Struct otter_api_tests::BufWriter 1.0.0[−][src]
pub struct BufWriter<W> where
W: Write, { /* fields omitted */ }
Expand description
Wraps a writer and buffers its output.
It can be excessively inefficient to work directly with something that
implements Write
. For example, every call to
write
on TcpStream
results in a system call. A
BufWriter<W>
keeps an in-memory buffer of data and writes it to an underlying
writer in large, infrequent batches.
BufWriter<W>
can improve the speed of programs that make small and
repeated write calls to the same file or network socket. It does not
help when writing very large amounts at once, or writing just one or a few
times. It also provides no advantage when writing to a destination that is
in memory, like a Vec
<u8>
.
It is critical to call flush
before BufWriter<W>
is dropped. Though
dropping will attempt to flush the contents of the buffer, any errors
that happen in the process of dropping will be ignored. Calling flush
ensures that the buffer is empty and thus dropping will not even attempt
file operations.
Examples
Let’s write the numbers one through ten to a TcpStream
:
use std::io::prelude::*; use std::net::TcpStream; let mut stream = TcpStream::connect("127.0.0.1:34254").unwrap(); for i in 0..10 { stream.write(&[i+1]).unwrap(); }
Because we’re not buffering, we write each one in turn, incurring the
overhead of a system call per byte written. We can fix this with a
BufWriter<W>
:
use std::io::prelude::*; use std::io::BufWriter; use std::net::TcpStream; let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); for i in 0..10 { stream.write(&[i+1]).unwrap(); } stream.flush().unwrap();
By wrapping the stream with a BufWriter<W>
, these ten writes are all grouped
together by the buffer and will all be written out in one system call when
the stream
is flushed.
Implementations
Creates a new BufWriter<W>
with a default buffer capacity. The default is currently 8 KB,
but may change in the future.
Examples
use std::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
Creates a new BufWriter<W>
with the specified buffer capacity.
Examples
Creating a buffer with a buffer of a hundred bytes.
use std::io::BufWriter; use std::net::TcpStream; let stream = TcpStream::connect("127.0.0.1:34254").unwrap(); let mut buffer = BufWriter::with_capacity(100, stream);
Gets a reference to the underlying writer.
Examples
use std::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); // we can use reference just like buffer let reference = buffer.get_ref();
Gets a mutable reference to the underlying writer.
It is inadvisable to directly write to the underlying writer.
Examples
use std::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); // we can use reference just like buffer let reference = buffer.get_mut();
Returns a reference to the internally buffered data.
Examples
use std::io::BufWriter; use std::net::TcpStream; let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); // See how many bytes are currently buffered let bytes_buffered = buf_writer.buffer().len();
Returns the number of bytes the internal buffer can hold without flushing.
Examples
use std::io::BufWriter; use std::net::TcpStream; let buf_writer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); // Check the capacity of the inner buffer let capacity = buf_writer.capacity(); // Calculate how many bytes can be written without flushing let without_flush = capacity - buf_writer.buffer().len();
Unwraps this BufWriter<W>
, returning the underlying writer.
The 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::io::BufWriter; use std::net::TcpStream; let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap()); // unwrap the TcpStream and flush the buffer let stream = buffer.into_inner().unwrap();
🔬 This is a nightly-only experimental API. (bufwriter_into_raw_parts
)
bufwriter_into_raw_parts
)Disassembles this BufWriter<W>
, returning the underlying writer, and any buffered but
unwritten data.
If the underlying writer panicked, it is not known what portion of the data was written.
In this case, we return WriterPanicked
for the buffered data (from which the buffer
contents can still be recovered).
into_raw_parts
makes no attempt to flush data and cannot fail.
