// Copyright 2012-2023 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms.
// FIXME(Gankro): BitVec and BitSet are very tightly coupled. Ideally (for // maintenance), they should be in separate files/modules, with BitSet only // using BitVec's public API. This will be hard for performance though, because // `BitVec` will not want to leak its internal representation while its internal // representation as `u32`s must be assumed for best performance.
// (1) Be careful, most things can overflow here because the amount of bits in // memory can overflow `usize`. // (2) Make sure that the underlying vector has no excess length: // E. g. `nbits == 16`, `storage.len() == 2` would be excess length, // because the last word isn't used at all. This is important because some // methods rely on it (for *CORRECTNESS*). // (3) Make sure that the unused bits in the last word are zeroed out, again // other methods rely on it for *CORRECTNESS*. // (4) `BitSet` is tightly coupled with `BitVec`, so any changes you make in // `BitVec` will need to be reflected in `BitSet`.
//! # Description //! //! Dynamic collections implemented with compact bit vectors. //! //! # Examples //! //! This is a simple example of the [Sieve of Eratosthenes][sieve] //! which calculates prime numbers up to a given limit. //! //! [sieve]: http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes //! //! ``` //! use bit_vec::BitVec; //! //! let max_prime = 10000; //! //! // Store the primes as a BitVec //! let primes = { //! // Assume all numbers are prime to begin, and then we //! // cross off non-primes progressively //! let mut bv = BitVec::from_elem(max_prime, true); //! //! // Neither 0 nor 1 are prime //! bv.set(0, false); //! bv.set(1, false); //! //! for i in 2.. 1 + (max_prime as f64).sqrt() as usize { //! // if i is a prime //! if bv[i] { //! // Mark all multiples of i as non-prime (any multiples below i * i //! // will have been marked as non-prime previously) //! for j in i.. { //! if i * j >= max_prime { //! break; //! } //! bv.set(i * j, false) //! } //! } //! } //! bv //! }; //! //! // Simple primality tests below our max bound //! let print_primes = 20; //! print!("The primes below {} are: ", print_primes); //! for x in 0..print_primes { //! if primes.get(x).unwrap_or(false) { //! print!("{} ", x); //! } //! } //! println!(); //! //! let num_primes = primes.iter().filter(|x| *x).count(); //! println!("There are {} primes below {}", num_primes, max_prime); //! assert_eq!(num_primes, 1_229); //! ```
#[cfg(not(feature = "std"))] #[macro_use] externcrate alloc; #[cfg(not(feature = "std"))] use alloc::rc::Rc; #[cfg(not(feature = "std"))] use alloc::string::String; #[cfg(not(feature = "std"))] use alloc::vec::Vec;
use core::cell::RefCell; use core::cmp; use core::cmp::Ordering; use core::fmt::{self, Write}; use core::hash; use core::iter::repeat; use core::iter::FromIterator; use core::mem; use core::ops::*; use core::slice;
type MutBlocks<'a, B> = slice::IterMut<'a, B>;
/// Abstracts over a pile of bits (basically unsigned primitives) pubtrait BitBlock:
Copy
+ Add<Self, Output = Self>
+ Sub<Self, Output = Self>
+ Shl<usize, Output = Self>
+ Shr<usize, Output = Self>
+ Not<Output = Self>
+ BitAnd<Self, Output = Self>
+ BitOr<Self, Output = Self>
+ BitXor<Self, Output = Self>
+ Rem<Self, Output = Self>
+ Eq
+ Ord
+ hash::Hash
{ /// How many bits it has fn bits() -> usize; /// How many bytes it has #[inline] fn bytes() -> usize { Self::bits() / 8
} /// Convert a byte into this type (lowest-order bits set) fn from_byte(byte: u8) -> Self; /// Count the number of 1's in the bitwise repr fn count_ones(self) -> usize; /// Count the number of 0's in the bitwise repr fn count_zeros(self) -> usize { Self::bits() - self.count_ones()
} /// Get `0` fn zero() -> Self; /// Get `1` fn one() -> Self;
}
/// Computes how many blocks are needed to store that many bits fn blocks_for_bits<B: BitBlock>(bits: usize) -> usize { // If we want 17 bits, dividing by 32 will produce 0. So we add 1 to make sure we // reserve enough. But if we want exactly a multiple of 32, this will actually allocate // one too many. So we need to check if that's the case. We can do that by computing if // bitwise AND by `32 - 1` is 0. But LLVM should be able to optimize the semantically // superior modulo operator on a power of two to this. // // Note that we can technically avoid this branch with the expression // `(nbits + U32_BITS - 1) / 32::BITS`, but if nbits is almost usize::MAX this will overflow. if bits % B::bits() == 0 {
bits / B::bits()
} else {
bits / B::bits() + 1
}
}
/// Computes the bitmask for the final word of the vector fn mask_for_bits<B: BitBlock>(bits: usize) -> B { // Note especially that a perfect multiple of U32_BITS should mask all 1s.
