Struct bytes::Bytes [] [src]

pub struct Bytes { /* fields omitted */ }

A reference counted contiguous slice of memory.

Bytes is an efficient container for storing and operating on contiguous slices of memory. It is intended for use primarily in networking code, but could have applications elsewhere as well.

Bytes values facilitate zero-copy network programming by allowing multiple Bytes objects to point to the same underlying memory. This is managed by using a reference count to track when the memory is no longer needed and can be freed.

use bytes::Bytes;

let mut mem = Bytes::from(&b"Hello world"[..]);
let a = mem.slice(0, 5);

assert_eq!(&a[..], b"Hello");

let b = mem.split_to(6);

assert_eq!(&mem[..], b"world");
assert_eq!(&b[..], b"Hello ");

Memory layout

The Bytes struct itself is fairly small, limited to a pointer to the memory and 4 usize fields used to track information about which segment of the underlying memory the Bytes handle has access to.

The memory layout looks like this:

+-------+
| Bytes |
+-------+
 /      \_____
|              \
v               v
+-----+------------------------------------+
| Arc |         |      Data     |          |
+-----+------------------------------------+

Bytes keeps both a pointer to the shared Arc containing the full memory slice and a pointer to the start of the region visible by the handle. Bytes also tracks the length of its view into the memory.

Sharing

The memory itself is reference counted, and multiple Bytes objects may point to the same region. Each Bytes handle point to different sections within the memory region, and Bytes handle may or may not have overlapping views into the memory.


   Arc ptrs                   +---------+
   ________________________ / | Bytes 2 |
  /                           +---------+
 /          +-----------+     |         |
|_________/ |  Bytes 1  |     |         |
|           +-----------+     |         |
|           |           | ___/ data     | tail
|      data |      tail |/              |
v           v           v               v
+-----+---------------------------------+-----+
| Arc |     |           |               |     |
+-----+---------------------------------+-----+

Mutating

While Bytes handles may potentially represent overlapping views of the underlying memory slice and may not be mutated, BytesMut handles are guaranteed to be the only handle able to view that slice of memory. As such, BytesMut handles are able to mutate the underlying memory. Note that holding a unique view to a region of memory does not mean that there are no other Bytes and BytesMut handles with disjoint views of the underlying memory.

Inline bytes

As an optimization, when the slice referenced by a Bytes or BytesMut handle is small enough 1, with_capacity will avoid the allocation by inlining the slice directly in the handle. In this case, a clone is no longer "shallow" and the data will be copied. Converting from a Vec will never use inlining.


  1. Small enough: 31 bytes on 64 bit systems, 15 on 32 bit systems. 

Methods

impl Bytes
[src]

Creates a new Bytes with the specified capacity.

The returned Bytes will be able to hold at least capacity bytes without reallocating. If capacity is under 4 * size_of::<usize>() - 1, then BytesMut will not allocate.

It is important to note that this function does not specify the length of the returned Bytes, but only the capacity.

Examples

use bytes::Bytes;

let mut bytes = Bytes::with_capacity(64);

// `bytes` contains no data, even though there is capacity
assert_eq!(bytes.len(), 0);

bytes.extend_from_slice(&b"hello world"[..]);

assert_eq!(&bytes[..], b"hello world");

Creates a new empty Bytes.

This will not allocate and the returned Bytes handle will be empty.

Examples

use bytes::Bytes;

let b = Bytes::new();
assert_eq!(&b[..], b"");

Creates a new Bytes from a static slice.

The returned Bytes will point directly to the static slice. There is no allocating or copying.

Examples

use bytes::Bytes;

let b = Bytes::from_static(b"hello");
assert_eq!(&b[..], b"hello");

Returns the number of bytes contained in this Bytes.

Examples

use bytes::Bytes;

let b = Bytes::from(&b"hello"[..]);
assert_eq!(b.len(), 5);

Returns true if the Bytes has a length of 0.

Examples

use bytes::Bytes;

let b = Bytes::new();
assert!(b.is_empty());

Return true if the Bytes uses inline allocation

Examples

use bytes::Bytes;

assert!(Bytes::with_capacity(4).is_inline());
assert!(!Bytes::from(Vec::with_capacity(4)).is_inline());
assert!(!Bytes::with_capacity(1024).is_inline());

Returns a slice of self for the index range [begin..end).

This will increment the reference count for the underlying memory and return a new Bytes handle set to the slice.

