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    const SHOULD_MASK: bool = BITS > 0 && Self::MASK != u64::MAX;
171
172    /// The size of this integer type in bits.
173    pub const BITS: usize = BITS;
174
175    /// The value zero. This is the only value that exists in all [`Uint`]
176    /// types.
177    pub const ZERO: Self = Self::from_limbs([0; LIMBS]);
178
179    /// The value one. This is useful to have as a constant for use in const fn.
180    ///
181    /// Zero if `BITS` is zero.
182    pub const ONE: Self = Self::const_from_u64(1);
183
184    /// The smallest value that can be represented by this integer type.
185    /// Synonym for [`Self::ZERO`].
186    pub const MIN: Self = Self::ZERO;
187
188    /// The largest value that can be represented by this integer type,
189    /// $2^{\mathtt{BITS}} − 1$.
190    pub const MAX: Self = Self::from_limbs_unmasked([u64::MAX; LIMBS]);
191
192    /// View the array of limbs.
193    #[inline(always)]
194    #[must_use]
195    pub const fn as_limbs(&self) -> &[u64; LIMBS] {
196        &self.limbs
197    }
198
199    /// Access the array of limbs.
200    ///
201    /// # Safety
202    ///
203    /// This function is unsafe because it allows setting a bit outside the bit
204    /// size if the bit-size is not limb-aligned.
205    #[inline(always)]
206    #[must_use]
207    pub unsafe fn as_limbs_mut(&mut self) -> &mut [u64; LIMBS] {
208        &mut self.limbs
209    }
210
211    /// Convert to a array of limbs.
212    ///
213    /// Limbs are least significant first.
214    #[inline(always)]
215    #[must_use]
216    pub const fn into_limbs(self) -> [u64; LIMBS] {
217        self.limbs
218    }
219
220    /// Construct a new integer from little-endian a array of limbs.
221    ///
222    /// # Panics
223    ///
224    /// Panics it `LIMBS` is not equal to `nlimbs(BITS)`.
225    ///
226    /// Panics if the value is too large for the bit-size of the Uint.
227    #[inline(always)]
228    #[must_use]
229    #[track_caller]
230    pub const fn from_limbs(limbs: [u64; LIMBS]) -> Self {
231        if Self::SHOULD_MASK {
232            // FEATURE: (BLOCKED) Add `<{BITS}>` to the type when Display works in const fn.
233            assert!(
234                limbs[Self::LIMBS - 1] <= Self::MASK,
235                "Value too large for this Uint"
236            );
237        }
238        Self { limbs }
239    }
240
241    #[inline(always)]
242    #[must_use]
243    const fn from_limbs_unmasked(limbs: [u64; LIMBS]) -> Self {
244        Self { limbs }.masked()
245    }
246
247    /// Construct a new integer from little-endian a slice of limbs.
248    ///
249    /// # Panics
250    ///
251    /// Panics if the value is too large for the bit-size of the Uint.
252    #[inline]
253    #[must_use]
254    #[track_caller]
255    pub fn from_limbs_slice(slice: &[u64]) -> Self {
256        match Self::overflowing_from_limbs_slice(slice) {
257            (n, false) => n,
258            (_, true) => panic!("Value too large for this Uint"),
259        }
260    }
261
262    /// Construct a new integer from little-endian a slice of limbs, or `None`
263    /// if the value is too large for the [`Uint`].
264    #[inline]
265    #[must_use]
266    pub fn checked_from_limbs_slice(slice: &[u64]) -> Option<Self> {
267        match Self::overflowing_from_limbs_slice(slice) {
268            (n, false) => Some(n),
269            (_, true) => None,
270        }
271    }
272
273    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
274    /// a potentially truncated value.
275    #[inline]
276    #[must_use]
277    pub fn wrapping_from_limbs_slice(slice: &[u64]) -> Self {
278        Self::overflowing_from_limbs_slice(slice).0
279    }
280
281    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
282    /// a potentially truncated value and a boolean indicating whether the value
283    /// was truncated.
