Struct tokio::io::BufWriter

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pub struct BufWriter<W> { /* private fields */ }
Expand description

Wraps a writer and buffers its output.

It can be excessively inefficient to work directly with something that implements AsyncWrite. A BufWriter keeps an in-memory buffer of data and writes it to an underlying writer in large, infrequent batches.

BufWriter 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>.

When the BufWriter is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufWriter on the same stream can cause data loss. If you need to write out the contents of its buffer, you must manually call flush before the writer is dropped.

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impl<W: AsyncWrite> BufWriter<W>

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pub fn new(inner: W) -> Self

Creates a new BufWriter with a default buffer capacity. The default is currently 8 KB, but may change in the future.

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pub fn with_capacity(cap: usize, inner: W) -> Self

Creates a new BufWriter with the specified buffer capacity.

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pub fn get_ref(&self) -> &W

Gets a reference to the underlying writer.

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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.

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pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut W>

Gets a pinned mutable reference to the underlying writer.

It is inadvisable to directly write to the underlying writer.

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pub fn into_inner(self) -> W

Consumes this BufWriter, returning the underlying writer.

Note that any leftover data in the internal buffer is lost.

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pub fn buffer(&self) -> &[u8] ⓘ

Returns a reference to the internally buffered data.

Trait Implementations§

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impl<W: AsyncWrite + AsyncBufRead> AsyncBufRead for BufWriter<W>

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fn poll_fill_buf( self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<Result<&[u8]>>

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
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fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read. Read more
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impl<W: AsyncWrite + AsyncRead> AsyncRead for BufWriter<W>

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fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut ReadBuf<'_> ) -> Poll<Result<()>>

Attempts to read from the AsyncRead into buf. Read more
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impl<W: AsyncWrite + AsyncSeek> AsyncSeek for BufWriter<W>

Seek to the offset, in bytes, in the underlying writer.

Seeking always writes out the internal buffer before seeking.

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fn start_seek(self: Pin<&mut Self>, pos: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream. Read more
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fn poll_complete( self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<Result<u64>>

Waits for a seek operation to complete. Read more
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impl<W: AsyncWrite> AsyncWrite for BufWriter<W>

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fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8] ) -> Poll<Result<usize>>

Attempt to write bytes from buf into the object. Read more
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fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>] ) -> Poll<Result<usize>>

Like poll_write, except that it writes from a slice of buffers. Read more
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fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation. Read more
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fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
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impl<W: Debug> Debug for BufWriter<W>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<RW> From<BufWriter<BufReader<RW>>> for BufStream<RW>

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fn from(b: BufWriter<BufReader<RW>>) -> Self

Converts to this type from the input type.
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impl<'__pin, W> Unpin for BufWriter<W>
where __Origin<'__pin, W>: Unpin,

Auto Trait Implementations§

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impl<W> RefUnwindSafe for BufWriter<W>
where W: RefUnwindSafe,

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impl<W> Send for BufWriter<W>
where W: Send,

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impl<W> Sync for BufWriter<W>
where W: Sync,

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impl<W> UnwindSafe for BufWriter<W>
where W: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<R> AsyncBufReadExt for R
where R: AsyncBufRead + ?Sized,

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fn read_until<'a>( &'a mut self, byte: u8, buf: &'a mut Vec<u8> ) -> ReadUntil<'a, Self>
where Self: Unpin,

Reads all bytes into buf until the delimiter byte or EOF is reached. Read more
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fn read_line<'a>(&'a mut self, buf: &'a mut String) -> ReadLine<'a, Self>
where Self: Unpin,

Reads all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. Read more
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fn split(self, byte: u8) -> Split<Self>
where Self: Sized + Unpin,

Returns a stream of the contents of this reader split on the byte byte. Read more
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fn fill_buf(&mut self) -> FillBuf<'_, Self>
where Self: Unpin,

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
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fn consume(&mut self, amt: usize)
where Self: Unpin,

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more
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fn lines(self) -> Lines<Self>
where Self: Sized,

