#bit #numeric


Types for manipulating numeric primitives at the bit level

2 stable releases

1.1.0 Jan 4, 2019
1.0.0 Dec 23, 2018
0.0.0 Jun 30, 2017

#844 in Rust patterns

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MIT license

500 lines


Types for manipulating numeric primitives at the bit level.

Build Status Coverage Status Docs.rs

The quark crate provides traits for accessing parts of numeric primitives and adds new types to represent numbers using bit counts that aren't included in the standard library.

Bit Indexing

Accessing a bit or range of bits in a numeric primitive can be awkward and less than readable using shifts and masks:

let big: u16 = 0x35;
let small = big >> 2 & 0x1f;
assert_eq!(small, 0xd);

At a glance, it's not easy to parse things like:

  • How many bits are contributing to the resulting value and which ones are definitely zero?
  • Which bits in the original value are in the result?

Using the BitIndex trait, the above example can be written as:

use quark::BitIndex;

let big: u16 = 0x35;
let small = big.bits(2..7);
assert_eq!(small, 0xd);

Bit Masks

The BitMask trait allows for easily generating a bit mask using just the length and apply masks:

use quark::BitMask;

let mask = u32::mask(8);
assert_eq!(mask, 0xff);

let value: u32 = 0x1234_5678;
assert_eq!(value.mask_to(16), 0x5678);

Bit Sizes

When implementing a trait on numeric types, sometimes the number of bits of a type will be required. One way around this is adding a bit_size() or bit_length() method to the trait in order to return a constant for each type. The BitSize trait adds a BIT_SIZE constant to the numeric types that can be used in implementing traits without needing another method.

Sign Extension

The Signs trait adds methods for checking the sign bit on unsigned primitives (and signed ones) and for sign-extending values an arbitrary number of bits:

use quark::Signs;

let unsigned = 0x00ff_ffffu32;
let signed = unsigned.sign_extend(8);
assert_eq!(signed, 0xffff_ffff);

Why quark?

Because our programs are primitives at the very lowest level, types like i32, u8, and usize are like atomic pieces of data. The quark crate goes to the next level down, and quarks are at that next level w.r.t. atoms.

Also, I have an affinity for names with a 'Q' because my last name starts with one.

No runtime deps