futures_lite::io

Struct Cursor

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pub struct Cursor<T> { /* private fields */ }
Expand description

Gives an in-memory buffer a cursor for reading and writing.

§Examples

use futures_lite::io::{AsyncReadExt, AsyncSeekExt, AsyncWriteExt, Cursor, SeekFrom};

let mut bytes = b"hello".to_vec();
let mut cursor = Cursor::new(&mut bytes);

// Overwrite 'h' with 'H'.
cursor.write_all(b"H").await?;

// Move the cursor one byte forward.
cursor.seek(SeekFrom::Current(1)).await?;

// Read a byte.
let mut byte = [0];
cursor.read_exact(&mut byte).await?;
assert_eq!(&byte, b"l");

// Check the final buffer.
assert_eq!(bytes, b"Hello");

Implementations§

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impl<T> Cursor<T>

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pub fn new(inner: T) -> Cursor<T>

Creates a cursor for an in-memory buffer.

Cursor’s initial position is 0 even if the underlying buffer is not empty. Writing using Cursor will overwrite the existing contents unless the cursor is moved to the end of the buffer using set_position() or seek().

§Examples
use futures_lite::io::Cursor;

let cursor = Cursor::new(Vec::<u8>::new());
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pub fn get_ref(&self) -> &T

Gets a reference to the underlying buffer.

§Examples
use futures_lite::io::Cursor;

let cursor = Cursor::new(Vec::<u8>::new());
let r = cursor.get_ref();
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pub fn get_mut(&mut self) -> &mut T

Gets a mutable reference to the underlying buffer.

§Examples
use futures_lite::io::Cursor;

let mut cursor = Cursor::new(Vec::<u8>::new());
let r = cursor.get_mut();
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pub fn into_inner(self) -> T

Unwraps the cursor, returning the underlying buffer.

§Examples
use futures_lite::io::Cursor;

let cursor = Cursor::new(vec![1, 2, 3]);
assert_eq!(cursor.into_inner(), [1, 2, 3]);
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pub fn position(&self) -> u64

Returns the current position of this cursor.

§Examples
use futures_lite::io::{AsyncSeekExt, Cursor, SeekFrom};

let mut cursor = Cursor::new(b"hello");
assert_eq!(cursor.position(), 0);

cursor.seek(SeekFrom::Start(2)).await?;
assert_eq!(cursor.position(), 2);
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pub fn set_position(&mut self, pos: u64)

Sets the position of this cursor.

§Examples
use futures_lite::io::Cursor;

let mut cursor = Cursor::new(b"hello");
assert_eq!(cursor.position(), 0);

cursor.set_position(2);
assert_eq!(cursor.position(), 2);

Trait Implementations§

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impl<T> AsyncBufRead for Cursor<T>
where T: AsRef<[u8]> + Unpin,

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

Attempt 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<T> AsyncRead for Cursor<T>
where T: AsRef<[u8]> + Unpin,

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

Attempt to read from the AsyncRead into buf. Read more
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fn poll_read_vectored( self: Pin<&mut Self>, _: &mut Context<'_>, bufs: &mut [IoSliceMut<'_>], ) -> Poll<Result<usize>>

Attempt to read from the AsyncRead into bufs using vectored IO operations. Read more
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impl<T> AsyncSeek for Cursor<T>
where T: AsRef<[u8]> + Unpin,

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fn poll_seek( self: Pin<&mut Self>, _: &mut Context<'_>, pos: SeekFrom, ) -> Poll<Result<u64>>

Attempt to seek to an offset, in bytes, in a stream. Read more
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impl AsyncWrite for Cursor<&mut [u8]>

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

Attempt to write bytes from bufs into the object using vectored IO operations. Read more
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fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>

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

Attempt to close the object. Read more
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impl AsyncWrite for Cursor<&mut Vec<u8>>

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

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

Attempt to close the object. Read more
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fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>

Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

Attempt to write bytes from bufs into the object using vectored IO operations. Read more
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impl AsyncWrite for Cursor<Vec<u8>>

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

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

Attempt to close the object. Read more
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fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Result<()>>

Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

Attempt to write bytes from bufs into the object using vectored IO operations. Read more
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impl<T: Clone> Clone for Cursor<T>

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fn clone(&self) -> Cursor<T>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<T: Debug> Debug for Cursor<T>

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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<T: Default> Default for Cursor<T>

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fn default() -> Cursor<T>

Returns the “default value” for a type. Read more

Auto Trait Implementations§

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impl<T> Freeze for Cursor<T>
where T: Freeze,

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impl<T> RefUnwindSafe for Cursor<T>
where T: RefUnwindSafe,