Returns a stream over the lines of this reader. This method is the async equivalent to BufRead::lines. Read more
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impl<R> AsyncReadExt for R
where R: AsyncRead + ?Sized,

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fn chain<R>(self, next: R) -> Chain<Self, R>
where Self: Sized, R: AsyncRead,

Creates a new AsyncRead instance that chains this stream with next. Read more
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fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self>
where Self: Unpin,

Pulls some bytes from this source into the specified buffer, returning how many bytes were read. Read more
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fn read_buf<'a, B>(&'a mut self, buf: &'a mut B) -> ReadBuf<'a, Self, B>
where Self: Sized + Unpin, B: BufMut,

Pulls some bytes from this source into the specified buffer, advancing the buffer’s internal cursor. Read more
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fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExact<'a, Self>
where Self: Unpin,

Reads the exact number of bytes required to fill buf. Read more
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fn read_u8<'a>(&'a mut self) -> ReadU8<&'a mut Self>
where Self: Unpin,

Reads an unsigned 8 bit integer from the underlying reader. Read more
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fn read_i8<'a>(&'a mut self) -> ReadI8<&'a mut Self>
where Self: Unpin,

Reads a signed 8 bit integer from the underlying reader. Read more
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fn read_u16<'a>(&'a mut self) -> ReadU16<&'a mut Self>
where Self: Unpin,

Reads an unsigned 16-bit integer in big-endian order from the underlying reader. Read more
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fn read_i16<'a>(&'a mut self) -> ReadI16<&'a mut Self>
where Self: Unpin,

Reads a signed 16-bit integer in big-endian order from the underlying reader. Read more
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fn read_u32<'a>(&'a mut self) -> ReadU32<&'a mut Self>
where Self: Unpin,

Reads an unsigned 32-bit integer in big-endian order from the underlying reader. Read more
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fn read_i32<'a>(&'a mut self) -> ReadI32<&'a mut Self>
where Self: Unpin,

Reads a signed 32-bit integer in big-endian order from the underlying reader. Read more
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fn read_u64<'a>(&'a mut self) -> ReadU64<&'a mut Self>
where Self: Unpin,

Reads an unsigned 64-bit integer in big-endian order from the underlying reader. Read more
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fn read_i64<'a>(&'a mut self) -> ReadI64<&'a mut Self>
where Self: Unpin,

Reads an signed 64-bit integer in big-endian order from the underlying reader. Read more
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fn read_u128<'a>(&'a mut self) -> ReadU128<&'a mut Self>
where Self: Unpin,

Reads an unsigned 128-bit integer in big-endian order from the underlying reader. Read more
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fn read_i128<'a>(&'a mut self) -> ReadI128<&'a mut Self>
where Self: Unpin,

Reads an signed 128-bit integer in big-endian order from the underlying reader. Read more
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fn read_f32<'a>(&'a mut self) -> ReadF32<&'a mut Self>
where Self: Unpin,

Reads an 32-bit floating point type in big-endian order from the underlying reader. Read more
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fn read_f64<'a>(&'a mut self) -> ReadF64<&'a mut Self>
where Self: Unpin,

Reads an 64-bit floating point type in big-endian order from the underlying reader. Read more
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fn read_u16_le<'a>(&'a mut self) -> ReadU16Le<&'a mut Self>
where Self: Unpin,

Reads an unsigned 16-bit integer in little-endian order from the underlying reader. Read more
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fn read_i16_le<'a>(&'a mut self) -> ReadI16Le<&'a mut Self>
where Self: Unpin,

Reads a signed 16-bit integer in little-endian order from the underlying reader. Read more
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fn read_u32_le<'a>(&'a mut self) -> ReadU32Le<&'a mut Self>
where Self: Unpin,

Reads an unsigned 32-bit integer in little-endian order from the underlying reader. Read more
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fn read_i32_le<'a>(&'a mut self) -> ReadI32Le<&'a mut Self>
where Self: Unpin,

Reads a signed 32-bit integer in little-endian order from the underlying reader. Read more
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fn read_u64_le<'a>(&'a mut self) -> ReadU64Le<&'a mut Self>
where Self: Unpin,

