Struct std::io::Take

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

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.

Methods

impl<T> Take<T>

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(())
}

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(())
}

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(())
}

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

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(())
}

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

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(())
}

Trait Implementations

impl<T: Debug> Debug for Take<T>

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

Formats the value using the given formatter.

impl<T: Read> Read for Take<T>

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.

unsafe fn initializer(&self) -> Initializer

🔬 This is a nightly-only experimental API. (read_initializer #42788)

Determines if this Reader can work with buffers of uninitialized memory.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>

Read all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize>

Read all bytes until EOF in this source, appending them to buf.

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

Read the exact number of bytes required to fill buf.

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

fn by_ref(&mut self) -> &mut Self where     Self: Sized,

Creates a "by reference" adaptor for this instance of Read.

Important traits for Bytes<R>

impl<R: Read> Iterator for Bytes<R> type Item = Result<u8>;

fn bytes(self) -> Bytes<Self> where     Self: Sized,

Transforms this Read instance to an [Iterator] over its bytes.

Important traits for Chars<R>

impl<R: Read> Iterator for Chars<R> type Item = Result<char, CharsError>;

fn chars(self) -> Chars<Self> where     Self: Sized,

Deprecated since 1.27.0

: Use str::from_utf8 instead: https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples

🔬 This is a nightly-only experimental API. (io #27802)

the semantics of a partial read/write of where errors happen is currently unclear and may change

Transforms this Read instance to an [Iterator] over [char]s.

Important traits for Chain<T, U>

impl<T: Read, U: Read> Read for Chain<T, U>

fn chain<R: Read>(self, next: R) -> Chain<Self, R> where     Self: Sized,

Creates an adaptor which will chain this stream with another.

Important traits for Take<T>

impl<T: Read> Read for Take<T>

fn take(self, limit: u64) -> Take<Self> where     Self: Sized,

Creates an adaptor which will read at most limit bytes from it.

impl<T: BufRead> BufRead for Take<T>

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

Fills the internal buffer of this object, returning the buffer contents.

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.

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.

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 buffer.

Important traits for Split<B>

impl<B: BufRead> Iterator for Split<B> type Item = Result<Vec<u8>>;

fn split(self, byte: u8) -> Split<Self> where     Self: Sized,

Returns an iterator over the contents of this reader split on the byte byte.

Important traits for Lines<B>

impl<B: BufRead> Iterator for Lines<B> type Item = Result<String>;

fn lines(self) -> Lines<Self> where     Self: Sized,

Returns an iterator over the lines of this reader.