Crate bit_ops

bit_ops

About

Common bit-oriented operations on primitive integer types with a focus on no_std and const compatibility. Unlike other crates that provide tooling to create sophisticated high-level types with bitfields, the focus of bit_ops is on raw primitive integer types.

API

This crate exports a Function API and a Trait API. The Function API is the foundation and provides no_std and const-compatible functions. The Trait API won’t be const-compatible unless const trait methods are supported by Rust (stable). This is not the case in Mid-2024 and the next months in Rust stable. bit_ops will adapt, as soon as this changes.

Note that the most trivial bit operations, such as "shift_bits" or "keep_bits" won’t be covered by the API, as this would introduce a convoluted way around the standard operators <<, >>, and &. Only non-trivial non-oneliners are covered by the API as well as operations, where the semantic name provides a value-add over a (possible even oneliner) (combination of) bit operation.

Function API

For each primitive unsigned integer type, there is a module with the same set of functions:

• bitops_u8
• bitops_u16
• bitops_u32
• bitops_u64
• bitops_u128
• bitops_usize

Example

The following example shows a real-world scenario where several properties are encoded in a single u64 representing an x86 IOAPIC redirection entry.

// PREREQUISITES: Some Definitions

/// See specification of the x86 IOAPIC redirection entry for more details.
mod x86_ioapic {
    pub const VECTOR_BITS: u64 = 8;
    pub const VECTOR_SHIFT: u64 = 0;
    pub const DELIVERY_MODE_BITS: u64 = 3;
    pub const DELIVERY_MODE_SHIFT: u64 = 8;
    pub const DESTINATION_MODE_BITS: u64 = 1;
    pub const DESTINATION_MODE_SHIFT: u64 = 11;
    pub const PIN_POLARITY_BITS: u64 = 1;
    pub const PIN_POLARITY_SHIFT: u64 = 13;
    pub const TRIGGER_MODE_BITS: u64 = 1;
    pub const TRIGGER_MODE_SHIFT: u64 = 15;
    pub const MASKED_BITS: u64 = 1;
    pub const MASKED_SHIFT: u64 = 16;
    pub const DESTINATION_BITS: u64 = 8;
    pub const DESTINATION_SHIFT: u64 = 56;
}

use x86_ioapic::*;

 // ACTUAL LIBRARY USAGE BEGINS HERE

let redirection_entry = bit_ops::bitops_u64::set_bits_exact_n(
    0,
    &[
        (7, VECTOR_BITS, VECTOR_SHIFT),
        (0b111 /* ExtInt */, DELIVERY_MODE_BITS, DELIVERY_MODE_SHIFT),
        (0 /* physical */, DESTINATION_MODE_BITS, DESTINATION_MODE_SHIFT),
        (1 /* low-active */, PIN_POLARITY_BITS, PIN_POLARITY_SHIFT),
        (1 /* level-triggered */, TRIGGER_MODE_BITS, TRIGGER_MODE_SHIFT),
        (1 /* masked */, MASKED_BITS, MASKED_SHIFT),
        (13 /* APIC ID */, DESTINATION_BITS, DESTINATION_SHIFT),
    ],
);
assert_eq!(redirection_entry, 0xd0000000001a707);

Trait API

The trait BitOps is implemented for u8, u16, u32, u64, u128, and usize. It provides the same functionality as the function API, but you call each operation as associated function.

Example

Unlike in the Function API, you can use chaining here:

use bit_ops::BitOps;

let raw = 0_u64.set_bit(1).set_bit(2);
assert_eq!(raw, 0b110);

Comparison to other Crates

bit_ops (this crate) is fresher, more feature-complete, and fully no_std and const compatible compared to bit_op, bitops, and bitwise. Unlike in bitwise for example, functionality from libcore is not replicated.

MSRV

1.57.0 stable

License

MIT License.

Modules

bitops_u8

Various bit manipulation operations for the primitive type u8.

bitops_u16

Various bit manipulation operations for the primitive type u16.

bitops_u32

Various bit manipulation operations for the primitive type u32.

bitops_u64

Various bit manipulation operations for the primitive type u64.

bitops_u128

Various bit manipulation operations for the primitive type u128.

bitops_usize

Various bit manipulation operations for the primitive type usize.

Traits

BitOps

Common bitwise operations to manipulate the bits in raw integers.