Examples
#![feature(bufwriter_into_raw_parts)] use std::io::{BufWriter, Write}; let mut buffer = [0u8; 10]; let mut stream = BufWriter::new(buffer.as_mut()); write!(stream, "too much data").unwrap(); stream.flush().expect_err("it doesn't fit"); let (recovered_writer, buffered_data) = stream.into_raw_parts(); assert_eq!(recovered_writer.len(), 0); assert_eq!(&buffered_data.unwrap(), b"ata");
Trait Implementations
Seek to the offset, in bytes, in the underlying writer.
Seeking always writes out the internal buffer before seeking.
seek_rewind
)Rewind to the beginning of a stream. Read more
seek_stream_len
)Returns the length of this stream (in bytes). Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Attempts to write an entire buffer into this writer. Read more
can_vector
)Determines if this Write
r has an efficient write_vectored
implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
write_all_vectored
)Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Auto Trait Implementations
impl<W> RefUnwindSafe for BufWriter<W> where
W: RefUnwindSafe,
impl<W> UnwindSafe for BufWriter<W> where
W: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
pub fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<R, Global>
impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
A: Allocator,
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
A: Allocator + 'static,
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
pub fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<R, Global>
impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<I, A> Iterator for Box<I, A> where
A: Allocator,
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
A: Allocator + 'static,
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;
Convert Box<dyn Trait>
(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
can
then be further downcast
into Box<ConcreteType>
where ConcreteType
implements Trait
. Read more
pub fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
pub fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
. Read more
Convert &Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
pub fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
pub fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert &mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s. Read more
impl<A> DynCastExt for A
impl<A> DynCastExt for A
pub fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
T: ?Sized,
A: DynCastExtHelper<T>,
pub fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
T: ?Sized,
A: DynCastExtHelper<T>,
Use this to cast from one trait object type to another. Read more
pub fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
T: ?Sized,
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
pub fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
T: ?Sized,
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
Use this to upcast a trait to one of its supertraits. Read more
pub fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
T: ?Sized,
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
pub fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
T: ?Sized,
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
pub fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
pub fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
Use this to cast from one trait object type to another. With this method the type parameter is a config type that uniquely specifies which cast should be preformed. Read more
fn instrument(self, span: Span) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>
impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
[src]
fn instrument(self, span: Span) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>
impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
[src]Instruments this type with the provided Span
, returning an
Instrumented
wrapper. Read more
fn in_current_span(self) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>
impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
[src]
fn in_current_span(self) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>
impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
[src]pub fn vzip(self) -> V
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
Writes an unsigned 8 bit integer to the underlying writer. Read more
Writes a signed 8 bit integer to the underlying writer. Read more
Writes an unsigned 16 bit integer to the underlying writer. Read more
Writes a signed 16 bit integer to the underlying writer. Read more
Writes an unsigned 24 bit integer to the underlying writer. Read more
Writes a signed 24 bit integer to the underlying writer. Read more
Writes an unsigned 32 bit integer to the underlying writer. Read more
Writes a signed 32 bit integer to the underlying writer. Read more
Writes an unsigned 48 bit integer to the underlying writer. Read more
Writes a signed 48 bit integer to the underlying writer. Read more
Writes an unsigned 64 bit integer to the underlying writer. Read more
Writes a signed 64 bit integer to the underlying writer. Read more
fn write_u128<T>(&mut self, n: u128) -> Result<(), Error> where
T: ByteOrder,
fn write_u128<T>(&mut self, n: u128) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 128 bit integer to the underlying writer.
fn write_i128<T>(&mut self, n: i128) -> Result<(), Error> where
T: ByteOrder,
fn write_i128<T>(&mut self, n: i128) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 128 bit integer to the underlying writer.
Writes an unsigned n-bytes integer to the underlying writer. Read more
Writes a signed n-bytes integer to the underlying writer. Read more
Writes an unsigned n-bytes integer to the underlying writer. Read more
Writes a signed n-bytes integer to the underlying writer. Read more
Writes a IEEE754 single-precision (4 bytes) floating point number to the underlying writer. Read more