Macro bitvec::bitarr

macro_rules! bitarr {
    (for $len : literal, in $order : path, $store : ident) => { ... };
    (for $len : literal, in $store : ident) => { ... };
    (for $len : literal) => { ... };
    ($order : ident, $store : ident ; $($val : expr), * $(,) ?) => { ... };
    ($order : path, $store : ident ; $($val : expr), * $(,) ?) => { ... };
    ($order : ident ; $($val : expr), * $(,) ?) => { ... };
    ($order : path ; $($val : expr), * $(,) ?) => { ... };
    ($($val : expr), * $(,) ?) => { ... };
    ($order : ident, $store : ident ; $val : expr ; $len : expr) => { ... };
    ($order : path, $store : ident ; $val : expr ; $len : expr) => { ... };
    ($order : ident ; $val : expr ; $len : expr) => { ... };
    ($order : path ; $val : expr ; $len : expr) => { ... };
    ($val : expr ; $len : expr) => { ... };
}

Constructs a BitArray wrapper out of a literal array in source code, like bits!

As with all macro constructors, bitarr! can be invoked with either a sequence of individual bit expressions (expr, expr) or a repeated bit (expr; count). Additionally, the bit-ordering and element type can be provided as optional prefix arguments.

The produced value is of type BitArray<O, [T; N]>, and is subject to [BitArray]’s restricitons of element T length N. For instance, attempting to produce a bit array that fills more than 32 T elements will fail.

In addition, bitarr! can be used to produce a type name instead of a value by using the syntax bitarr!(for N [, in [O,] T]). This syntax allows the production of a monomorphized BitArray<O, V> type that is capable of holding N bits. It can be used to type static sites such as struct fields and const or static declarations, and in these positions must specify both type arguments as well as the length. It can also be used to type let-bindings, but as type inference is permitted here, it is less useful in this position.

Examples

use bitvec::prelude::*;

bitarr![Msb0, u8; 0, 1];
bitarr![Msb0; 0, 1];
bitarr![0, 1];
bitarr![0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0];
bitarr![Msb0, u8; 1; 5];
bitarr![1; 5];

This example shows how the for N, in O, T syntax can be used to type locations that cannot use inference:

use bitvec::prelude::*;

struct ContainsBitfield {
  data: bitarr!(for 10, in Msb0, u8),
}

fn zero() -> ContainsBitfield {
  ContainsBitfield { data: bitarr![Msb0, u8; 0; 10] }
}

The order/store type parameters must be repeated in the macros to construct both the typename and the value. Mismatches will result in a compiler error.