[][src]Struct bytes::BytesMut

pub struct BytesMut { /* fields omitted */ }

A unique reference to a contiguous slice of memory.

BytesMut represents a unique view into a potentially shared memory region. Given the uniqueness guarantee, owners of BytesMut handles are able to mutate the memory. It is similar to a Vec<u8> but with less copies and allocations.

Growth

BytesMut's BufMut implementation will implicitly grow its buffer as necessary. However, explicitly reserving the required space up-front before a series of inserts will be more efficient.

Examples

use bytes::{BytesMut, BufMut};

let mut buf = BytesMut::with_capacity(64);

buf.put_u8(b'h');
buf.put_u8(b'e');
buf.put(&b"llo"[..]);

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

// Freeze the buffer so that it can be shared
let a = buf.freeze();

// This does not allocate, instead `b` points to the same memory.
let b = a.clone();

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

Implementations

impl BytesMut[src]

pub fn with_capacity(capacity: usize) -> BytesMut[src]

Creates a new BytesMut with the specified capacity.

The returned BytesMut 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 BytesMut, but only the capacity.

Examples

use bytes::{BytesMut, BufMut};

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

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

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

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

pub fn new() -> BytesMut[src]

Creates a new BytesMut with default capacity.

Resulting object has length 0 and unspecified capacity. This function does not allocate.

Examples

use bytes::{BytesMut, BufMut};

let mut bytes = BytesMut::new();

assert_eq!(0, bytes.len());

bytes.reserve(2);
bytes.put_slice(b"xy");

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

pub fn len(&self) -> usize[src]

Returns the number of bytes contained in this BytesMut.

Examples

use bytes::BytesMut;

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

pub fn is_empty(&self) -> bool[src]

Returns true if the BytesMut has a length of 0.

Examples

use bytes::BytesMut;

let b = BytesMut::with_capacity(64);
assert!(b.is_empty());

pub fn capacity(&self) -> usize[src]

Returns the number of bytes the BytesMut can hold without reallocating.

Examples

use bytes::BytesMut;

let b = BytesMut::with_capacity(64);
assert_eq!(b.capacity(), 64);

pub fn freeze(self) -> Bytes[src]

Converts self into an immutable Bytes.

The conversion is zero cost and is used to indicate that the slice referenced by the handle will no longer be mutated. Once the conversion is done, the handle can be cloned and shared across threads.

Examples

use bytes::{BytesMut, BufMut};
use std::thread;

let mut b = BytesMut::with_capacity(64);
b.put(&b"hello world"[..]);
let b1 = b.freeze();
let b2 = b1.clone();

let th = thread::spawn(move || {
    assert_eq!(&b1[..], b"hello world");
});

assert_eq!(&b2[..], b"hello world");
th.join().unwrap();

#[must_use = "consider BytesMut::truncate if you don't need the other half"]pub fn split_off(&mut self, at: usize) -> BytesMut[src]

Splits the bytes into two at the given index.

Afterwards self contains elements [0, at), and the returned BytesMut contains elements [at, capacity).

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

Examples

use bytes::BytesMut;

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

a[0] = b'j';
b[0] = b'!';

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

Panics

Panics if at > capacity.

#[must_use = "consider BytesMut::advance(len()) if you don't need the other half"]pub fn split(&mut self) -> BytesMut[src]

Removes the bytes from the current view, returning them in a new BytesMut handle.

Afterwards, self will be empty, but will retain any additional capacity that it had before the operation. This is identical to self.split_to(self.len()).

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

Examples

use bytes::{BytesMut, BufMut};

let mut buf = BytesMut::with_capacity(1024);
buf.put(&b"hello world"[..]);

let other = buf.split();

assert!(buf.is_empty());
assert_eq!(1013, buf.capacity());

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

#[must_use = "consider BytesMut::advance if you don't need the other half"]pub fn split_to(&mut self, at: usize) -> BytesMut[src]

Splits the buffer into two at the given index.

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

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

Examples

use bytes::BytesMut;

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

a[0] = b'!';
b[0] = b'j';

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

Panics

Panics if at > len.

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

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::BytesMut;

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

pub fn clear(&mut self)[src]

Clears the buffer, removing all data.

Examples

use bytes::BytesMut;

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

pub fn resize(&mut self, new_len: usize, value: u8)[src]

Resizes the buffer so that len is equal to new_len.

If new_len is greater than len, the buffer is extended by the difference with each additional byte set to value. If new_len is less than len, the buffer is simply truncated.

Examples

use bytes::BytesMut;

let mut buf = BytesMut::new();

buf.resize(3, 0x1);
assert_eq!(&buf[..], &[0x1, 0x1, 0x1]);

buf.resize(2, 0x2);
assert_eq!(&buf[..], &[0x1, 0x1]);

buf.resize(4, 0x3);
assert_eq!(&buf[..], &[0x1, 0x1, 0x3, 0x3]);

pub unsafe fn set_len(&mut self, len: usize)[src]

Sets the length of the buffer.

This will explicitly set the size of the buffer without actually modifying the data, so it is up to the caller to ensure that the data has been initialized.

