Move std::io::Seek to core::io

library/alloc/src/io/impls.rs

@@ -1,5 +1,7 @@
 use crate::boxed::Box;
-use crate::io::SizeHint;
+use crate::io::{self, Seek, SeekFrom, SizeHint};
+#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
+use crate::sync::Arc;
 
 // =============================================================================
 // Forwarding implementations
@@ -18,5 +20,66 @@ impl<T> SizeHint for Box<T> {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<S: Seek + ?Sized> Seek for Box<S> {
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
+
+    #[inline]
+    fn rewind(&mut self) -> io::Result<()> {
+        (**self).rewind()
+    }
+
+    #[inline]
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (**self).stream_len()
+    }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
+
+    #[inline]
+    fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
+        (**self).seek_relative(offset)
+    }
+}
+
 // =============================================================================
 // In-memory buffer implementations
+
+#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
+#[stable(feature = "io_traits_arc", since = "1.73.0")]
+impl<S: Seek + ?Sized> Seek for Arc<S>
+where
+    for<'a> &'a S: Seek,
+    S: crate::io::IoHandle,
+{
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (&**self).seek(pos)
+    }
+
+    #[inline]
+    fn rewind(&mut self) -> io::Result<()> {
+        (&**self).rewind()
+    }
+
+    #[inline]
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (&**self).stream_len()
+    }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (&**self).stream_position()
+    }
+
+    #[inline]
+    fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
+        (&**self).seek_relative(offset)
+    }
+}

library/alloc/src/io/mod.rs

@@ -13,9 +13,9 @@ pub use core::io::const_error;
 pub use core::io::{BorrowedBuf, BorrowedCursor};
 #[unstable(feature = "alloc_io", issue = "154046")]
 pub use core::io::{
-    Chain, Cursor, Empty, Error, ErrorKind, IoSlice, IoSliceMut, Repeat, Result, Sink, Take, empty,
-    repeat, sink,
+    Chain, Cursor, Empty, Error, ErrorKind, IoSlice, IoSliceMut, Repeat, Result, Seek, SeekFrom,
+    Sink, Take, empty, repeat, sink,
 };
 #[doc(hidden)]
 #[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
-pub use core::io::{IoHandle, OsFunctions, SizeHint, chain, take};
+pub use core::io::{IoHandle, OsFunctions, SizeHint, chain, stream_len_default, take};

library/alloc/src/lib.rs

@@ -155,6 +155,7 @@
 #![feature(ptr_metadata)]
 #![feature(raw_os_error_ty)]
 #![feature(rev_into_inner)]
+#![feature(seek_stream_len)]
 #![feature(set_ptr_value)]
 #![feature(share_trait)]
 #![feature(sized_type_properties)]

library/core/src/io/cursor.rs

@@ -1,3 +1,5 @@
+use crate::io::{self, ErrorKind, SeekFrom};
+
 /// A `Cursor` wraps an in-memory buffer and provides it with a
 /// [`Seek`] implementation.
 ///
@@ -21,7 +23,7 @@
 /// [`File`]: ../../std/fs/struct.File.html
 /// [`Read`]: ../../std/io/trait.Read.html
 /// [`Write`]: ../../std/io/trait.Write.html
-/// [`Seek`]: ../../std/io/trait.Seek.html
+/// [`Seek`]: crate::io::Seek
 /// [Vec]: ../../alloc/vec/struct.Vec.html
 ///
 /// ```no_run
@@ -291,3 +293,38 @@ where
         self.pos = other.pos;
     }
 }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> io::Seek for Cursor<T>
+where
+    T: AsRef<[u8]>,
+{
+    fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
+        let (base_pos, offset) = match style {
+            SeekFrom::Start(n) => {
+                self.set_position(n);
+                return Ok(n);
+            }
+            SeekFrom::End(n) => (self.get_ref().as_ref().len() as u64, n),
+            SeekFrom::Current(n) => (self.position(), n),
+        };
+        match base_pos.checked_add_signed(offset) {
+            Some(n) => {
+                self.set_position(n);
+                Ok(n)
+            }
+            None => Err(io::const_error!(
+                ErrorKind::InvalidInput,
+                "invalid seek to a negative or overflowing position",
+            )),
+        }
+    }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        Ok(self.get_ref().as_ref().len() as u64)
+    }
+
+    fn stream_position(&mut self) -> io::Result<u64> {
+        Ok(self.position())
+    }
+}

library/core/src/io/error.rs

@@ -80,7 +80,7 @@ pub type Result<T> = result::Result<T, Error>;
 // FIXME(#74481): Hard-links required to link from `core` to `std`
 /// [Read]: ../../std/io/trait.Read.html
 /// [Write]: ../../std/io/trait.Write.html
-/// [Seek]: ../../std/io/trait.Seek.html
+/// [Seek]: crate::io::Seek
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_has_incoherent_inherent_impls]
 pub struct Error {

library/core/src/io/impls.rs

@@ -1,4 +1,4 @@
-use crate::io::SizeHint;
+use crate::io::{self, Seek, SeekFrom, SizeHint};
 
 // =============================================================================
 // Forwarding implementations
@@ -17,6 +17,34 @@ impl<T> SizeHint for &mut T {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<S: Seek + ?Sized> Seek for &mut S {
+    #[inline]
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
+
+    #[inline]
+    fn rewind(&mut self) -> io::Result<()> {
+        (**self).rewind()
+    }
+
+    #[inline]
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (**self).stream_len()
+    }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
+
+    #[inline]
+    fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
+        (**self).seek_relative(offset)
+    }
+}
+
 // =============================================================================
 // In-memory buffer implementations
 

library/core/src/io/mod.rs

@@ -5,6 +5,7 @@ mod cursor;
 mod error;
 mod impls;
 mod io_slice;
+mod seek;
 mod size_hint;
 mod util;
 
@@ -21,12 +22,14 @@ pub use self::{
     cursor::Cursor,
     error::{Error, ErrorKind, Result},
     io_slice::{IoSlice, IoSliceMut},
+    seek::{Seek, SeekFrom},
     util::{Chain, Empty, Repeat, Sink, Take, empty, repeat, sink},
 };
 #[doc(hidden)]
 #[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
 pub use self::{
     error::{Custom, CustomOwner, OsFunctions},
+    seek::stream_len_default,
     size_hint::SizeHint,
     util::{chain, take},
 };
@@ -46,7 +49,7 @@ pub use self::{
 /// [file]: ../../std/fs/struct.File.html
 /// [arc]: ../../alloc/sync/struct.Arc.html
 /// [`Write`]: ../../std/io/trait.Write.html
-/// [`Seek`]: ../../std/io/trait.Seek.html
+/// [`Seek`]: crate::io::Seek
 #[doc(hidden)]
 #[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
 pub trait IoHandle {}