(!B::zero()) >> ((B::bits() - bits % B::bits()) % B::bits())
}
/// Creates a `BitVec` that holds `nbits` elements, setting each element /// to `bit`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(10, false); /// assert_eq!(bv.len(), 10); /// for x in bv.iter() { /// assert_eq!(x, false); /// } /// ``` #[inline] pubfn from_elem(nbits: usize, bit: bool) -> Self { let nblocks = blocks_for_bits::<B>(nbits); letmut bit_vec = BitVec {
storage: vec![if bit { !B::zero() } else { B::zero() }; nblocks],
nbits,
};
bit_vec.fix_last_block();
bit_vec
}
/// Constructs a new, empty `BitVec` with the specified capacity. /// /// The bitvector will be able to hold at least `capacity` bits without /// reallocating. If `capacity` is 0, it will not allocate. /// /// It is important to note that this function does not specify the /// *length* of the returned bitvector, but only the *capacity*. #[inline] pubfn with_capacity(nbits: usize) -> Self {
BitVec {
storage: Vec::with_capacity(blocks_for_bits::<B>(nbits)),
nbits: 0,
}
}
/// Transforms a byte-vector into a `BitVec`. Each byte becomes eight bits, /// with the most significant bits of each byte coming first. Each /// bit becomes `true` if equal to 1 or `false` if equal to 0. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_bytes(&[0b10100000, 0b00010010]); /// assert!(bv.eq_vec(&[true, false, true, false, /// false, false, false, false, /// false, false, false, true, /// false, false, true, false])); /// ``` pubfn from_bytes(bytes: &[u8]) -> Self { let len = bytes
.len()
.checked_mul(u8::bits())
.expect("capacity overflow"); letmut bit_vec = BitVec::with_capacity(len); let complete_words = bytes.len() / B::bytes(); let extra_bytes = bytes.len() % B::bytes();
bit_vec.nbits = len;
for i in0..complete_words { letmut accumulator = B::zero(); for idx in0..B::bytes() {
accumulator |= B::from_byte(reverse_bits(bytes[i * B::bytes() + idx])) << (idx * 8)
}
bit_vec.storage.push(accumulator);
}
if extra_bytes > 0 { letmut last_word = B::zero(); for (i, &byte) in bytes[complete_words * B::bytes()..].iter().enumerate() {
last_word |= B::from_byte(reverse_bits(byte)) << (i * 8);
}
bit_vec.storage.push(last_word);
}
bit_vec
}
/// Creates a `BitVec` of the specified length where the value at each index /// is `f(index)`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_fn(5, |i| { i % 2 == 0 }); /// assert!(bv.eq_vec(&[true, false, true, false, true])); /// ``` #[inline] pubfn from_fn<F>(len: usize, mut f: F) -> Self where
F: FnMut(usize) -> bool,
{ letmut bit_vec = BitVec::from_elem(len, false); for i in0..len {
bit_vec.set(i, f(i));
}
bit_vec
}
}
impl<B: BitBlock> BitVec<B> { /// Applies the given operation to the blocks of self and other, and sets /// self to be the result. This relies on the caller not to corrupt the /// last word. #[inline] fn process<F>(&mutself, other: &BitVec<B>, mut op: F) -> bool where
F: FnMut(B, B) -> B,
{
assert_eq!(self.len(), other.len());
debug_assert_eq!(self.storage.len(), other.storage.len()); letmut changed_bits = B::zero(); for (a, b) inself.blocks_mut().zip(other.blocks()) { let w = op(*a, b);
changed_bits = changed_bits | (*a ^ w);
*a = w;
}
changed_bits != B::zero()
}
/// Iterator over mutable refs to the underlying blocks of data. #[inline] fn blocks_mut(&mutself) -> MutBlocks<B> { // (2) self.storage.iter_mut()
}
/// Iterator over the underlying blocks of data #[inline] pubfn blocks(&self) -> Blocks<B> { // (2)
Blocks {
iter: self.storage.iter(),
}
}
/// Exposes the raw block storage of this `BitVec`. /// /// Only really intended for `BitSet`. #[inline] pubfn storage(&self) -> &[B] {
&self.storage
}
/// Exposes the raw block storage of this `BitVec`. /// /// # Safety /// /// Can probably cause unsafety. Only really intended for `BitSet`. #[inline] pubunsafefn storage_mut(&mutself) -> &mut Vec<B> {
&mutself.storage
}
/// Helper for procedures involving spare space in the last block. #[inline] fn last_block_with_mask(&self) -> Option<(B, B)> { let extra_bits = self.len() % B::bits(); if extra_bits > 0 { let mask = (B::one() << extra_bits) - B::one(); let storage_len = self.storage.len();
Some((self.storage[storage_len - 1], mask))
} else {
None
}
}
/// Helper for procedures involving spare space in the last block. #[inline] fn last_block_mut_with_mask(&mutself) -> Option<(&mut B, B)> { let extra_bits = self.len() % B::bits(); if extra_bits > 0 { let mask = (B::one() << extra_bits) - B::one(); let storage_len = self.storage.len();