Examples

use bytes::BytesMut;

let mut b = BytesMut::from(&b"hello world"[..]);

unsafe {
    b.set_len(5);
}

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

unsafe {
    b.set_len(11);
}

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

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

Reserves capacity for at least additional more bytes to be inserted into the given BytesMut.

More than additional bytes may be reserved in order to avoid frequent reallocations. A call to reserve may result in an allocation.

Before allocating new buffer space, the function will attempt to reclaim space in the existing buffer. If the current handle references a small view in the original buffer and all other handles have been dropped, and the requested capacity is less than or equal to the existing buffer's capacity, then the current view will be copied to the front of the buffer and the handle will take ownership of the full buffer.

Examples

In the following example, a new buffer is allocated.

use bytes::BytesMut;

let mut buf = BytesMut::from(&b"hello"[..]);
buf.reserve(64);
assert!(buf.capacity() >= 69);

In the following example, the existing buffer is reclaimed.

use bytes::{BytesMut, BufMut};

let mut buf = BytesMut::with_capacity(128);
buf.put(&[0; 64][..]);

let ptr = buf.as_ptr();
let other = buf.split();

assert!(buf.is_empty());
assert_eq!(buf.capacity(), 64);

drop(other);
buf.reserve(128);

assert_eq!(buf.capacity(), 128);
assert_eq!(buf.as_ptr(), ptr);

Panics

Panics if the new capacity overflows usize.

pub fn extend_from_slice(&mut self, extend: &[u8])[src]

Appends given bytes to this BytesMut.

If this BytesMut object does not have enough capacity, it is resized first.

Examples

use bytes::BytesMut;

let mut buf = BytesMut::with_capacity(0);
buf.extend_from_slice(b"aaabbb");
buf.extend_from_slice(b"cccddd");

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

pub fn unsplit(&mut self, other: BytesMut)[src]

Absorbs a BytesMut that was previously split off.

If the two BytesMut objects were previously contiguous, i.e., if other was created by calling split_off on this BytesMut, then this is an O(1) operation that just decreases a reference count and sets a few indices. Otherwise this method degenerates to self.extend_from_slice(other.as_ref()).

Examples

use bytes::BytesMut;

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

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

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

Trait Implementations

impl AsMut<[u8]> for BytesMut[src]

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

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

impl BorrowMut<[u8]> for BytesMut[src]

impl Buf for BytesMut[src]

impl BufMut for BytesMut[src]

impl Clone for BytesMut[src]

impl Debug for BytesMut[src]

impl Default for BytesMut[src]

impl Deref for BytesMut[src]

type Target = [u8]

The resulting type after dereferencing.

impl DerefMut for BytesMut[src]

impl Drop for BytesMut[src]

impl Eq for BytesMut[src]

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

impl Extend<u8> for BytesMut[src]

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

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

impl From<BytesMut> for Bytes[src]

impl<'a> FromIterator<&'a u8> for BytesMut[src]

impl FromIterator<u8> for BytesMut[src]

impl Hash for BytesMut[src]

impl IntoIterator for BytesMut[src]

type Item = u8

The type of the elements being iterated over.

type IntoIter = IntoIter<BytesMut>

Which kind of iterator are we turning this into?

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

type Item = &'a u8

The type of the elements being iterated over.

type IntoIter = Iter<'a, u8>

Which kind of iterator are we turning this into?

impl LowerHex for BytesMut[src]

impl Ord for BytesMut[src]

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

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

impl PartialEq<Bytes> for BytesMut[src]

impl PartialEq<BytesMut> for BytesMut[src]

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

impl PartialEq<BytesMut> for str[src]

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

impl PartialEq<BytesMut> for String[src]

impl<'_> PartialEq<BytesMut> for &'_ [u8][src]

impl<'_> PartialEq<BytesMut> for &'_ str[src]

impl PartialEq<BytesMut> for Bytes[src]

impl PartialEq<String> for BytesMut[src]

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

impl PartialEq<str> for BytesMut[src]

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

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

impl PartialOrd<BytesMut> for BytesMut[src]

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

impl PartialOrd<BytesMut> for str[src]

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

impl PartialOrd<BytesMut> for String[src]

impl<'_> PartialOrd<BytesMut> for &'_ [u8][src]

impl<'_> PartialOrd<BytesMut> for &'_ str[src]

impl PartialOrd<String> for BytesMut[src]

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

impl PartialOrd<str> for BytesMut[src]

impl Send for BytesMut[src]

impl Sync for BytesMut[src]

impl UpperHex for BytesMut[src]

impl Write for BytesMut[src]

Auto Trait Implementations

impl RefUnwindSafe for BytesMut

impl Unpin for BytesMut

impl UnwindSafe for BytesMut

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<B> BufExt for B where
    B: Buf + ?Sized
[src]

impl<B> BufMutExt for B where
    B: BufMut + ?Sized
[src]

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<I> IntoIterator for I where
    I: Iterator
[src]

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

type IntoIter = I

Which kind of iterator are we turning this into?

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.