Struct heapless::Vec [−][src]
pub struct Vec<T, const N: usize> { /* fields omitted */ }
Expand description
A fixed capacity Vec
Examples
use heapless::Vec; // A vector with a fixed capacity of 8 elements allocated on the stack let mut vec = Vec::<_, 8>::new(); vec.push(1); vec.push(2); assert_eq!(vec.len(), 2); assert_eq!(vec[0], 1); assert_eq!(vec.pop(), Some(2)); assert_eq!(vec.len(), 1); vec[0] = 7; assert_eq!(vec[0], 7); vec.extend([1, 2, 3].iter().cloned()); for x in &vec { println!("{}", x); } assert_eq!(*vec, [7, 1, 2, 3]);
Implementations
Constructs a new vector with a fixed capacity of N
and fills it
with the provided slice.
This is equivalent to the following code:
use heapless::Vec; let mut v: Vec<u8, 16> = Vec::new(); v.extend_from_slice(&[1, 2, 3]).unwrap();
Extracts a slice containing the entire vector.
Equivalent to &s[..]
.
Examples
use heapless::Vec; let buffer: Vec<u8, 5> = Vec::from_slice(&[1, 2, 3, 5, 8]).unwrap(); assert_eq!(buffer.as_slice(), &[1, 2, 3, 5, 8]);
Returns the contents of the vector as an array of length M
if the length
of the vector is exactly M
, otherwise returns Err(self)
.
Examples
use heapless::Vec; let buffer: Vec<u8, 42> = Vec::from_slice(&[1, 2, 3, 5, 8]).unwrap(); let array: [u8; 5] = buffer.into_array().unwrap(); assert_eq!(array, [1, 2, 3, 5, 8]);
Returns the maximum number of elements the vector can hold.
Clones and appends all elements in a slice to the Vec
.
Iterates over the slice other
, clones each element, and then appends
it to this Vec
. The other
vector is traversed in-order.
Examples
use heapless::Vec; let mut vec = Vec::<u8, 8>::new(); vec.push(1).unwrap(); vec.extend_from_slice(&[2, 3, 4]).unwrap(); assert_eq!(*vec, [1, 2, 3, 4]);
Removes the last element from a vector and returns it, or None
if it’s empty
Appends an item
to the back of the collection
Returns back the item
if the vector is full
Removes the last element from a vector and returns it
Safety
This assumes the vec to have at least one element.
Shortens the vector, keeping the first len
elements and dropping the rest.
Resizes the Vec in-place so that len is equal to new_len.
If new_len is greater than len, the Vec is extended by the difference, with each additional slot filled with value. If new_len is less than len, the Vec is simply truncated.
See also resize_default
.
Resizes the Vec
in-place so that len
is equal to new_len
.
If new_len
is greater than len
, the Vec
is extended by the
difference, with each additional slot filled with Default::default()
.
If new_len
is less than len
, the Vec
is simply truncated.
See also resize
.
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
.
Safety
new_len
must be less than or equal tocapacity()
.- The elements at
old_len..new_len
must be initialized.
Examples
This method can be useful for situations in which the vector is serving as a buffer for other code, particularly over FFI:
use heapless::Vec; pub fn get_dictionary(&self) -> Option<Vec<u8, 32768>> { // Per the FFI method's docs, "32768 bytes is always enough". let mut dict = Vec::new(); let mut dict_length = 0; // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that: // 1. `dict_length` elements were initialized. // 2. `dict_length` <= the capacity (32_768) // which makes `set_len` safe to call. unsafe { // Make the FFI call... let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length); if r == Z_OK { // ...and update the length to what was initialized. dict.set_len(dict_length); Some(dict) } else { None } } }
While the following example is sound, there is a memory leak since
the inner vectors were not freed prior to the set_len
call:
use core::iter::FromIterator; use heapless::Vec; let mut vec = Vec::<Vec<u8, 3>, 3>::from_iter( [ Vec::from_iter([1, 0, 0].iter().cloned()), Vec::from_iter([0, 1, 0].iter().cloned()), Vec::from_iter([0, 0, 1].iter().cloned()), ] .iter() .cloned() ); // SAFETY: // 1. `old_len..0` is empty so no elements need to be initialized. // 2. `0 <= capacity` always holds whatever `capacity` is. unsafe { vec.set_len(0); }
Normally, here, one would use clear
instead to correctly drop
the contents and thus not leak memory.
Removes an element from the vector and returns it.
The removed element is replaced by the last element of the vector.
This does not preserve ordering, but is O(1).
Panics
Panics if index
is out of bounds.
Examples
use heapless::Vec; let mut v: Vec<_, 8> = Vec::new(); v.push("foo").unwrap(); v.push("bar").unwrap(); v.push("baz").unwrap(); v.push("qux").unwrap(); assert_eq!(v.swap_remove(1), "bar"); assert_eq!(&*v, ["foo", "qux", "baz"]); assert_eq!(v.swap_remove(0), "foo"); assert_eq!(&*v, ["baz", "qux"]);
Removes an element from the vector and returns it.
The removed element is replaced by the last element of the vector.
This does not preserve ordering, but is O(1).
Safety
Assumes index
within bounds.
Examples
use heapless::Vec; let mut v: Vec<_, 8> = Vec::new(); v.push("foo").unwrap(); v.push("bar").unwrap(); v.push("baz").unwrap(); v.push("qux").unwrap(); assert_eq!(unsafe { v.swap_remove_unchecked(1) }, "bar"); assert_eq!(&*v, ["foo", "qux", "baz"]); assert_eq!(unsafe { v.swap_remove_unchecked(0) }, "foo"); assert_eq!(&*v, ["baz", "qux"]);
Returns true
if needle
is a prefix of the Vec.
Always returns true
if needle
is an empty slice.
Examples
use heapless::Vec; let v: Vec<_, 8> = Vec::from_slice(b"abc").unwrap(); assert_eq!(v.starts_with(b""), true); assert_eq!(v.starts_with(b"ab"), true); assert_eq!(v.starts_with(b"bc"), false);
Returns true
if needle
is a suffix of the Vec.
Always returns true
if needle
is an empty slice.
Examples
use heapless::Vec; let v: Vec<_, 8> = Vec::from_slice(b"abc").unwrap(); assert_eq!(v.ends_with(b""), true); assert_eq!(v.ends_with(b"ab"), false); assert_eq!(v.ends_with(b"bc"), true);
Trait Implementations
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
impl<T, const N1: usize, const N2: usize> PartialOrd<Vec<T, N2>> for Vec<T, N1> where
T: PartialOrd,
impl<T, const N1: usize, const N2: usize> PartialOrd<Vec<T, N2>> for Vec<T, N1> where
T: PartialOrd,
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
Writes a string slice into this writer, returning whether the write succeeded. Read more