Some((&mutself.storage[storage_len - 1], mask))
} else {
None
}
}
/// An operation might screw up the unused bits in the last block of the /// `BitVec`. As per (3), it's assumed to be all 0s. This method fixes it up. fn fix_last_block(&mutself) { iflet Some((last_block, used_bits)) = self.last_block_mut_with_mask() {
*last_block = *last_block & used_bits;
}
}
/// Operations such as change detection for xnor, nor and nand are easiest /// to implement when unused bits are all set to 1s. fn fix_last_block_with_ones(&mutself) { iflet Some((last_block, used_bits)) = self.last_block_mut_with_mask() {
*last_block = *last_block | !used_bits;
}
}
/// Ensure the invariant for the last block. /// /// An operation might screw up the unused bits in the last block of the /// `BitVec`. /// /// This method fails in case the last block is not fixed. The check /// is skipped outside testing. #[inline] fn ensure_invariant(&self) { if cfg!(test) {
debug_assert!(self.is_last_block_fixed());
}
}
/// Retrieves the value at index `i`, or `None` if the index is out of bounds. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_bytes(&[0b01100000]); /// assert_eq!(bv.get(0), Some(false)); /// assert_eq!(bv.get(1), Some(true)); /// assert_eq!(bv.get(100), None); /// /// // Can also use array indexing /// assert_eq!(bv[1], true); /// ``` #[inline] pubfn get(&self, i: usize) -> Option<bool> { self.ensure_invariant(); if i >= self.nbits { return None;
} let w = i / B::bits(); let b = i % B::bits(); self.storage
.get(w)
.map(|&block| (block & (B::one() << b)) != B::zero())
}
/// Retrieves the value at index `i`, without doing bounds checking. /// /// For a safe alternative, see `get`. /// /// # Safety /// /// Calling this method with an out-of-bounds index is undefined behavior /// even if the resulting reference is not used. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_bytes(&[0b01100000]); /// unsafe { /// assert_eq!(bv.get_unchecked(0), false); /// assert_eq!(bv.get_unchecked(1), true); /// } /// ``` #[inline] pubunsafefn get_unchecked(&self, i: usize) -> bool { self.ensure_invariant(); let w = i / B::bits(); let b = i % B::bits(); let block = *self.storage.get_unchecked(w);
block & (B::one() << b) != B::zero()
}
/// Retrieves a smart pointer to the value at index `i`, or `None` if the index is out of bounds. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_bytes(&[0b01100000]); /// *bv.get_mut(0).unwrap() = true; /// *bv.get_mut(1).unwrap() = false; /// assert!(bv.get_mut(100).is_none()); /// assert_eq!(bv, BitVec::from_bytes(&[0b10100000])); /// ``` #[inline] pubfn get_mut(&mutself, index: usize) -> Option<MutBorrowedBit<B>> { self.get(index).map(move |value| MutBorrowedBit {
vec: Rc::new(RefCell::new(self)),
index, #[cfg(debug_assertions)]
old_value: value,
new_value: value,
})
}
/// Retrieves a smart pointer to the value at index `i`, without doing bounds checking. /// /// # Safety /// /// Calling this method with out-of-bounds `index` may cause undefined behavior even when /// the result is not used. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_bytes(&[0b01100000]); /// unsafe { /// *bv.get_unchecked_mut(0) = true; /// *bv.get_unchecked_mut(1) = false; /// } /// assert_eq!(bv, BitVec::from_bytes(&[0b10100000])); /// ``` #[inline] pubunsafefn get_unchecked_mut(&mutself, index: usize) -> MutBorrowedBit<B> { let value = self.get_unchecked(index);
MutBorrowedBit { #[cfg(debug_assertions)]
old_value: value,
new_value: value,
vec: Rc::new(RefCell::new(self)),
index,
}
}
/// Sets the value of a bit at an index `i`. /// /// # Panics /// /// Panics if `i` is out of bounds. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(5, false); /// bv.set(3, true); /// assert_eq!(bv[3], true); /// ``` #[inline] pubfn set(&mutself, i: usize, x: bool) { self.ensure_invariant();
assert!(
i < self.nbits, "index out of bounds: {:?} >= {:?}",
i, self.nbits
); let w = i / B::bits(); let b = i % B::bits(); let flag = B::one() << b; let val = if x { self.storage[w] | flag
} else { self.storage[w] & !flag
}; self.storage[w] = val;
}
/// Sets all bits to 1. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let before = 0b01100000; /// let after = 0b11111111; /// /// let mut bv = BitVec::from_bytes(&[before]); /// bv.set_all(); /// assert_eq!(bv, BitVec::from_bytes(&[after])); /// ``` #[inline] pubfn set_all(&mutself) { self.ensure_invariant(); for w in &mutself.storage {
