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Struct std::io::LineWriter

pub struct LineWriter<W: Write> { /* fields omitted */ }

Wraps a writer and buffers output to it, flushing whenever a newline (0x0a, '\n') is detected.

The BufWriter struct wraps a writer and buffers its output. But it only does this batched write when it goes out of scope, or when the internal buffer is full. Sometimes, you'd prefer to write each line as it's completed, rather than the entire buffer at once. Enter LineWriter. It does exactly that.

If there's still a partial line in the buffer when the LineWriter is dropped, it will flush those contents.

Examples

We can use LineWriter to write one line at a time, significantly reducing the number of actual writes to the file.

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

let road_not_taken = b"I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I -
I took the one less traveled by,
And that has made all the difference.";

let file = File::create("poem.txt")?;
let mut file = LineWriter::new(file);

for &byte in road_not_taken.iter() {
   file.write(&[byte]).unwrap();
}

// let's check we did the right thing.
let mut file = File::open("poem.txt")?;
let mut contents = String::new();

file.read_to_string(&mut contents)?;

assert_eq!(contents.as_bytes(), &road_not_taken[..]);

Methods

impl<W: Write> LineWriter<W> [src]

Creates a new LineWriter.

Examples

use std::fs::File;
use std::io::LineWriter;

let file = File::create("poem.txt")?;
let file = LineWriter::new(file);

Creates a new LineWriter with a specified capacity for the internal buffer.

Examples

use std::fs::File;
use std::io::LineWriter;

let file = File::create("poem.txt")?;
let file = LineWriter::with_capacity(100, file);

Gets a reference to the underlying writer.

Examples

use std::fs::File;
use std::io::LineWriter;

let file = File::create("poem.txt")?;
let file = LineWriter::new(file);

let reference = file.get_ref();

Gets a mutable reference to the underlying writer.

Caution must be taken when calling methods on the mutable reference returned as extra writes could corrupt the output stream.

Examples

use std::fs::File;
use std::io::LineWriter;

let file = File::create("poem.txt")?;
let mut file = LineWriter::new(file);

// we can use reference just like file
let reference = file.get_mut();

Unwraps this LineWriter, returning the underlying writer.

The internal buffer is written out before returning the writer.

Examples

use std::fs::File;
use std::io::LineWriter;

let file = File::create("poem.txt")?;

let writer: LineWriter<File> = LineWriter::new(file);

let file: File = writer.into_inner()?;

Trait Implementations

impl<W: Write> Write for LineWriter<W> [src]

Write a buffer into this object, returning how many bytes were written. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Attempts to write an entire buffer into this write. Read more

Writes a formatted string into this writer, returning any error encountered. Read more

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

impl<W: Write> Debug for LineWriter<W> where
    W: Debug
[src]

Formats the value using the given formatter.

© 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.LineWriter.html