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.
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[..]); impl<W: Write> LineWriter<W>
[src]
fn new(inner: W) -> LineWriter<W>Creates a new LineWriter.
use std::fs::File;
use std::io::LineWriter;
let file = File::create("poem.txt")?;
let file = LineWriter::new(file); fn with_capacity(cap: usize, inner: W) -> LineWriter<W>Creates a new LineWriter with a specified capacity for the internal buffer.
use std::fs::File;
use std::io::LineWriter;
let file = File::create("poem.txt")?;
let file = LineWriter::with_capacity(100, file); fn get_ref(&self) -> &WGets a reference to the underlying writer.
use std::fs::File;
use std::io::LineWriter;
let file = File::create("poem.txt")?;
let file = LineWriter::new(file);
let reference = file.get_ref(); fn get_mut(&mut self) -> &mut WGets 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.
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(); fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>>Unwraps this LineWriter, returning the underlying writer.
The internal buffer is written out before returning the writer.
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()?; impl<W: Write> Write for LineWriter<W>
[src]
fn write(&mut self, buf: &[u8]) -> Result<usize>Write a buffer into this object, returning how many bytes were written. Read more
fn flush(&mut self) -> Result<()>Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
fn write_all(&mut self, buf: &[u8]) -> Result<()>Attempts to write an entire buffer into this write. Read more
fn write_fmt(&mut self, fmt: Arguments) -> Result<()>Writes a formatted string into this writer, returning any error encountered. Read more
fn by_ref(&mut self) -> &mut Self where Self: SizedCreates a "by reference" adaptor for this instance of Write. Read more
impl<W: Write> Debug for LineWriter<W> where W: Debug
[src]
fn fmt(&self, fmt: &mut Formatter) -> ResultFormats 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