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Relax implicit W: Sized bound on BufWriter<W>

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This commit is contained in:
Maybe Waffle 2023-05-01 17:52:28 +00:00
parent e77b14e2ac
commit a49753373b
3 changed files with 72 additions and 70 deletions
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138
library/std/src/io/buffered/bufwriter.rs
View File

@ -67,8 +67,7 @@
/// [`TcpStream`]: crate::net::TcpStream
/// [`flush`]: BufWriter::flush
#[stable(feature = "rust1", since = "1.0.0")]
pub struct BufWriter<W: Write> {
inner: W,
pub struct BufWriter<W: ?Sized + Write> {
// The buffer. Avoid using this like a normal `Vec` in common code paths.
// That is, don't use `buf.push`, `buf.extend_from_slice`, or any other
// methods that require bounds checking or the like. This makes an enormous
@ -78,6 +77,7 @@ pub struct BufWriter<W: Write> {
// write the buffered data a second time in BufWriter's destructor. This
// flag tells the Drop impl if it should skip the flush.
panicked: bool,
inner: W,
}
impl<W: Write> BufWriter<W> {
@ -115,6 +115,69 @@ pub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W> {
BufWriter { inner, buf: Vec::with_capacity(capacity), panicked: false }
}
/// 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
///
/// ```no_run
/// 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();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
match self.flush_buf() {
Err(e) => Err(IntoInnerError::new(self, e)),
Ok(()) => Ok(self.into_parts().0),
}
}
/// 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");
/// ```
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
pub fn into_parts(mut self) -> (W, Result<Vec<u8>, WriterPanicked>) {
let buf = mem::take(&mut self.buf);
let buf = if !self.panicked { Ok(buf) } else { Err(WriterPanicked { buf }) };
// SAFETY: forget(self) prevents double dropping inner
let inner = unsafe { ptr::read(&self.inner) };
mem::forget(self);
(inner, buf)
}
}
impl<W: ?Sized + Write> BufWriter<W> {
/// Send data in our local buffer into the inner writer, looping as
/// necessary until either it's all been sent or an error occurs.
///
@ -284,67 +347,6 @@ pub fn capacity(&self) -> usize {
self.buf.capacity()
}
/// 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
///
/// ```no_run
/// 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();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
match self.flush_buf() {
Err(e) => Err(IntoInnerError::new(self, e)),
Ok(()) => Ok(self.into_parts().0),
}
}
/// 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");
/// ```
#[stable(feature = "bufwriter_into_parts", since = "1.56.0")]
pub fn into_parts(mut self) -> (W, Result<Vec<u8>, WriterPanicked>) {
let buf = mem::take(&mut self.buf);
let buf = if !self.panicked { Ok(buf) } else { Err(WriterPanicked { buf }) };
// SAFETY: forget(self) prevents double dropping inner
let inner = unsafe { ptr::read(&self.inner) };
mem::forget(self);
(inner, buf)
}
// Ensure this function does not get inlined into `write`, so that it
// remains inlineable and its common path remains as short as possible.
// If this function ends up being called frequently relative to `write`,
@ -511,7 +513,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> Write for BufWriter<W> {
impl<W: ?Sized + Write> Write for BufWriter<W> {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
// Use < instead of <= to avoid a needless trip through the buffer in some cases.
@ -640,20 +642,20 @@ fn flush(&mut self) -> io::Result<()> {
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> fmt::Debug for BufWriter<W>
impl<W: ?Sized + Write> fmt::Debug for BufWriter<W>
where
W: fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("BufWriter")
.field("writer", &self.inner)
.field("writer", &&self.inner)
.field("buffer", &format_args!("{}/{}", self.buf.len(), self.buf.capacity()))
.finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write + Seek> Seek for BufWriter<W> {
impl<W: ?Sized + Write + Seek> Seek for BufWriter<W> {
/// Seek to the offset, in bytes, in the underlying writer.
///
/// Seeking always writes out the internal buffer before seeking.
@ -664,7 +666,7 @@ fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> Drop for BufWriter<W> {
impl<W: ?Sized + Write> Drop for BufWriter<W> {
fn drop(&mut self) {
if !self.panicked {
// dtors should not panic, so we ignore a failed flush

2
library/std/src/io/copy.rs
View File

@ -86,7 +86,7 @@ impl<W: Write + ?Sized> BufferedCopySpec for W {
}
}
impl<I: Write> BufferedCopySpec for BufWriter<I> {
impl<I: ?Sized + Write> BufferedCopySpec for BufWriter<I> {
fn copy_to<R: Read + ?Sized>(reader: &mut R, writer: &mut Self) -> Result<u64> {
if writer.capacity() < DEFAULT_BUF_SIZE {
return stack_buffer_copy(reader, writer);

2
library/std/src/sys/unix/kernel_copy.rs
View File

@ -495,7 +495,7 @@ fn properties(&self) -> CopyParams {
}
}
impl<T: CopyWrite> CopyWrite for BufWriter<T> {
impl<T: ?Sized + CopyWrite> CopyWrite for BufWriter<T> {
fn properties(&self) -> CopyParams {
self.get_ref().properties()
}