Struct bitvec::vec::BitVec [−][src]
#[repr(C)]pub struct BitVec<O = Lsb0, T = usize> where
O: BitOrder,
T: BitStore, { /* fields omitted */ }
Expand description
A vector of individual bits, allocated on the heap.
This is a managed, heap-allocated, buffer that contains a BitSlice
region. It
is analagous to Vec<bool>
, and is written to be as close as possible to
drop-in replacabale for it. This type contains little interesting behavior in
its own right, dereferencing instead to BitSlice
for manipulation of the
buffer contents, and serves primarily as an interface to the allocator. If you
require statically-allocated, fixed-size, owned buffers, you should use the
BitArray
type.
Because BitVec
directly owns its memory, and can guarantee that no other
object in a program has access to its buffers, BitVec
is able to override some
behavior from BitSlice
in more efficient manners.
Documentation
All APIs that mirror something in the standard library will have an Original
section linking to the corresponding item. All APIs that have a different
signature or behavior than the original will have an API Differences
section
explaining what has changed, and how to adapt your existing code to the change.
These sections look like this:
Original
API Differences
The buffer type Vec<bool>
has no type parameters. BitVec<O, T>
has the same
two type parameters as BitSlice<O, T>
. Otherwise, BitVec
is able to
implement the full API surface of Vec<bool>
.
Behavior
Because BitVec
is a fully-owned buffer, it is able to operate on its memory
without concern for any other views that may alias. This enables it to
specialize some BitSlice
behavior to be faster or more efficient.
Type Parameters
This takes the same two type parameters, O: BitOrder
and T: BitStore
, as
BitSlice
.
Safety
Like BitSlice
, BitVec
is exactly equal in size to Vec
, and is also
absolutely representation-incompatible with it. You must never attempt to
type-cast between Vec<T>
and BitVec
in any way, nor attempt to modify the
memory value of a BitVec
handle. Doing so will cause allocator and memory
errors in your program, likely inducing a panic.
Everything in the BitVec
public API, even the unsafe
parts, are guaranteed
to have no more unsafety than their equivalent items in the standard library.
All unsafe
APIs will have documentation explicitly detailing what the API
requires you to uphold in order for it to function safely and correctly. All
safe APIs will do so themselves.
Performance
The choice of T: BitStore
type parameter can impact your vector’s performance,
as the allocator operates in units of T
rather than in bits. This means that
larger register types will increase the amount of memory reserved in each call
to the allocator, meaning fewer calls to .push()
will actually cause a
reällocation. In addition, iteration over the vector is governed by the
BitSlice
characteristics on the type parameter. You are generally better off
using larger types when your vector is a data collection rather than a specific
I/O protocol buffer.
Macro Construction
Heap allocation can only occur at runtime, but the bitvec!
macro will
construct an appropriate BitSlice
buffer at compile-time, and at run-time,
only copy the buffer into a heap allocation.
Implementations
Constructs a new, empty BitVec<O, T>
with the specified capacity.
The vector will be able to hold at least capacity
bits without
reällocating. If capacity
is 0, the vector will not allocate.
It is important to note that although the returned vector has the capacity specified, the vector will have a zero length. For an explanation of the difference between length and capacity, see Capacity and reällocation.
Original
Panics
Panics if the requested capacity exceeds the vector’s limits.
Examples
use bitvec::prelude::*;
let mut bv = BitVec::<LocalBits, usize>::with_capacity(10);
// The vector contains no items, even though it has capacity for more
assert_eq!(bv.len(), 0);
// These are all done without reallocating...
for i in 0..10 {
bv.push(true);
}
// ...but this may make the vector reallocate
bv.push(false);
Creates a BitVec<O, T>
directly from the raw components of another
bit-vector.
Original
API Differences
Ordinary vectors decompose into their buffer pointer and element length
separately; bit vectors must keep these two components bundled into the
*BitSlice
region pointer. As such, this only accepts two components;
the slice pointer and the buffer capacity.
Vec
could define its raw parts as *[T]
and usize
also, but Rust
does not make working with raw slice pointers easy.
Panics
This function panics if pointer
is the null pointer.
Safety
This is highly unsafe, due to the number of invariants that aren’t checked:
pointer
needs to have been previously allocated viaBitVec<O, T>
(at least, it’s highly likely to be incorrect if it wasn’t).T
needs to have the same size and alignment as whatpointer
was allocated with. (T
having a less strict alignment is not sufficient; the alignment really needs to be equal to satisfy the [dealloc
] requirement that memory must be allocated and deällocated with the same layout.)capacity
needs to be the capacity that the pointer was allocated with.
In addition to the invariants inherited from Vec::from_raw_parts
, the
fact that this function takes a bit-slice pointer adds another one:
pointer
MUST NOT have had its value modified in any way in the time when it was outside of abitvec
container type.
Violating these will cause problems like corrupting the allocator’s
internal data structures. For example it is not safe to build a
BitVec<_, u8>
from a pointer to a C char
array with length size_t
.
It’s also not safe to build one from a BitVec<_, u16>
and its length,
becauset the allocator cares about the alignment, and these two types
have different alignments. The buffer was allocated with alignment 2
(for u16
), but after turning it into a BitVec<_, u8>
, it’ll be
deällocated with alignment 1.
The ownership of pointer
is effectively transferred to the BitVec<O, T>
which may then deällocate, reällocate, or change the contents of
memory pointed to by the pointer at will. Ensure that nothing else uses
the pointer after calling this function.
Examples
use bitvec::prelude::*;
use bitvec as bv;
use core::mem;
let bv = bitvec![0, 1, 0, 1];
// Prevent running `bv`’s destructor so we are in complete control
// of the allocation.
let mut bv = mem::ManuallyDrop::new(bv);
// Pull out the various important pieces of information about `bv`
let p = bv.as_mut_ptr();
let e = bv.elements();
let cap = bv.capacity();
unsafe {
let bits = bv::slice::from_raw_parts_mut::<LocalBits, _>(p, e);
let len = bits.len();
// Overwrite memory with a new pattern
bits.iter_mut().for_each(|mut b| *b = true);
// Put everything back together into a BitVec
let rebuilt = BitVec::from_raw_parts(bits as *mut _, cap);
assert_eq!(rebuilt.len(), len);
}
Reserves capacity for at least additional
more bits to be inserted in
the given BitVec<O, T>
. The collection may reserve more space to avoid
frequent reällocations. After calling reserve
, capacity will be
greater than or equal to self.len() + additional
. Does nothing if
capacity is already sufficient.
Original
Panics
Panics if the new capacity exceeds the vector’s limits.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![1];
bv.reserve(100);
assert!(bv.capacity() >= 101);
Reserves the minimum capacity for exactly additional
more bits to be
inserted in the given BitVec<O, T>
. After calling reserve_exact
,
capacity will be greater than or equal to self.len() + additional
.
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.
Original
Panics
Panics if the new capacity exceeds the vector’s limits.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![1];
bv.reserve_exact(100);
assert!(bv.capacity() >= 101);
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 bits.
Original
Examples
use bitvec::prelude::*;
let mut bv = BitVec::<LocalBits, usize>::with_capacity(100);
bv.extend([false, true, false].iter().copied());
assert!(bv.capacity() >= 100);
bv.shrink_to_fit();
assert!(bv.capacity() >= 3);
Converts the vector into [Box<[T]>
].
Note that this will drop any excess capacity.
Original
Analogue
See [into_boxed_bitslice
] for a BitVec -> BitBox
transform.
Examples
use bitvec::prelude::*;
let bv = bitvec![0, 1, 0];
let slice = bv.into_boxed_slice();
assert_eq!(slice.len(), 1);
Any excess capacity is removed:
use bitvec::prelude::*;
let mut bv: BitVec = BitVec::with_capacity(100);
bv.extend([false, true, false].iter().copied());
assert!(bv.capacity() >= 100);
let slice = bv.into_boxed_slice();
assert_eq!(slice.into_vec().capacity(), 1);
[Box<[T]>
]: https://doc.rust-lang.org/alloc/boxed/struct.Box.html
[into_boxed_bitslice
]: #method.into_boxed_bitslice
Shortens the vector, keeping the first len
bits 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 bits
to be returned instead of dropped.
Note that this method has no effect on the allocated capacity of the
vector, nor does it erase truncated memory. Bits in the allocated
memory that are outside of the .as_bitslice()
view always have
unspecified values, and cannot be relied upon to be zero.
Original
Examples
Truncating a five bit vector to two bits:
use bitvec::prelude::*;
let mut bv = bitvec![1; 5];
bv.truncate(2);
assert_eq!(bv.len(), 2);
assert!(bv.as_slice()[0].count_ones() >= 5);
No truncation occurs when len
is greater than the vector’s current
length:
use bitvec::prelude::*;
let mut bv = bitvec![1; 3];
bv.truncate(8);
assert_eq!(bv.len(), 3);
Truncating when len == 0
is equivalent to calling the clear
method.
use bitvec::prelude::*;
let mut bv = bitvec![0; 3];
bv.truncate(0);
assert!(bv.is_empty());
Extracts an element slice containing the entire vector.
Original
Analogue
See as_bitslice
for a &BitVec -> &BitSlice
transform.
Examples
use bitvec::prelude::*;
use std::io::{self, Write};
let buffer = bitvec![Msb0, u8; 0, 1, 0, 1, 1, 0, 0, 0];
io::sink().write(buffer.as_slice()).unwrap();
Extracts a mutable slice of the entire vector.
Original
Analogue
See as_mut_bitslice
for a &mut BitVec -> &mut BitSlice
transform.
Examples
use bitvec::prelude::*;
use std::io::{self, Read};
let mut buffer = bitvec![Msb0, u8; 0; 24];
io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();
Returns a raw pointer to the vector’s buffer.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up pointing to garbage. Modifying the vector may cause its buffer to be reällocated, which would also make any pointers to it invalid.
The caller must also ensure that the memory the pointer
(non-transitively) points to is never written to (except inside an
UnsafeCell
) using this pointer or any pointer derived from it. If you
need to mutate the contents of the slice, use [as_mut_ptr
].
Original
Analogue
See [as_bitptr
] for a &BitVec -> *const BitSlice
transform.
Examples
use bitvec::prelude::*;
let bv = bitvec![Lsb0; 0, 1, 0, 1];
let bv_ptr = bv.as_ptr();
unsafe {
assert_eq!(*bv_ptr, 0b1010);
}
Returns an unsafe mutable pointer to the vector’s buffer.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up pointing to garbage. Modifying the vector may cause its buffer to be reällocated, which would also make any pointers to it invalid.
