Struct vob::Vob

pub struct Vob<T = usize> { /* fields omitted */ }

A Vob is a "vector of bits": a sequence of bits which exposes a Vec-like interface. Whereas Vec<bool> requires 1 byte of storage per bit, Vob requires only 1 bit of storage per bit. For larger numbers of bits, Vobs can lead to a significant memory decrease and performance increase.

Examples

The vob! macro makes creating small Vobs easy:

let mut v = vob![true, false, true];
assert_eq!(v[1], false);

Operations such as anding two Vobs together are quick; one can also quickly identify which bits are set:

use vob::Vob;
let mut v1 = Vob::from_elem(256, false);
let mut v2 = Vob::from_elem(256, false);
v1.set(67, true);
v2.set(67, true);
v1.set(188, true);
v1.and(&v2);
let num_bits_set = v1.iter_set_bits(..).count();
assert_eq!(num_bits_set, 1);

Storage backing type

Vobs default to using usize as a storage backing type. This is generally a substantial win over using smaller storage types if you use functions such as or(). In such cases, usize on a 64-bit machine is almost exactly twice as fast as using u32. If you only ever set and get individual bits, a smaller data type might be marginally more effective: for such use cases u32 is around 1% faster than usize on a 64-bit machine. You can choose your own storage type with the new_with_storage_type() constructor. In general we recommend using the default usize backing storage unless you have rigorously benchmarked your particular use case and are sure that a different storage type is superior.

Migrating from Vec<bool>

As far as possible, Vob is intended to have a superset of Vec<bool>'s interface, which should make porting most code fairly simple. However, Vec<bool> contains several functions which are not yet implemented in Vob: these are missing simply due to a lack of a current use-case rather than because of any fundamental incompatibilities.

There is one missing feature which, currently, is impossible to implement: assignment to an index. In other words one cannot currently express v[0] = true for a Vob v. Until IndexGet / IndexMove and equivalents are implemented in rustc, this restriction appears to be inevitable. Note that referencing by index works (though via a hack identical to that used in BitVec): one can write println!("{}", v[0]) for a Vob v, for example.

Migrating from BitVec

Vob is directly inspired by the BitVec, but aims to provide an interface more closely aligned to Vec<bool> Several functions in BitVec have different names in Vob, but porting is in general fairly simple. The main semantic difference is that Vobs clear() function empties the Vob of contents (i.e. sets its length to 0), whereas BitVec's function of the same name unsets all bits (keeping the length unchanged). The same effect as BitVec's clear can be achieved by using Vob's set_all(false) function.

Methods

impl Vob<usize>

pub fn new() -> Vob<usize>

Constructs a new, empty Vob (with usize backing storage, which is likely to be the best choice in nearly all situations).

The Vob will not allocate until elements are pushed onto it.

pub fn with_capacity(capacity: usize) -> Vob<usize>

Constructs a new, empty Vob (with usize backing storage, which is likely to be the best choice in nearly all situations) with the specified capacity.

The Vob will be able to hold at least capacity elements without reallocating. If capacity is 0, the vector will not allocate.

pub fn from_elem(len: usize, value: bool) -> Vob<usize>

Creates a Vob that holds len elements, setting each element to value.

Examples

use vob::Vob;
let v = Vob::from_elem(2, true);
assert_eq!(v.len(), 2);
assert_eq!(v.get(0), Some(true));

pub fn from_bytes(slice: &[u8]) -> Vob<usize>

Create a Vob from a u8 slice. The most significant bit of each byte comes first in the resulting Vob.

Examples

use vob::{Vob, vob};
fn main() {
    let v = Vob::from_bytes(&[0b10100000, 0b00010010]);
    assert_eq!(v, vob![true, false, true, false, false, false, false, false,
                       false, false, false, true, false, false, true, false]);
}

impl<T: Debug + PrimInt + One + Zero> Vob<T>

pub fn new_with_storage_type(capacity: usize) -> Vob<T>

Constructs a new, empty Vob (with a user-defined backing storage type) with the given capacity.

Examples

use vob::Vob;
let mut v = Vob::<u32>::new_with_storage_type(0);
v.push(true);
assert_eq!(v[0], true);

pub fn capacity(&self) -> usize

Returns the number of bits the Vob can hold without reallocating.

Examples

use vob::Vob;
assert_eq!(Vob::new().capacity(), 0);
assert!(Vob::with_capacity(1).capacity() >= 1);

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more bits to be inserted in the Vob. The Vob may reserve more space to avoid frequent reallocations. After calling reserve, capacity will be greater than or equal to self.len() + additional. Does nothing if capacity is already sufficient.

Examples

use vob::Vob;
let mut v = Vob::new();
v.reserve(1);
assert!(v.capacity() >= 1);

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the vector as much as possible.