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impl<T> Send for Cursor<T>
where T: Send,

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impl<T> Sync for Cursor<T>
where T: Sync,

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impl<T> Unpin for Cursor<T>
where T: Unpin,

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impl<T> UnwindSafe for Cursor<T>
where T: UnwindSafe,

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<R> AsyncBufReadExt for R
where R: AsyncBufRead + ?Sized,

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fn fill_buf(&mut self) -> FillBuf<'_, Self>
where Self: Unpin,

Returns the contents of the internal buffer, filling it with more data if empty. Read more
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fn consume(&mut self, amt: usize)
where Self: Unpin,

Consumes amt buffered bytes. Read more
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fn read_until<'a>( &'a mut self, byte: u8, buf: &'a mut Vec<u8>, ) -> ReadUntilFuture<'_, Self>
where Self: Unpin,

Reads all bytes and appends them into buf until the delimiter byte or EOF is found. Read more
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fn read_line<'a>(&'a mut self, buf: &'a mut String) -> ReadLineFuture<'_, Self>
where Self: Unpin,

Reads all bytes and appends them into buf until a newline (the 0xA byte) or EOF is found. Read more
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fn lines(self) -> Lines<Self>
where Self: Unpin + Sized,

Returns a stream over the lines of this byte stream. Read more
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fn split(self, byte: u8) -> Split<Self>
where Self: Sized,

Returns a stream over the contents of this reader split on the specified byte. Read more
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impl<R> AsyncReadExt for R
where R: AsyncRead + ?Sized,

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fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadFuture<'a, Self>
where Self: Unpin,

Reads some bytes from the byte stream. Read more
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fn read_vectored<'a>( &'a mut self, bufs: &'a mut [IoSliceMut<'a>], ) -> ReadVectoredFuture<'a, Self>
where Self: Unpin,

Like read(), except it reads into a slice of buffers. Read more
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fn read_to_end<'a>( &'a mut self, buf: &'a mut Vec<u8>, ) -> ReadToEndFuture<'a, Self>
where Self: Unpin,

Reads the entire contents and appends them to a Vec. Read more
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fn read_to_string<'a>( &'a mut self, buf: &'a mut String, ) -> ReadToStringFuture<'a, Self>
where Self: Unpin,

Reads the entire contents and appends them to a String. Read more
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fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExactFuture<'a, Self>
where Self: Unpin,

Reads the exact number of bytes required to fill buf. Read more
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fn take(self, limit: u64) -> Take<Self>
where Self: Sized,

Creates an adapter which will read at most limit bytes from it. Read more
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fn bytes(self) -> Bytes<Self>
where Self: Sized,

Converts this AsyncRead into a Stream of bytes. Read more
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fn chain<R: AsyncRead>(self, next: R) -> Chain<Self, R>
where Self: Sized,

Creates an adapter which will chain this stream with another. Read more
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fn boxed_reader<'a>(self) -> Pin<Box<dyn AsyncRead + Send + 'a>>
where Self: Sized + Send + 'a,

Boxes the reader and changes its type to dyn AsyncRead + Send + 'a. Read more
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impl<S> AsyncSeekExt for S
where S: AsyncSeek + ?Sized,

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fn seek(&mut self, pos: SeekFrom) -> SeekFuture<'_, Self>
where Self: Unpin,

Seeks to a new position in a byte stream. Read more
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impl<W> AsyncWriteExt for W
where W: AsyncWrite + ?Sized,

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fn write<'a>(&'a mut self, buf: &'a [u8]) -> WriteFuture<'a, Self>
where Self: Unpin,

Writes some bytes into the byte stream. Read more
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fn write_vectored<'a>( &'a mut self, bufs: &'a [IoSlice<'a>], ) -> WriteVectoredFuture<'a, Self>
where Self: Unpin,

Like write(), except that it writes a slice of buffers. Read more
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fn write_all<'a>(&'a mut self, buf: &'a [u8]) -> WriteAllFuture<'a, Self>
where Self: Unpin,

Writes an entire buffer into the byte stream. Read more
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fn flush(&mut self) -> FlushFuture<'_, Self>
where Self: Unpin,

Flushes the stream to ensure that all buffered contents reach their destination. Read more
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fn close(&mut self) -> CloseFuture<'_, Self>
where Self: Unpin,

Closes the writer. Read more
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fn boxed_writer<'a>(self) -> Pin<Box<dyn AsyncWrite + Send + 'a>>
where Self: Sized + Send + 'a,

Boxes the writer and changes its type to dyn AsyncWrite + Send + 'a. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

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

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

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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

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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> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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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 T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.