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Rollup merge of #111074 - WaffleLapkin:🌟unsizes_your_buf_reader🌟, r=A…
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…manieu

Relax implicit `T: Sized` bounds on `BufReader<T>`, `BufWriter<T>` and `LineWriter<T>`

TL;DR:
```diff,rust
-pub struct BufReader<R> { /* ... */ }
+pub struct BufReader<R: ?Sized> { /* ... */ }

-pub struct BufWriter<W: Write> { /* ... */ }
+pub struct BufWriter<W: ?Sized + Write> { /* ... */ }

-pub struct LineWriter<W: Write> { /* ... */ }
+pub struct LineWriter<W: ?Sized + Write> { /* ... */ }
```

This allows using `&mut BufReader<dyn Read>`, for example.

**This is an insta-stable change**.
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@compiler-errors
compiler-errors authored Jun 16, 2023
2 parents 6a94e87 + 29302a2 commit c55af41
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Showing 7 changed files with 118 additions and 111 deletions.
27 changes: 15 additions & 12 deletions library/std/src/io/buffered/bufreader.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,9 +47,9 @@ use buffer::Buffer;
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct BufReader<R> {
inner: R,
pub struct BufReader<R: ?Sized> {
buf: Buffer,
inner: R,
}

impl<R: Read> BufReader<R> {
Expand Down Expand Up @@ -95,7 +95,7 @@ impl<R: Read> BufReader<R> {
}
}

impl<R> BufReader<R> {
impl<R: ?Sized> BufReader<R> {
/// Gets a reference to the underlying reader.
///
/// It is inadvisable to directly read from the underlying reader.
Expand Down Expand Up @@ -213,7 +213,10 @@ impl<R> BufReader<R> {
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(self) -> R {
pub fn into_inner(self) -> R
where
R: Sized,
{
self.inner
}

Expand All @@ -226,13 +229,13 @@ impl<R> BufReader<R> {

// This is only used by a test which asserts that the initialization-tracking is correct.
#[cfg(test)]
impl<R> BufReader<R> {
impl<R: ?Sized> BufReader<R> {
pub fn initialized(&self) -> usize {
self.buf.initialized()
}
}

impl<R: Seek> BufReader<R> {
impl<R: ?Sized + Seek> BufReader<R> {
/// Seeks relative to the current position. If the new position lies within the buffer,
/// the buffer will not be flushed, allowing for more efficient seeks.
/// This method does not return the location of the underlying reader, so the caller
Expand All @@ -257,7 +260,7 @@ impl<R: Seek> BufReader<R> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<R: Read> Read for BufReader<R> {
impl<R: ?Sized + Read> Read for BufReader<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
// If we don't have any buffered data and we're doing a massive read
// (larger than our internal buffer), bypass our internal buffer
Expand Down Expand Up @@ -371,7 +374,7 @@ impl<R: Read> Read for BufReader<R> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<R: Read> BufRead for BufReader<R> {
impl<R: ?Sized + Read> BufRead for BufReader<R> {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
self.buf.fill_buf(&mut self.inner)
}
Expand All @@ -384,11 +387,11 @@ impl<R: Read> BufRead for BufReader<R> {
#[stable(feature = "rust1", since = "1.0.0")]
impl<R> fmt::Debug for BufReader<R>
where
R: fmt::Debug,
R: ?Sized + fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("BufReader")
.field("reader", &self.inner)
.field("reader", &&self.inner)
.field(
"buffer",
&format_args!("{}/{}", self.buf.filled() - self.buf.pos(), self.capacity()),
Expand All @@ -398,7 +401,7 @@ where
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<R: Seek> Seek for BufReader<R> {
impl<R: ?Sized + Seek> Seek for BufReader<R> {
/// Seek to an offset, in bytes, in the underlying reader.
///
/// The position used for seeking with <code>[SeekFrom::Current]\(_)</code> is the
Expand Down Expand Up @@ -491,7 +494,7 @@ impl<R: Seek> Seek for BufReader<R> {
}
}