Reads an unsigned 64-bit integer in little-endian order from the underlying reader. Read more
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fn read_i64_le<'a>(&'a mut self) -> ReadI64Le<&'a mut Self>
where Self: Unpin,

Reads an signed 64-bit integer in little-endian order from the underlying reader. Read more
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fn read_u128_le<'a>(&'a mut self) -> ReadU128Le<&'a mut Self>
where Self: Unpin,

Reads an unsigned 128-bit integer in little-endian order from the underlying reader. Read more
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fn read_i128_le<'a>(&'a mut self) -> ReadI128Le<&'a mut Self>
where Self: Unpin,

Reads an signed 128-bit integer in little-endian order from the underlying reader. Read more
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fn read_f32_le<'a>(&'a mut self) -> ReadF32Le<&'a mut Self>
where Self: Unpin,

Reads an 32-bit floating point type in little-endian order from the underlying reader. Read more
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fn read_f64_le<'a>(&'a mut self) -> ReadF64Le<&'a mut Self>
where Self: Unpin,

Reads an 64-bit floating point type in little-endian order from the underlying reader. Read more
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fn read_to_end<'a>(&'a mut self, buf: &'a mut Vec<u8>) -> ReadToEnd<'a, Self>
where Self: Unpin,

Reads all bytes until EOF in this source, placing them into buf. Read more
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fn read_to_string<'a>( &'a mut self, dst: &'a mut String ) -> ReadToString<'a, Self>
where Self: Unpin,

Reads all bytes until EOF in this source, appending them to buf. Read more
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fn take(self, limit: u64) -> Take<Self>
where Self: Sized,

Creates an adaptor which reads at most limit bytes from it. Read more
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impl<S> AsyncSeekExt for S
where S: AsyncSeek + ?Sized,

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fn seek(&mut self, pos: SeekFrom) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more
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fn rewind(&mut self) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will rewind to the beginning of the stream. Read more
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fn stream_position(&mut self) -> Seek<'_, Self>
where Self: Unpin,

Creates a future which will return the current seek position from the start of the stream. Read more
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impl<W> AsyncWriteExt for W
where W: AsyncWrite + ?Sized,

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fn write<'a>(&'a mut self, src: &'a [u8]) -> Write<'a, Self>
where Self: Unpin,

Writes a buffer into this writer, returning how many bytes were written. Read more
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fn write_vectored<'a, 'b>( &'a mut self, bufs: &'a [IoSlice<'b>] ) -> WriteVectored<'a, 'b, Self>
where Self: Unpin,

Like write, except that it writes from a slice of buffers. Read more
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fn write_buf<'a, B>(&'a mut self, src: &'a mut B) -> WriteBuf<'a, Self, B>
where Self: Sized + Unpin, B: Buf,

Writes a buffer into this writer, advancing the buffer’s internal cursor. Read more
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fn write_all_buf<'a, B>( &'a mut self, src: &'a mut B ) -> WriteAllBuf<'a, Self, B>
where Self: Sized + Unpin, B: Buf,

Attempts to write an entire buffer into this writer. Read more
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fn write_all<'a>(&'a mut self, src: &'a [u8]) -> WriteAll<'a, Self>
where Self: Unpin,

Attempts to write an entire buffer into this writer. Read more
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fn write_u8<'a>(&'a mut self, n: u8) -> WriteU8<&'a mut Self>
where Self: Unpin,

Writes an unsigned 8-bit integer to the underlying writer. Read more
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fn write_i8<'a>(&'a mut self, n: i8) -> WriteI8<&'a mut Self>
where Self: Unpin,

Writes a signed 8-bit integer to the underlying writer. Read more
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fn write_u16<'a>(&'a mut self, n: u16) -> WriteU16<&'a mut Self>
where Self: Unpin,

Writes an unsigned 16-bit integer in big-endian order to the underlying writer. Read more
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fn write_i16<'a>(&'a mut self, n: i16) -> WriteI16<&'a mut Self>
where Self: Unpin,

Writes a signed 16-bit integer in big-endian order to the underlying writer. Read more
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fn write_u32<'a>(&'a mut self, n: u32) -> WriteU32<&'a mut Self>
where Self: Unpin,