*w = !B::zero();
} self.fix_last_block();
}
/// Flips all bits. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let before = 0b01100000; /// let after = 0b10011111; /// /// let mut bv = BitVec::from_bytes(&[before]); /// bv.negate(); /// assert_eq!(bv, BitVec::from_bytes(&[after])); /// ``` #[inline] pubfn negate(&mutself) { self.ensure_invariant(); for w in &mutself.storage {
*w = !*w;
} self.fix_last_block();
}
/// Calculates the union of two bitvectors. This acts like the bitwise `or` /// function. /// /// Sets `self` to the union of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different lengths. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100100; /// let b = 0b01011010; /// let res = 0b01111110; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.union(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[deprecated(since = "0.7.0", note = "Please use the 'or' function instead")] #[inline] pubfn union(&mutself, other: &Self) -> bool { self.or(other)
}
/// Calculates the intersection of two bitvectors. This acts like the /// bitwise `and` function. /// /// Sets `self` to the intersection of `self` and `other`. Both bitvectors /// must be the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different lengths. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100100; /// let b = 0b01011010; /// let res = 0b01000000; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.intersect(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[deprecated(since = "0.7.0", note = "Please use the 'and' function instead")] #[inline] pubfn intersect(&mutself, other: &Self) -> bool { self.and(other)
}
/// Calculates the bitwise `or` of two bitvectors. /// /// Sets `self` to the union of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different lengths. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100100; /// let b = 0b01011010; /// let res = 0b01111110; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.or(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn or(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.process(other, |w1, w2| (w1 | w2))
}
/// Calculates the bitwise `and` of two bitvectors. /// /// Sets `self` to the intersection of `self` and `other`. Both bitvectors /// must be the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different lengths. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100100; /// let b = 0b01011010; /// let res = 0b01000000; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.and(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn and(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.process(other, |w1, w2| (w1 & w2))
}
/// Calculates the difference between two bitvectors. /// /// Sets each element of `self` to the value of that element minus the /// element of `other` at the same index. Both bitvectors must be the same /// length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100100; /// let b = 0b01011010; /// let a_b = 0b00100100; // a - b /// let b_a = 0b00011010; // b - a /// /// let mut bva = BitVec::from_bytes(&[a]); /// let bvb = BitVec::from_bytes(&[b]); /// /// assert!(bva.difference(&bvb)); /// assert_eq!(bva, BitVec::from_bytes(&[a_b])); /// /// let bva = BitVec::from_bytes(&[a]); /// let mut bvb = BitVec::from_bytes(&[b]); /// /// assert!(bvb.difference(&bva)); /// assert_eq!(bvb, BitVec::from_bytes(&[b_a])); /// ``` #[inline] pubfn difference(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.process(other, |w1, w2| (w1 & !w2))
}
/// Calculates the xor of two bitvectors. /// /// Sets `self` to the xor of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100110; /// let b = 0b01010100; /// let res = 0b00110010; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.xor(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn xor(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.process(other, |w1, w2| (w1 ^ w2))
}
/// Calculates the nand of two bitvectors. /// /// Sets `self` to the nand of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100110; /// let b = 0b01010100; /// let res = 0b10111011; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.nand(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn nand(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.fix_last_block_with_ones(); let result = self.process(other, |w1, w2| !(w1 & w2)); self.fix_last_block();
result
}
