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|
//! Implements a generic bit iterator.
//!
//! Works with built-in integer types or bitflags. You just have to implement
//! the `BitIterable` trait.
use std::ops::BitXorAssign;
pub trait BitIterable: Copy + BitXorAssign {
fn lsb(self) -> Option<Self>;
fn msb(self) -> Option<Self>;
}
pub struct BitIter<T: BitIterable>(pub T);
impl<T: BitIterable> Iterator for BitIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
self.0.lsb().map(|bit| {
self.0 ^= bit;
bit
})
}
}
impl<T: BitIterable> DoubleEndedIterator for BitIter<T> {
fn next_back(&mut self) -> Option<T> {
self.0.msb().map(|bit| {
self.0 ^= bit;
bit
})
}
}
////////////////////////////////////////////////////////////////////////////////
#[cfg(test)]
mod bititer_tests {
#![allow(clippy::unreadable_literal)]
use super::*;
use bitflags::bitflags;
impl BitIterable for u32 {
fn lsb(self) -> Option<Self> {
if self == 0 {
return None;
}
Some(1 << self.trailing_zeros())
}
fn msb(self) -> Option<Self> {
if self == 0 {
return None;
}
Some(1 << (31 - self.leading_zeros()))
}
}
#[test]
fn test_bititer_u32() {
assert!(BitIter(0).next().is_none());
let v = BitIter(1).collect::<Vec<u32>>();
assert_eq!(v, vec![1]);
let v = BitIter(1 << 31).collect::<Vec<u32>>();
assert_eq!(v, vec![1 << 31]);
let v = BitIter(2 + 4 + 16 + 64).collect::<Vec<u32>>();
assert_eq!(v, vec![2, 4, 16, 64]);
let v = BitIter(u32::MAX).collect::<Vec<u32>>();
assert_eq!(v.len(), 32);
assert_eq!(
v,
vec![
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536,
131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432,
67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648
]
);
}
#[test]
fn test_bititer_u32_rev() {
assert!(BitIter(0).rev().next().is_none());
let v = BitIter(1).rev().collect::<Vec<u32>>();
assert_eq!(v, vec![1]);
let v = BitIter(1 << 31).rev().collect::<Vec<u32>>();
assert_eq!(v, vec![1 << 31]);
let v = BitIter(2 + 4 + 16 + 64).rev().collect::<Vec<u32>>();
assert_eq!(v, vec![64, 16, 4, 2]);
let v = BitIter(u32::MAX).rev().collect::<Vec<u32>>();
assert_eq!(v.len(), 32);
assert_eq!(
v,
vec![
2147483648, 1073741824, 536870912, 268435456, 134217728, 67108864, 33554432,
16777216, 8388608, 4194304, 2097152, 1048576, 524288, 262144, 131072, 65536, 32768,
16384, 8192, 4096, 2048, 1024, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1
]
);
}
bitflags! {
#[derive(Default)]
struct TestBit: u32 {
const BIT1 = 1 << 0;
const BIT2 = 1 << 1;
const BIT3 = 1 << 5;
}
}
impl BitIterable for TestBit {
fn lsb(self) -> Option<Self> {
if self.is_empty() {
return None;
}
Some(TestBit {
bits: 1 << self.bits.trailing_zeros(),
})
}
fn msb(self) -> Option<Self> {
#[allow(clippy::cast_possible_truncation)]
const MAX_BITS: u32 = 8 * std::mem::size_of::<TestBit>() as u32 - 1;
if self.is_empty() {
return None;
}
Some(TestBit {
bits: 1 << (MAX_BITS - self.bits.leading_zeros()),
})
}
}
#[test]
fn test_bititer_bitflags() {
let bits = TestBit::BIT1 | TestBit::BIT2 | TestBit::BIT3;
let v = BitIter(TestBit::empty()).collect::<Vec<TestBit>>();
assert_eq!(v, vec![]);
let v = BitIter(bits.bits).collect::<Vec<u32>>();
assert_eq!(v, vec![1, 2, 32]);
let v = BitIter(bits).collect::<Vec<TestBit>>();
assert_eq!(
v,
vec![
TestBit { bits: 1 },
TestBit { bits: 2 },
TestBit { bits: 32 }
]
);
}
#[test]
fn test_bititer_bitflags_rev() {
let bits = TestBit::BIT1 | TestBit::BIT2 | TestBit::BIT3;
let v = BitIter(TestBit::empty()).rev().collect::<Vec<TestBit>>();
assert_eq!(v, vec![]);
let v = BitIter(bits.bits).rev().collect::<Vec<u32>>();
assert_eq!(v, vec![32, 2, 1]);
let v = BitIter(bits).rev().collect::<Vec<TestBit>>();
assert_eq!(
v,
vec![
TestBit { bits: 32 },
TestBit { bits: 2 },
TestBit { bits: 1 }
]
);
}
}
|
