Struct otter_nodejs_tests::BufWriter
1.0.0 · source · [−]pub struct BufWriter<W> where
W: Write, { /* private fields */ }
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
sourceimpl<W> BufWriter<W> where
W: Write,
impl<W> BufWriter<W> where
W: Write,
sourcepub fn new(inner: W) -> BufWriter<W>ⓘNotable traits for BufWriter<W>impl<W> Write for BufWriter<W> where
W: Write,
pub fn new(inner: W) -> BufWriter<W>ⓘNotable traits for BufWriter<W>impl<W> Write for BufWriter<W> where
W: Write,
W: Write,
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());
sourcepub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W>ⓘNotable traits for BufWriter<W>impl<W> Write for BufWriter<W> where
W: Write,
pub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W>ⓘNotable traits for BufWriter<W>impl<W> Write for BufWriter<W> where
W: Write,
W: Write,
Creates a new BufWriter<W>
with at least the specified buffer capacity.
Examples
Creating a buffer with a buffer of at least 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);
sourcepub fn get_ref(&self) -> &W
pub fn get_ref(&self) -> &W
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();
sourcepub fn get_mut(&mut self) -> &mut W
pub fn get_mut(&mut self) -> &mut W
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();
1.37.0 · sourcepub fn buffer(&self) -> &[u8]ⓘNotable traits for &mut [u8]impl<'_> Write for &mut [u8]impl<'_> Read for &[u8]
pub fn buffer(&self) -> &[u8]ⓘNotable traits for &mut [u8]impl<'_> Write for &mut [u8]impl<'_> Read for &[u8]
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();
1.46.0 · sourcepub fn capacity(&self) -> usize
pub fn capacity(&self) -> usize
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();
sourcepub fn into_inner(self) -> Result<W, IntoInnerError<BufWriter<W>>>
pub fn into_inner(self) -> Result<W, IntoInnerError<BufWriter<W>>>
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();
1.56.0 · sourcepub fn into_parts(self) -> (W, Result<Vec<u8, Global>, WriterPanicked>)
pub fn into_parts(self) -> (W, Result<Vec<u8, Global>, WriterPanicked>)
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_parts
makes no attempt to flush data and cannot fail.
Examples
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_parts();
assert_eq!(recovered_writer.len(), 0);
assert_eq!(&buffered_data.unwrap(), b"ata");
Trait Implementations
sourceimpl<W> Seek for BufWriter<W> where
W: Write + Seek,
impl<W> Seek for BufWriter<W> where
W: Write + Seek,
sourcefn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>
Seek to the offset, in bytes, in the underlying writer.
Seeking always writes out the internal buffer before seeking.
1.55.0 · sourcefn rewind(&mut self) -> Result<(), Error>
fn rewind(&mut self) -> Result<(), Error>
Rewind to the beginning of a stream. Read more
sourceimpl<W> Write for BufWriter<W> where
W: Write,
impl<W> Write for BufWriter<W> where
W: Write,
sourcefn write(&mut self, buf: &[u8]) -> Result<usize, Error>
fn write(&mut self, buf: &[u8]) -> Result<usize, Error>
Write a buffer into this writer, returning how many bytes were written. Read more
sourcefn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>
Attempts to write an entire buffer into this writer. Read more
sourcefn is_write_vectored(&self) -> bool
fn is_write_vectored(&self) -> bool
can_vector
)Determines if this Write
r has an efficient write_vectored
implementation. Read more
sourcefn flush(&mut self) -> Result<(), Error>
fn flush(&mut self) -> Result<(), Error>
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
sourcefn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>
write_all_vectored
)Attempts to write multiple buffers into this writer. Read more
Auto Trait Implementations
impl<W> RefUnwindSafe for BufWriter<W> where
W: RefUnwindSafe,
impl<W> Send for BufWriter<W> where
W: Send,
impl<W> Sync for BufWriter<W> where
W: Sync,
impl<W> Unpin for BufWriter<W> where
W: Unpin,
impl<W> UnwindSafe for BufWriter<W> where
W: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
impl<T> Downcast for T where
T: Any,
impl<T> Downcast for T where
T: Any,
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
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
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
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
fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert &Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
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
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
Use this to cast from one trait object type to another. Read more
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
Use this to upcast a trait to one of its supertraits. Read more
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
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>,
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
sourceimpl<T> Instrument for T
impl<T> Instrument for T
sourcefn 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;
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;
T: Future, type Output = <T as Future>::Output;
sourcefn 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;
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;
T: Future, type Output = <T as Future>::Output;
impl<T> RmpWrite for T where
T: Write,
impl<T> RmpWrite for T where
T: Write,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
fn vzip(self) -> V
sourceimpl<T> WithSubscriber for T
impl<T> WithSubscriber for T
sourcefn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
where
S: Into<Dispatch>,
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
where
S: Into<Dispatch>,
T: Future, type Output = <T as Future>::Output;
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
sourcefn with_current_subscriber(self) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
fn with_current_subscriber(self) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
T: Future, type Output = <T as Future>::Output;
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
impl<W> WriteBytesExt for W where
W: Write + ?Sized,
fn write_u8(&mut self, n: u8) -> Result<(), Error>
fn write_u8(&mut self, n: u8) -> Result<(), Error>
Writes an unsigned 8 bit integer to the underlying writer. Read more
fn write_i8(&mut self, n: i8) -> Result<(), Error>
fn write_i8(&mut self, n: i8) -> Result<(), Error>
Writes a signed 8 bit integer to the underlying writer. Read more
fn write_u16<T>(&mut self, n: u16) -> Result<(), Error> where
T: ByteOrder,
fn write_u16<T>(&mut self, n: u16) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 16 bit integer to the underlying writer. Read more
fn write_i16<T>(&mut self, n: i16) -> Result<(), Error> where
T: ByteOrder,
fn write_i16<T>(&mut self, n: i16) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 16 bit integer to the underlying writer. Read more
fn write_u24<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
fn write_u24<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 24 bit integer to the underlying writer. Read more
fn write_i24<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
fn write_i24<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 24 bit integer to the underlying writer. Read more
fn write_u32<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
fn write_u32<T>(&mut self, n: u32) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 32 bit integer to the underlying writer. Read more
fn write_i32<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
fn write_i32<T>(&mut self, n: i32) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 32 bit integer to the underlying writer. Read more
fn write_u48<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
fn write_u48<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 48 bit integer to the underlying writer. Read more
fn write_i48<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
fn write_i48<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
Writes a signed 48 bit integer to the underlying writer. Read more
fn write_u64<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
fn write_u64<T>(&mut self, n: u64) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned 64 bit integer to the underlying writer. Read more
fn write_i64<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
fn write_i64<T>(&mut self, n: i64) -> Result<(), Error> where
T: ByteOrder,
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.
fn write_uint<T>(&mut self, n: u64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_uint<T>(&mut self, n: u64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned n-bytes integer to the underlying writer. Read more
fn write_int<T>(&mut self, n: i64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_int<T>(&mut self, n: i64, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes a signed n-bytes integer to the underlying writer. Read more
fn write_uint128<T>(&mut self, n: u128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_uint128<T>(&mut self, n: u128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes an unsigned n-bytes integer to the underlying writer. Read more
fn write_int128<T>(&mut self, n: i128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
fn write_int128<T>(&mut self, n: i128, nbytes: usize) -> Result<(), Error> where
T: ByteOrder,
Writes a signed n-bytes integer to the underlying writer. Read more