284    #[inline]
285    #[must_use]
286    pub fn overflowing_from_limbs_slice(slice: &[u64]) -> (Self, bool) {
287        if slice.len() < LIMBS {
288            let mut limbs = [0; LIMBS];
289            limbs[..slice.len()].copy_from_slice(slice);
290            (Self::from_limbs(limbs), false)
291        } else {
292            let (head, tail) = slice.split_at(LIMBS);
293            let mut limbs = [0; LIMBS];
294            limbs.copy_from_slice(head);
295            let mut overflow = tail.iter().any(|&limb| limb != 0);
296            if LIMBS > 0 {
297                overflow |= limbs[LIMBS - 1] > Self::MASK;
298                limbs[LIMBS - 1] &= Self::MASK;
299            }
300            (Self::from_limbs(limbs), overflow)
301        }
302    }
303
304    /// Construct a new [`Uint`] from a little-endian slice of limbs. Returns
305    /// the maximum value if the value is too large for the [`Uint`].
306    #[inline]
307    #[must_use]
308    pub fn saturating_from_limbs_slice(slice: &[u64]) -> Self {
309        match Self::overflowing_from_limbs_slice(slice) {
310            (n, false) => n,
311            (_, true) => Self::MAX,
312        }
313    }
314
315    #[inline(always)]
316    fn apply_mask(&mut self) {
317        if Self::SHOULD_MASK {
318            self.limbs[LIMBS - 1] &= Self::MASK;
319        }
320    }
321
322    #[inline(always)]
323    const fn masked(mut self) -> Self {
324        if Self::SHOULD_MASK {
325            self.limbs[LIMBS - 1] &= Self::MASK;
326        }
327        self
328    }
329}
330
331impl<const BITS: usize, const LIMBS: usize> Default for Uint<BITS, LIMBS> {
332    #[inline]
333    fn default() -> Self {
334        Self::ZERO
335    }
336}
337
338/// Number of `u64` limbs required to represent the given number of bits.
339/// This needs to be public because it is used in the `Uint` type.
340#[inline]
341#[must_use]
342pub const fn nlimbs(bits: usize) -> usize {
343    (bits + 63) / 64
344}
345
346/// Mask to apply to the highest limb to get the correct number of bits.
347#[inline]
348#[must_use]
349pub const fn mask(bits: usize) -> u64 {
350    if bits == 0 {
351        return 0;
352    }
353    let bits = bits % 64;
354    if bits == 0 {
355        u64::MAX
356    } else {
357        (1 << bits) - 1
358    }
359}
360
361// Not public API.
362#[doc(hidden)]
363pub mod __private {
364    pub use ruint_macro;
365}
366
367#[cfg(test)]
368mod test {
369    use super::*;
370
371    #[test]
372    fn test_mask() {
373        assert_eq!(mask(0), 0);
374        assert_eq!(mask(1), 1);
375        assert_eq!(mask(5), 0x1f);
376        assert_eq!(mask(63), u64::MAX >> 1);
377        assert_eq!(mask(64), u64::MAX);
378    }
379
380    #[test]
381    fn test_max() {
382        assert_eq!(Uint::<0, 0>::MAX, Uint::ZERO);
383        assert_eq!(Uint::<1, 1>::MAX, Uint::from_limbs([1]));
384        assert_eq!(Uint::<7, 1>::MAX, Uint::from_limbs([127]));
385        assert_eq!(Uint::<64, 1>::MAX, Uint::from_limbs([u64::MAX]));
386        assert_eq!(
387            Uint::<100, 2>::MAX,
388            Uint::from_limbs([u64::MAX, u64::MAX >> 28])
389        );
390    }
391
392    #[test]
393    fn test_constants() {
394        const_for!(BITS in SIZES {
395            const LIMBS: usize = nlimbs(BITS);
396            assert_eq!(Uint::<BITS, LIMBS>::MIN, Uint::<BITS, LIMBS>::ZERO);
397            let _ = Uint::<BITS, LIMBS>::MAX;
398        });
399    }
400}
ruint/lib.rs

ruint/
lib.rs
