-aligned.
204    #[inline(always)]
205    #[must_use]
206    pub unsafe fn as_limbs_mut(&mut self) -> &mut [u64; LIMBS] {
207        &mut self.limbs
208    }
209
210    /// Convert to a array of limbs.
211    ///
212    /// Limbs are least significant first.
213    #[inline(always)]
214    #[must_use]
215    pub const fn into_limbs(self) -> [u64; LIMBS] {
216        self.limbs
217    }
218
219    /// Construct a new integer from little-endian a array of limbs.
220    ///
221    /// # Panics
222    ///
223    /// Panics it `LIMBS` is not equal to `nlimbs(BITS)`.
224    ///
225    /// Panics if the value is too large for the bit-size of the Uint.
226    #[inline(always)]
227    #[must_use]
228    #[track_caller]
229    pub const fn from_limbs(limbs: [u64; LIMBS]) -> Self {
230        if BITS > 0 && Self::MASK != u64::MAX {
231            // FEATURE: (BLOCKED) Add `<{BITS}>` to the type when Display works in const fn.
232            assert!(
233                limbs[Self::LIMBS - 1] <= Self::MASK,
234                "Value too large for this Uint"
235            );
236        }
237        Self { limbs }
238    }
239
240    /// Construct a new integer from little-endian a slice of limbs.
241    ///
242    /// # Panics
243    ///
244    /// Panics if the value is too large for the bit-size of the Uint.
245    #[inline]
246    #[must_use]
247    #[track_caller]
248    pub fn from_limbs_slice(slice: &[u64]) -> Self {
249        match Self::overflowing_from_limbs_slice(slice) {
250            (n, false) => n,
251            (_, true) => panic!("Value too large for this Uint"),
252        }
253    }
254
255    /// Construct a new integer from little-endian a slice of limbs, or `None`
256    /// if the value is too large for the [`Uint`].
257    #[inline]
258    #[must_use]
259    pub fn checked_from_limbs_slice(slice: &[u64]) -> Option<Self> {
260        match Self::overflowing_from_limbs_slice(slice) {
261            (n, false) => Some(n),
262            (_, true) => None,
263        }
264    }
265
266    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
267    /// a potentially truncated value.
268    #[inline]
269    #[must_use]
270    pub fn wrapping_from_limbs_slice(slice: &[u64]) -> Self {
271        Self::overflowing_from_limbs_slice(slice).0
272    }
273
274    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
275    /// a potentially truncated value and a boolean indicating whether the value
276    /// was truncated.
277    #[inline]
278    #[must_use]
279    pub fn overflowing_from_limbs_slice(slice: &[u64]) -> (Self, bool) {
280        if slice.len() < LIMBS {
281            let mut limbs = [0; LIMBS];
282            limbs[..slice.len()].copy_from_slice(slice);
283            (Self::from_limbs(limbs), false)
284        } else {
285            let (head, tail) = slice.split_at(LIMBS);
286            let mut limbs = [0; LIMBS];
287            limbs.copy_from_slice(head);
288            let mut overflow = tail.iter().any(|&limb| limb != 0);
289            if LIMBS > 0 {
290                overflow |= limbs[LIMBS - 1] > Self::MASK;
291                limbs[LIMBS - 1] &= Self::MASK;
292            }
293            (Self::from_limbs(limbs), overflow)
294        }
295    }
296
297    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
298    /// the maximum value if the value is too large for the [`Uint`].
299    #[inline]
300    #[must_use]
301    pub fn saturating_from_limbs_slice(slice: &[u64]) -> Self {
302        match Self::overflowing_from_limbs_slice(slice) {
303            (n, false) => n,
304            (_, true) => Self::MAX,
305        }
306    }
307}
308
309impl<const BITS: usize, const LIMBS: usize> Default for Uint<BITS, LIMBS> {
310    #[inline]
311    fn default() -> Self {
312        Self::ZERO
313    }
314}
315
316/// Number of `u64` limbs required to represent the given number of bits.
317/// This needs to be public because it is used in the `Uint` type.
318#[inline]
319#[must_use]
320pub const fn nlimbs(bits: usize) -> usize {
321    (bits + 63) / 64
322}
323
324/// Mask to apply to the highest limb to get the correct number of bits.
325#[inline]
326#[must_use]
327pub const fn mask(bits: usize) -> u64 {
328    if bits == 0 {
329        return 0;
330    }
331    let bits = bits % 64;
332    if bits == 0 {
333        u64::MAX
334    } else {
335        (1 << bits) - 1
336    }
337}
338
339// Not public API.
340#[doc(hidden)]
341pub mod __private {
342    pub use ruint_macro;
343}
344
345#[cfg(test)]
346mod test {
347    use super::*;
348
349    #[test]
350    fn test_mask() {
351        assert_eq!(mask(0), 0);
352        assert_eq!(mask(1), 1);
353        assert_eq!(mask(5), 0x1f);
354        assert_eq!(mask(63), u64::MAX >> 1);
355        assert_eq!(mask(64), u64::MAX);
356    }
357
358    #[test]
359    fn test_max() {
360        assert_eq!(Uint::<0, 0>::MAX, Uint::ZERO);
361        assert_eq!(Uint::<1, 1>::MAX, Uint::from_limbs([1]));
362        assert_eq!(Uint::<7, 1>::MAX, Uint::from_limbs([127]));
363        assert_eq!(Uint::<64, 1>::MAX, Uint::from_limbs([u64::MAX]));
364        assert_eq!(
365            Uint::<100, 2>::MAX,
366            Uint::from_limbs([u64::MAX, u64::MAX >> 28])
367        );
368    }
369
370    #[test]
371    fn test_constants() {
372        const_for!(BITS in SIZES {
373            const LIMBS: usize = nlimbs(BITS);
374            assert_eq!(Uint::<BITS, LIMBS>::MIN, Uint::<BITS, LIMBS>::ZERO);
375            let _ = Uint::<BITS, LIMBS>::MAX;
376        });
377    }
378}
ruint/lib.rs

ruint/
lib.rs
