Struct tokio::io::BufReader

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pub struct BufReader<R> { /* private fields */ }
Expand description

The BufReader struct adds buffering to any reader.

It can be excessively inefficient to work directly with a AsyncRead instance. A BufReader performs large, infrequent reads on the underlying AsyncRead and maintains an in-memory buffer of the results.

BufReader can improve the speed of programs that make small and repeated read calls to the same file or network socket. It does not help when reading very large amounts at once, or reading just one or a few times. It also provides no advantage when reading from a source that is already in memory, like a Vec<u8>.

When the BufReader is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader on the same stream can cause data loss.

Implementations§

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impl<R: AsyncRead> BufReader<R>

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pub fn new(inner: R) -> Self

Creates a new BufReader with a default buffer capacity. The default is currently 8 KB, but may change in the future.

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pub fn with_capacity(capacity: usize, inner: R) -> Self

Creates a new BufReader with the specified buffer capacity.

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pub fn get_ref(&self) -> &R

Gets a reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

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pub fn get_mut(&mut self) -> &mut R

Gets a mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

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pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut R>

Gets a pinned mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

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pub fn into_inner(self) -> R

Consumes this BufReader, returning the underlying reader.

Note that any leftover data in the internal buffer is lost.

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

Returns a reference to the internally buffered data.

Unlike fill_buf, this will not attempt to fill the buffer if it is empty.

Trait Implementations§

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impl<R: AsyncRead> AsyncBufRead for BufReader<R>

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fn poll_fill_buf( self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<Result<&[u8]>>

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
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fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read. Read more
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impl<R: AsyncRead> AsyncRead for BufReader<R>

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fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut ReadBuf<'_> ) -> Poll<Result<()>>

Attempts to read from the AsyncRead into buf. Read more
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impl<R: AsyncRead + AsyncSeek> AsyncSeek for BufReader<R>

Seeks to an offset, in bytes, in the underlying reader.

The position used for seeking with SeekFrom::Current(_) is the position the underlying reader would be at if the BufReader had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling .into_inner() immediately after a seek yields the underlying reader at the same position.

See AsyncSeek for more details.

Note: In the edge case where you’re seeking with SeekFrom::Current(n) where n minus the internal buffer length overflows an i64, two seeks will be performed instead of one. If the second seek returns Err, the underlying reader will be left at the same position it would have if you called seek with SeekFrom::Current(0).

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fn start_seek(self: Pin<&mut Self>, pos: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream. Read more
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fn poll_complete( self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<Result<u64>>

Waits for a seek operation to complete. Read more
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impl<R: AsyncRead + AsyncWrite> AsyncWrite for BufReader<R>

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fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8] ) -> Poll<Result<usize>>

Attempt to write bytes from buf into the object. Read more
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fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>] ) -> Poll<Result<usize>>

Like poll_write, except that it writes from a slice of buffers. Read more
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fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation. Read more
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fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
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impl<R: Debug> Debug for BufReader<R>

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

Formats the value using the given formatter. Read more
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impl<RW> From<BufReader<BufWriter<RW>>> for BufStream<RW>

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fn from(b: BufReader<BufWriter<RW>>) -> Self

Converts to this type from the input type.
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impl<'__pin, R> Unpin for BufReader<R>where __Origin<'__pin, R>: Unpin,

Auto Trait Implementations§

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impl<R> RefUnwindSafe for BufReader<R>where R: RefUnwindSafe,

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impl<R> Send for BufReader<R>where R: Send,

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impl<R> Sync for BufReader<R>where R: Sync,

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impl<R> UnwindSafe for BufReader<R>where R: UnwindSafe,

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.