This operation is O(1).

Examples

use bytes::Bytes;

let a = Bytes::from(&b"hello world"[..]);
let b = a.slice(2, 5);

assert_eq!(&b[..], b"llo");

Panics

Requires that begin <= end and end <= self.len(), otherwise slicing will panic.

Returns a slice of self for the index range [begin..self.len()).

This will increment the reference count for the underlying memory and return a new Bytes handle set to the slice.

This operation is O(1) and is equivalent to self.slice(begin, self.len()).

Examples

use bytes::Bytes;

let a = Bytes::from(&b"hello world"[..]);
let b = a.slice_from(6);

assert_eq!(&b[..], b"world");

Panics

Requires that begin <= self.len(), otherwise slicing will panic.

Returns a slice of self for the index range [0..end).

This will increment the reference count for the underlying memory and return a new Bytes handle set to the slice.

This operation is O(1) and is equivalent to self.slice(0, end).

Examples

use bytes::Bytes;

let a = Bytes::from(&b"hello world"[..]);
let b = a.slice_to(5);

assert_eq!(&b[..], b"hello");

Panics

Requires that end <= self.len(), otherwise slicing will panic.

Splits the bytes into two at the given index.

Afterwards self contains elements [0, at), and the returned Bytes contains elements [at, len).

This is an O(1) operation that just increases the reference count and sets a few indices.

Examples

use bytes::Bytes;

let mut a = Bytes::from(&b"hello world"[..]);
let b = a.split_off(5);

assert_eq!(&a[..], b"hello");
assert_eq!(&b[..], b" world");

Panics

Panics if at > len.

Splits the bytes into two at the given index.

Afterwards self contains elements [at, len), and the returned Bytes contains elements [0, at).

This is an O(1) operation that just increases the reference count and sets a few indices.

Examples

use bytes::Bytes;

let mut a = Bytes::from(&b"hello world"[..]);
let b = a.split_to(5);

assert_eq!(&a[..], b" world");
assert_eq!(&b[..], b"hello");

Panics

Panics if at > len.

Shortens the buffer, keeping the first len bytes and dropping the rest.

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

The split_off method can emulate truncate, but this causes the excess bytes to be returned instead of dropped.

Examples

use bytes::Bytes;

let mut buf = Bytes::from(&b"hello world"[..]);
buf.truncate(5);
assert_eq!(buf, b"hello"[..]);

Shortens the buffer, dropping the first cnt bytes and keeping the rest.

This is the same function as Buf::advance, and in the next breaking release of bytes, this implementation will be removed in favor of having Bytes implement Buf.

Panics

This function panics if cnt is greater than self.len()

Clears the buffer, removing all data.

Examples

use bytes::Bytes;

let mut buf = Bytes::from(&b"hello world"[..]);
buf.clear();
assert!(buf.is_empty());

Attempts to convert into a BytesMut handle.

This will only succeed if there are no other outstanding references to the underlying chunk of memory. Bytes handles that contain inlined bytes will always be convertable to BytesMut.

Examples

use bytes::Bytes;

let a = Bytes::from(&b"Mary had a little lamb, little lamb, little lamb..."[..]);

// Create a shallow clone
let b = a.clone();

// This will fail because `b` shares a reference with `a`
let a = a.try_mut().unwrap_err();

drop(b);

// This will succeed
let mut a = a.try_mut().unwrap();

a[0] = b'b';

assert_eq!(&a[..4], b"bary");

Acquires a mutable reference to the owned form of the data.

Clones the data if it is not already owned.

Appends given bytes to this object.

If this Bytes object has not enough capacity, it is resized first. If it is shared (refcount > 1), it is copied first.

This operation can be less effective than the similar operation on BytesMut, especially on small additions.

Examples

use bytes::Bytes;

let mut buf = Bytes::from("aabb");
buf.extend_from_slice(b"ccdd");
buf.extend_from_slice(b"eeff");

assert_eq!(b"aabbccddeeff", &buf[..]);

Combine splitted Bytes objects back as contiguous.

If Bytes objects were not contiguous originally, they will be extended.

Examples

use bytes::Bytes;

let mut buf = Bytes::with_capacity(64);
buf.extend_from_slice(b"aaabbbcccddd");

let splitted = buf.split_off(6);
assert_eq!(b"aaabbb", &buf[..]);
assert_eq!(b"cccddd", &splitted[..]);

buf.unsplit(splitted);
assert_eq!(b"aaabbbcccddd", &buf[..]);

Methods from Deref<Target=[u8]>

Returns the number of elements in the slice.

