Move std::io into alloc and core

library/alloc/src/io/copy.rs

@@ -0,0 +1,79 @@
+mod generic;
+mod specialization;
+
+use self::generic::generic_copy;
+#[doc(hidden)]
+#[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
+pub use self::specialization::SpecCopy;
+use self::specialization::specialized_copy;
+use crate::io::{Read, Result, Write};
+
+#[derive(Debug)]
+#[doc(hidden)]
+#[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
+pub enum CopyState {
+    Ended(u64),
+    Fallback(u64),
+}
+
+/// Copies the entire contents of a reader into a writer.
+///
+/// This function will continuously read data from `reader` and then
+/// write it into `writer` in a streaming fashion until `reader`
+/// returns EOF.
+///
+/// On success, the total number of bytes that were copied from
+/// `reader` to `writer` is returned.
+///
+/// If you want to copy the contents of one file to another and you’re
+/// working with filesystem paths, see the [`fs::copy`] function.
+///
+// FIXME(#74481): Hard-links required to link from `alloc` to `std`
+/// [`fs::copy`]: ../../std/fs/fn.copy.html
+///
+/// # Errors
+///
+/// This function will return an error immediately if any call to [`read`] or
+/// [`write`] returns an error. All instances of [`ErrorKind::Interrupted`] are
+/// handled by this function and the underlying operation is retried.
+///
+/// [`read`]: Read::read
+/// [`write`]: Write::write
+/// [`ErrorKind::Interrupted`]: crate::io::ErrorKind::Interrupted
+///
+/// # Examples
+///
+/// ```
+/// use std::io;
+///
+/// fn main() -> io::Result<()> {
+///     let mut reader: &[u8] = b"hello";
+///     let mut writer: Vec<u8> = vec![];
+///
+///     io::copy(&mut reader, &mut writer)?;
+///
+///     assert_eq!(&b"hello"[..], &writer[..]);
+///     Ok(())
+/// }
+/// ```
+///
+/// # Platform-specific behavior
+///
+/// On Linux (including Android), this function uses `copy_file_range(2)`,
+/// `sendfile(2)` or `splice(2)` syscalls to move data directly between file
+/// descriptors if possible.
+///
+/// Note that platform-specific behavior may change in the future.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
+where
+    R: Read,
+    W: Write,
+{
+    match specialized_copy(reader, writer)? {
+        CopyState::Ended(copied) => Ok(copied),
+        CopyState::Fallback(copied) => {
+            generic_copy(reader, writer).map(|additional| copied + additional)
+        }
+    }
+}