Writes an unsigned 32-bit integer in big-endian order to the underlying writer. Read more
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fn write_i32<'a>(&'a mut self, n: i32) -> WriteI32<&'a mut Self>
where Self: Unpin,

Writes a signed 32-bit integer in big-endian order to the underlying writer. Read more
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fn write_u64<'a>(&'a mut self, n: u64) -> WriteU64<&'a mut Self>
where Self: Unpin,

Writes an unsigned 64-bit integer in big-endian order to the underlying writer. Read more
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fn write_i64<'a>(&'a mut self, n: i64) -> WriteI64<&'a mut Self>
where Self: Unpin,

Writes an signed 64-bit integer in big-endian order to the underlying writer. Read more
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fn write_u128<'a>(&'a mut self, n: u128) -> WriteU128<&'a mut Self>
where Self: Unpin,

Writes an unsigned 128-bit integer in big-endian order to the underlying writer. Read more
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fn write_i128<'a>(&'a mut self, n: i128) -> WriteI128<&'a mut Self>
where Self: Unpin,

Writes an signed 128-bit integer in big-endian order to the underlying writer. Read more
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fn write_f32<'a>(&'a mut self, n: f32) -> WriteF32<&'a mut Self>
where Self: Unpin,

Writes an 32-bit floating point type in big-endian order to the underlying writer. Read more
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fn write_f64<'a>(&'a mut self, n: f64) -> WriteF64<&'a mut Self>
where Self: Unpin,

Writes an 64-bit floating point type in big-endian order to the underlying writer. Read more
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fn write_u16_le<'a>(&'a mut self, n: u16) -> WriteU16Le<&'a mut Self>
where Self: Unpin,

Writes an unsigned 16-bit integer in little-endian order to the underlying writer. Read more
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fn write_i16_le<'a>(&'a mut self, n: i16) -> WriteI16Le<&'a mut Self>
where Self: Unpin,

Writes a signed 16-bit integer in little-endian order to the underlying writer. Read more
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fn write_u32_le<'a>(&'a mut self, n: u32) -> WriteU32Le<&'a mut Self>
where Self: Unpin,

Writes an unsigned 32-bit integer in little-endian order to the underlying writer. Read more
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fn write_i32_le<'a>(&'a mut self, n: i32) -> WriteI32Le<&'a mut Self>
where Self: Unpin,

Writes a signed 32-bit integer in little-endian order to the underlying writer. Read more
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fn write_u64_le<'a>(&'a mut self, n: u64) -> WriteU64Le<&'a mut Self>
where Self: Unpin,

Writes an unsigned 64-bit integer in little-endian order to the underlying writer. Read more
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fn write_i64_le<'a>(&'a mut self, n: i64) -> WriteI64Le<&'a mut Self>
where Self: Unpin,

Writes an signed 64-bit integer in little-endian order to the underlying writer. Read more
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fn write_u128_le<'a>(&'a mut self, n: u128) -> WriteU128Le<&'a mut Self>
where Self: Unpin,

Writes an unsigned 128-bit integer in little-endian order to the underlying writer. Read more
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fn write_i128_le<'a>(&'a mut self, n: i128) -> WriteI128Le<&'a mut Self>
where Self: Unpin,

Writes an signed 128-bit integer in little-endian order to the underlying writer. Read more
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fn write_f32_le<'a>(&'a mut self, n: f32) -> WriteF32Le<&'a mut Self>
where Self: Unpin,

Writes an 32-bit floating point type in little-endian order to the underlying writer. Read more
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fn write_f64_le<'a>(&'a mut self, n: f64) -> WriteF64Le<&'a mut Self>
where Self: Unpin,

Writes an 64-bit floating point type in little-endian order to the underlying writer. Read more
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fn flush(&mut self) -> Flush<'_, Self>
where Self: Unpin,

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
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fn shutdown(&mut self) -> Shutdown<'_, Self>
where Self: Unpin,

Shuts down the output stream, ensuring that the value can be dropped cleanly. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.