Example

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

Returns true if the slice has a length of 0.

Example

let a = [1, 2, 3];
assert!(!a.is_empty());

Returns the first element of a slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&10), v.first());

let w: &[i32] = &[];
assert_eq!(None, w.first());

Returns the first and all the rest of the elements of a slice.

Examples

let x = &[0, 1, 2];

if let Some((first, elements)) = x.split_first() {
    assert_eq!(first, &0);
    assert_eq!(elements, &[1, 2]);
}

Returns the last and all the rest of the elements of a slice.

Examples

let x = &[0, 1, 2];

if let Some((last, elements)) = x.split_last() {
    assert_eq!(last, &2);
    assert_eq!(elements, &[0, 1]);
}

Returns the last element of a slice, or None if it is empty.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&30), v.last());

let w: &[i32] = &[];
assert_eq!(None, w.last());

Returns the element of a slice at the given index, or None if the index is out of bounds.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(None, v.get(3));

Returns a pointer to the element at the given index, without doing bounds checking. So use it very carefully!

Examples

let x = &[1, 2, 4];

unsafe {
    assert_eq!(x.get_unchecked(1), &2);
}

Returns an raw pointer to the slice's buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

Modifying the slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

Examples

let x = &[1, 2, 4];
let x_ptr = x.as_ptr();

unsafe {
    for i in 0..x.len() {
        assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
    }
}

Returns an iterator over the slice.

Examples

let x = &[1, 2, 4];
let mut iterator = x.iter();

assert_eq!(iterator.next(), Some(&1));
assert_eq!(iterator.next(), Some(&2));
assert_eq!(iterator.next(), Some(&4));
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.

Panics

Panics if size is 0.

Example

let slice = ['r', 'u', 's', 't'];
let mut iter = slice.windows(2);
assert_eq!(iter.next().unwrap(), &['r', 'u']);
assert_eq!(iter.next().unwrap(), &['u', 's']);
assert_eq!(iter.next().unwrap(), &['s', 't']);
assert!(iter.next().is_none());

If the slice is shorter than size:

let slice = ['f', 'o', 'o'];
let mut iter = slice.windows(4);
assert!(iter.next().is_none());

Returns an iterator over size elements of the slice at a time. The chunks are slices and do not overlap. If size does not divide the length of the slice, then the last chunk will not have length size.

Panics

Panics if size is 0.

Example

let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert_eq!(iter.next().unwrap(), &['m']);
assert!(iter.next().is_none());

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).

Panics

Panics if mid > len.

Examples

let v = [10, 40, 30, 20, 50];
let (v1, v2) = v.split_at(2);
assert_eq!([10, 40], v1);
assert_eq!([30, 20, 50], v2);

Returns an iterator over subslices separated by elements that match pred. The matched element is not contained in the subslices.

Examples

let slice = [10, 40, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the first element 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:

let slice = [10, 40, 33];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[]);
assert!(iter.next().is_none());

If two matched elements are directly adjacent, an empty slice will be present between them:

let slice = [10, 6, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10]);
assert_eq!(iter.next().unwrap(), &[]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once by numbers divisible by 3 (i.e. [10, 40], [20, 60, 50]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.splitn(2, |num| *num % 3 == 0) {
    println!("{:?}", group);
}

Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once, starting from the end, by numbers divisible by 3 (i.e. [50], [10, 40, 30, 20]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.rsplitn(2, |num| *num % 3 == 0) {
    println!("{:?}", group);
}

Returns true if the slice contains an element with the given value.

Examples

let v = [10, 40, 30];
assert!(v.contains(&30));
assert!(!v.contains(&50));

Returns true if needle is a prefix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.starts_with(&[10]));
assert!(v.starts_with(&[10, 40]));
assert!(!v.starts_with(&[50]));
assert!(!v.starts_with(&[10, 50]));

Returns true if needle is a suffix of the slice.

Examples

let v = [10, 40, 30];
assert!(v.ends_with(&[30]));
assert!(v.ends_with(&[40, 30]));
assert!(!v.ends_with(&[50]));
assert!(!v.ends_with(&[50, 30]));

Binary search a sorted slice for a given element.

