Auto merge of #122393 - a1phyr:specialize_read_buf_exact, r=joboet

Specialize many implementations of `Read::read_buf_exact` This makes all implementations of `Read` that have a specialized `read_exact` implementation also have one for `read_buf_exact`.
rust-lang · Apr 10, 2024 · e908cfd · e908cfd
2 parents b14d8b2 8734809
commit e908cfd
Show file tree

Hide file tree

Showing 5 changed files with 74 additions and 18 deletions.
diff --git a/library/std/src/io/buffered/bufreader.rs b/library/std/src/io/buffered/bufreader.rs
@@ -322,6  322,14 @@ impl<R: ?Sized   Read> Read for BufReader<R> {
         crate::io::default_read_exact(self, buf)
     }
 
     fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
         if self.buf.consume_with(cursor.capacity(), |claimed| cursor.append(claimed)) {
             return Ok(());
         }
 
         crate::io::default_read_buf_exact(self, cursor)
     }
 
     fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         let total_len = bufs.iter().map(|b| b.len()).sum::<usize>();
         if self.buf.pos() == self.buf.filled() && total_len >= self.capacity() {

diff --git a/library/std/src/io/cursor.rs b/library/std/src/io/cursor.rs
@@ -357,6  357,13 @@ where
         self.pos  = n as u64;
         Ok(())
     }
 
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         let n = cursor.capacity();
         Read::read_buf_exact(&mut self.remaining_slice(), cursor)?;
         self.pos  = n as u64;
         Ok(())
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

diff --git a/library/std/src/io/impls.rs b/library/std/src/io/impls.rs
@@ -50,6  50,10 @@ impl<R: Read   ?Sized> Read for &mut R {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         (**self).read_exact(buf)
     }
     #[inline]
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         (**self).read_buf_exact(cursor)
     }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write   ?Sized> Write for &mut W {
@@ -154,6  158,10 @@ impl<R: Read   ?Sized> Read for Box<R> {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         (**self).read_exact(buf)
     }
     #[inline]
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         (**self).read_buf_exact(cursor)
     }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write   ?Sized> Write for Box<W> {
@@ -301,6  309,22 @@ impl Read for &[u8] {
         Ok(())
     }
 
     #[inline]
     fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
         if cursor.capacity() > self.len() {
             return Err(io::const_io_error!(
                 ErrorKind::UnexpectedEof,
                 "failed to fill whole buffer"
             ));
         }
         let (a, b) = self.split_at(cursor.capacity());
 
         cursor.append(a);
 
         *self = b;
         Ok(())
     }
 
     #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         let len = self.len();

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
@@ -582,6  582,29 @@ where
     Ok(())
 }
 
 pub(crate) fn default_read_buf_exact<R: Read   ?Sized>(
     this: &mut R,
     mut cursor: BorrowedCursor<'_>,
 ) -> Result<()> {
     while cursor.capacity() > 0 {
         let prev_written = cursor.written();
         match this.read_buf(cursor.reborrow()) {
             Ok(()) => {}
             Err(e) if e.is_interrupted() => continue,
             Err(e) => return Err(e),
         }
 
         if cursor.written() == prev_written {
             return Err(error::const_io_error!(
                 ErrorKind::UnexpectedEof,
                 "failed to fill whole buffer"
             ));
         }
     }
 
     Ok(())
 }
 
 /// The `Read` trait allows for reading bytes from a source.
 ///
 /// Implementors of the `Read` trait are called 'readers'.
@@ -978,24  1001,8 @@ pub trait Read {
     ///
     /// If this function returns an error, all bytes read will be appended to `cursor`.
     #[unstable(feature = "read_buf", issue = "78485")]
-    fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> Result<()> {
-        while cursor.capacity() > 0 {
-            let prev_written = cursor.written();
-            match self.read_buf(cursor.reborrow()) {
-                Ok(()) => {}
-                Err(e) if e.is_interrupted() => continue,
-                Err(e) => return Err(e),
-            }
-
-            if cursor.written() == prev_written {
-                return Err(error::const_io_error!(
-                    ErrorKind::UnexpectedEof,
-                    "failed to fill whole buffer"
-                ));
-            }
-        }
-
-        Ok(())
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<()> {
         default_read_buf_exact(self, cursor)
     }
 
     /// Creates a "by reference" adaptor for this instance of `Read`.

diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
@@ -451,6  451,9 @@ impl Read for Stdin {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         self.lock().read_exact(buf)
     }
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         self.lock().read_buf_exact(cursor)
     }
 }
 
 #[stable(feature = "read_shared_stdin", since = "1.78.0")]
@@ -477,6  480,9 @@ impl Read for &Stdin {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         self.lock().read_exact(buf)
     }
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         self.lock().read_buf_exact(cursor)
     }
 }
 
 // only used by platform-dependent io::copy specializations, i.e. unused on some platforms
@@ -517,6  523,10 @@ impl Read for StdinLock<'_> {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         self.inner.read_exact(buf)
     }
 
     fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
         self.inner.read_buf_exact(cursor)
     }
 }
 
 impl SpecReadByte for StdinLock<'_> {