Struct std::io::LineWriter
[−]
[src]
pub struct LineWriter<W: Write> {
// some 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 = try!(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 = try!(File::open("poem.txt")); let mut contents = String::new(); try!(file.read_to_string(&mut contents)); assert_eq!(contents.as_bytes(), &road_not_taken[..]);
Methods
impl<W: Write> LineWriter<W>
fn new(inner: W) -> LineWriter<W>
Creates a new LineWriter.
Examples
fn main() { use std::fs::File; use std::io::LineWriter; fn foo() -> std::io::Result<()> { let file = try!(File::create("poem.txt")); let file = LineWriter::new(file); Ok(()) } }use std::fs::File; use std::io::LineWriter; let file = try!(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.
Examples
fn main() { use std::fs::File; use std::io::LineWriter; fn foo() -> std::io::Result<()> { let file = try!(File::create("poem.txt")); let file = LineWriter::with_capacity(100, file); Ok(()) } }use std::fs::File; use std::io::LineWriter; let file = try!(File::create("poem.txt")); let file = LineWriter::with_capacity(100, file);
fn get_ref(&self) -> &W
Gets a reference to the underlying writer.
Examples
fn main() { use std::fs::File; use std::io::LineWriter; fn foo() -> std::io::Result<()> { let file = try!(File::create("poem.txt")); let file = LineWriter::new(file); let reference = file.get_ref(); Ok(()) } }use std::fs::File; use std::io::LineWriter; let file = try!(File::create("poem.txt")); let file = LineWriter::new(file); let reference = file.get_ref();
fn get_mut(&mut self) -> &mut W
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
fn main() { use std::fs::File; use std::io::LineWriter; fn foo() -> std::io::Result<()> { let file = try!(File::create("poem.txt")); let mut file = LineWriter::new(file); // we can use reference just like file let reference = file.get_mut(); Ok(()) } }use std::fs::File; use std::io::LineWriter; let file = try!(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.
Examples
fn main() { use std::fs::File; use std::io::LineWriter; fn foo() -> std::io::Result<()> { let file = try!(File::create("poem.txt")); let writer: LineWriter<File> = LineWriter::new(file); let file: File = try!(writer.into_inner()); Ok(()) } }use std::fs::File; use std::io::LineWriter; let file = try!(File::create("poem.txt")); let writer: LineWriter<File> = LineWriter::new(file); let file: File = try!(writer.into_inner());