It will drop down as close as possible to the length but the allocator may still inform the vector that there is space for a few more elements.

pub fn truncate(&mut self, len: usize)

Shortens the Vob, keeping the first len elements and dropping the rest.

If len is greater than the vector's current length, this has no effect.

The drain method can emulate truncate, but causes the excess elements to be returned instead of dropped.

Note that this method has no effect on the allocated capacity of the vector.

Examples

use vob::vob;
fn main() {
    let mut v = vob![true, false, true];
    v.truncate(2);
    assert_eq!(v, vob![true, false]);
}

pub fn push(&mut self, value: bool)

Appends a bool to the back of the Vob.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(true);
v.push(false);
assert_eq!(v.get(0), Some(true));
assert_eq!(v.get(1), Some(false));

pub fn pop(&mut self) -> Option<bool>

Removes the last element from the Vob and returns it, or None if it is empty.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(true);
assert_eq!(v.pop(), Some(true));
assert_eq!(v.pop(), None);

pub fn len(&self) -> usize

Returns the number of elements in the Vob.

pub fn is_empty(&self) -> bool

Returns true if the Vob has a length of 0.

Examples

use vob::Vob;
assert_eq!(Vob::from_elem(2, true).is_empty(), false);
assert_eq!(Vob::new().is_empty(), true);

pub fn split_off(&mut self, at: usize) -> Vob<T>

Splits the collection into two at the given index.

Returns a newly allocated Self. self contains elements [0, at), and the returned Self contains elements [at, len).

Note that the capacity of self does not change.

Examples

use vob::Vob;
let mut v1 = Vob::new();
v1.push(true);
v1.push(false);
let v2 = v1.split_off(1);
assert_eq!(v1, Vob::from_elem(1, true));
assert_eq!(v2, Vob::from_elem(1, false));

pub fn get(&self, index: usize) -> Option<bool>

Returns the value of the element at position index or None if out of bounds.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
assert_eq!(v.get(0), Some(false));
assert_eq!(v.get(1), None);

pub fn set(&mut self, index: usize, value: bool) -> bool

Sets the value of the element at position index. Returns true if this led to a change in the underlying storage or false otherwise.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
v.set(0, true);
assert_eq!(v.get(0), Some(true));
assert_eq!(v.set(0, false), true);
assert_eq!(v.set(0, false), false);

Panics

If index is out of bounds.

Important traits for Iter<'a, T>

impl<'a, T: Debug + One + PrimInt + Zero> Iterator for Iter<'a, T> type Item = bool;

pub fn iter(&self) -> Iter<T>

Returns an iterator over the slice.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
v.push(true);
let mut iterator = v.iter();
assert_eq!(iterator.next(), Some(false));
assert_eq!(iterator.next(), Some(true));
assert_eq!(iterator.next(), None);

Important traits for IterSetBits<'a, T>

impl<'a, T: Debug + One + PrimInt + Zero> Iterator for IterSetBits<'a, T> type Item = usize;

pub fn iter_set_bits<R>(&self, range: R) -> IterSetBits<T> where
    R: RangeBounds<usize>, 

Returns an iterator which efficiently produces the index of each set bit in the specified range. Assuming appropriate support from your CPU, this is much more efficient than checking each bit individually.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
v.push(true);
let mut iterator = v.iter_set_bits(..);
assert_eq!(iterator.next(), Some(1));
assert_eq!(iterator.next(), None);

Important traits for IterUnsetBits<'a, T>

impl<'a, T: Debug + One + PrimInt + Zero> Iterator for IterUnsetBits<'a, T> type Item = usize;

pub fn iter_unset_bits<R>(&self, range: R) -> IterUnsetBits<T> where
    R: RangeBounds<usize>, 

Returns an iterator which efficiently produces the index of each unset bit in the specified range. Assuming appropriate support from your CPU, this is much more efficient than checking each bit individually.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
v.push(true);
let mut iterator = v.iter_unset_bits(..);
assert_eq!(iterator.next(), Some(0));
assert_eq!(iterator.next(), None);

Important traits for StorageIter<'a, T>

impl<'a, T: Debug + One + PrimInt + Zero> Iterator for StorageIter<'a, T> type Item = T;

pub fn iter_storage(&self) -> StorageIter<T>

Return an iterator over the underlying storage blocks. The last block is guaranteed to have "unused" bits (i.e. those past self.len()) set to 0.

Examples

use vob::Vob;
let v1 = Vob::from_elem(10, true);
assert_eq!(v1.iter_storage().next(), Some((1 << 10) - 1));
let v2 = Vob::from_elem(129, true);
assert_eq!(v2.iter_storage().last(), Some(1));

pub fn resize(&mut self, new_len: usize, value: bool)

Resizes the Vob in-place so that len is equal to new_len.

If new_len is greater than len, the Vob is extended by the difference, with each additional slot filled with value. If new_len is less than len, the vob is simply truncated.

