#bitfield

proc-bitfield

A crate to expressively declare bitfield-like structs

6 releases

0.2.2 Dec 22, 2022
0.2.1 Sep 19, 2022
0.1.1 Jul 30, 2022
0.0.2 Jul 7, 2022

#133 in Procedural macros

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122 downloads per month
Used in 2 crates (via n64-pac)

MIT/Apache

30KB
353 lines

proc-bitfield

crates.io docs.rs

A Rust crate to expressively declare bitfield-like structs, automatically ensuring their correctness at compile time and declaring accessors.

API and syntax docs

Usage examples

Bit ranges (generated)

bitfield! {
    #[derive(Clone, Copy, PartialEq, Eq)]
    pub struct BitRanges(pub u16): Debug {
        // A single field spanning the entire bitfield, using an unbounded range:
        pub whole_bitfield: u16 @ ..,                 // Bits 0 to 15

        // Multi-bit field, specified using an inclusive range:
        pub inclusive_range: u8 @ 0..=3,              // Bits 0 to 3

        // Multi-bit field, specified using an exclusive range:
        pub exclusive_range: u8 @ 4..7,               // Bits 4 to 6

        // Multi-bit field specified using its start bit and length:
        pub start_and_length: u8 @ 7; 5,              // Bits 7 to 11

        // Single-bit field, specified using an inclusive range:
        pub single_bit_inclusive_range: u8 @ 12..=12, // Bit 12

        // Single-bit field, specified using an exclusive range:
        pub single_bit_exclusive_range: u8 @ 13..14,  // Bit 13

        // Single-bit field, specified using its start bit and a length of 1:
        pub single_bit_start_and_length: u8 @ 14; 1,  // Bit 14

        // Single-bit boolean flag, specified using a single bit position.
        // This is equivalent to the single-bit exclusive range, but uses the `Bit` trait instead of
        // `BitRange<T>`, and is specific to `bool` (which is conversely not allowed using bit
        // ranges).
        pub flag: bool @ 15,                          // Bit 15
    }
}

Field access restrictions (generated)

bitfield! {
    pub struct AccessRestrictions(pub u8): Debug {
        // By specifying `read_only` (or `ro`), only `Example::read_only_flag` will be generated (no
        // setters):
        pub read_only_flag: bool [read_only] @ 0,
        // Equivalent:
        // pub read_only_flag: bool [ro] @ 0,

        // By specifying `write_only` (or `wo`), only `Example::set_write_only_flag` and
        // `Example::with_write_only_flag` will be generated (no getters):
        pub write_only_flag: bool [write_only] @ 1,
        // Equivalent:
        // pub read_only_flag: bool [wo] @ 0,

        // Both getters and setters will be generated without any explicit access restrictions:
        // `Example::read_write_flag`, `Example::set_read_write_flag` and
        // `Example::with_read_write_flag` will all be generated.
        pub read_write_flag: bool @ 2,
    }
}

Field type conversions (generated)

// Types and `UnsafeFrom<T>`/`UnsafeInto<T>` implementations omitted, they can be found in
// src/example/support.rs

bitfield! {
    pub struct FieldTypeConversions(pub u16): Debug {
        // Infallible conversions

        // Will:
        // - Return a `U8WithParity` on reads, calling `<U8WithParity as From<u8>>::from`
        // - Take a `u8` for writes
        pub read_as_u8_with_parity: u8 [get U8WithParity] @ 0..=3,

        // Will:
        // - Return a `u8` on reads
        // - Take a `U8WithParity` for writes, calling `<U8WithParity as Into<u8>>::into`
        pub write_as_u8_with_parity: u8 [set U8WithParity] @ 4..=7,

        // Will:
        // - Return a `U8WithParity` on reads, calling `<U8WithParity as From<u8>>::from`
        // - Take a `U8WithParity` for writes, calling `<U8WithParity as Into<u8>>::into`
        pub as_u8_with_parity: u8 [U8WithParity] @ 8..=11,
        // Equivalent to:
        // pub u8_with_parity: u8 [get U8WithParity, set U8WithParity] @ 8..=11,


        // Fallible conversions

        // Will:
        // - Return a `Result<NonZeroU8, TryFromIntError>` on reads, calling
        //   `<NonZeroU8 as TryFrom<u8>>::try_from`
        // - Take a `u8` for writes
        pub try_read_as_non_zero_u8: u8 [try_get NonZeroU8] @ 0..=3,