Original
Analogue
See as_mut_bitptr
for a &mut BitVec -> *mut BitSlice
transform.
Eaxmples
use bitvec::prelude::*;
let size = 4;
let mut bv: BitVec<Msb0, usize> = BitVec::with_capacity(size);
let bv_ptr = bv.as_mut_ptr();
unsafe {
*bv_ptr = !0;
bv.set_len(size);
}
assert_eq!(bv.len(), 4);
assert!(bv.all());
Forces the length of the vector to new_len
.
This is a low-level operation that maintains none of the normal
invariants of the type. Normally changing the length of a vector is done
using one of the safe operations instead, such as truncate
,
resize
, extend
, or clear
.
Original
Safety
new_len
must be less than or equal tocapacity()
.
Examples
This method can be useful for situations in which the vector is serving as a buffer for other code, particularly over FFI:
use bitvec::prelude::*;
// `bitvec` could pair with `rustler` for a better bitstream
type ErlBitstring = BitVec<Msb0, u8>;
let mut bits_read = 0;
// An imaginary Erlang function wants a large bit buffer.
let mut buf = ErlBitstring::with_capacity(32_768);
// SAFETY: When `erl_read_bits` returns `ERL_OK`, it holds that:
// 1. `bits_read` bits were initialized.
// 2. `bits_read` <= the capacity (32_768)
// which makes `set_len` safe to call.
unsafe {
// Make the FFI call...
let status = erl_read_bits(&mut buf, 10, &mut bits_read);
if status == ERL_OK {
// ...and update the length to what was read in.
buf.set_len(bits_read);
}
}
Removes a bit from the vector and returns it.
The removed bit is replaced by the last bit of the vector.
This does not preserve ordering, but is O(1).
Original
Panics
Panics if index
is out of bounds.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0, 0, 1, 0, 1];
assert!(!bv.swap_remove(1));
assert_eq!(bv, bits![0, 1, 1, 0]);
assert!(!bv.swap_remove(0));
assert_eq!(bv, bits![0, 1, 1]);
Inserts a bit at position index
within the vector, shifting all bits
after it to the right.
Original
Panics
Panics if index > len
.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0; 5];
bv.insert(4, true);
assert_eq!(bv, bits![0, 0, 0, 0, 1, 0]);
bv.insert(2, true);
assert_eq!(bv, bits![0, 0, 1, 0, 0, 1, 0]);
Retains only the bits specified by the predicate.
In other words, remove all bits b
such that func(idx(b), &b)
returns
false
. This method operates in place, visiting each bit exactly once
in the original order, and preserves the order of the retained bits.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0, 1, 1, 0, 0, 1];
bv.retain(|i, b| (i % 2 == 0) ^ b);
assert_eq!(bv, bits![0, 1, 0, 1]);
Moves all the bits of other
into self
, leaving other
empty.
Original
Panics
Panics if the number of bits overflows the maximum vector capacity.
Examples
use bitvec::prelude::*;
let mut bv1 = bitvec![0; 10];
let mut bv2 = bitvec![1; 10];
bv1.append(&mut bv2);
assert_eq!(bv1.count_ones(), 10);
assert!(bv2.is_empty());
Creates a draining iterator that removes the specified range in the vector and yields the removed items.
Note 1: The bit range is removed even if the iterator is only partially consumed or not consumed at all.
Note 2: It is unspecified how many bits are removed from the vector if
the Drain
value is leaked.
Original
Panics
Panics if the starting point is greater than the end point or if the end point is greater than the length of the vector.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0, 1, 1];
let bv2: BitVec = bv.drain(1 ..).collect();
assert_eq!(bv, bits![0]);
assert_eq!(bv2, bits![1, 1]);
// A full range clears the vector
bv.drain(..);
assert_eq!(bv, bits![]);
Splits the collection into two at the given index.
Returns a newly allocated vector containing the elements in range [at, len)
. After the call, the original vector will be left containing the
bits [0, at)
with its previous capacity unchanged.
Original
Panics
Panics if at > len
.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0, 0, 1];
let bv2 = bv.split_off(1);
assert_eq!(bv, bits![0]);
assert_eq!(bv2, bits![0, 1]);
Resizes the BitVec
in-place so that len
is equal to new_len
.
If new_len
is greater than len
, the BitVec
is extended by the
difference, with each additional slot filled with the result of calling
the closure func
. The return values from func
will end up in the
BitVec
in the order they have been generated.
If new_len
is less than len
, the Vec
is simply truncated.
This method uses a closure to create new values on every push. If you’d
rather Clone
a given bit, use resize
. If you want to use the
Default
trait to generate values, you can pass Default::default
as the second argument.
Original
Examples
use bitvec::prelude::*;
let mut bv = bitvec![1; 3];
bv.resize_with(5, Default::default);
assert_eq!(bv, bits![1, 1, 1, 0, 0]);
let mut bv = bitvec![];
let mut p = 0;
bv.resize_with(4, || { p += 1; p % 2 == 0 });
assert_eq!(bv, bits![0, 1, 0, 1]);
Resizes the BitVec
in-place so that len
is equal to new_len
.
If new_len
is greater than len
, the BitVec
is extended by the
difference, with each additional slot filled with value
. If new_len
is less than len
, the BitVec
is simply truncated.
This method requires a single bool
value. If you need more
flexibility, use resize_with
.
Original
Examples
use bitvec::prelude::*;
let mut bv = bitvec![1];
bv.resize(3, false);
assert_eq!(bv, bits![1, 0, 0]);
let mut bv = bitvec![1; 4];
bv.resize(2, false);
assert_eq!(bv, bits![1; 2]);
Clones and appends all bool
s in a slice to the BitVec
.
Iterates over the slice other
, clones each bool
, and then appends it
to the BitVec
. The other
slice is traversed in-order.
Prefer the Extend
implementation; this method is retained only for
API compatibility, and offers no performance benefit.
Original
Analogue
See [extend_from_bitslice
] for the method to append a bit-slice of the
same type parameters to a bit-vector.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0];
bv.extend_from_slice(&[true]);
assert_eq!(bv, bits![0, 1]);
[extend
]: #impl-Extend<%26’a bool>
[extend_from_bitslice
]: #method.extend_from_bitslice
pub fn splice<R, I>(
&mut self,
range: R,
replace_with: I
) -> Splice<'_, O, T, I::IntoIter>ⓘ where
R: RangeBounds<usize>,
I: IntoIterator<Item = bool>,
pub fn splice<R, I>(
&mut self,
range: R,
replace_with: I
) -> Splice<'_, O, T, I::IntoIter>ⓘ where
R: RangeBounds<usize>,
I: IntoIterator<Item = bool>,
Creates a splicing iterator that replaces the specified range in the
vector with the given replace_with
iterator and yields the removed
items. replace_with
does not need to be the same length as range
.
The element range is removed even if the iterator is not consumed until the end.
It is unspecified how many bits are removed from the vector if the
Splice
value is leaked.
The input iterator replace_with
is only consumed when the Splice
value is dropped.
This is optimal if:
- the tail (bits in the vector after
range
) is empty - or
replace_with
yields fewer bits thanrange
’s length - or the lower bound of its
size_hint()
is exact
Otherwise, a temporary vector is allocated and the tail is moved twice.
Original
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0, 1, 0];
let new = bits![1, 0];
let old: BitVec = bv.splice(.. 2, new.iter().copied()).collect();
assert_eq!(bv, bits![1, 0, 0]);
assert_eq!(old, bits![0, 1]);
Methods specific to BitVec<_, T>
, and not present on Vec<T>
.
Constructs a BitVec
from a value repeated many times.
This function is equivalent to the bitvec![O, T; bit; len]
macro call,
and is in fact the implementation of that macro syntax.
Parameters
bit
: The bit value to which alllen
allocated bits will be set.len
: The number of live bits in the constructedBitVec
.
Returns
A BitVec
with len
live bits, all set to bit
.
Examples
use bitvec::prelude::*;
let bv = BitVec::<Msb0, u8>::repeat(true, 20);
assert_eq!(bv, bits![1; 20]);
Clones a &BitSlice
into a BitVec
.
Original
<Vec<T: Clone> as Clone>::clone
Effects
This performs a direct element-wise copy from the source slice to the
newly-allocated buffer, then sets the vector to have the same starting
bit as the slice did. This allows for faster behavior. If you require
that the vector start at the leading edge of the first element, use
force_align
to guarantee this.
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 1, 1, 0, 1, 1];
let bv = BitVec::from_bitslice(&bits[2 ..]);
assert_eq!(bv, bits[2 ..]);
Converts a Vec<T>
into a BitVec<O, T>
without copying its buffer.
Parameters
vec
: A vector to view as bits.
Returns
A BitVec
over the vec
buffer.
Panics
This panics if vec
is too long to convert into a BitVec
. See
BitSlice::MAX_ELTS
.
Examples
use bitvec::prelude::*;
let vec = vec![0u8; 4];
let bv = BitVec::<LocalBits, _>::from_vec(vec);
assert_eq!(bv, bits![0; 32]);
Converts a Vec<T>
into a BitVec<O, T>
without copying its buffer.
This method takes ownership of a memory buffer and enables it to be used
as a bit-vector. Because Vec
can be longer than BitVec
s, this is a
fallible method, and the original vector will be returned if it cannot
be converted.
Parameters
vec
: Some vector of memory, to be viewed as bits.
Returns
If vec
is short enough to be viewed as a BitVec
, then this returns
a BitVec
over the vec
buffer. If vec
is too long, then this
returns vec
unmodified.
Examples
use bitvec::prelude::*;
let vec = vec![0u8; 4];
let bv = BitVec::<LocalBits, _>::try_from_vec(vec).unwrap();
assert_eq!(bv, bits![0; 32]);
An example showing this function failing would require an allocation
exceeding !0usize >> 3
bytes in size, which is infeasible to produce.
Copies all bits in a BitSlice
into the BitVec
.
This is provided for API completeness; it has no performance benefits
compared to use of the Extend
implementation.
Parameters
&mut self
other
: ABitSlice
reference of the same type parameters asself
.
Behavior
self
is extended by the length of other
, and then the contents of
other
are copied into the newly-allocated end of self
.
use bitvec::prelude::*;
let mut bv = bitvec![0, 1];
bv.extend_from_bitslice(bits![1, 1, 0, 1]);
assert_eq!(bv, bits![0, 1, 1, 1, 0, 1]);
Extend
: #impl-Extend<%26’a bool>
[.as_bitslice()
]: #method.as_bitslice()
Converts the vector into BitBox<O, T>
.
