Struct std::io::ReadBuf

pub struct ReadBuf<'a> { /* private fields */ }

🔬 This is a nightly-only experimental API. (read_buf #78485)

A wrapper around a byte buffer that is incrementally filled and initialized.

This type is a sort of “double cursor”. It tracks three regions in the buffer: a region at the beginning of the buffer that has been logically filled with data, a region that has been initialized at some point but not yet logically filled, and a region at the end that is fully uninitialized. The filled region is guaranteed to be a subset of the initialized region.

In summary, the contents of the buffer can be visualized as:

[             capacity              ]
[ filled |         unfilled         ]
[    initialized    | uninitialized ]

Implementations

impl<'a> ReadBuf<'a>

pub fn new(buf: &'a mut [u8]) -> ReadBuf<'a>

🔬 This is a nightly-only experimental API. (read_buf #78485)

Creates a new ReadBuf from a fully initialized buffer.

pub fn uninit(buf: &'a mut [MaybeUninit<u8>]) -> ReadBuf<'a>

🔬 This is a nightly-only experimental API. (read_buf #78485)

Creates a new ReadBuf from a fully uninitialized buffer.

Use assume_init if part of the buffer is known to be already initialized.

pub fn capacity(&self) -> usize

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns the total capacity of the buffer.

pub fn filled(&self) -> &[u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a shared reference to the filled portion of the buffer.

pub fn filled_mut(&mut self) -> &mut [u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the filled portion of the buffer.

pub fn initialized(&self) -> &[u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a shared reference to the initialized portion of the buffer.

This includes the filled portion.

pub fn initialized_mut(&mut self) -> &mut [u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the initialized portion of the buffer.

This includes the filled portion.

pub unsafe fn unfilled_mut(&mut self) -> &mut [MaybeUninit<u8>]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the unfilled part of the buffer without ensuring that it has been fully initialized.

Safety

The caller must not de-initialize portions of the buffer that have already been initialized.

pub fn uninitialized_mut(&mut self) -> &mut [MaybeUninit<u8>]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the uninitialized part of the buffer.

It is safe to uninitialize any of these bytes.

pub fn initialize_unfilled(&mut self) -> &mut [u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the unfilled part of the buffer, ensuring it is fully initialized.

Since ReadBuf tracks the region of the buffer that has been initialized, this is effectively “free” after the first use.

pub fn initialize_unfilled_to(&mut self, n: usize) -> &mut [u8]

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns a mutable reference to the first n bytes of the unfilled part of the buffer, ensuring it is fully initialized.

Panics

Panics if self.remaining() is less than n.

pub fn remaining(&self) -> usize

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns the number of bytes at the end of the slice that have not yet been filled.

pub fn clear(&mut self) -> &mut Self

🔬 This is a nightly-only experimental API. (read_buf #78485)

Clears the buffer, resetting the filled region to empty.

The number of initialized bytes is not changed, and the contents of the buffer are not modified.

pub fn add_filled(&mut self, n: usize) -> &mut Self

🔬 This is a nightly-only experimental API. (read_buf #78485)

Increases the size of the filled region of the buffer.

The number of initialized bytes is not changed.

Panics

Panics if the filled region of the buffer would become larger than the initialized region.

pub fn set_filled(&mut self, n: usize) -> &mut Self

🔬 This is a nightly-only experimental API. (read_buf #78485)

Sets the size of the filled region of the buffer.

The number of initialized bytes is not changed.

Note that this can be used to shrink the filled region of the buffer in addition to growing it (for example, by a Read implementation that compresses data in-place).

Panics

Panics if the filled region of the buffer would become larger than the initialized region.

pub unsafe fn assume_init(&mut self, n: usize) -> &mut Self

🔬 This is a nightly-only experimental API. (read_buf #78485)

Asserts that the first n unfilled bytes of the buffer are initialized.

ReadBuf assumes that bytes are never de-initialized, so this method does nothing when called with fewer bytes than are already known to be initialized.

Safety

The caller must ensure that the first n unfilled bytes of the buffer have already been initialized.

pub fn append(&mut self, buf: &[u8])

🔬 This is a nightly-only experimental API. (read_buf #78485)

Appends data to the buffer, advancing the written position and possibly also the initialized position.

Panics

Panics if self.remaining() is less than buf.len().

pub fn filled_len(&self) -> usize

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns the amount of bytes that have been filled.

pub fn initialized_len(&self) -> usize

🔬 This is a nightly-only experimental API. (read_buf #78485)

Returns the amount of bytes that have been initialized.

Trait Implementations

impl Debug for ReadBuf<'_>

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

Formats the value using the given formatter.