Examples

use vob::Vob;
let mut v = Vob::new();
v.push(false);
v.resize(129, true);
assert_eq!(v.len(), 129);
assert_eq!(v.get(0), Some(false));
assert_eq!(v.get(128), Some(true));

pub fn extend_from_slice(&mut self, other: &[bool])

Appends all elements in a slice to the Vob.

Iterates over the slice other and appends elements in order.

Note that this function is same as extend except that it is specialized to work with slices instead. If and when Rust gets specialization this function will likely be deprecated (but still available).

Examples

use vob::vob;
fn main() {
    let mut v = vob![true];
    v.extend_from_slice(&vec![false, true]);
    assert_eq!(v, vob![true, false, true]);
}

pub fn extend_from_vob(&mut self, other: &Vob<T>)

Append all elements from a second Vob to this Vob.

Use this instead of extend() when extending with a Vob, because this method is a lot faster.

Examples

use vob::vob;
fn main() {
    let mut v1 = vob![true];
    let v2 = vob![false, false];
    v1.extend_from_vob(&v2);
    assert_eq!(v1, vob![true, false, false]);
}

pub fn clear(&mut self)

Clears the Vob, removing all values.

Note that this method has no effect on the allocated capacity of the Vob.

pub fn set_all(&mut self, value: bool)

Sets all bits in the Vob to value. Notice that this does not change the number of bits stored in the Vob.

Examples

use vob::vob;
fn main() {
    let mut v = vob![true, false, true];
    v.set_all(false);
    assert_eq!(v, vob![false, false, false]);
}

pub fn negate(&mut self)

Negates all bits in the Vob.

Examples

use vob::vob;
fn main() {
    let mut v = vob![true, false];
    v.negate();
    assert_eq!(v, vob![false, true]);
}

pub fn and(&mut self, other: &Vob<T>) -> bool

For each bit in this Vob, and it with the corresponding bit in other, returning true if this led to any changes or false otherwise. The two Vobs must have the same number of bits.

Panics

If the two Vobs are of different length.

Examples

use vob::vob;
fn main() {
    let mut v1 = vob![true, false, false];
    let v2 = vob![true, true, false];
    assert_eq!(v1.and(&v2), false);
    assert_eq!(v1, vob![true, false, false]);
}

pub fn or(&mut self, other: &Vob<T>) -> bool

For each bit in this Vob, or it with the corresponding bit in other, returning true if this led to any changes or false otherwise. The two Vobs must have the same number of bits.

Panics

If the two Vobs are of different length.

Examples

use vob::vob;
fn main() {
    let mut v1 = vob![true, false, false];
    let v2 = vob![false, true, false];
    assert_eq!(v1.or(&v2), true);
    assert_eq!(v1, vob![true, true, false]);
}

pub fn xor(&mut self, other: &Vob<T>) -> bool

For each bit in this Vob, xor it with the corresponding bit in other, returning true if this led to any changes or false otherwise. The two Vobs must have the same number of bits.

Panics

If the two Vobs are of different length.

Examples

use vob::vob;
fn main() {
    let mut v1 = vob![true, false, true];
    let v2 = vob![false, true, true];
    assert_eq!(v1.xor(&v2), true);
    assert_eq!(v1, vob![true, true, false]);
}

Trait Implementations

impl<T: Debug + One + PrimInt + Zero> Extend<bool> for Vob<T>

fn extend<I: IntoIterator<Item = bool>>(&mut self, iterable: I)

Extends a collection with the contents of an iterator.

impl<'a, T: Debug + One + PrimInt + Zero> IntoIterator for &'a Vob<T>

type Item = bool

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

Important traits for Iter<'a, T>

impl<'a, T: Debug + One + PrimInt + Zero> Iterator for Iter<'a, T> type Item = bool;

fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value.

impl<T: Clone> Clone for Vob<T>

fn clone(&self) -> Vob<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Default for Vob<usize>

fn default() -> Self

Returns the "default value" for a type.

impl<T: Debug + One + PrimInt + Zero> Eq for Vob<T>

impl<T: Debug + One + PrimInt + Zero> PartialEq<Vob<T>> for Vob<T>

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T: Debug + One + PrimInt + Zero> Debug for Vob<T>

fn fmt(&self, fmt: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T: Debug + One + PrimInt + Zero> Index<usize> for Vob<T>

type Output = bool

The returned type after indexing.

fn index(&self, index: usize) -> &bool

Performs the indexing (container[index]) operation.

impl<T: Debug + Hash + One + PrimInt + Zero> Hash for Vob<T>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl FromIterator<bool> for Vob<usize>

fn from_iter<I: IntoIterator<Item = bool>>(iter: I) -> Self

Create a Vob from an iterator.

Examples

use std::iter::FromIterator;
use vob::Vob;
let v = Vob::from_iter(vec![true, false]);
assert_eq!(v, Vob::from_iter(vec![true, false]));