Note that this will drop any excess capacity.
Original
Examples
use bitvec::prelude::*;
let mut bv = bitvec![1; 50];
let bb: BitBox = bv.into_boxed_bitslice();
assert_eq!(bb, bits![1; 50]);
Converts the vector back into an ordinary vector of memory elements.
This does not affect the vector’s buffer, only the handle used to control it.
Parameters
self
Returns
An ordinary vector containing all of the bit-vector’s memory buffer.
Examples
use bitvec::prelude::*;
let bv = bitvec![0; 5];
let vec = bv.into_vec();
assert_eq!(vec, [0]);
Gets the number of elements T
that contain live bits of the vector.
Examples
use bitvec::prelude::*;
let bv = bitvec![LocalBits, u16; 1; 50];
assert_eq!(bv.elements(), 4);
Sets the uninitialized bits of the vector to a fixed value.
This method modifies all bits in the allocated buffer that are outside
the self.as_bitslice()
view so that they have a consistent value. This
can be used to zero the uninitialized memory so that when viewed as a
raw memory slice, bits outside the live region have a predictable value.
Examples
use bitvec::prelude::*;
let mut bv = 220u8.view_bits::<Lsb0>().to_bitvec();
assert_eq!(bv.as_slice(), &[220u8]);
bv.truncate(4);
assert_eq!(bv.count_ones(), 2);
assert_eq!(bv.as_slice(), &[220u8]);
bv.set_uninitialized(false);
assert_eq!(bv.as_slice(), &[12u8]);
bv.set_uninitialized(true);
assert_eq!(bv.as_slice(), &[!3u8]);
Ensures that the live region of the vector’s contents begins at the leading edge of the buffer.
Examples
use bitvec::prelude::*;
let data = 0x3Cu8;
let bits = data.view_bits::<Msb0>();
let mut bv = bits[2 .. 6].to_bitvec();
assert_eq!(bv, bits[2 .. 6]);
assert_eq!(bv.as_slice()[0], data);
bv.force_align();
assert_eq!(bv, bits[2 .. 6]);
// It is not specified what happens to bits that are no longer used.
assert_eq!(bv.as_slice()[0] & 0xF0, 0xF0);
Writes a value into every element that the vector considers live.
This unconditionally writes element
into each live location in the
backing buffer, without altering the BitVec
’s length or capacity.
It is unspecified what effects this has on the allocated but dead elements in the buffer.
Parameters
&mut self
element
: The value which will be written to each live location in the vector’s buffer.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![LocalBits, u8; 0; 10];
assert_eq!(bv.as_slice(), [0, 0]);
bv.set_elements(0xA5);
assert_eq!(bv.as_slice(), [0xA5, 0xA5]);
pub fn as_bitslice(&self) -> &BitSlice<O, T>ⓘ
pub fn as_bitslice(&self) -> &BitSlice<O, T>ⓘ
pub fn as_mut_bitslice(&mut self) -> &mut BitSlice<O, T>ⓘ
pub fn as_mut_bitslice(&mut self) -> &mut BitSlice<O, T>ⓘ
Returns a raw pointer to the vector’s region.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up pointing to garbage. Modifying the vector may cause its buffer to be reallocated, which would also make any pointers to it invalid.
The caller must also ensure that the memory the pointer
(non-transitively) points to is never written to (except inside an
UnsafeCell
) using this pointer or any pointer derived from it. If you
need to mutate the contents of the region, use as_mut_bitptr
.
This pointer is an opaque crate-internal type. Its in-memory
representation is unsafe to modify in any way. The only safe action to
take with this pointer is to pass it, unchanged, back into a bitvec
API.
Examples
use bitvec::prelude::*;
let bv = bitvec![0; 20];
let ptr = bv.as_bitptr();
let bits = unsafe { &*ptr };
assert_eq!(bv, bits);
Returns an unsafe mutable pointer to the vector’s region.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up pointing to garbage. Modifying the vector may cause its buffer to be reallocated, which would also make any pointers to it invalid.
This pointer is an opaque crate-internal type. Its in-memory
representation is unsafe to modify in any way. The only safe action to
take with this pointer is to pass it, unchanged, back into a bitvec
API.
Examples
use bitvec::prelude::*;
let mut bv = bitvec![0; 20];
let ptr = bv.as_mut_bitptr();
let bits = unsafe { &mut *ptr };
assert_eq!(bv, bits);
Methods from Deref<Target = BitSlice<O, T>>
Returns a mutable pointer to the first bit of the slice, or None
if it
is empty.
Original
API Differences
This crate cannot manifest &mut bool
references, and must use the
BitMut
proxy type where &mut bool
exists in the standard library
API. The proxy value must be bound as mut
in order to write through
it.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0];
assert!(!bits[0]);
if let Some(mut first) = bits.first_mut() {
*first = true;
}
assert!(bits[0]);
Returns the first and all the rest of the bits of the slice, or None
if it is empty.
Original
API Differences
This crate cannot manifest &mut bool
references, and must use the
BitMut
proxy type where &mut bool
exists in the standard library
API. The proxy value must be bound as mut
in order to write through
it.
Because the references are permitted to use the same memory address, they are marked as aliasing in order to satisfy Rust’s requirements about freedom from data races.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0; 3];
if let Some((mut first, rest)) = bits.split_first_mut() {
*first = true;
*rest.get_mut(1).unwrap() = true;
}
assert_eq!(bits.count_ones(), 2);
assert!(bits![mut].split_first_mut().is_none());
Returns the last and all the rest of the bits of the slice, or None
if
it is empty.
Original
API Differences
This crate cannot manifest &mut bool
references, and must use the
BitMut
proxy type where &mut bool
exists in the standard library
API. The proxy value must be bound as mut
in order to write through
it.
Because the references are permitted to use the same memory address, they are marked as aliasing in order to satisfy Rust’s requirements about freedom from data races.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0; 3];
if let Some((mut last, rest)) = bits.split_last_mut() {
*last = true;
*rest.get_mut(1).unwrap() = true;
}
assert_eq!(bits.count_ones(), 2);
assert!(bits![mut].split_last_mut().is_none());
Returns a mutable pointer to the last bit of the slice, or None
if it
is empty.
Original
API Differences
This crate cannot manifest &mut bool
references, and must use the
BitMut
proxy type where &mut bool
exists in the standard library
API. The proxy value must be bound as mut
in order to write through
it.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0];
if let Some(mut last) = bits.last_mut() {
*last = true;
}
assert!(bits[0]);
Returns a reference to an element or subslice depending on the type of index.
- If given a position, returns a reference to the element at that
position or
None
if out of bounds. - If given a range, returns the subslice corresponding to that range, or
None
if out of bounds.
Original
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 0];
assert_eq!(Some(&true), bits.get(1));
assert_eq!(Some(&bits[1 .. 3]), bits.get(1 .. 3));
assert!(bits.get(9).is_none());
assert!(bits.get(8 .. 10).is_none());
pub fn get_mut<'a, I>(&'a mut self, index: I) -> Option<I::Mut> where
I: BitSliceIndex<'a, O, T>,
pub fn get_mut<'a, I>(&'a mut self, index: I) -> Option<I::Mut> where
I: BitSliceIndex<'a, O, T>,
Returns a mutable reference to an element or subslice depending on the
type of index (see get
) or None
if the index is out of bounds.
Original
API Differences
When I
is usize
, this returns BitMut
instead of &mut bool
.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0; 2];
assert!(!bits.get(1).unwrap());
*bits.get_mut(1).unwrap() = true;
assert!(bits.get(1).unwrap());
pub unsafe fn get_unchecked<'a, I>(&'a self, index: I) -> I::Immut where
I: BitSliceIndex<'a, O, T>,
pub unsafe fn get_unchecked<'a, I>(&'a self, index: I) -> I::Immut where
I: BitSliceIndex<'a, O, T>,
Returns a reference to an element or subslice, without doing bounds checking.
This is generally not recommended; use with caution!
Unlike the original slice function, calling this with an out-of-bounds
index is not technically compile-time undefined behavior, as the
references produced do not actually describe local memory. However, the
use of an out-of-bounds index will eventually cause an out-of-bounds
memory read, which is a runtime safety violation. For a safe alternative
see get
.
Original
Examples
use bitvec::prelude::*;
let bits = bits![0, 1];
unsafe {
assert!(*bits.get_unchecked(1));
}
pub unsafe fn get_unchecked_mut<'a, I>(&'a mut self, index: I) -> I::Mut where
I: BitSliceIndex<'a, O, T>,
pub unsafe fn get_unchecked_mut<'a, I>(&'a mut self, index: I) -> I::Mut where
I: BitSliceIndex<'a, O, T>,
Returns a mutable reference to the output at this location, without doing bounds checking.
This is generally not recommended; use with caution!
Unlike the original slice function, calling this with an out-of-bounds
index is not technically compile-time undefined behavior, as the
references produced do not actually describe local memory. However, the
use of an out-of-bounds index will eventually cause an out-of-bounds
memory write, which is a runtime safety violation. For a safe
alternative see get_mut
.
Original
Examples
use bitvec::prelude::*;
let bits = bits![mut 0; 2];
unsafe {
let mut bit = bits.get_unchecked_mut(1);
*bit = true;
}
assert!(bits[1]);
Returns a raw bit-slice pointer to the region.
The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.
The caller must also ensure that the memory the pointer
(non-transitively) points to is only written to if T
allows shared
mutation, using this pointer or any pointer derived from it. If you need
to mutate the contents of the slice, use as_mut_ptr
.
Modifying the container (such as BitVec
) referenced by this slice may
cause its buffer to be reällocated, which would also make any pointers
to it invalid.
Original
API Differences
This returns *const BitSlice
, which is the equivalent of *const [T]
instead of *const T
. The pointer encoding used requires more than one
CPU word of space to address a single bit, so there is no advantage to
removing the length information from the encoded pointer value.
Notes
You cannot use any of the methods in the pointer
fundamental type
or the core::ptr
module on the *_ BitSlice
type. This pointer
retains the bitvec
-specific value encoding, and is incomprehensible by
the Rust standard library.
The only thing you can do with this pointer is dereference it.
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 1, 0];
let bits_ptr = bits.as_ptr();
for i in 0 .. bits.len() {
assert_eq!(bits[i], unsafe {
(&*bits_ptr)[i]
});
}
Returns an unsafe mutable bit-slice pointer to the region.
The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.
Modifying the container (such as BitVec
) referenced by this slice may
cause its buffer to be reällocated, which would also make any pointers
to it invalid.