impl<T> SizeHint for BufReader<T> {
impl<T: ?Sized> SizeHint for BufReader<T> {
#[inline]
fn lower_bound(&self) -> usize {
SizeHint::lower_bound(self.get_ref()) + self.buffer().len()
Expand Down
138 changes: 70 additions & 68 deletions library/std/src/io/buffered/bufwriter.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -67,8 +67,7 @@ use crate::ptr;
/// [`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
Expand All @@ -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> {
Expand Down Expand Up @@ -115,6 +115,69 @@ impl<W: Write> 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.
///
Expand Down Expand Up @@ -284,67 +347,6 @@ impl<W: Write> BufWriter<W> {
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`,
Expand Down Expand Up @@ -511,7 +513,7 @@ impl fmt::Debug for WriterPanicked {
}

#[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.
Expand Down Expand Up @@ -640,20 +642,20 @@ impl<W: Write> Write for BufWriter<W> {
}

#[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.
Expand All @@ -664,7 +666,7 @@ impl<W: Write + Seek> Seek for BufWriter<W> {
}

#[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
Expand Down
50 changes: 26 additions & 24 deletions library/std/src/io/buffered/linewriter.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ use crate::io::{self, buffered::LineWriterShim, BufWriter, IntoInnerError, IoSli
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct LineWriter<W: Write> {
pub struct LineWriter<W: ?Sized + Write> {
inner: BufWriter<W>,
}

Expand Down Expand Up @@ -109,27 +109,6 @@ impl<W: Write> LineWriter<W> {
LineWriter { inner: BufWriter::with_capacity(capacity, inner) }
}

/// Gets a reference to the underlying writer.
///
/// # Examples
///
/// ```no_run
/// 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(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &W {
self.inner.get_ref()
}

/// Gets a mutable reference to the underlying writer.
///
/// Caution must be taken when calling methods on the mutable reference
Expand Down Expand Up @@ -184,8 +163,31 @@ impl<W: Write> LineWriter<W> {
}
}

impl<W: ?Sized + Write> LineWriter<W> {
/// Gets a reference to the underlying writer.
///
/// # Examples
///
/// ```no_run
/// 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(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &W {
self.inner.get_ref()
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> Write for LineWriter<W> {
impl<W: ?Sized + Write> Write for LineWriter<W> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
LineWriterShim::new(&mut self.inner).write(buf)
}
Expand Down Expand Up @@ -216,7 +218,7 @@ impl<W: Write> Write for LineWriter<W> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<W: Write> fmt::Debug for LineWriter<W>
impl<W: ?Sized + Write> fmt::Debug for LineWriter<W>
where
W: fmt::Debug,
{
Expand Down
6 changes: 3 additions & 3 deletions library/std/src/io/buffered/linewritershim.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,11 +11,11 @@ use crate::sys_common::memchr;
/// `BufWriters` to be temporarily given line-buffering logic; this is what
/// enables Stdout to be alternately in line-buffered or block-buffered mode.
#[derive(Debug)]
pub struct LineWriterShim<'a, W: Write> {
pub struct LineWriterShim<'a, W: ?Sized + Write> {
buffer: &'a mut BufWriter<W>,
}

impl<'a, W: Write> LineWriterShim<'a, W> {
impl<'a, W: ?Sized + Write> LineWriterShim<'a, W> {
pub fn new(buffer: &'a mut BufWriter<W>) -> Self {
Self { buffer }
}
Expand Down Expand Up @@ -49,7 +49,7 @@ impl<'a, W: Write> LineWriterShim<'a, W> {
}
}

impl<'a, W: Write> Write for LineWriterShim<'a, W> {
impl<'a, W: ?Sized + Write> Write for LineWriterShim<'a, W> {
/// Write some data into this BufReader with line buffering. This means
/// that, if any newlines are present in the data, the data up to the last
/// newline is sent directly to the underlying writer, and data after it
Expand Down
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