/// Calculates the nor of two bitvectors. /// /// Sets `self` to the nor of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100110; /// let b = 0b01010100; /// let res = 0b10001001; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.nor(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn nor(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.fix_last_block_with_ones(); let result = self.process(other, |w1, w2| !(w1 | w2)); self.fix_last_block();
result
}
/// Calculates the xnor of two bitvectors. /// /// Sets `self` to the xnor of `self` and `other`. Both bitvectors must be /// the same length. Returns `true` if `self` changed. /// /// # Panics /// /// Panics if the bitvectors are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let a = 0b01100110; /// let b = 0b01010100; /// let res = 0b11001101; /// /// let mut a = BitVec::from_bytes(&[a]); /// let b = BitVec::from_bytes(&[b]); /// /// assert!(a.xnor(&b)); /// assert_eq!(a, BitVec::from_bytes(&[res])); /// ``` #[inline] pubfn xnor(&mutself, other: &Self) -> bool { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed()); self.fix_last_block_with_ones(); let result = self.process(other, |w1, w2| !(w1 ^ w2)); self.fix_last_block();
result
}
/// Returns `true` if all bits are 1. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(5, true); /// assert_eq!(bv.all(), true); /// /// bv.set(1, false); /// assert_eq!(bv.all(), false); /// ``` #[inline] pubfn all(&self) -> bool { self.ensure_invariant(); letmut last_word = !B::zero(); // Check that every block but the last is all-ones... self.blocks().all(|elem| { let tmp = last_word;
last_word = elem;
tmp == !B::zero() // and then check the last one has enough ones
}) && (last_word == mask_for_bits(self.nbits))
}
/// Returns the number of ones in the binary representation. /// /// Also known as the /// [Hamming weight](https://en.wikipedia.org/wiki/Hamming_weight). /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(100, true); /// assert_eq!(bv.count_ones(), 100); /// /// bv.set(50, false); /// assert_eq!(bv.count_ones(), 99); /// ``` #[inline] pubfn count_ones(&self) -> u64 { self.ensure_invariant(); // Add the number of ones of each block. self.blocks().map(|elem| elem.count_ones() as u64).sum()
}
/// Returns the number of zeros in the binary representation. /// /// Also known as the opposite of /// [Hamming weight](https://en.wikipedia.org/wiki/Hamming_weight). /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(100, false); /// assert_eq!(bv.count_zeros(), 100); /// /// bv.set(50, true); /// assert_eq!(bv.count_zeros(), 99); /// ``` #[inline] pubfn count_zeros(&self) -> u64 { self.ensure_invariant(); // Add the number of zeros of each block. let extra_zeros = (B::bits() - (self.len() % B::bits())) % B::bits(); self.blocks()
.map(|elem| elem.count_zeros() as u64)
.sum::<u64>()
- extra_zeros as u64
}
/// Returns an iterator over the elements of the vector in order. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_bytes(&[0b01110100, 0b10010010]); /// assert_eq!(bv.iter().filter(|x| *x).count(), 7); /// ``` #[inline] pubfn iter(&self) -> Iter<B> { self.ensure_invariant();
Iter {
bit_vec: self,
range: 0..self.nbits,
}
}
/// Returns an iterator over mutable smart pointers to the elements of the vector in order. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut a = BitVec::from_elem(8, false); /// a.iter_mut().enumerate().for_each(|(index, mut bit)| { /// *bit = if index % 2 == 1 { true } else { false }; /// }); /// assert!(a.eq_vec(&[ /// false, true, false, true, false, true, false, true /// ])); /// ``` #[inline] pubfn iter_mut(&mutself) -> IterMut<B> { self.ensure_invariant(); let nbits = self.nbits;
IterMut {
vec: Rc::new(RefCell::new(self)),
range: 0..nbits,
}
}
/// Moves all bits from `other` into `Self`, leaving `other` empty. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut a = BitVec::from_bytes(&[0b10000000]); /// let mut b = BitVec::from_bytes(&[0b01100001]); /// /// a.append(&mut b); /// /// assert_eq!(a.len(), 16); /// assert_eq!(b.len(), 0); /// assert!(a.eq_vec(&[true, false, false, false, false, false, false, false, /// false, true, true, false, false, false, false, true])); /// ``` pubfn append(&mutself, other: &mutSelf) { self.ensure_invariant();
debug_assert!(other.is_last_block_fixed());
let b = self.len() % B::bits(); let o = other.len() % B::bits(); let will_overflow = (b + o > B::bits()) || (o == 0 && b != 0);