Original
API Differences
This returns *mut BitSlice
, which is the equivalont of *mut [T]
instead of *mut T
. The pointer encoding used requires more than one
CPU word of space to address a single bit, so there is no advantage to
removing the length information from the encoded pointer value.
Notes
You cannot use any of the methods in the pointer
fundamental type
or the core::ptr
module on the *_ BitSlice
type. This pointer
retains the bitvec
-specific value encoding, and is incomprehensible by
the Rust standard library.
Examples
use bitvec::prelude::*;
let bits = bits![mut Lsb0, u8; 0; 8];
let bits_ptr = bits.as_mut_ptr();
for i in 0 .. bits.len() {
unsafe { &mut *bits_ptr }.set(i, i % 3 == 0);
}
assert_eq!(bits.as_slice()[0], 0b0100_1001);
Returns an iterator over the slice.
Original
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 0, 0, 0, 0, 1];
let mut iterator = bits.iter();
assert_eq!(iterator.next(), Some(&false));
assert_eq!(iterator.next(), Some(&true));
assert_eq!(iterator.nth(5), Some(&true));
assert_eq!(iterator.next(), None);
Returns an iterator over all contiguous windows of length size
. The
windows overlap. If the slice is shorter than size
, the iterator
returns no values.
Original
Panics
Panics if size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![1, 0, 1, 0, 0, 1, 0, 1];
let mut iter = bits.windows(6);
assert_eq!(iter.next().unwrap(), &bits[.. 6]);
assert_eq!(iter.next().unwrap(), &bits[1 .. 7]);
assert_eq!(iter.next().unwrap(), &bits[2 ..]);
assert!(iter.next().is_none());
If the slice is shorter than size
:
use bitvec::prelude::*;
let bits = BitSlice::<LocalBits, usize>::empty();
let mut iter = bits.windows(1);
assert!(iter.next().is_none());
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the beginning of the slice.
The chunks are slices and do not overlap. If chunk_size
does not
divide the length of the slice, then the last chunk will not have length
chunk_size
.
See chunks_exact
for a variant of this iterator that returns chunks
of always exactly chunk_size
bits, and rchunks
for the same
iterator but starting at the end of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![0, 0, 1, 1, 1, 1, 0, 0];
let mut iter = bits.chunks(3);
assert_eq!(iter.next().unwrap(), &bits[.. 3]);
assert_eq!(iter.next().unwrap(), &bits[3 .. 6]);
assert_eq!(iter.next().unwrap(), &bits[6 ..]);
assert!(iter.next().is_none());
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the beginning of the slice.
The chunks are mutable slices, and do not overlap. If chunk_size
does
not divide the length of the slice, then the last chunk will not have
length chunk_size
.
See chunks_exact_mut
for a variant of this iterator that returns
chunks of always exactly chunk_size
bits, and rchunks_mut
for the
same iterator but starting at the end of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![mut Lsb0, u8; 0; 8];
for (idx, chunk) in bits.chunks_mut(3).enumerate() {
chunk.set(2 - idx, true);
}
assert_eq!(bits.as_slice()[0], 0b01_010_100);
pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, O, T>ⓘNotable traits for ChunksExact<'a, O, T>impl<'a, O, T> Iterator for ChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, O, T>ⓘNotable traits for ChunksExact<'a, O, T>impl<'a, O, T> Iterator for ChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
impl<'a, O, T> Iterator for ChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the beginning of the slice.
The chunks are slices and do not overlap. If chunk_size
does not
divide the length of the slice, then the last up to chunk_size-1
bits
will be omitted and can be retrieved from the remainder
function of
the iterator.
Due to each chunk having exactly chunk_size
bits, the compiler may
optimize the resulting code better than in the case of chunks
.
See chunks
for a variant of this iterator that also returns the
remainder as a smaller chunk, and rchunks_exact
for the same
iterator but starting at the end of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 0, 1, 0, 1, 1];
let mut iter = bits.chunks_exact(3);
assert_eq!(iter.next().unwrap(), &bits[.. 3]);
assert_eq!(iter.next().unwrap(), &bits[3 .. 6]);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &bits[6 ..]);
pub fn chunks_exact_mut(
&mut self,
chunk_size: usize
) -> ChunksExactMut<'_, O, T>ⓘNotable traits for ChunksExactMut<'a, O, T>impl<'a, O, T> Iterator for ChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
pub fn chunks_exact_mut(
&mut self,
chunk_size: usize
) -> ChunksExactMut<'_, O, T>ⓘNotable traits for ChunksExactMut<'a, O, T>impl<'a, O, T> Iterator for ChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
impl<'a, O, T> Iterator for ChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the beginning of the slice.
The chunks are mutable slices, and do not overlap. If chunk_size
does
not divide the beginning length of the slice, then the last up to
chunk_size-1
bits will be omitted and can be retrieved from the
into_remainder
function of the iterator.
Due to each chunk having exactly chunk_size
bits, the compiler may
optimize the resulting code better than in the case of chunks_mut
.
See chunks_mut
for a variant of this iterator that also returns the
remainder as a smaller chunk, and rchunks_exact_mut
for the same
iterator but starting at the end of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![mut Lsb0, u8; 0; 8];
for (idx, chunk) in bits.chunks_exact_mut(3).enumerate() {
chunk.set(idx, true);
}
assert_eq!(bits.as_slice()[0], 0b00_010_001);
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the end of the slice.
The chunks are slices and do not overlap. If chunk_size
does not
divide the length of the slice, then the last chunk will not have length
chunk_size
.
See rchunks_exact
for a variant of this iterator that returns chunks
of always exactly chunk_size
bits, and chunks
for the same
iterator but starting at the beginning of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![0, 0, 1, 1, 0, 1, 1, 0];
let mut iter = bits.rchunks(3);
assert_eq!(iter.next().unwrap(), &bits[5 ..]);
assert_eq!(iter.next().unwrap(), &bits[2 .. 5]);
assert_eq!(iter.next().unwrap(), &bits[.. 2]);
assert!(iter.next().is_none());
pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, O, T>ⓘNotable traits for RChunksMut<'a, O, T>impl<'a, O, T> Iterator for RChunksMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, O, T>ⓘNotable traits for RChunksMut<'a, O, T>impl<'a, O, T> Iterator for RChunksMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
impl<'a, O, T> Iterator for RChunksMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the end of the slice.
The chunks are mutable slices, and do not overlap. If chunk_size
does
not divide the length of the slice, then the last chunk will not have
length chunk_size
.
See rchunks_exact_mut
for a variant of this iterator that returns
chunks of always exactly chunk_size
bits, and chunks_mut
for the
same iterator but starting at the beginning of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![mut Lsb0, u8; 0; 8];
for (idx, chunk) in bits.rchunks_mut(3).enumerate() {
chunk.set(2 - idx, true);
}
assert_eq!(bits.as_slice()[0], 0b100_010_01);
pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, O, T>ⓘNotable traits for RChunksExact<'a, O, T>impl<'a, O, T> Iterator for RChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, O, T>ⓘNotable traits for RChunksExact<'a, O, T>impl<'a, O, T> Iterator for RChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
impl<'a, O, T> Iterator for RChunksExact<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a BitSlice<O, T>;
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the end of the slice.
The chunks are slices and do not overlap. If chunk_size
does not
divide the length of the slice, then the last up to chunk_size-1
bits
will be omitted and can be retrieved from the remainder
function of
the iterator.
Due to each chunk having exactly chunk_size
bits, the compiler can
often optimize the resulting code better than in the case of chunks
.
See rchunks
for a variant of this iterator that also returns the
remainder as a smaller chunk, and chunks_exact
for the same iterator
but starting at the beginning of the slice.
Original
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![mut 0, 1, 1, 1, 0, 0, 1, 0];
let mut iter = bits.rchunks_exact(3);
assert_eq!(iter.next().unwrap(), &bits[5 ..]);
assert_eq!(iter.next().unwrap(), &bits[2 .. 5]);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &bits[.. 2]);
pub fn rchunks_exact_mut(
&mut self,
chunk_size: usize
) -> RChunksExactMut<'_, O, T>ⓘNotable traits for RChunksExactMut<'a, O, T>impl<'a, O, T> Iterator for RChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
pub fn rchunks_exact_mut(
&mut self,
chunk_size: usize
) -> RChunksExactMut<'_, O, T>ⓘNotable traits for RChunksExactMut<'a, O, T>impl<'a, O, T> Iterator for RChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
impl<'a, O, T> Iterator for RChunksExactMut<'a, O, T> where
O: BitOrder,
T: 'a + BitStore, type Item = &'a mut BitSlice<O, T::Alias>;
Returns an iterator over chunk_size
bits of the slice at a time,
starting at the end of the slice.
The chunks are mutable slices, and do not overlap. If chunk_size
does
not divide the length of the slice, then the last up to chunk_size-1
bits will be omitted and can be retrieved from the into_remainder
function of the iterator.
Due to each chunk having exactly chunk_size
bits, the compiler can
often optimize the resulting code better than in the case of
chunks_mut
.
See rchunks_mut
for a variant of this iterator that also returns the
remainder as a smaller chunk, and chunks_exact_mut
for the same
iterator but starting at the beginning of the slice.
Panics
Panics if chunk_size
is 0.
Examples
use bitvec::prelude::*;
let bits = bits![mut Lsb0, u8; 0; 8];
for (idx, chunk) in bits.rchunks_exact_mut(3).enumerate() {
chunk.set(idx, true);
}
assert_eq!(bits.as_slice()[0], 0b001_010_00);
Divides one slice into two at an index.
The first will contain all indices from [0, mid)
(excluding the index
mid
itself) and the second will contain all indices from [mid, len)
(excluding the index len
itself).
Original
Panics
Panics if mid > len
.
Behavior
When mid
is 0
or self.len()
, then the left or right return values,
respectively, are empty slices. Empty slice references produced by this
method are specified to have the address information you would expect:
a left empty slice has the same base address and start bit as self
,
and a right empty slice will have its address raised by self.len()
.
Examples
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 0, 0, 0, 1, 1];
let (left, right) = bits.split_at(0);
assert!(left.is_empty());
assert_eq!(right, bits);
let (left, right) = bits.split_at(2);
assert_eq!(left, &bits[.. 2]);
assert_eq!(right, &bits[2 ..]);
let (left, right) = bits.split_at(8);
assert_eq!(left, bits);
assert!(right.is_empty());
Divides one mutable slice into two at an index.
The first will contain all indices from [0, mid)
(excluding the index
mid
itself) and the second will contain all indices from [mid, len)
(excluding the index len
itself).
