# Struct std::io::Take

1.0.0 · source ·

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

Expand description

Reader adapter 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 std::io;
    use std::io::prelude::*;
    use std::fs::File;

    fn main() -> io::Result<()> {
        let f = File::open("foo.txt")?;

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

        println!("limit: {}", handle.limit());
        Ok(())
    }

Run
1.27.0 · source

#### 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 std::io;
    use std::io::prelude::*;
    use std::fs::File;

    fn main() -> io::Result<()> {
        let f = File::open("foo.txt")?;

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

        assert_eq!(handle.limit(), 10);
        Ok(())
    }

Run
1.15.0 · source

#### pub fn into_inner(self) -> T

Consumes the `Take`, returning the wrapped reader.

##### Examples

    use std::io;
    use std::io::prelude::*;
    use std::fs::File;

    fn main() -> io::Result<()> {
        let mut file = File::open("foo.txt")?;

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

        let file = handle.into_inner();
        Ok(())
    }

Run
1.20.0 · source

#### pub fn get_ref(&self) -> &T

Gets a reference to the underlying reader.

##### Examples

    use std::io;
    use std::io::prelude::*;
    use std::fs::File;

    fn main() -> io::Result<()> {
        let mut file = File::open("foo.txt")?;

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

        let file = handle.get_ref();
        Ok(())
    }

Run
1.20.0 · source

#### 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 std::io;
    use std::io::prelude::*;
    use std::fs::File;

    fn main() -> io::Result<()> {
        let mut file = File::open("foo.txt")?;

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

        let file = handle.get_mut();
        Ok(())
    }

Run

## Trait Implementations§

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

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#### fn fill_buf(&mut self) -> Result<&[u8]>

Returns 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(&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 `read`. Read more
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#### fn has_data_left(&mut self) -> Result<bool>

🔬This is a nightly-only experimental API. (`buf_read_has_data_left` #86423)
Check if the underlying `Read` has any data left to be read. Read more
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#### fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes into `buf` until the delimiter `byte` or EOF is reached. Read more
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#### fn read_line(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until a newline (the `0xA` byte) is reached, and append them to the provided `String` buffer. Read more
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#### fn split(self, byte: u8) -> Split<Self> ⓘwhere Self: Sized,

Returns an iterator over the contents of this reader split on the byte `byte`. Read more
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#### fn lines(self) -> Lines<Self> ⓘwhere Self: Sized,

Returns an iterator over the lines of this reader. 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<T: Read> Read for Take<T>

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#### fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
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#### fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Pull some bytes from this source into the specified buffer. Read more
1.36.0 · source§

#### fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>

Like `read`, except that it reads into a slice of buffers. Read more
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#### fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (`can_vector` #69941)
Determines if this `Read`er has an efficient `read_vectored` implementation. Read more
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#### fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes until EOF in this source, placing them into `buf`. Read more
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#### fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until EOF in this source, appending them to `buf`. Read more
1.6.0 · source§

#### fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>

Read the exact number of bytes required to fill `buf`. Read more
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#### fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()>

🔬This is a nightly-only experimental API. (`read_buf` #78485)
Read the exact number of bytes required to fill `cursor`. 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 an `Iterator` over its bytes. Read more
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#### fn chain<R: Read>(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 take(self, limit: u64) -> Take<Self> ⓘwhere Self: Sized,

Creates an adapter which will read at most `limit` bytes from it. Read more

## 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> Unpin for Take<T>where T: Unpin,

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### impl<T> UnwindSafe for Take<T>where T: 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,

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

Performs the conversion.