self.nbits += other.len();
other.nbits = 0;
if b == 0 { self.storage.append(&mut other.storage);
} else { self.storage.reserve(other.storage.len());
for block in other.storage.drain(..) {
{ let last = self.storage.last_mut().unwrap();
*last = *last | (block << b);
} self.storage.push(block >> (B::bits() - b));
}
// Remove additional block if the last shift did not overflow if !will_overflow { self.storage.pop();
}
}
}
/// Splits the `BitVec` into two at the given bit, /// retaining the first half in-place and returning the second one. /// /// # Panics /// /// Panics if `at` is out of bounds. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// let mut a = BitVec::new(); /// a.push(true); /// a.push(false); /// a.push(false); /// a.push(true); /// /// let b = a.split_off(2); /// /// assert_eq!(a.len(), 2); /// assert_eq!(b.len(), 2); /// assert!(a.eq_vec(&[true, false])); /// assert!(b.eq_vec(&[false, true])); /// ``` pubfn split_off(&mutself, at: usize) -> Self { self.ensure_invariant();
assert!(at <= self.len(), "`at` out of bounds");
letmut other = BitVec::<B>::default();
if at == 0 {
mem::swap(self, &mut other); return other;
} elseif at == self.len() { return other;
}
let w = at / B::bits(); let b = at % B::bits();
other.nbits = self.nbits - at; self.nbits = at; if b == 0 { // Split at block boundary
other.storage = self.storage.split_off(w);
} else {
other.storage.reserve(self.storage.len() - w);
{ letmut iter = self.storage[w..].iter(); letmut last = *iter.next().unwrap(); for &cur in iter {
other.storage.push((last >> b) | (cur << (B::bits() - b)));
last = cur;
}
other.storage.push(last >> b);
}
/// Returns `true` if all bits are 0. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(10, false); /// assert_eq!(bv.none(), true); /// /// bv.set(3, true); /// assert_eq!(bv.none(), false); /// ``` #[inline] pubfn none(&self) -> bool { self.blocks().all(|w| w == B::zero())
}
/// Returns `true` if any bit is 1. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(10, false); /// assert_eq!(bv.any(), false); /// /// bv.set(3, true); /// assert_eq!(bv.any(), true); /// ``` #[inline] pubfn any(&self) -> bool {
!self.none()
}
/// Organises the bits into bytes, such that the first bit in the /// `BitVec` becomes the high-order bit of the first byte. If the /// size of the `BitVec` is not a multiple of eight then trailing bits /// will be filled-in with `false`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(3, true); /// bv.set(1, false); /// /// assert_eq!(bv.to_bytes(), [0b10100000]); /// /// let mut bv = BitVec::from_elem(9, false); /// bv.set(2, true); /// bv.set(8, true); /// /// assert_eq!(bv.to_bytes(), [0b00100000, 0b10000000]); /// ``` pubfn to_bytes(&self) -> Vec<u8> { self.ensure_invariant(); // Oh lord, we're mapping this to bytes bit-by-bit! fn bit<B: BitBlock>(bit_vec: &BitVec<B>, byte: usize, bit: usize) -> u8 { let offset = byte * 8 + bit; if offset >= bit_vec.nbits { 0
} else {
(bit_vec[offset] as u8) << (7 - bit)
}
}
let len = self.nbits / 8 + ifself.nbits % 8 == 0 { 0 } else { 1 };
(0..len)
.map(|i| {
bit(self, i, 0)
| bit(self, i, 1)
| bit(self, i, 2)
| bit(self, i, 3)
| bit(self, i, 4)
| bit(self, i, 5)
| bit(self, i, 6)
| bit(self, i, 7)
})
.collect()
}
/// Compares a `BitVec` to a slice of `bool`s. /// Both the `BitVec` and slice must have the same length. /// /// # Panics /// /// Panics if the `BitVec` and slice are of different length. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let bv = BitVec::from_bytes(&[0b10100000]); /// /// assert!(bv.eq_vec(&[true, false, true, false, /// false, false, false, false])); /// ``` #[inline] pubfn eq_vec(&self, v: &[bool]) -> bool {
assert_eq!(self.nbits, v.len()); self.iter().zip(v.iter().cloned()).all(|(b1, b2)| b1 == b2)
}
/// Shortens a `BitVec`, dropping excess elements. /// /// If `len` is greater than the vector's current length, this has no /// effect. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_bytes(&[0b01001011]); /// bv.truncate(2); /// assert!(bv.eq_vec(&[false, true])); /// ``` #[inline] pubfn truncate(&mutself, len: usize) { self.ensure_invariant(); if len < self.len() { self.nbits = len; // This fixes (2). self.storage.truncate(blocks_for_bits::<B>(len)); self.fix_last_block();
}
}
