1 files changed, 5 insertions, 15 deletions
diff --git a/library/std/src/sys/pal/windows/pipe.rs b/library/std/src/sys/pal/windows/pipe.rs
index 19364617e74..7a309b9638b 100644
--- a/library/std/src/sys/pal/windows/pipe.rs
+++ b/library/std/src/sys/pal/windows/pipe.rs
@@ -5,7 +5,6 @@ use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut, Read};
 use crate::mem;
 use crate::path::Path;
 use crate::ptr;
-use crate::slice;
 use crate::sync::atomic::AtomicUsize;
 use crate::sync::atomic::Ordering::Relaxed;
 use crate::sys::c;
@@ -479,8 +478,11 @@ impl<'a> AsyncPipe<'a> {
     fn schedule_read(&mut self) -> io::Result<bool> {
         assert_eq!(self.state, State::NotReading);
         let amt = unsafe {
-            let slice = slice_to_end(self.dst);
-            self.pipe.read_overlapped(slice, &mut *self.overlapped)?
+            if self.dst.capacity() == self.dst.len() {
+                let additional = if self.dst.capacity() == 0 { 16 } else { 1 };
+                self.dst.reserve(additional);
+            }
+            self.pipe.read_overlapped(self.dst.spare_capacity_mut(), &mut *self.overlapped)?
         };
 
         // If this read finished immediately then our overlapped event will
@@ -560,15 +562,3 @@ impl<'a> Drop for AsyncPipe<'a> {
         }
     }
 }
-
-#[allow(unsafe_op_in_unsafe_fn)]
-unsafe fn slice_to_end(v: &mut Vec<u8>) -> &mut [u8] {
-    if v.capacity() == 0 {
-        v.reserve(16);
-    }
-    if v.capacity() == v.len() {
-        v.reserve(1);
-    }
-    // FIXME: Isn't this just spare_capacity_mut but worse?
-    slice::from_raw_parts_mut(v.as_mut_ptr().add(v.len()), v.capacity() - v.len())
-}