If the value is found then Ok is returned, containing the index of the matching element; if the value is not found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Example

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

assert_eq!(s.binary_search(&13),  Ok(9));
assert_eq!(s.binary_search(&4),   Err(7));
assert_eq!(s.binary_search(&100), Err(13));
let r = s.binary_search(&1);
assert!(match r { Ok(1...4) => true, _ => false, });

Binary search a sorted slice with a comparator function.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is Less, Equal or Greater the desired target.

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Example

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

let seek = 13;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
let seek = 4;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
let seek = 100;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
let seek = 1;
let r = s.binary_search_by(|probe| probe.cmp(&seek));
assert!(match r { Ok(1...4) => true, _ => false, });

Binary search a sorted slice with a key extraction function.

Assumes that the slice is sorted by the key, for instance with sort_by_key using the same key extraction function.

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements in a slice of pairs sorted by their second elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
         (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
         (1, 21), (2, 34), (4, 55)];

assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b),  Ok(9));
assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b),   Err(7));
assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
let r = s.binary_search_by_key(&1, |&(a,b)| b);
assert!(match r { Ok(1...4) => true, _ => false, });

Copies self into a new Vec.

Examples

let s = [10, 40, 30];
let x = s.to_vec();
// Here, `s` and `x` can be modified independently.

Converts self into a vector without clones or allocation.

Examples

let s: Box<[i32]> = Box::new([10, 40, 30]);
let x = s.into_vec();
// `s` cannot be used anymore because it has been converted into `x`.

assert_eq!(x, vec![10, 40, 30]);

Trait Implementations

impl FromBuf for Bytes
[src]

Creates a value from a buffer. Read more

impl IntoBuf for Bytes
[src]

The Buf type that self is being converted into

Creates a Buf from a value. Read more

impl<'a> IntoBuf for &'a Bytes
[src]

The Buf type that self is being converted into

Creates a Buf from a value. Read more

impl Clone for Bytes
[src]

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl AsRef<[u8]> for Bytes
[src]

Performs the conversion.

impl Deref for Bytes
[src]

The resulting type after dereferencing

The method called to dereference a value

impl From<BytesMut> for Bytes
[src]

Performs the conversion.

impl From<Vec<u8>> for Bytes
[src]

Convert a Vec into a Bytes

This constructor may be used to avoid the inlining optimization used by with_capacity. A Bytes constructed this way will always store its data on the heap.

impl From<String> for Bytes
[src]

Performs the conversion.

impl<'a> From<&'a [u8]> for Bytes
[src]

Performs the conversion.

impl<'a> From<&'a str> for Bytes
[src]

Performs the conversion.

impl FromIterator<u8> for Bytes
[src]

Creates a value from an iterator. Read more

impl PartialEq for Bytes
[src]

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

This method tests for !=.

impl PartialOrd for Bytes
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl Ord for Bytes
[src]

This method returns an Ordering between self and other. Read more

impl Eq for Bytes
[src]

impl Default for Bytes
[src]

Returns the "default value" for a type. Read more

impl Debug for Bytes
[src]

Formats the value using the given formatter.

impl Hash for Bytes
[src]

Feeds this value into the state given, updating the hasher as necessary.

Feeds a slice of this type into the state provided.

impl Borrow<[u8]> for Bytes
[src]

Immutably borrows from an owned value. Read more

impl IntoIterator for Bytes
[src]

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

impl<'a> IntoIterator for &'a Bytes
[src]

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

impl Extend<u8> for Bytes
[src]

Extends a collection with the contents of an iterator. Read more

impl<'a> Extend<&'a u8> for Bytes
[src]

Extends a collection with the contents of an iterator. Read more

impl PartialEq<[u8]> for Bytes
[src]

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

This method tests for !=.

impl PartialOrd<[u8]> for Bytes
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl PartialEq<str> for Bytes
[src]

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

This method tests for !=.

impl PartialOrd<str> for Bytes
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl PartialEq<Vec<u8>> for Bytes
[src]

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

This method tests for !=.

impl PartialOrd<Vec<u8>> for Bytes
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl PartialEq<String> for Bytes
[src]

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

This method tests for !=.

impl PartialOrd<String> for Bytes
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes where Bytes: PartialEq<T>
[src]

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

This method tests for !=.

impl<'a, T: ?Sized> PartialOrd<&'a T> for Bytes where Bytes: PartialOrd<T>
[src]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl PartialEq<BytesMut> for Bytes
[src]

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

This method tests for !=.