pub struct BufReader<R> { /* fields omitted */ }
The BufReader<R> struct adds buffering to any reader.
It can be excessively inefficient to work directly with a Read instance. For example, every call to read on TcpStream results in a system call. A BufReader<R> performs large, infrequent reads on the underlying Read and maintains an in-memory buffer of the results.
BufReader<R> 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<R> is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader<R> on the same stream can cause data loss. Reading from the underlying reader after unwrapping the BufReader<R> with BufReader::into_inner can also cause data loss.
use std::io::prelude::*;
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f = File::open("log.txt")?;
let mut reader = BufReader::new(f);
let mut line = String::new();
let len = reader.read_line(&mut line)?;
println!("First line is {} bytes long", len);
Ok(())
}impl<R: Read> BufReader<R>[src]
pub fn new(inner: R) -> BufReader<R>ⓘNotable traits for BufReader<R>
impl<R: Read> Read for BufReader<R>
[src]
Creates a new BufReader<R> with a default buffer capacity. The default is currently 8 KB, but may change in the future.
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f = File::open("log.txt")?;
let reader = BufReader::new(f);
Ok(())
}pub fn with_capacity(capacity: usize, inner: R) -> BufReader<R>ⓘNotable traits for BufReader<R>
impl<R: Read> Read for BufReader<R>
[src]
Creates a new BufReader<R> with the specified buffer capacity.
Creating a buffer with ten bytes of capacity:
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f = File::open("log.txt")?;
let reader = BufReader::with_capacity(10, f);
Ok(())
}impl<R> BufReader<R>[src]
pub fn get_ref(&self) -> &RⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Gets a reference to the underlying reader.
It is inadvisable to directly read from the underlying reader.
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f1 = File::open("log.txt")?;
let reader = BufReader::new(f1);
let f2 = reader.get_ref();
Ok(())
}pub fn get_mut(&mut self) -> &mut RⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Gets a mutable reference to the underlying reader.
It is inadvisable to directly read from the underlying reader.
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f1 = File::open("log.txt")?;
let mut reader = BufReader::new(f1);
let f2 = reader.get_mut();
Ok(())
}pub fn buffer(&self) -> &[u8]ⓘNotable traits for &'_ [u8]
impl<'_> Read for &'_ [u8]
impl<'_> Write for &'_ mut [u8]
[src]1.37.0
Returns a reference to the internally buffered data.
Unlike fill_buf, this will not attempt to fill the buffer if it is empty.
use std::io::{BufReader, BufRead};
use std::fs::File;
fn main() -> std::io::Result<()> {
let f = File::open("log.txt")?;
let mut reader = BufReader::new(f);
assert!(reader.buffer().is_empty());
if reader.fill_buf()?.len() > 0 {
assert!(!reader.buffer().is_empty());
}
Ok(())
}pub fn capacity(&self) -> usize[src]1.46.0
Returns the number of bytes the internal buffer can hold at once.
use std::io::{BufReader, BufRead};
use std::fs::File;
fn main() -> std::io::Result<()> {
let f = File::open("log.txt")?;
let mut reader = BufReader::new(f);
let capacity = reader.capacity();
let buffer = reader.fill_buf()?;
assert!(buffer.len() <= capacity);
Ok(())
}pub fn into_inner(self) -> R[src]
Unwraps this BufReader<R>, returning the underlying reader.
Note that any leftover data in the internal buffer is lost. Therefore, a following read from the underlying reader may lead to data loss.
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()> {
let f1 = File::open("log.txt")?;
let reader = BufReader::new(f1);
let f2 = reader.into_inner();
Ok(())
}impl<R: Seek> BufReader<R>[src]
pub fn seek_relative(&mut self, offset: i64) -> Result<()>[src]
Seeks relative to the current position. If the new position lies within the buffer, the buffer will not be flushed, allowing for more efficient seeks. This method does not return the location of the underlying reader, so the caller must track this information themselves if it is required.
impl<R: Read> BufRead for BufReader<R>[src]
fn fill_buf(&mut self) -> Result<&[u8]>[src]
fn consume(&mut self, amt: usize)[src]
fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>[src]
fn read_line(&mut self, buf: &mut String) -> Result<usize>[src]
fn split(self, byte: u8) -> Split<Self>ⓘNotable traits for Split<B>
impl<B: BufRead> Iterator for Split<B>
type Item = Result<Vec<u8>>;
where
Self: Sized, [src]
fn lines(self) -> Lines<Self>ⓘNotable traits for Lines<B>
impl<B: BufRead> Iterator for Lines<B>
type Item = Result<String>;
where
Self: Sized, [src]
impl<R> Debug for BufReader<R> where
R: Debug, [src]
impl<R: Read> Read for BufReader<R>[src]
fn read(&mut self, buf: &mut [u8]) -> Result<usize>[src]
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>[src]
fn is_read_vectored(&self) -> bool[src]
unsafe fn initializer(&self) -> Initializer[src]
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>[src]
fn read_to_string(&mut self, buf: &mut String) -> Result<usize>[src]
fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>[src]1.6.0
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
fn bytes(self) -> Bytes<Self>ⓘNotable traits for Bytes<R>
impl<R: Read> Iterator for Bytes<R>
type Item = Result<u8>;
where
Self: Sized, [src]
fn chain<R: Read>(self, next: R) -> Chain<Self, R>ⓘNotable traits for Chain<T, U>
impl<T: Read, U: Read> Read for Chain<T, U>
where
Self: Sized, [src]
fn take(self, limit: u64) -> Take<Self>ⓘNotable traits for Take<T>
impl<T: Read> Read for Take<T>
where
Self: Sized, [src]
impl<R: Seek> Seek for BufReader<R>[src]
fn seek(&mut self, pos: SeekFrom) -> Result<u64>[src]
Seek 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<R> had no internal buffer.
Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling BufReader::into_inner() immediately after a seek yields the underlying reader at the same position.
To seek without discarding the internal buffer, use BufReader::seek_relative.
See std::io::Seek 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).
fn stream_len(&mut self) -> Result<u64>[src]
fn stream_position(&mut self) -> Result<u64>[src]
impl<R> RefUnwindSafe for BufReader<R> where
R: RefUnwindSafe, impl<R> Send for BufReader<R> where
R: Send, impl<R> Sync for BufReader<R> where
R: Sync, impl<R> Unpin for BufReader<R> where
R: Unpin, impl<R> UnwindSafe for BufReader<R> where
R: UnwindSafe, impl<T> Any for T where
T: 'static + ?Sized, [src]
impl<T> Borrow<T> for T where
T: ?Sized, [src]
fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized, [src]
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> From<T> for T[src]
impl<T, U> Into<U> for T where
U: From<T>, [src]
impl<T, U> TryFrom<U> for T where
U: Into<T>, [src]
type Error = InfallibleThe type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>[src]
impl<T, U> TryInto<U> for T where
U: TryFrom<T>, [src]
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/io/struct.BufReader.html