Original
API Differences
Because the partition point mid
is permitted to occur in the interior
of a memory element T
, this method is required to mark the returned
slices as being to aliased memory. This marking ensures that writes to
the covered memory use the appropriate synchronization behavior of your
build to avoid data races – by default, this makes all writes atomic; on
builds with the atomic
feature disabled, this uses Cell
s and
forbids the produced subslices from leaving the current thread.
See the BitStore
documentation for more information.
Panics
Panics if mid > len
.
Behavior
When mid
is 0
or self.len()
, then the left or right return values,
respectively, are empty slices. Empty slice references produced by this
method are specified to have the address information you would expect:
a left empty slice has the same base address and start bit as self
,
and a right empty slice will have its address raised by self.len()
.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0; 8];
// scoped to restrict the lifetime of the borrows
{
let (left, right) = bits.split_at_mut(3);
*left.get_mut(1).unwrap() = true;
*right.get_mut(2).unwrap() = true;
}
assert_eq!(bits.as_slice()[0], 0b010_00100);
Returns an iterator over subslices separated by bits that match pred
.
The matched bit is not contained in the subslices.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 0, 1, 0, 0, 0];
let mut iter = bits.split(|_pos, bit| *bit);
assert_eq!(iter.next().unwrap(), &bits[.. 1]);
assert_eq!(iter.next().unwrap(), &bits[2 .. 4]);
assert_eq!(iter.next().unwrap(), &bits[5 ..]);
assert!(iter.next().is_none());
If the first bit is matched, an empty slice will be the first item returned by the iterator. Similarly, if the last element in the slice is matched, an empty slice will be the last item returned by the iterator:
use bitvec::prelude::*;
let bits = bits![0, 0, 0, 1];
let mut iter = bits.split(|_pos, bit| *bit);
assert_eq!(iter.next().unwrap(), &bits[.. 3]);
assert!(iter.next().unwrap().is_empty());
assert!(iter.next().is_none());
If two matched bits are directly adjacent, an empty slice will be present between them:
use bitvec::prelude::*;
let bits = bits![0, 0, 1, 1, 0, 0, 0, 0,];
let mut iter = bits.split(|pos, bit| *bit);
assert_eq!(iter.next().unwrap(), &bits[0 .. 2]);
assert!(iter.next().unwrap().is_empty());
assert_eq!(iter.next().unwrap(), &bits[4 .. 8]);
assert!(iter.next().is_none());
Returns an iterator over mutable subslices separated by bits that match
pred
. The matched bit is not contained in the subslices.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0, 0, 1, 0, 0, 0, 1, 0];
for group in bits.split_mut(|_pos, bit| *bit) {
*group.get_mut(0).unwrap() = true;
}
assert_eq!(bits.as_slice()[0], 0b101_100_11);
Returns an iterator over subslices separated by bits that match pred
,
starting at the end of the slice and working backwards. The matched bit
is not contained in the subslices.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0, 0, 0, 1, 0, 0, 0, 0];
let mut iter = bits.rsplit(|_pos, bit| *bit);
assert_eq!(iter.next().unwrap(), &bits[4 ..]);
assert_eq!(iter.next().unwrap(), &bits[.. 3]);
assert!(iter.next().is_none());
As with split()
, if the first or last bit is matched, an empty slice
will be the first (or last) item returned by the iterator.
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 1, 0, 0, 1, 0, 0, 0, 1];
let mut iter = bits.rsplit(|_pos, bit| *bit);
assert!(iter.next().unwrap().is_empty());
assert_eq!(iter.next().unwrap(), &bits[4 .. 7]);
assert_eq!(iter.next().unwrap(), &bits[1 .. 3]);
assert!(iter.next().unwrap().is_empty());
assert!(iter.next().is_none());
Returns an iterator over mutable subslices separated by bits that match
pred
, starting at the end of the slice and working backwards. The
matched bit is not contained in the subslices.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0, 0, 1, 0, 0, 0, 1, 0];
for group in bits.rsplit_mut(|_pos, bit| *bit) {
*group.get_mut(0).unwrap() = true;
}
assert_eq!(bits.as_slice()[0], 0b101_100_11);
Returns an iterator over subslices separated by bits that match pred
,
limited to returning at most n
items. The matched bit is not contained
in the subslices.
The last item returned, if any, will contain the remainder of the slice.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![1, 0, 1, 0, 0, 1, 0, 1];
for group in bits.splitn(2, |pos, _bit| pos % 3 == 2) {
println!("{}", group.len());
}
// 2
// 5
Returns an iterator over subslices separated by bits that match pred
,
limited to returning at most n
items. The matched element is not
contained in the subslices.
The last item returned, if any, will contain the remainder of the slice.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0, 0, 1, 0, 0, 0, 1, 0];
for group in bits.splitn_mut(2, |_pos, bit| *bit) {
*group.get_mut(0).unwrap() = true;
}
assert_eq!(bits.as_slice()[0], 0b101_100_10);
Returns an iterator over subslices separated by bits that match pred
limited to returining at most n
items. This starts at the end of the
slice and works backwards. The matched bit is not contained in the
subslices.
The last item returned, if any, will contain the remainder of the slice.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![Msb0, u8; 1, 0, 1, 0, 0, 1, 0, 1];
for group in bits.rsplitn(2, |pos, _bit| pos % 3 == 2) {
println!("{}", group.len());
}
// 2
// 5
pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, O, T, F>ⓘ where
F: FnMut(usize, &bool) -> bool,
pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, O, T, F>ⓘ where
F: FnMut(usize, &bool) -> bool,
Returns an iterator over subslices separated by bits that match pred
limited to returning at most n
items. This starts at the end of the
slice and works backwards. The matched bit is not contained in the
subslices.
The last item returned, if any, will contain the remainder of the slice.
Original
API Differences
In order to allow more than one bit of information for the split decision, the predicate receives the index of each bit, as well as its value.
Examples
use bitvec::prelude::*;
let bits = bits![mut Msb0, u8; 0, 0, 1, 0, 0, 0, 1, 0];
for group in bits.rsplitn_mut(2, |_pos, bit| *bit) {
*group.get_mut(0).unwrap() = true;
}
assert_eq!(bits.as_slice()[0], 0b101_000_11);
Returns true
if the slice contains a subslice that matches the given
span.
Original
API Differences
This searches for a matching subslice (allowing different type
parameters) rather than for a specific bit. Searching for a contained
element with a given value is not as useful on a collection of bool
.
Furthermore, BitSlice
defines any
and not_all
, which are
optimized searchers for any true
or false
bit, respectively, in a
sequence.
Examples
use bitvec::prelude::*;
let data = 0b0101_1010u8;
let bits_msb = data.view_bits::<Msb0>();
let bits_lsb = data.view_bits::<Lsb0>();
assert!(bits_msb.contains(&bits_lsb[1 .. 5]));
This example uses a palindrome pattern to demonstrate that the slice being searched for does not need to have the same type parameters as the slice being searched.
Returns true
if needle
is a prefix of the slice.
Original
Examples
use bitvec::prelude::*;
let data = 0b0100_1011u8;
let haystack = data.view_bits::<Msb0>();
let needle = &data.view_bits::<Lsb0>()[2 .. 5];
assert!(haystack.starts_with(&needle[.. 2]));
assert!(haystack.starts_with(needle));
assert!(!haystack.starts_with(&haystack[2 .. 4]));
Always returns true
if needle
is an empty slice:
use bitvec::prelude::*;
let empty = BitSlice::<LocalBits, usize>::empty();
assert!(0u8.view_bits::<LocalBits>().starts_with(empty));
assert!(empty.starts_with(empty));
Returns true
if needle
is a suffix of the slice.
Original
Examples
use bitvec::prelude::*;
let data = 0b0100_1011u8;
let haystack = data.view_bits::<Lsb0>();
let needle = &data.view_bits::<Msb0>()[3 .. 6];
assert!(haystack.ends_with(&needle[1 ..]));
assert!(haystack.ends_with(needle));
assert!(!haystack.ends_with(&haystack[2 .. 4]));
Always returns true
if needle
is an empty slice:
use bitvec::prelude::*;
let empty = BitSlice::<LocalBits, usize>::empty();
assert!(0u8.view_bits::<LocalBits>().ends_with(empty));
assert!(empty.ends_with(empty));
Rotates the slice in-place such that the first by
bits of the slice
move to the end while the last self.len() - by
bits move to the front.
After calling rotate_left
, the bit previously at index by
will
become the first bit in the slice.
Original
Panics
This function will panic if by
is greater than the length of the
slice. Note that by == self.len()
does not panic and is a no-op
rotation.
Complexity
Takes linear (in self.len()
) time.
Examples
use bitvec::prelude::*;
let mut data = 0xF0u8;
let bits = data.view_bits_mut::<Msb0>();
bits.rotate_left(2);
assert_eq!(data, 0xC3);
Rotating a subslice:
use bitvec::prelude::*;
let mut data = 0xF0u8;
let bits = data.view_bits_mut::<Msb0>();
bits[1 .. 5].rotate_left(1);
assert_eq!(data, 0b1_1101_000);
Rotates the slice in-place such that the first self.len() - by
bits of
the slice move to the end while the last by
bits move to the front.
After calling rotate_right
, the bit previously at index self.len() - by
will become the first bit in the slice.
Original
Panics
This function will panic if by
is greater than the length of the
slice. Note that by == self.len()
does not panic and is a no-op
rotation.
Complexity
Takes linear (in self.len()
) time.
Examples
use bitvec::prelude::*;
let mut data = 0xF0u8;
let bits = data.view_bits_mut::<Msb0>();
bits.rotate_right(2);
assert_eq!(data, 0x3C);
Rotate a subslice:
use bitvec::prelude::*;
let mut data = 0xF0u8;
let bits = data.view_bits_mut::<Msb0>();
bits[1 .. 5].rotate_right(1);
assert_eq!(data, 0b1_0111_000);
pub fn clone_from_bitslice<O2, T2>(&mut self, src: &BitSlice<O2, T2>) where
O2: BitOrder,
T2: BitStore,
pub fn clone_from_bitslice<O2, T2>(&mut self, src: &BitSlice<O2, T2>) where
O2: BitOrder,
T2: BitStore,
Copies the bits from src
into self
.
The length of src
must be the same as self
.
If you are attempting to write an integer value into a BitSlice
, see
the BitField::store
trait function.
Implementation
This method is by necessity a bit-by-bit individual walk across both
slices. Benchmarks indicate that where the slices share type parameters,
this is very close in performance to an element-wise memcpy
. You
should use this method as the default transfer behavior, and only switch
to [.copy_from_bitslice()
] where you know that your performance is an
issue and you can demonstrate that .copy_from_bitslice()
is
meaningfully better.