/// Reserves capacity for at least `additional` more bits to be inserted in the given /// `BitVec`. The collection may reserve more space to avoid frequent reallocations. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(3, false); /// bv.reserve(10); /// assert_eq!(bv.len(), 3); /// assert!(bv.capacity() >= 13); /// ``` #[inline] pubfn reserve(&mutself, additional: usize) { let desired_cap = self
.len()
.checked_add(additional)
.expect("capacity overflow"); let storage_len = self.storage.len(); if desired_cap > self.capacity() { self.storage
.reserve(blocks_for_bits::<B>(desired_cap) - storage_len);
}
}
/// Reserves the minimum capacity for exactly `additional` more bits to be inserted in the /// given `BitVec`. Does nothing if the capacity is already sufficient. /// /// Note that the allocator may give the collection more space than it requests. Therefore /// capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future /// insertions are expected. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_elem(3, false); /// bv.reserve(10); /// assert_eq!(bv.len(), 3); /// assert!(bv.capacity() >= 13); /// ``` #[inline] pubfn reserve_exact(&mutself, additional: usize) { let desired_cap = self
.len()
.checked_add(additional)
.expect("capacity overflow"); let storage_len = self.storage.len(); if desired_cap > self.capacity() { self.storage
.reserve_exact(blocks_for_bits::<B>(desired_cap) - storage_len);
}
}
/// Returns the capacity in bits for this bit vector. Inserting any /// element less than this amount will not trigger a resizing. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::new(); /// bv.reserve(10); /// assert!(bv.capacity() >= 10); /// ``` #[inline] pubfn capacity(&self) -> usize { self.storage.capacity().saturating_mul(B::bits())
}
/// Grows the `BitVec` in-place, adding `n` copies of `value` to the `BitVec`. /// /// # Panics /// /// Panics if the new len overflows a `usize`. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_bytes(&[0b01001011]); /// bv.grow(2, true); /// assert_eq!(bv.len(), 10); /// assert_eq!(bv.to_bytes(), [0b01001011, 0b11000000]); /// ``` pubfn grow(&mutself, n: usize, value: bool) { self.ensure_invariant();
// Note: we just bulk set all the bits in the last word in this fn in multiple places // which is technically wrong if not all of these bits are to be used. However, at the end // of this fn we call `fix_last_block` at the end of this fn, which should fix this.
let new_nbits = self.nbits.checked_add(n).expect("capacity overflow"); let new_nblocks = blocks_for_bits::<B>(new_nbits); let full_value = if value { !B::zero() } else { B::zero() };
// Correct the old tail word, setting or clearing formerly unused bits let num_cur_blocks = blocks_for_bits::<B>(self.nbits); ifself.nbits % B::bits() > 0 { let mask = mask_for_bits::<B>(self.nbits); if value { let block = &mutself.storage[num_cur_blocks - 1];
*block = *block | !mask;
} else { // Extra bits are already zero by invariant.
}
}
// Fill in words after the old tail word let stop_idx = cmp::min(self.storage.len(), new_nblocks); for idx in num_cur_blocks..stop_idx { self.storage[idx] = full_value;
}
// Allocate new words, if needed if new_nblocks > self.storage.len() { let to_add = new_nblocks - self.storage.len(); self.storage.extend(repeat(full_value).take(to_add));
}
// Adjust internal bit count self.nbits = new_nbits;
self.fix_last_block();
}
/// Removes the last bit from the `BitVec`, and returns it. Returns `None` if the `BitVec` is empty. /// /// # Examples /// /// ``` /// use bit_vec::BitVec; /// /// let mut bv = BitVec::from_bytes(&[0b01001001]); /// assert_eq!(bv.pop(), Some(true)); /// assert_eq!(bv.pop(), Some(false)); /// assert_eq!(bv.len(), 6); /// ``` #[inline] pubfn pop(&mutself) -> Option<bool> { self.ensure_invariant();
ifself.is_empty() {
None
} else { let i = self.nbits - 1; let ret = self[i]; // (3) self.set(i, false); self.nbits = i; ifself.nbits % B::bits() == 0 { // (2) self.storage.pop();
}
Some(ret)
}
}
/// Returns the total number of bits in this vector #[inline] pubfn len(&self) -> usize { self.nbits
}
/// Sets the number of bits that this `BitVec` considers initialized. /// /// # Safety /// /// Almost certainly can cause bad stuff. Only really intended for `BitSet`. #[inline] pubunsafefn set_len(&mutself, len: usize) { self.nbits = len;
}
/// Returns true if there are no bits in this vector #[inline] pubfn is_empty(&self) -> bool { self.len() == 0
}
/// Clears all bits in this vector. #[inline] pubfn clear(&mutself) { self.ensure_invariant(); for w in &mutself.storage {
*w = B::zero();
}
}
