Struct typed_headers::AcceptEncoding

pub struct AcceptEncoding(pub Vec<QualityItem<ContentCoding>>);

Accept-Encoding header, defined in RFC7231

The Accept-Encoding header field can be used by user agents to indicate what response content-codings are acceptable in the response. An identity token is used as a synonym for "no encoding" in order to communicate when no encoding is preferred.

ABNF

Accept-Encoding  = #( codings [ weight ] )
codings          = content-coding / "identity" / "*"

Example values

• compress, gzip
• ``
• *
• compress;q=0.5, gzip;q=1
• gzip;q=1.0, identity; q=0.5, *;q=0

Methods from Deref<Target = Vec<QualityItem<ContentCoding>>>

pub fn capacity(&self) -> usize

Returns the number of elements the vector can hold without reallocating.

Examples

let vec: Vec<i32> = Vec::with_capacity(10);
assert_eq!(vec.capacity(), 10);

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

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

Panics

Panics if the new capacity overflows usize.

Examples

let mut vec = vec![1];
vec.reserve(10);
assert!(vec.capacity() >= 11);

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

Reserves the minimum capacity for exactly additional more elements to be inserted in the given Vec<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.

Panics

Panics if the new capacity overflows usize.

Examples

let mut vec = vec![1];
vec.reserve_exact(10);
assert!(vec.capacity() >= 11);

pub fn try_reserve(
    &mut self,
    additional: usize
) -> Result<(), CollectionAllocErr>

🔬 This is a nightly-only experimental API. (try_reserve)

new API

Tries to reserve capacity for at least additional more elements to be inserted in the given Vec<T>. The collection may reserve more space to avoid frequent reallocations. After calling reserve, capacity will be greater than or equal to self.len() + additional. Does nothing if capacity is already sufficient.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

#![feature(try_reserve)]
use std::collections::CollectionAllocErr;

fn process_data(data: &[u32]) -> Result<Vec<u32>, CollectionAllocErr> {
    let mut output = Vec::new();

    // Pre-reserve the memory, exiting if we can't
    output.try_reserve(data.len())?;

    // Now we know this can't OOM in the middle of our complex work
    output.extend(data.iter().map(|&val| {
        val * 2 + 5 // very complicated
    }));

    Ok(output)
}

pub fn try_reserve_exact(
    &mut self,
    additional: usize
) -> Result<(), CollectionAllocErr>

🔬 This is a nightly-only experimental API. (try_reserve)

new API

Tries to reserves the minimum capacity for exactly additional more elements to be inserted in the given Vec<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.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

#![feature(try_reserve)]
use std::collections::CollectionAllocErr;

fn process_data(data: &[u32]) -> Result<Vec<u32>, CollectionAllocErr> {
    let mut output = Vec::new();

    // Pre-reserve the memory, exiting if we can't
    output.try_reserve(data.len())?;

    // Now we know this can't OOM in the middle of our complex work
    output.extend(data.iter().map(|&val| {
        val * 2 + 5 // very complicated
    }));

    Ok(output)
}

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the vector as much as possible.

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

Examples

let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3].iter().cloned());
assert_eq!(vec.capacity(), 10);
vec.shrink_to_fit();
assert!(vec.capacity() >= 3);

pub fn shrink_to(&mut self, min_capacity: usize)

🔬 This is a nightly-only experimental API. (shrink_to)

new API

Shrinks the capacity of the vector with a lower bound.

The capacity will remain at least as large as both the length and the supplied value.

Panics if the current capacity is smaller than the supplied minimum capacity.

Examples

#![feature(shrink_to)]
let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3].iter().cloned());
assert_eq!(vec.capacity(), 10);
vec.shrink_to(4);
assert!(vec.capacity() >= 4);
vec.shrink_to(0);
assert!(vec.capacity() >= 3);

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

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

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

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

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

Examples

Truncating a five element vector to two elements:

let mut vec = vec![1, 2, 3, 4, 5];
vec.truncate(2);
assert_eq!(vec, [1, 2]);

No truncation occurs when len is greater than the vector's current length:

let mut vec = vec![1, 2, 3];
vec.truncate(8);
assert_eq!(vec, [1, 2, 3]);

Truncating when len == 0 is equivalent to calling the clear method.

let mut vec = vec![1, 2, 3];
vec.truncate(0);
assert_eq!(vec, []);

pub fn as_slice(&self) -> &[T]

Extracts a slice containing the entire vector.

Equivalent to &s[..].

Examples

use std::io::{self, Write};
let buffer = vec![1, 2, 3, 5, 8];
io::sink().write(buffer.as_slice()).unwrap();

pub fn as_mut_slice(&mut self) -> &mut [T]

Extracts a mutable slice of the entire vector.

Equivalent to &mut s[..].