Where self
and src
are not of the same type parameters, crate
benchmarks show a roughly halved runtime performance.
Original
API Differences
This method is renamed, as it takes a bit slice rather than an element slice.
Panics
This function will panic if the two slices have different lengths.
Examples
Cloning two bits from a slice into another:
use bitvec::prelude::*;
let mut data = 0u8;
let bits = data.view_bits_mut::<Msb0>();
let src = 0x0Fu16.view_bits::<Lsb0>();
bits[.. 2].clone_from_bitslice(&src[2 .. 4]);
assert_eq!(data, 0xC0);
Rust enforces that there can only be one mutable reference with no
immutable references to a particular piece of data in a particular
scope. Because of this, attempting to use clone_from_bitslice
on a
single slice will result in a compile failure:
use bitvec::prelude::*;
let mut data = 3u8;
let bits = data.view_bits_mut::<Msb0>();
bits[.. 2].clone_from_bitslice(&bits[6 ..]);
To work around this, we can use split_at_mut
to create two distinct
sub-slices from a slice:
use bitvec::prelude::*;
let mut data = 3u8;
let bits = data.view_bits_mut::<Msb0>();
let (head, tail) = bits.split_at_mut(4);
head.clone_from_bitslice(tail);
assert_eq!(data, 0x33);
Copies all bits from src
into self
.
The length of src
must be the same as self
.
If you are attempting to write an integer value into a BitSlice
, see
the BitField::store
trait function.
Implementation
This method attempts to use memcpy
element-wise copy acceleration
where possible. This will only occur when both src
and self
are
exactly similar: in addition to having the same type parameters and
length, they must begin at the same offset in an element.
Benchmarks do not indicate that memcpy
element-wise copy is
significantly faster than .clone_from_bitslice()
’s bit-wise crawl.
This implementation is retained so that you have the ability to observe
performance characteristics on your own targets and choose as
appropriate.
Original
API Differences
This method is renamed, as it takes a bit slice rather than an element slice.
Panics
This function will panic if the two slices have different lengths.
Examples
Copying two bits from a slice into another:
use bitvec::prelude::*;
let mut dst = bits![mut 0; 200];
let src = bits![1; 200];
assert!(dst.not_any());
dst.copy_from_bitslice(src);
assert!(dst.all());
Copies bits from one part of the slice to another part of itself.
src
is the range within self
to copy from. dest
is the starting
index of the range within self
to copy to, which will have the same
length as src
. The two ranges may overlap. The ends of the two ranges
must be less than or equal to self.len()
.
Original
Panics
This function will panic if either range exceeds the end of the slice,
or if the end of src
is before the start.
Examples
Copying four bytes within a slice:
use bitvec::prelude::*;
let mut data = 0x07u8;
let bits = data.view_bits_mut::<Msb0>();
bits.copy_within(5 .., 0);
assert_eq!(data, 0xE7);
pub fn swap_with_bitslice<O2, T2>(&mut self, other: &mut BitSlice<O2, T2>) where
O2: BitOrder,
T2: BitStore,
pub fn swap_with_bitslice<O2, T2>(&mut self, other: &mut BitSlice<O2, T2>) where
O2: BitOrder,
T2: BitStore,
Swaps all bits in self
with those in other
.
The length of other
must be the same as self
.
Original
API Differences
This method is renamed, as it takes a bit slice rather than an element slice.
Panics
This function will panic if the two slices have different lengths.
Examples
use bitvec::prelude::*;
let mut one = [0xA5u8, 0x69];
let mut two = 0x1234u16;
let one_bits = one.view_bits_mut::<Msb0>();
let two_bits = two.view_bits_mut::<Lsb0>();
one_bits.swap_with_bitslice(two_bits);
assert_eq!(one, [0x2C, 0x48]);
assert_eq!(two, 0x96A5);
Transmute the bitslice to a bitslice of another type, ensuring alignment of the types is maintained.
This method splits the bitslice into three distinct bitslices: prefix, correctly aligned middle bitslice of a new type, and the suffix bitslice. The method may make the middle bitslice the greatest length possible for a given type and input bitslice, but only your algorithm’s performance should depend on that, not its correctness. It is permissible for all of the input data to be returned as the prefix or suffix bitslice.
Original
API Differences
Type U
is required to have the same type family as type T
.
Whatever T
is of the fundamental integers, atomics, or Cell
wrappers, U
must be a different width in the same family. Changing the
type family with this method is unsound and strictly forbidden.
Unfortunately, it cannot be guaranteed by this function, so you are
required to abide by this limitation.
Safety
This method is essentially a transmute
with respect to the elements in
the returned middle bitslice, so all the usual caveats pertaining to
transmute::<T, U>
also apply here.
Examples
Basic usage:
use bitvec::prelude::*;
unsafe {
let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
let bits = bytes.view_bits::<LocalBits>();
let (prefix, shorts, suffix) = bits.align_to::<u16>();
match prefix.len() {
0 => {
assert_eq!(shorts, bits[.. 48]);
assert_eq!(suffix, bits[48 ..]);
},
8 => {
assert_eq!(prefix, bits[.. 8]);
assert_eq!(shorts, bits[8 ..]);
},
_ => unreachable!("This case will not occur")
}
}
Transmute the bitslice to a bitslice of another type, ensuring alignment of the types is maintained.
This method splits the bitslice into three distinct bitslices: prefix, correctly aligned middle bitslice of a new type, and the suffix bitslice. The method may make the middle bitslice the greatest length possible for a given type and input bitslice, but only your algorithm’s performance should depend on that, not its correctness. It is permissible for all of the input data to be returned as the prefix or suffix bitslice.
Original
API Differences
Type U
is required to have the same type family as type T
.
Whatever T
is of the fundamental integers, atomics, or Cell
wrappers, U
must be a different width in the same family. Changing the
type family with this method is unsound and strictly forbidden.
Unfortunately, it cannot be guaranteed by this function, so you are
required to abide by this limitation.
Safety
This method is essentially a transmute
with respect to the elements in
the returned middle bitslice, so all the usual caveats pertaining to
transmute::<T, U>
also apply here.
Examples
Basic usage:
use bitvec::prelude::*;
unsafe {
let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
let bits = bytes.view_bits_mut::<LocalBits>();
let (prefix, shorts, suffix) = bits.align_to_mut::<u16>();
// same access and behavior as in `align_to`
}
Creates a vector by repeating a slice n
times.
Original
Panics
This function will panic if the capacity would overflow.
Examples
Basic usage:
use bitvec::prelude::*;
assert_eq!(bits![0, 1].repeat(3), bits![0, 1, 0, 1, 0, 1]);
A panic upon overflow:
use bitvec::prelude::*;
// this will panic at runtime
bits![0, 1].repeat(BitSlice::<LocalBits, usize>::MAX_BITS);
Sets the bit value at the given position.
Parameters
&mut self
index
: The bit index to set. It must be in the range0 .. self.len()
.value
: The value to be set,true
for1
andfalse
for0
.
Effects
If index
is valid, then the bit to which it refers is set to value
.
Panics
This method panics if index
is outside the slice domain.
Examples
use bitvec::prelude::*;
let mut data = 0u8;
let bits = data.view_bits_mut::<Msb0>();
assert!(!bits.get(7).unwrap());
bits.set(7, true);
assert!(bits.get(7).unwrap());
assert_eq!(data, 1);
This example panics when it attempts to set a bit that is out of bounds.
use bitvec::prelude::*;
let bits = bits![mut 0];
bits.set(1, false);
Sets a bit at an index, without checking boundary conditions.
This is generally not recommended; use with caution! For a safe
alternative, see set
.
Parameters
&mut self
index
: The bit index to set. It must be in the range0 .. self.len()
. It will not be checked.
Effects
The bit at index
is set to value
.
Safety
This method is not safe. It performs raw pointer arithmetic to seek
from the start of the slice to the requested index, and set the bit
there. It does not inspect the length of self
, and it is free to
perform out-of-bounds memory write access.
Use this method only when you have already performed the bounds check, and can guarantee that the call occurs with a safely in-bounds index.
Examples
This example uses a bit slice of length 2, and demonstrates out-of-bounds access to the last bit in the element.
use bitvec::prelude::*;
let mut data = 0u8;
let bits = &mut data.view_bits_mut::<Msb0>()[2 .. 4];
assert_eq!(bits.len(), 2);
unsafe {
bits.set_unchecked(5, true);
}
assert_eq!(data, 1);
Tests if all bits in the slice domain are set (logical ∧
).
Truth Table
0 0 => 0
0 1 => 0
1 0 => 0
1 1 => 1
Parameters
&self
Returns
Whether all bits in the slice domain are set. The empty slice returns
true
.
Examples
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 1];
assert!(bits[.. 2].all());
assert!(!bits[2 ..].all());
Tests if any bit in the slice is set (logical ∨
).
Truth Table
0 0 => 0
0 1 => 1
1 0 => 1
1 1 => 1
Parameters
&self
Returns
Whether any bit in the slice domain is set. The empty slice returns
false
.
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 0];
assert!(bits[.. 2].any());
assert!(!bits[2 ..].any());
Tests if any bit in the slice is unset (logical ¬∧
).
Truth Table
0 0 => 1
0 1 => 1
1 0 => 1
1 1 => 0
Parameters
- `&self
Returns
Whether any bit in the slice domain is unset.
Examples
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 1];
assert!(!bits[.. 2].not_all());
assert!(bits[2 ..].not_all());
Tests if all bits in the slice are unset (logical ¬∨
).
Truth Table
0 0 => 1
0 1 => 0
1 0 => 0
1 1 => 0
Parameters
&self
Returns
Whether all bits in the slice domain are unset.
Examples
use bitvec::prelude::*;
let bits = bits![0, 1, 0, 0];
assert!(!bits[.. 2].not_any());
assert!(bits[2 ..].not_any());
Tests whether the slice has some, but not all, bits set and some, but not all, bits unset.
This is false
if either .all
or .not_any
are true
.
Truth Table
0 0 => 0
0 1 => 1
1 0 => 1
1 1 => 0
Parameters
&self
Returns
Whether the slice domain has mixed content. The empty slice returns
false
.
Examples
use bitvec::prelude::*;
let data = 0b111_000_10u8;
let bits = bits![1, 1, 0, 0, 1, 0];
assert!(!bits[.. 2].some());
assert!(!bits[2 .. 4].some());
assert!(bits.some());
Returns the number of ones in the memory region backing self
.
