Macro bit_fiddler::is_set

macro_rules! is_set {
    ($bitmap: tt, $ty: ty, [..]) => { ... };
    ($bitmap: tt, $ty: ty, rev [..]) => { ... };
    ($bitmap: tt, $ty: ty, [$( $bit_pos: tt),*]) => { ... };
    ($bitmap: tt, $ty: ty, rev [$( $bit_pos: tt),*]) => { ... };
    ($bitmap: tt, $ty: ty, [$start_pos: tt .. $end_pos: tt]) => { ... };
    ($bitmap: tt, $ty: ty, [$start_pos: tt ..]) => { ... };
    ($bitmap: tt, $ty: ty, [.. $end_pos: tt]) => { ... };
    ($bitmap: tt, $ty: ty, [start = $start_pos: tt, count = $count: tt]) => { ... };
    ($bitmap: tt, $ty: ty, rev [$start_pos: tt .. $end_pos: tt]) => { ... };
    ($bitmap: tt, $ty: ty, rev [$start_pos: tt ..]) => { ... };
    ($bitmap: tt, $ty: ty, rev [.. $end_pos: tt]) => { ... };
    ($bitmap: tt, $ty: ty, rev [start = $start_pos: tt, count = $count: tt]) => { ... };
    ($bitmap: tt, $ty: ty, rev $bit_pos: tt) => { ... };
    ($bitmap: tt, $ty: ty, $bit_pos: tt) => { ... };
}

Macro for checking if single, multiple or range of bits are set. It accepts multiple patterns for different use cases. It doesn't do any overflow or underflow checks. Behaviour on passing invalid args is undefined.

A common thing in these patterns is rev. All patterns support this. Putting rev before the bits being checked makes the macro check the bits from left hand side. Without rev, bits will be checked from right hand side.

For example,

let mut bitmap: u8 = 0b_0001_0100;

// Checking 2nd bit from rhs
let res = is_set!(bitmap, u8, 2);
assert_eq!(res, true);

// Unsetting 3rd bit from lhs
let res = is_set!(bitmap, u8, rev 3);
assert_eq!(res, true);

Examples

use bit_fiddler::is_set;

// Check third bit from the right.
let bitmap = 0b100;
let res = is_set!(bitmap, u8, 2);
assert_eq!(res, true);

// Check third bit from the left.
let bitmap: u8 = 0b_0000_0100;
let res = is_set!(bitmap, u8, rev 2);
assert_eq!(res, false);

// Check second, third & fourth bit from the right.
let bitmap = 0b1010;
let res = is_set!(bitmap, u8, [1, 2, 3]);
assert_eq!(res, false); // as third bit is not set

// Check second, third & fourth bit from the left.
let bitmap: u8 = 0b0111_0000;
let res = is_set!(bitmap, u8, rev [1, 2, 3]);
assert_eq!(res, true);

// Check second & third (1 and 2) bit from the right.
let bitmap = 0b110;
let res = is_set!(bitmap, u8, [1..3]);
assert_eq!(res, true);

// Starting from second bit, check 2 bits from the right.
let bitmap = 0b110;
let res = is_set!(bitmap, u8, [start = 1, count = 2]);
assert_eq!(res, true);

// Check second & third bit (1 and 2) from the left.
let bitmap: u8 = 0b_0110_0000;
let res = is_set!(bitmap, u8, rev [1..3]);
assert_eq!(res, true);

// Starting from second bit, check 2 bits from the left.
let bitmap: u8 = 0b_0110_0000;
let res = is_set!(bitmap, u8, rev [start = 1, count = 2]);
assert_eq!(res, true);