Examples

use std::io::{self, Read};
let mut buffer = vec![0; 3];
io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();

pub unsafe fn set_len(&mut self, new_len: usize)

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 to capacity().
• 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:

pub fn get_dictionary(&self) -> Option<Vec<u8>> {
    // Per the FFI method's docs, "32768 bytes is always enough".
    let mut dict = Vec::with_capacity(32_768);
    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:

let mut vec = vec![vec![1, 0, 0],
                   vec![0, 1, 0],
                   vec![0, 0, 1]];
// 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.

pub fn swap_remove(&mut self, index: usize) -> T

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

let mut v = vec!["foo", "bar", "baz", "qux"];

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"]);

pub fn insert(&mut self, index: usize, element: T)

Inserts an element at position index within the vector, shifting all elements after it to the right.

Panics

Panics if index > len.

Examples

let mut vec = vec![1, 2, 3];
vec.insert(1, 4);
assert_eq!(vec, [1, 4, 2, 3]);
vec.insert(4, 5);
assert_eq!(vec, [1, 4, 2, 3, 5]);

pub fn remove(&mut self, index: usize) -> T

Removes and returns the element at position index within the vector, shifting all elements after it to the left.

Panics

Panics if index is out of bounds.

Examples

let mut v = vec![1, 2, 3];
assert_eq!(v.remove(1), 2);
assert_eq!(v, [1, 3]);

pub fn retain<F>(&mut self, f: F) where
    F: FnMut(&T) -> bool, 

Retains only the elements specified by the predicate.

In other words, remove all elements e such that f(&e) returns false. This method operates in place and preserves the order of the retained elements.

Examples

let mut vec = vec![1, 2, 3, 4];
vec.retain(|&x| x%2 == 0);
assert_eq!(vec, [2, 4]);

pub fn dedup_by_key<F, K>(&mut self, key: F) where
    F: FnMut(&mut T) -> K,
    K: PartialEq<K>, 

Removes all but the first of consecutive elements in the vector that resolve to the same key.

If the vector is sorted, this removes all duplicates.

Examples

let mut vec = vec![10, 20, 21, 30, 20];

vec.dedup_by_key(|i| *i / 10);

assert_eq!(vec, [10, 20, 30, 20]);

pub fn dedup_by<F>(&mut self, same_bucket: F) where
    F: FnMut(&mut T, &mut T) -> bool, 

Removes all but the first of consecutive elements in the vector satisfying a given equality relation.

The same_bucket function is passed references to two elements from the vector and must determine if the elements compare equal. The elements are passed in opposite order from their order in the slice, so if same_bucket(a, b) returns true, a is removed.

If the vector is sorted, this removes all duplicates.

Examples

let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];

vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));

assert_eq!(vec, ["foo", "bar", "baz", "bar"]);

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

Appends an element to the back of a collection.

Panics

Panics if the number of elements in the vector overflows a usize.

Examples

let mut vec = vec![1, 2];
vec.push(3);
assert_eq!(vec, [1, 2, 3]);

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

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

Examples

let mut vec = vec![1, 2, 3];
assert_eq!(vec.pop(), Some(3));
assert_eq!(vec, [1, 2]);

pub fn append(&mut self, other: &mut Vec<T>)

Moves all the elements of other into Self, leaving other empty.

Panics

Panics if the number of elements in the vector overflows a usize.

Examples

let mut vec = vec![1, 2, 3];
let mut vec2 = vec![4, 5, 6];
vec.append(&mut vec2);
assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
assert_eq!(vec2, []);

pub fn drain<R>(&mut self, range: R) -> Drain<T> where
    R: RangeBounds<usize>, 

Creates a draining iterator that removes the specified range in the vector and yields the removed items.

Note 1: The element range is removed even if the iterator is only partially consumed or not consumed at all.

Note 2: It is unspecified how many elements are removed from the vector if the Drain value is leaked.

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

let mut v = vec![1, 2, 3];
let u: Vec<_> = v.drain(1..).collect();
assert_eq!(v, &[1]);
assert_eq!(u, &[2, 3]);

// A full range clears the vector
v.drain(..);
assert_eq!(v, &[]);

pub fn clear(&mut self)

Clears the vector, removing all values.

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

Examples

let mut v = vec![1, 2, 3];

v.clear();

assert!(v.is_empty());

pub fn len(&self) -> usize

Returns the number of elements in the vector, also referred to as its 'length'.

Examples

let a = vec![1, 2, 3];
assert_eq!(a.len(), 3);

pub fn is_empty(&self) -> bool

Returns true if the vector contains no elements.

Examples

let mut v = Vec::new();
assert!(v.is_empty());

v.push(1);
assert!(!v.is_empty());

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

Splits the collection into two at the given index.

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

Note that the capacity of self does not change.

Panics

Panics if at > len.

Examples

let mut vec = vec![1,2,3];
let vec2 = vec.split_off(1);
assert_eq!(vec, [1]);
assert_eq!(vec2, [2, 3]);

pub fn resize_with<F>(&mut self, new_len: usize, f: F) where
    F: FnMut() -> T, 

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 the result of calling the closure f. The return values from f will end up in the Vec 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 value, use resize. If you want to use the Default trait to generate values, you can pass Default::default() as the second argument.