Parameters
&self
Returns
The number of high bits in the slice domain.
Examples
Basic usage:
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 0];
assert_eq!(bits[.. 2].count_ones(), 2);
assert_eq!(bits[2 ..].count_ones(), 0);
Returns the number of zeros in the memory region backing self
.
Parameters
&self
Returns
The number of low bits in the slice domain.
Examples
Basic usage:
use bitvec::prelude::*;
let bits = bits![1, 1, 0, 0];
assert_eq!(bits[.. 2].count_zeros(), 0);
assert_eq!(bits[2 ..].count_zeros(), 2);
Sets all bits in the slice to a value.
Parameters
&mut self
value
: The bit value to which all bits in the slice will be set.
Examples
use bitvec::prelude::*;
let mut src = 0u8;
let bits = src.view_bits_mut::<Msb0>();
bits[2 .. 6].set_all(true);
assert_eq!(bits.as_slice(), &[0b0011_1100]);
bits[3 .. 5].set_all(false);
assert_eq!(bits.as_slice(), &[0b0010_0100]);
bits[.. 1].set_all(true);
assert_eq!(bits.as_slice(), &[0b1010_0100]);
Applies a function to each bit in the slice.
BitSlice
cannot implement IndexMut
, as it cannot manifest &mut bool
references, and the BitMut
proxy reference has an unavoidable
overhead. This method bypasses both problems, by applying a function to
each pair of index and value in the slice, without constructing a proxy
reference.
Parameters
&mut self
func
: A function which receives two arguments,index: usize
andvalue: bool
, and returns abool
.
Effects
For each index in the slice, the result of invoking func
with the
index number and current bit value is written into the slice.
Examples
use bitvec::prelude::*;
let mut data = 0u8;
let bits = data.view_bits_mut::<Msb0>();
bits.for_each(|idx, _bit| idx % 3 == 0);
assert_eq!(data, 0b100_100_10);
Accesses the total backing storage of the BitSlice
, as a slice of its
elements.
This method produces a slice over all the memory elements it touches, using the current storage parameter. This is safe to do, as any events that would create an aliasing view into the elements covered by the returned slice will also have caused the slice to use its alias-aware type.
Parameters
&self
Returns
A view of the entire memory region this slice covers, including the edge elements.
Examples
use bitvec::prelude::*;
let data = 0x3Cu8;
let bits = &data.view_bits::<LocalBits>()[2 .. 6];
assert!(bits.all());
assert_eq!(bits.len(), 4);
assert_eq!(bits.as_slice(), &[0x3Cu8]);
Views the wholly-filled elements of the BitSlice
.
This will not include partially-owned edge elements, as they may be
aliased by other handles. To gain access to all elements that the
BitSlice
region covers, use one of the following:
.as_slice
produces a shared slice over all elements, marked aliased as appropriate..domain
produces a view describing each component of the region, marking only the contended edges as aliased and the uncontended interior as unaliased.
Parameters
&self
Returns
A slice of all the wholly-filled elements in the BitSlice
backing
storage.
Examples
use bitvec::prelude::*;
let data = [1u8, 66];
let bits = data.view_bits::<Msb0>();
let accum = bits
.as_raw_slice()
.iter()
.copied()
.map(u8::count_ones)
.sum::<u32>();
assert_eq!(accum, 3);
Views the wholly-filled elements of the BitSlice
.
This will not include partially-owned edge elements, as they may be
aliased by other handles. To gain access to all elements that the
BitSlice
region covers, use one of the following:
.as_aliased_slice
produces a shared slice over all elements, marked as aliased to allow for the possibliity of mutation..domain_mut
produces a view describing each component of the region, marking only the contended edges as aliased and the uncontended interior as unaliased.
Parameters
&mut self
Returns
A mutable slice of all the wholly-filled elements in the BitSlice
backing storage.
Examples
use bitvec::prelude::*;
let mut data = [1u8, 64];
let bits = data.view_bits_mut::<Msb0>();
for elt in bits.as_raw_slice_mut() {
*elt |= 2;
}
assert_eq!(&[3, 66], bits.as_slice());
Splits the slice into the logical components of its memory domain.
This produces a set of read-only subslices, marking as much as possible
as affirmatively lacking any write-capable view (T::NoAlias
). The
unaliased view is able to safely perform unsynchronized reads from
memory without causing undefined behavior, as the type system is able to
statically prove that no other write-capable views exist.
Parameters
&self
Returns
A BitDomain
structure representing the logical components of the
memory region.
Safety Exception
The following snippet describes a means of constructing a T::NoAlias
view into memory that is, in fact, aliased:
use bitvec::prelude::*;
use core::sync::atomic::AtomicU8;
type Bs<T> = BitSlice<LocalBits, T>;
let data = [AtomicU8::new(0), AtomicU8::new(0), AtomicU8::new(0)];
let bits: &Bs<AtomicU8> = data.view_bits::<LocalBits>();
let subslice: &Bs<AtomicU8> = &bits[4 .. 20];
let (_, noalias, _): (_, &Bs<u8>, _) =
subslice.bit_domain().region().unwrap();
The noalias
reference, which has memory type u8
, assumes that it can
act as an &u8
reference: unsynchronized loads are permitted, as no
handle exists which is capable of modifying the middle bit of data
.
This means that LLVM is permitted to issue loads from memory wherever
it wants in the block during which noalias
is live, as all loads are
equivalent.
Use of the bits
or subslice
handles, which are still live for the
lifetime of noalias
, to issue .set_aliased
calls into the middle
element introduce undefined behavior. bitvec
permits safe code to
introduce this undefined behavior solely because it requires deliberate
opt-in – you must start from atomic data; this cannot occur when data
is non-atomic – and use of the shared-mutation facility simultaneously
with the unaliasing view.
The .set_aliased
method is speculative, and will be marked as
unsafe
or removed at any suspicion that its presence in the library
has any costs.
Examples
This method can be used to accelerate reads from a slice that is marked as aliased.
use bitvec::prelude::*;
type Bs<T> = BitSlice<LocalBits, T>;
let bits = bits![mut LocalBits, u8; 0; 24];
let (a, b): (
&mut Bs<<u8 as BitStore>::Alias>,
&mut Bs<<u8 as BitStore>::Alias>,
) = bits.split_at_mut(4);
let (partial, full, _): (
&Bs<<u8 as BitStore>::Alias>,
&Bs<<u8 as BitStore>::Mem>,
_,
) = b.bit_domain().region().unwrap();
read_from(partial); // uses alias-aware reads
read_from(full); // uses ordinary reads
Splits the slice into the logical components of its memory domain.
This produces a set of mutable subslices, marking as much as possible as
affirmatively lacking any other view (T::Mem
). The bare view is able
to safely perform unsynchronized reads from and writes to memory without
causing undefined behavior, as the type system is able to statically
prove that no other views exist.
Why This Is More Sound Than .bit_domain
The &mut
exclusion rule makes it impossible to construct two
references over the same memory where one of them is marked &mut
. This
makes it impossible to hold a live reference to memory separately from
any references produced from this method. For the duration of all
references produced by this method, all ancestor references used to
reach this method call are either suspended or dead, and the compiler
will not allow you to use them.
As such, this method cannot introduce undefined behavior where a reference incorrectly believes that the referent memory region is immutable.
Splits the slice into immutable references to its underlying memory components.
Unlike .bit_domain
and .bit_domain_mut
, this does not return
smaller BitSlice
handles but rather appropriately-marked references to
the underlying memory elements.
The aliased references allow mutation of these elements. You are
required to not use mutating methods on these references at all. This
function is not marked unsafe
, but this is a contract you must uphold.
Use .domain_mut
to modify the underlying elements.
It is not currently possible to forbid mutation through these references. This may change in the future.
Safety Exception
As with .bit_domain
, this produces unsynchronized immutable
references over the fully-populated interior elements. If this view is
constructed from a BitSlice
handle over atomic memory, then it will
remove the atomic access behavior for the interior elements. This by
itself is safe, as long as no contemporaneous atomic writes to that
memory can occur. You must not retain and use an atomic reference to the
memory region marked as NoAlias
for the duration of this view’s
existence.
Parameters
&self
Returns
A read-only descriptor of the memory elements backing *self
.
Splits the slice into mutable references to its underlying memory elements.
Like .domain
, this returns appropriately-marked references to the
underlying memory elements. These references are all writable.
The aliased edge references permit modifying memory beyond their bit
marker. You are required to only mutate the region of these edge
elements that you currently govern. This function is not marked
unsafe
, but this is a contract you must uphold.
It is not currently possible to forbid out-of-bounds mutation through these references. This may change in the future.
Parameters
&mut self
Returns
A descriptor of the memory elements underneath *self
, permitting
mutation.
Splits a slice at some mid-point, without checking boundary conditions.
This is generally not recommended; use with caution! For a safe
alternative, see split_at
.
Parameters
&self
mid
: The index at which to split the slice. This must be in the range0 .. self.len()
.
Returns
.0
:&self[.. mid]
.1
:&self[mid ..]
Safety
This function is not safe. It performs raw pointer arithmetic to
construct two new references. If mid
is out of bounds, then the first
slice will be too large, and the second will be catastrophically
incorrect. As both are references to invalid memory, they are undefined
to construct, and may not ever be used.
Examples
use bitvec::prelude::*;
let data = 0x0180u16;
let bits = data.view_bits::<Msb0>();
let (one, two) = unsafe { bits.split_at_unchecked(8) };
assert!(one[7]);
assert!(two[0]);
Splits a mutable slice at some mid-point, without checking boundary conditions.
This is generally not recommended; use with caution! For a safe
alternative, see split_at_mut
.
Parameters
&mut self
mid
: The index at which to split the slice. This must be in the range0 .. self.len()
.
Returns
.0
:&mut self[.. mid]
.1
:&mut self[mid ..]
Safety
This function is not safe. It performs raw pointer arithmetic to
construct two new references. If mid
is out of bounds, then the first
slice will be too large, and the second will be catastrophically
incorrect. As both are references to invalid memory, they are undefined
to construct, and may not ever be used.
Examples
use bitvec::prelude::*;
let mut data = 0u16;
let bits = data.view_bits_mut::<Msb0>();
let (one, two) = unsafe { bits.split_at_unchecked_mut(8) };
one.set(7, true);
two.set(0, true);
assert_eq!(data, 0x0180u16);
Swaps the bits at two indices without checking boundary conditions.
This is generally not recommended; use with caution! For a safe
alternative, see swap
.
Parameters
&mut self
a
: One index to swap.b
: The other index to swap.
