Merging upstream version 1.73.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 79 insertions, 2 deletions

diff --git a/library/std/src/io/copy.rs b/library/std/src/io/copy.rs
index ef1f4031e..3322940d2 100644
--- a/library/std/src/io/copy.rs
+++ b/library/std/src/io/copy.rs
@@ -1,4 +1,8 @@
 use super::{BorrowedBuf, BufReader, BufWriter, ErrorKind, Read, Result, Write, DEFAULT_BUF_SIZE};
+use crate::alloc::Allocator;
+use crate::cmp;
+use crate::collections::VecDeque;
+use crate::io::IoSlice;
 use crate::mem::MaybeUninit;
 
 #[cfg(test)]
@@ -86,7 +90,7 @@ where
 
 /// Specialization of the read-write loop that reuses the internal
 /// buffer of a BufReader. If there's no buffer then the writer side
-/// should be used intead.
+/// should be used instead.
 trait BufferedReaderSpec {
     fn buffer_size(&self) -> usize;
 
@@ -104,7 +108,39 @@ where
     }
 
     default fn copy_to(&mut self, _to: &mut (impl Write + ?Sized)) -> Result<u64> {
-        unimplemented!("only called from specializations");
+        unreachable!("only called from specializations")
+    }
+}
+
+impl BufferedReaderSpec for &[u8] {
+    fn buffer_size(&self) -> usize {
+        // prefer this specialization since the source "buffer" is all we'll ever need,
+        // even if it's small
+        usize::MAX
+    }
+
+    fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
+        let len = self.len();
+        to.write_all(self)?;
+        *self = &self[len..];
+        Ok(len as u64)
+    }
+}
+
+impl<A: Allocator> BufferedReaderSpec for VecDeque<u8, A> {
+    fn buffer_size(&self) -> usize {
+        // prefer this specialization since the source "buffer" is all we'll ever need,
+        // even if it's small
+        usize::MAX
+    }
+
+    fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
+        let len = self.len();
+        let (front, back) = self.as_slices();
+        let bufs = &mut [IoSlice::new(front), IoSlice::new(back)];
+        to.write_all_vectored(bufs)?;
+        self.clear();
+        Ok(len as u64)
     }
 }
 
@@ -218,6 +254,47 @@ impl<I: Write + ?Sized> BufferedWriterSpec for BufWriter<I> {
     }
 }
 
+impl<A: Allocator> BufferedWriterSpec for Vec<u8, A> {
+    fn buffer_size(&self) -> usize {
+        cmp::max(DEFAULT_BUF_SIZE, self.capacity() - self.len())
+    }
+
+    fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
+        let mut bytes = 0;
+
+        // avoid allocating before we have determined that there's anything to read
+        if self.capacity() == 0 {
+            bytes = stack_buffer_copy(&mut reader.take(DEFAULT_BUF_SIZE as u64), self)?;
+            if bytes == 0 {
+                return Ok(0);
+            }
+        }
+
+        loop {
+            self.reserve(DEFAULT_BUF_SIZE);
+            let mut buf: BorrowedBuf<'_> = self.spare_capacity_mut().into();
+            match reader.read_buf(buf.unfilled()) {
+                Ok(()) => {}
+                Err(e) if e.kind() == ErrorKind::Interrupted => continue,
+                Err(e) => return Err(e),
+            };
+
+            let read = buf.filled().len();
+            if read == 0 {
+                break;
+            }
+
+            // SAFETY: BorrowedBuf guarantees all of its filled bytes are init
+            // and the number of read bytes can't exceed the spare capacity since
+            // that's what the buffer is borrowing from.
+            unsafe { self.set_len(self.len() + read) };
+            bytes += read as u64;
+        }
+
+        Ok(bytes)
+    }
+}
+
 fn stack_buffer_copy<R: Read + ?Sized, W: Write + ?Sized>(
     reader: &mut R,
     writer: &mut W,