/// Shrinks the capacity of the underlying storage as much as /// possible. /// /// It will drop down as close as possible to the length but the /// allocator may still inform the underlying storage that there /// is space for a few more elements/bits. pubfn shrink_to_fit(&mutself) { self.storage.shrink_to_fit();
}
/// Inserts a given bit at index `at`, shifting all bits after by one /// /// # Panics /// Panics if `at` is out of bounds for `BitVec`'s length (that is, if `at > BitVec::len()`) /// /// # Examples ///``` /// use bit_vec::BitVec; /// /// let mut b = BitVec::new(); /// /// b.push(true); /// b.push(true); /// b.insert(1, false); /// /// assert!(b.eq_vec(&[true, false, true])); ///``` /// /// # Time complexity /// Takes O([`len`]) time. All items after the insertion index must be /// shifted to the right. In the worst case, all elements are shifted when /// the insertion index is 0. /// /// [`len`]: Self::len pubfn insert(&mutself, at: usize, bit: bool) {
assert!(
at <= self.nbits, "insertion index (is {at}) should be <= nbits (is {nbits})",
nbits = self.nbits
);
let last_block_bits = self.nbits % B::bits(); let block_at = at / B::bits(); // needed block let bit_at = at % B::bits(); // index within the block
if last_block_bits == 0 { self.storage.push(B::zero());
}
/// An iterator for mutable references to the bits in a `BitVec`. pubstruct IterMut<'a, B: 'a + BitBlock = u32> {
vec: Rc<RefCell<&'a mut BitVec<B>>>,
range: Range<usize>,
}
impl<'a, B: 'a + BitBlock> IterMut<'a, B> { fn get(&mutself, index: Option<usize>) -> Option<MutBorrowedBit<'a, B>> { let index = index?; let value = (*self.vec).borrow().get(index)?;
Some(MutBorrowedBit {
vec: self.vec.clone(),
index, #[cfg(debug_assertions)]
old_value: value,
new_value: value,
})
}
}
impl<'a, B: BitBlock> Deref for MutBorrowedBit<'a, B> { type Target = bool;
impl<'a, B: BitBlock> Drop for MutBorrowedBit<'a, B> { fn drop(&mutself) { letmut vec = (*self.vec).borrow_mut(); #[cfg(debug_assertions)]
debug_assert_eq!(
Some(self.old_value),
vec.get(self.index), "Mutably-borrowed bit was modified externally!"
);
vec.set(self.index, self.new_value);
}
}
impl<'a, B: BitBlock> Iterator for Iter<'a, B> { type Item = bool;
#[inline] fn next(&mutself) -> Option<bool> { // NB: indexing is slow for extern crates when it has to go through &TRUE or &FALSE // variables. get is more direct, and unwrap is fine since we're sure of the range. self.range.next().map(|i| self.bit_vec.get(i).unwrap())
}
#[test] fn test_small_xor() { letmut a = BitVec::from_bytes(&[0b0011]); let b = BitVec::from_bytes(&[0b0101]); let c = BitVec::from_bytes(&[0b0110]);
assert!(a.xor(&b));
assert_eq!(a, c);
}
#[test] fn test_small_xnor() { letmut a = BitVec::from_bytes(&[0b0011]); let b = BitVec::from_bytes(&[0b1111_0101]); let c = BitVec::from_bytes(&[0b1001]);
assert!(a.xnor(&b));
assert_eq!(a, c);
}
#[test] fn test_small_nand() { letmut a = BitVec::from_bytes(&[0b1111_0011]); let b = BitVec::from_bytes(&[0b1111_0101]); let c = BitVec::from_bytes(&[0b1110]);
assert!(a.nand(&b));
assert_eq!(a, c);
}
#[test] fn test_small_nor() { letmut a = BitVec::from_bytes(&[0b0011]); let b = BitVec::from_bytes(&[0b1111_0101]); let c = BitVec::from_bytes(&[0b1000]);
assert!(a.nor(&b));
assert_eq!(a, c);
}
#[test] fn test_bit_vec_lt() { letmut a = BitVec::from_elem(5, false); letmut b = BitVec::from_elem(5, false);
assert!(a >= b && b >= a);
b.set(2, true);
assert!(a < b);
a.set(3, true);
assert!(a < b);
a.set(2, true);
assert!(a >= b && b < a);
b.set(0, true);
assert!(a < b);
}
#[test] fn test_ord() { letmut a = BitVec::from_elem(5, false); letmut b = BitVec::from_elem(5, false);
assert!(a == b);
a.set(1, true);
assert!(a > b && a >= b);
assert!(b < a && b <= a);
b.set(1, true);
b.set(2, true);
assert!(b > a && b >= a);
assert!(a < b && a <= b);
}
#[test] fn test_small_bit_vec_tests() { let v = BitVec::from_bytes(&[0]);
assert!(!v.all());
assert!(!v.any());
assert!(v.none());
let v = BitVec::from_bytes(&[0b00010100]);
assert!(!v.all());
assert!(v.any());
assert!(!v.none());
let v = BitVec::from_bytes(&[0xFF]);
assert!(v.all());
assert!(v.any());
assert!(!v.none());
}
#[test] fn test_bit_vec_append() { // Append to BitVec that holds a multiple of U32_BITS bits letmut a = BitVec::from_bytes(&[0b10100000, 0b00010010, 0b10010010, 0b00110011]); letmut b = BitVec::new();
b.push(false);
b.push(true);
b.push(true);
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