Effects
The bit at index a
is written into index b
, and the bit at index b
is written into a
.
Safety
Both a
and b
must be less than self.len()
. Indices greater than
the length will cause out-of-bounds memory access, which can lead to
memory unsafety and a program crash.
Examples
use bitvec::prelude::*;
let mut data = 8u8;
let bits = data.view_bits_mut::<Msb0>();
unsafe { bits.swap_unchecked(0, 4); }
assert_eq!(data, 128);
Copies a bit from one index to another without checking boundary conditions.
Parameters
&mut self
from
: The index whose bit is to be copiedto
: The index into which the copied bit is written.
Effects
The bit at from
is written into to
.
Safety
Both from
and to
must be less than self.len()
, in order for
self
to legally read from and write to them, respectively.
If self
had been split from a larger slice, reading from from
or
writing to to
may not necessarily cause a memory-safety violation in
the Rust model, due to the aliasing system bitvec
employs. However,
writing outside the bounds of a slice reference is always a logical
error, as it causes changes observable by another reference handle.
Examples
use bitvec::prelude::*;
let mut data = 1u8;
let bits = data.view_bits_mut::<Lsb0>();
unsafe { bits.copy_unchecked(0, 2) };
assert_eq!(data, 5);
pub unsafe fn copy_within_unchecked<R>(&mut self, src: R, dest: usize) where
R: RangeBounds<usize>,
pub unsafe fn copy_within_unchecked<R>(&mut self, src: R, dest: usize) where
R: RangeBounds<usize>,
Copies bits from one part of the slice to another part of itself.
src
is the range within self
to copy from. dest
is the starting
index of the range within self
to copy to, which will have the same
length as src
. The two ranges may overlap. The ends of the two ranges
must be less than or equal to self.len()
.
Effects
self[src]
is copied to self[dest .. dest + src.end() - src.start()]
.
Panics
This function will panic if either range exceeds the end of the slice,
or if the end of src
is before the start.
Safety
Both the src
range and the target range dest .. dest + src.len()
must not exceed the self.len()
slice range.
Examples
use bitvec::prelude::*;
let mut data = 0x07u8;
let bits = data.view_bits_mut::<Msb0>();
unsafe { bits.copy_within_unchecked(5 .., 0); }
assert_eq!(data, 0xE7);
Produces the absolute offset in bits between two slice heads.
While this method is sound for any two arbitrary bit slices, the answer it produces is meaningful only when one argument is a strict subslice of the other. If the two slices are created from different buffers entirely, a comparison is undefined; if the two slices are disjoint regions of the same buffer, then the semantically correct distance is between the tail of the lower and the head of the upper, which this does not measure.
Visual Description
Consider the following sequence of bits:
[ 0 1 2 3 4 5 6 7 8 9 a b ]
| ^^^^^^^ |
^^^^^^^^^^^^^^^^^^^^^^^
It does not matter whether there are bits between the tail of the smaller and the larger slices. The offset is computed from the bit distance between the two heads.
Behavior
This function computes the semantic distance between the heads, rather
than the *electrical. It does not take into account the BitOrder
implementation of the slice. See the [::electrical_distance
] method
for that comparison.
Safety and Soundness
One of self
or other
must contain the other for this comparison to
be meaningful.
Parameters
&self
other
: Another bit slice. This must be either a strict subregion or a strict superregion ofself
.
Returns
The distance in (semantic) bits betwen the heads of each region. The
value is positive when other
is higher in the address space than
self
, and negative when other
is lower in the address space than
self
.
[::electrical_distance]
: #method.electrical_comparison
Computes the electrical distance between the heads of two slices.
This method uses the slices’ BitOrder
implementation to compute the
bit position of their heads, then computes the shift distance, in bits,
between them.
This computation presumes that the bits are counted in the same direction as are bytes in the abstract memory map.
Parameters
&self
other
: Another bit slice. This must be either a strict subregion or a strict superregion ofself
.
Returns
The electrical bit distance between the heads of self
and other
.
Splits a mutable slice at some mid-point.
This method has the same behavior as split_at_mut
, except that it
does not apply an aliasing marker to the partitioned subslices.
Safety
Because this method is defined only on BitSlice
s whose T
type is
alias-safe, the subslices do not need to be additionally marked.
Trait Implementations
Performs the conversion.
Performs the conversion.
impl<O, T, Rhs> BitAndAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitAndAssign<Rhs>,
impl<O, T, Rhs> BitAndAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitAndAssign<Rhs>,
Performs the &=
operation. Read more
Loads from self
, using little-endian element T
ordering. Read more
Loads from self
, using big-endian element T
ordering. Read more
Stores into self
, using little-endian element ordering. Read more
Stores into self
, using big-endian element ordering. Read more
Loads the bits in the self
region into a local value. Read more
impl<O, T, Rhs> BitOrAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitOrAssign<Rhs>,
impl<O, T, Rhs> BitOrAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitOrAssign<Rhs>,
Performs the |=
operation. Read more
impl<O, T, Rhs> BitXorAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitXorAssign<Rhs>,
impl<O, T, Rhs> BitXorAssign<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
BitSlice<O, T>: BitXorAssign<Rhs>,
Performs the ^=
operation. Read more
Immutably borrows from an owned value. Read more
fn borrow_mut(&mut self) -> &mut BitSlice<O, T>ⓘ
fn borrow_mut(&mut self) -> &mut BitSlice<O, T>ⓘ
Mutably borrows from an owned value. Read more
Extends a collection with the contents of an iterator. Read more
extend_one
)Extends a collection with exactly one element.
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
Extends a collection with the contents of an iterator. Read more
extend_one
)Extends a collection with exactly one element.
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
Creates a value from an iterator. Read more
Creates a value from an iterator. Read more
type IntoIter = <&'a mut BitSlice<O, T> as IntoIterator>::IntoIter
type IntoIter = <&'a mut BitSlice<O, T> as IntoIterator>::IntoIter
Which kind of iterator are we turning this into?
type Item = <&'a mut BitSlice<O, T> as IntoIterator>::Item
type Item = <&'a mut BitSlice<O, T> as IntoIterator>::Item
The type of the elements being iterated over.
This implementation inverts all elements in the live buffer. You cannot rely
on the value of bits in the buffer that are outside the domain of
BitVec::as_mit_bitslice
.
This method returns an ordering between self
and other
values if one exists. Read more
This method tests less than (for self
and other
) and is used by the <
operator. Read more
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
impl<O, T, Rhs> PartialOrd<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
Rhs: ?Sized + PartialOrd<BitSlice<O, T>>,
impl<O, T, Rhs> PartialOrd<Rhs> for BitVec<O, T> where
O: BitOrder,
T: BitStore,
Rhs: ?Sized + PartialOrd<BitSlice<O, T>>,
This method returns an ordering between self
and other
values if one exists. Read more
This method tests less than (for self
and other
) and is used by the <
operator. Read more
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
Mirrors the implementation on Vec<u8>
(found here).
The implementation copies bytes from buf
into the tail end of self
. The
performance characteristics of this operation are dependent on the type
parameters of the BitVec
, and the position of its tail.
Write a buffer into this writer, returning how many bytes were written. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
can_vector
)Determines if this Write
r has an efficient write_vectored
implementation. Read more
Attempts to write an entire buffer into this writer. Read more
write_all_vectored
)Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Auto Trait Implementations
impl<O, T> RefUnwindSafe for BitVec<O, T> where
O: RefUnwindSafe,
T: RefUnwindSafe,
impl<O, T> UnwindSafe for BitVec<O, T> where
O: RefUnwindSafe,
T: RefUnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
Causes self
to use its Binary
implementation when Debug
-formatted.
Causes self
to use its Display
implementation when
Debug
-formatted. Read more
Causes self
to use its LowerExp
implementation when
Debug
-formatted. Read more
Causes self
to use its LowerHex
implementation when
Debug
-formatted. Read more
Causes self
to use its Octal
implementation when Debug
-formatted.
Causes self
to use its Pointer
implementation when
Debug
-formatted. Read more
Causes self
to use its UpperExp
implementation when
Debug
-formatted. Read more
Causes self
to use its UpperHex
implementation when
Debug
-formatted. Read more
Pipes by value. This is generally the method you want to use. Read more
Borrows self
and passes that borrow into the pipe function. Read more
Mutably borrows self
and passes that borrow into the pipe function. Read more
Borrows self
, then passes self.borrow()
into the pipe function. Read more
Mutably borrows self
, then passes self.borrow_mut()
into the pipe
function. Read more
Borrows self
, then passes self.as_ref()
into the pipe function.
Mutably borrows self
, then passes self.as_mut()
into the pipe
function. Read more
Borrows self
, then passes self.deref()
into the pipe function.
fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more
fn pipe_deref<'a, R>(&'a self, func: impl FnOnce(&'a Self::Target) -> R) -> R where
Self: Deref,
R: 'a,
fn pipe_deref<'a, R>(&'a self, func: impl FnOnce(&'a Self::Target) -> R) -> R where
Self: Deref,
R: 'a,
Pipes a dereference into a function that cannot normally be called in suffix position. Read more
Pipes a reference into a function that cannot ordinarily be called in suffix position. Read more
Immutable access to the Borrow<B>
of a value. Read more
Mutable access to the BorrowMut<B>
of a value. Read more
Immutable access to the AsRef<R>
view of a value. Read more
Mutable access to the AsMut<R>
view of a value. Read more
Immutable access to the Deref::Target
of a value. Read more
Mutable access to the Deref::Target
of a value. Read more
Calls .tap()
only in debug builds, and is erased in release builds.
Calls .tap_mut()
only in debug builds, and is erased in release
builds. Read more
Calls .tap_borrow()
only in debug builds, and is erased in release
builds. Read more
Calls .tap_borrow_mut()
only in debug builds, and is erased in release
builds. Read more
Calls .tap_ref()
only in debug builds, and is erased in release
builds. Read more
Calls .tap_ref_mut()
only in debug builds, and is erased in release
builds. Read more
Calls .tap_deref()
only in debug builds, and is erased in release
builds. Read more
Provides immutable access to the reference for inspection.
Calls tap_ref
in debug builds, and does nothing in release builds.
Provides mutable access to the reference for modification.
Calls tap_ref_mut
in debug builds, and does nothing in release builds.
Provides immutable access to the borrow for inspection. Read more
Calls tap_borrow
in debug builds, and does nothing in release builds.
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Provides mutable access to the borrow for modification.
Immutably dereferences self
for inspection.
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Calls tap_deref
in debug builds, and does nothing in release builds.
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Mutably dereferences self
for modification.