Examples

let mut vec = vec![1, 2, 3];
vec.resize_with(5, Default::default);
assert_eq!(vec, [1, 2, 3, 0, 0]);

let mut vec = vec![];
let mut p = 1;
vec.resize_with(4, || { p *= 2; p });
assert_eq!(vec, [2, 4, 8, 16]);

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

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.

This method requires Clone to be able clone the passed value. If you need more flexibility (or want to rely on Default instead of Clone), use resize_with.

Examples

let mut vec = vec!["hello"];
vec.resize(3, "world");
assert_eq!(vec, ["hello", "world", "world"]);

let mut vec = vec![1, 2, 3, 4];
vec.resize(2, 0);
assert_eq!(vec, [1, 2]);

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

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.

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

Examples

let mut vec = vec![1];
vec.extend_from_slice(&[2, 3, 4]);
assert_eq!(vec, [1, 2, 3, 4]);

pub fn resize_default(&mut self, new_len: usize)

Deprecated since 1.33.0:

This is moving towards being removed in favor of .resize_with(Default::default). If you disagree, please comment in the tracking issue.

🔬 This is a nightly-only experimental API. (vec_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.

This method uses Default to create new values on every push. If you'd rather Clone a given value, use resize.

Examples

#![feature(vec_resize_default)]

let mut vec = vec![1, 2, 3];
vec.resize_default(5);
assert_eq!(vec, [1, 2, 3, 0, 0]);

let mut vec = vec![1, 2, 3, 4];
vec.resize_default(2);
assert_eq!(vec, [1, 2]);

pub fn dedup(&mut self)

Removes consecutive repeated elements in the vector according to the PartialEq trait implementation.

If the vector is sorted, this removes all duplicates.

Examples

let mut vec = vec![1, 2, 2, 3, 2];

vec.dedup();

assert_eq!(vec, [1, 2, 3, 2]);

pub fn remove_item(&mut self, item: &T) -> Option<T>

🔬 This is a nightly-only experimental API. (vec_remove_item)

recently added

Removes the first instance of item from the vector if the item exists.

Examples

let mut vec = vec![1, 2, 3, 1];

vec.remove_item(&1);

assert_eq!(vec, vec![2, 3, 1]);

pub fn splice<R, I>(
    &mut self,
    range: R,
    replace_with: I
) -> Splice<<I as IntoIterator>::IntoIter> where
    I: IntoIterator<Item = T>,
    R: RangeBounds<usize>, 

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.

Note 1: The element range is removed even if the iterator is not consumed until the end.

Note 2: It is unspecified how many elements are removed from the vector, if the Splice value is leaked.

Note 3: The input iterator replace_with is only consumed when the Splice value is dropped.

Note 4: This is optimal if:

• The tail (elements in the vector after range) is empty,
• or replace_with yields fewer elements than range’s length
• or the lower bound of its size_hint() is exact.

Otherwise, a temporary vector is allocated and the tail is moved twice.

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

let mut v = vec![1, 2, 3];
let new = [7, 8];
let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect();
assert_eq!(v, &[7, 8, 3]);
assert_eq!(u, &[1, 2]);

pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<T, F> where
    F: FnMut(&mut T) -> bool, 

🔬 This is a nightly-only experimental API. (drain_filter)

recently added

Creates an iterator which uses a closure to determine if an element should be removed.

If the closure returns true, then the element is removed and yielded. If the closure returns false, the element will remain in the vector and will not be yielded by the iterator.

Using this method is equivalent to the following code:

let mut i = 0;
while i != vec.len() {
    if some_predicate(&mut vec[i]) {
        let val = vec.remove(i);
        // your code here
    } else {
        i += 1;
    }
}

But drain_filter is easier to use. drain_filter is also more efficient, because it can backshift the elements of the array in bulk.

Note that drain_filter also lets you mutate every element in the filter closure, regardless of whether you choose to keep or remove it.

Examples

Splitting an array into evens and odds, reusing the original allocation:

#![feature(drain_filter)]
let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];

let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
let odds = numbers;

assert_eq!(evens, vec![2, 4, 6, 8, 14]);
assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);

Trait Implementations

impl Header for AcceptEncoding

fn name() -> &'static HeaderName

Returns the name of this header.

fn from_values(
    values: &mut ValueIter<HeaderValue>
) -> Result<Option<AcceptEncoding>, Error>

Parses the header from the raw value bytes.

fn to_values(&self, values: &mut ToValues)

Serializes the header to raw values.

impl Clone for AcceptEncoding

fn clone(&self) -> AcceptEncoding

Returns a copy of the value.

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

Performs copy-assignment from source.

impl PartialEq<AcceptEncoding> for AcceptEncoding

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

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

fn ne(&self, other: &AcceptEncoding) -> bool

This method tests for !=.

impl DerefMut for AcceptEncoding

fn deref_mut(&mut self) -> &mut Vec<QualityItem<ContentCoding>>

Mutably dereferences the value.

impl Deref for AcceptEncoding

type Target = Vec<QualityItem<ContentCoding>>

The resulting type after dereferencing.

fn deref(&self) -> &Vec<QualityItem<ContentCoding>>

Dereferences the value.

impl Debug for AcceptEncoding

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

Formats the value using the given formatter.