mvbitfield

A bitfield library for Rust.

mvbitfield generates bitfield struct types that can insert and extract bit-aligned fields.

Bitfield structs serve roughly the same use cases as C/C++ structs with bit-field members.

The generated bitfield structs are:

• Endian-insensitive, packing fields within an integer rather than across bytes or array elements.
• Flexible and type-safe with optional user-defined field accessor types.
• Suitable for FFI and memory-mapped I/O with care, as always.

Demo

```rust // Recommended, but not required. The mvbitfield prelude includes the bitint // prelude. use mvbitfield::prelude::*;

bitfield! { #[lsbfirst] // Field packing order. #[derive(PartialOrd, Ord)] // Other attributes are passed through. pub struct MyBitfieldStruct: 32 { // The lowest 3 bits with public bitint::U3 accessors. pub somenumber: 3,

    // The next 8 bits with public bitint::U8 accessors.
    pub another_number: 8,

    // No accessors for field names starting with _.
    _padding: 2,

    // Private bitint::U11 accessors.
    internal_number: 11,

    // Skip unused bits, in this case 7 bits.
    ..,

    // Private bool accessors.
    high_bit_flag: 1 as bool,
}

}

[bitint_literals]

fn main() { // Use generated with* methods to build bitfield structs. let x = MyBitfieldStruct::zero() .withsomenumber(6U3) .withanothernumber(0xa5U8) .withinternalnumber(1025U11) .withhighbit_flag(true);

// Default accessors return bitints.
assert_eq!(x.some_number(), 6_U3);
assert_eq!(x.some_number().to_primitive(), 6);
assert_eq!(x.another_number(), 0xa5_U8);
assert_eq!(x.another_number().to_primitive(), 0xa5);
assert_eq!(x.internal_number(), 1025_U11);
assert_eq!(x.internal_number().to_primitive(), 1025);

// Custom accessors return the chosen type, which must have Into
// conversions to and from the default accessor bitint.
assert_eq!(x.high_bit_flag(), true);

// Zero-cost conversions to and from bitints and to primitive.
assert_eq!(x.to_bitint(), 0b1_0000000_10000000001_00_10100101_110_U32);
assert_eq!(x.to_primitive(), 0b1_0000000_10000000001_00_10100101_110);
assert_eq!(x, MyBitfieldStruct::from_bitint(0x8080252e_U32));

// Zero-cost conversion from primitive, only for primitive-sized
// bitfield structs.
assert_eq!(x, MyBitfieldStruct::from_primitive(0x8080252e));

} ```