Crate ruint

Expand description

Rust `uint` crate using const-generics

Implements Uint<BITS, LIMBS>, the ring of numbers modulo $2^{\mathtt{BITS}}$. It requires two generic arguments: the number of bits and the number of 64-bit ‘limbs’ required to store those bits.

let answer: Uint<256, 4> = Uint::from(42);

You can compute LIMBS yourself using $\mathtt{LIMBS} = \ceil{\mathtt{BITS} / 64}$, i.e.LIMBS equals BITS divided by $64$ rounded up. Uint will panic! if you try to construct it with incorrect arguments. Ideally this would be a compile time error, but that is blocked by Rust issue #60551.

A more convenient method on stable is to use the uint! macro, which constructs the right Uint for you.

let answer = uint!(42_U256);

You can also use one of the pre-computed type aliases:

use ruint::aliases::*;

let answer: U256 = Uint::from(42);

You can of course also create your own type alias if you need a funny size:

type U1337 = Uint<1337, 21>;

let answer: U1337 = Uint::from(42);

Rust nightly

If you are on nightly, you can use [Uint<BITS>][nightly::Uint] which will compute the number of limbs for you. Unfortunately this can not be made stable without generic_const_exprs support (Rust issue #76560).

use ruint::nightly::Uint;

let answer: Uint<256> = Uint::<256>::from(42);

Even on nightly, the ergonomics of Rust are limited. In the example above Rust requires explicit type annotation for Uint::from, where it did not require it in the stable version. There are a few more subtle issues that make this less ideal than it appears. It also looks like it may take some time before these nightly features are stabilized.

Examples

use ruint::{Uint, OverflowingAdd};

let a: Uint<256, 4> = Uint::from(0xf00f_u64);
let b: Uint<256, 4> = Uint::from(42_u64);
let (c, _carry) = a.overflowing_add(b);
assert_eq!(c, Uint::from(0xf039_u64));

There is a convenient macro uint! to create constants for you. It allows for arbitrary length constants using standard Rust integer syntax. The size of the Uint is specified with a U suffix followed by the number of bits. The standard Rust syntax of decimal, hexadecimal and even binary and octal is supported using their prefixes 0x, 0b and 0o. Literals can have underscores _ added for readability.

let cow = uint!(0xc85ef7d79691fe79573b1a7064c19c1a9819ebdbd1faaab1a8ec92344438aaf4_U256);

In fact, this macro recurses down the parse tree, so you can apply it to entire source files:

uint!{

let a = 42_U256;
let b = 0xf00f_1337_c0d3_U256;
let (c, _carry) = a.overflowing_add(b);
assert_eq!(c, 263947537596669_U256);

}

Feature flags

There is support for a number of crates. These are enabled by setting the identically named feature flag.

rand: Implements sampling from the Standard distribution, i.e. rng.gen().
arbitrary: Implements the Arbitrary trait, allowing Uints to be generated for fuzz testing.
quickcheck: Implements the Arbitrary trait, allowing Uints to be generated for property based testing.
proptest: Implements the Arbitrary trait, allowing Uints to be generated for property based testing. Proptest is used for the uints own test suite.
serde: Implements the Seralize and Deserialize traits for Uint using big-endian hex in human readable formats and big-endian byte strings in machine readable formats.
rlp: Implements the Encodable and Decodable traits for Uint to allow serialization to/from RLP.
fastrlp: Implements the Encodable and Decodable traits for Uint to allow serialization to/from RLP.
primitive-types: Implements the From<_> conversions between corresponding types.
postgres: Implements the ToSql trait supporting many column types.

Building and testing

Format, lint, build and test everything (I recommend creating a shell alias for this):

cargo fmt &&\
cargo clippy --all-features --all-targets &&\
cargo test --workspace --all-features --doc -- --nocapture &&\
cargo test --workspace --all-features --all-targets -- --nocapture &&\
cargo doc --workspace --all-features --no-deps

Run benchmarks with the provided .cargo/config.toml alias

cargo criterion

Check documentation coverage

RUSTDOCFLAGS="-Z unstable-options --show-coverage"  cargo doc --workspace --all-features --no-deps

To do

Goals:

All the quality of life features one could want.
Compatible with std u64, etc types. See Rust’s integer methods.
Builds no-std and wasm.
Fast platform agnostic generic algorithms.
Target specific assembly optimizations (where available).
Optional num-traits, etc, support.
Adhere to Rust API Guidelines

Maybe:

Run-time sized type with compatible interface.
Montgomery REDC and other algo’s for implementing prime fields.

Modules

aliases

Type aliases for common bit sizes of Uint.

Macros

const_for

Compile time for loops with a const variable for testing.

uint

The uint! macro for Uint literals

Structs

Bits

Bit vector

Uint

The ring of numbers modulo $2^{\mathtt{BITS}}$.

nlimbs

Number of u64 limbs required to represent the given number of bits. This needs to be public because it is used in the Uint type.