1.0.0[−][src]Struct std::io::LineWriter
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.
Like BufWriter
, a LineWriter
’s buffer will also be flushed when the
LineWriter
goes out of scope or when its internal buffer is full.
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::{self, File}; use std::io::prelude::*; use std::io::LineWriter; fn main() -> std::io::Result<()> { 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); file.write_all(b"I shall be telling this with a sigh")?; // No bytes are written until a newline is encountered (or // the internal buffer is filled). assert_eq!(fs::read_to_string("poem.txt")?, ""); file.write_all(b"\n")?; assert_eq!( fs::read_to_string("poem.txt")?, "I shall be telling this with a sigh\n", ); // Write the rest of the poem. file.write_all(b"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.")?; // The last line of the poem doesn't end in a newline, so // we have to flush or drop the `LineWriter` to finish // writing. file.flush()?; // Confirm the whole poem was written. assert_eq!(fs::read("poem.txt")?, &road_not_taken[..]); Ok(()) }Run
Methods
impl<W: Write> LineWriter<W>
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ⓘImportant traits for LineWriter<W>pub fn new(inner: W) -> LineWriter<W>
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Creates a new LineWriter
.
Examples
use std::fs::File; use std::io::LineWriter; fn main() -> std::io::Result<()> { let file = File::create("poem.txt")?; let file = LineWriter::new(file); Ok(()) }Run
ⓘImportant traits for LineWriter<W>pub fn with_capacity(capacity: usize, inner: W) -> LineWriter<W>
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Creates a new LineWriter
with a specified capacity for the internal
buffer.
Examples
use std::fs::File; use std::io::LineWriter; fn main() -> std::io::Result<()> { let file = File::create("poem.txt")?; let file = LineWriter::with_capacity(100, file); Ok(()) }Run
ⓘImportant traits for &'_ mut Fpub fn get_ref(&self) -> &W
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Gets a reference to the underlying writer.
Examples
use std::fs::File; use std::io::LineWriter; fn main() -> std::io::Result<()> { let file = File::create("poem.txt")?; let file = LineWriter::new(file); let reference = file.get_ref(); Ok(()) }Run
ⓘImportant traits for &'_ mut Fpub fn get_mut(&mut self) -> &mut W
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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; fn main() -> std::io::Result<()> { let file = File::create("poem.txt")?; let mut file = LineWriter::new(file); // we can use reference just like file let reference = file.get_mut(); Ok(()) }Run
pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>>
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Unwraps this LineWriter
, returning the underlying writer.
The internal buffer is written out before returning the writer.
Errors
An Err
will be returned if an error occurs while flushing the buffer.
Examples
use std::fs::File; use std::io::LineWriter; fn main() -> std::io::Result<()> { let file = File::create("poem.txt")?; let writer: LineWriter<File> = LineWriter::new(file); let file: File = writer.into_inner()?; Ok(()) }Run
Trait Implementations
impl<W: Write> Write for LineWriter<W>
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fn write(&mut self, buf: &[u8]) -> Result<usize>
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fn flush(&mut self) -> Result<()>
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fn write_vectored(&mut self, bufs: &[IoSlice]) -> Result<usize>
1.36.0[src]
fn write_all(&mut self, buf: &[u8]) -> Result<()>
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fn write_fmt(&mut self, fmt: Arguments) -> Result<()>
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ⓘImportant traits for &'_ mut Ffn by_ref(&mut self) -> &mut Self where
Self: Sized,
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Self: Sized,
impl<W: Write> Debug for LineWriter<W> where
W: Debug,
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W: Debug,
Auto Trait Implementations
impl<W> UnwindSafe for LineWriter<W> where
W: UnwindSafe,
W: UnwindSafe,
impl<W> RefUnwindSafe for LineWriter<W> where
W: RefUnwindSafe,
W: RefUnwindSafe,
impl<W> Unpin for LineWriter<W> where
W: Unpin,
W: Unpin,
impl<W> Send for LineWriter<W> where
W: Send,
W: Send,
impl<W> Sync for LineWriter<W> where
W: Sync,
W: Sync,
Blanket Implementations
impl<T> From<T> for T
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
ⓘImportant traits for &'_ mut Ffn borrow_mut(&mut self) -> &mut T
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,