        // Will:
        // - Return a `u8` on reads
        // - Take a `u16` for writes, returning `Result<(), TryFromIntError>` and calling
        //   `<u16 as TryInto<u8>>::try_into`
        pub try_write_as_u16: u8 [try_set u16] @ 4..=7,

        // Will:
        // - Return a `Result<SpuriouslyFailingU8, ()>` on reads, calling
        //   `<SpuriouslyFailingU8 as TryFrom<u8>>::try_from`
        // - Take a `SpuriouslyFailingU8` for writes, returning `Result<(), ()>` and calling
        //   `<SpuriouslyFailingU8 as TryInto<u8>>::try_into`
        pub try_both_as_spuriously_failing: u8 [try_both SpuriouslyFailingU8] @ 8..=11,
        // Equivalent to:
        // pub try_both_as_spuriously_failing: u8
        //  [try_get SpuriouslyFailingU8, try_set SpuriouslyFailingU8] @ 8..=11,

        // Will:
        // - Return a `Result<NonZeroU8, TryFromIntError>` on reads, calling
        //   `<NonZeroU8 as TryFrom<u8>>::try_from`
        // - Take a `NonZeroU8` for writes, calling `<NonZeroU8 as Into<u8>>::into`
        pub try_as_non_zero_u8: u8 [try NonZeroU8] @ 12..=15,
        // Equivalent to:
        // pub try_as_non_zero_u8: u8 [try_get NonZeroU8, set NonZeroU8] @ 12..=15,


        // Unsafe/unchecked conversions

        // Will:
        // - Return a `NonZeroU8` on reads, calling `<NonZeroU8 as UnsafeFrom<u8>>::unsafe_from`
        //   and assuming all its invariants are held
        // - Take a `u8` for writes
        pub unsafe_read_as_non_zero_u8: u8 [unsafe_get NonZeroU8] @ 0..=3,

        // Will:
        // - Return a `u8` on reads
        // - Take a `u16` for writes, calling `<u16 as UnsafeInto<u8>>::unsafe_into` and assuming
        //   all its invariants are held
        pub unsafe_write_as_u16: u8 [unsafe_set u16] @ 4..=7,

        // Will:
        // - Return a `SpuriouslyFailingU8` on reads, calling 
        //   `<SpuriouslyFailingU8 as UnsafeFrom<u8>>::unsafe_from` and assuming all its invariants
        //   are held
        // - Take a `SpuriouslyFailingU8` for writes, calling 
        //   `<SpuriouslyFailingU8 as UnsafeInto<u8>>::unsafe_into` and assuming all its invariants
        //   are held
        pub unsafe_as_spuriously_failing: u8 [unsafe_both SpuriouslyFailingU8] @ 8..=11,
        // Equivalent to:
        // pub unsafe_as_spuriously_failing: u8
        //  [unsafe_get SpuriouslyFailingU8, unsafe_set SpuriouslyFailingU8] @ 8..=11,

        // Will:
        // - Return a `NonZeroU8` on reads, calling `<NonZeroU8 as UnsafeFrom<u8>>::unsafe_from`
        //   and assuming all its invariants are held
        // - Take a `NonZeroU8` for writes, calling `<NonZeroU8 as Into<u8>>::into`
        pub unsafe_as_non_zero_u8: u8 [unsafe NonZeroU8] @ 12..=15,
        // Equivalent to:
        // pub unsafe_as_non_zero_u8: u8 [unsafe_get NonZeroU8, set NonZeroU8] @ 12..=15,
    }
}

const fn support (generated)

By using const struct, all getters and setters will be declared as const fns:

bitfield! {
    #[derive(Clone, Copy, PartialEq, Eq)]
    pub const struct ConstAccessors(pub u16): Debug {
        pub whole_bitfield: u16 @ ..,
        pub inclusive_range: u8 @ 0..=3,
        pub exclusive_range: u8 @ 4..7,
        pub start_and_length: u8 @ 7; 5,
        pub single_bit_inclusive_range: u8 @ 12..=12,
        pub single_bit_exclusive_range: u8 @ 13..14,
        pub single_bit_start_and_length: u8 @ 14; 1,
        pub flag: bool @ 15,
    }
}

License

This project is licensed under a dual MIT/Apache 2.0 license.

Dependencies

~235–630KB
~14K SLoC