Struct async_std::io::Take

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

Reader adaptor which limits the bytes read from an underlying reader.

This struct is generally created by calling take on a reader. Please see the documentation of take for more details.

Implementations§

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impl<T> Take<T>

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pub fn limit(&self) -> u64

Returns the number of bytes that can be read before this instance will return EOF.

Note

This instance may reach EOF after reading fewer bytes than indicated by this method if the underlying Read instance reaches EOF.

Examples
use async_std::prelude::*;
use async_std::fs::File;

let f = File::open("foo.txt").await?;

// read at most five bytes
let handle = f.take(5);

println!("limit: {}", handle.limit());
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pub fn set_limit(&mut self, limit: u64)

Sets the number of bytes that can be read before this instance will return EOF. This is the same as constructing a new Take instance, so the amount of bytes read and the previous limit value don’t matter when calling this method.

Examples
use async_std::prelude::*;
use async_std::fs::File;

let f = File::open("foo.txt").await?;

// read at most five bytes
let mut handle = f.take(5);
handle.set_limit(10);

assert_eq!(handle.limit(), 10);
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pub fn into_inner(self) -> T

Consumes the Take, returning the wrapped reader.

Examples
use async_std::prelude::*;
use async_std::fs::File;

let file = File::open("foo.txt").await?;

let mut buffer = [0; 5];
let mut handle = file.take(5);
handle.read(&mut buffer).await?;

let file = handle.into_inner();
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pub fn get_ref(&self) -> &T

Gets a reference to the underlying reader.

Examples
use async_std::prelude::*;
use async_std::fs::File;

let file = File::open("foo.txt").await?;

let mut buffer = [0; 5];
let mut handle = file.take(5);
handle.read(&mut buffer).await?;

let file = handle.get_ref();
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pub fn get_mut(&mut self) -> &mut T

Gets a mutable reference to the underlying reader.

Care should be taken to avoid modifying the internal I/O state of the underlying reader as doing so may corrupt the internal limit of this Take.

Examples
use async_std::prelude::*;
use async_std::fs::File;

let file = File::open("foo.txt").await?;

let mut buffer = [0; 5];
let mut handle = file.take(5);
handle.read(&mut buffer).await?;

let file = handle.get_mut();

Trait Implementations§

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impl<T: BufRead> AsyncBufRead for Take<T>

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fn poll_fill_buf( self: Pin<&mut Self>, cx: &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: Read> AsyncRead for Take<T>

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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.

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fn poll_read_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &mut [IoSliceMut<'_>] ) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into bufs using vectored IO operations. Read more
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impl<T: Debug> Debug for Take<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<'__pin, T> Unpin for Take<T>
where __Origin<'__pin, T>: Unpin,

Auto Trait Implementations§

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

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

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

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impl<T> UnwindSafe for Take<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<'a, 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<'a, 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>(self, next: R) -> Chain<Self, R>
where R: AsyncRead, 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<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> BufReadExt for T
where T: AsyncBufRead + ?Sized,

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fn read_until<'a>( &'a mut self, byte: u8, buf: &'a mut Vec<u8> ) -> ReadUntilFuture<'a, Self>
where Self: Unpin,

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

Reads all bytes and appends them into buf until a newline (the 0xA byte) is reached. 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 byte byte. 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> ReadExt for T
where T: 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 that 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 all bytes from the byte stream. 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 all bytes from the byte stream and appends them into 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 adaptor which will read at most limit bytes from it. Read more
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fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adaptor for this instance of Read. Read more
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fn bytes(self) -> Bytes<Self>
where Self: Sized,

Transforms this Read instance to a Stream over its bytes. Read more
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fn chain<R: Read>(self, next: R) -> Chain<Self, R>
where Self: Sized,

Creates an adaptor which will chain this stream with another. 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.