library/std/src/io/copy.rs → library/alloc/src/io/copy/generic.rs

@@ -1,80 +1,19 @@
-use super::{BorrowedBuf, BufReader, BufWriter, DEFAULT_BUF_SIZE, Read, Result, Write};
-use crate::alloc::Allocator;
-use crate::cmp;
+use core::cmp;
+use core::mem::MaybeUninit;
+
+#[cfg(not(no_global_oom_handling))]
 use crate::collections::VecDeque;
-use crate::io::IoSlice;
-use crate::mem::MaybeUninit;
-use crate::sys::io::{CopyState, kernel_copy};
-
-#[cfg(test)]
-mod tests;
-
-/// Copies the entire contents of a reader into a writer.
-///
-/// This function will continuously read data from `reader` and then
-/// write it into `writer` in a streaming fashion until `reader`
-/// returns EOF.
-///
-/// On success, the total number of bytes that were copied from
-/// `reader` to `writer` is returned.
-///
-/// If you want to copy the contents of one file to another and you’re
-/// working with filesystem paths, see the [`fs::copy`] function.
-///
-/// [`fs::copy`]: crate::fs::copy
-///
-/// # Errors
-///
-/// This function will return an error immediately if any call to [`read`] or
-/// [`write`] returns an error. All instances of [`ErrorKind::Interrupted`] are
-/// handled by this function and the underlying operation is retried.
-///
-/// [`read`]: Read::read
-/// [`write`]: Write::write
-/// [`ErrorKind::Interrupted`]: crate::io::ErrorKind::Interrupted
-///
-/// # Examples
-///
-/// ```
-/// use std::io;
-///
-/// fn main() -> io::Result<()> {
-///     let mut reader: &[u8] = b"hello";
-///     let mut writer: Vec<u8> = vec![];
-///
-///     io::copy(&mut reader, &mut writer)?;
-///
-///     assert_eq!(&b"hello"[..], &writer[..]);
-///     Ok(())
-/// }
-/// ```
-///
-/// # Platform-specific behavior
-///
-/// On Linux (including Android), this function uses `copy_file_range(2)`,
-/// `sendfile(2)` or `splice(2)` syscalls to move data directly between file
-/// descriptors if possible.
-///
-/// Note that platform-specific behavior [may change in the future][changes].
-///
-/// [changes]: crate::io#platform-specific-behavior
-#[stable(feature = "rust1", since = "1.0.0")]
-pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
-where
-    R: Read,
-    W: Write,
-{
-    match kernel_copy(reader, writer)? {
-        CopyState::Ended(copied) => Ok(copied),
-        CopyState::Fallback(copied) => {
-            generic_copy(reader, writer).map(|additional| copied + additional)
-        }
-    }
-}
+use crate::io::{BorrowedBuf, BufReader, BufWriter, DEFAULT_BUF_SIZE, Read, Result, Write};
+use crate::vec::Vec;
+#[cfg_attr(
+    no_global_oom_handling,
+    expect(unused_imports, reason = "only required for VecDeque specialization")
+)]
+use crate::{alloc::Allocator, io::IoSlice};
 
 /// The userspace read-write-loop implementation of `io::copy` that is used when
 /// OS-specific specializations for copy offloading are not available or not applicable.
-fn generic_copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
+pub(super) fn generic_copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
 where
     R: Read,
     W: Write,
@@ -128,6 +67,7 @@ impl BufferedReaderSpec for &[u8] {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
 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,

library/alloc/src/io/copy/specialization.rs

@@ -0,0 +1,75 @@
+//! Provides specialization for `io::copy`.
+
+use super::CopyState;
+use crate::io::{BufReader, Read, Result, Take, Write};
+
+/// The implementation of `io::copy` that can rely on platform specific specialization
+/// provided by `libstd`.
+pub(super) fn specialized_copy<R: ?Sized, W: ?Sized>(
+    reader: &mut R,
+    writer: &mut W,
+) -> Result<CopyState>
+where
+    R: Read,
+    W: Write,
+{
+    SpecCopyInner::copy((reader, writer))
+}
+
+trait SpecCopyInner {
+    fn copy(self) -> Result<CopyState>;
+}
+
+impl<R: Read + ?Sized, W: Write + ?Sized> SpecCopyInner for (&mut R, &mut W) {
+    default fn copy(self) -> Result<CopyState> {
+        Ok(CopyState::Fallback(0))
+    }
+}
+
+impl<R: SpecCopy, W: Write> SpecCopyInner for (&mut R, &mut W) {
+    fn copy(self) -> Result<CopyState> {
+        <R as SpecCopy>::copy(self.0, self.1)
+    }
+}
+
+#[doc(hidden)]
+#[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")]
+#[rustc_specialization_trait]
+pub trait SpecCopy: Read {
+    /// Attempt to copy from this reader to the provided writer using a specialized
+    /// process.
+    fn copy<R: Read + ?Sized, W: Write + ?Sized>(
+        _reader: &mut R,
+        _writer: &mut W,
+    ) -> Result<CopyState>;
+}
+
+impl<T> SpecCopy for &mut T
+where
+    T: SpecCopy,
+{
+    fn copy<R: Read + ?Sized, W: Write + ?Sized>(
+        reader: &mut R,
+        writer: &mut W,
+    ) -> Result<CopyState> {
+        <T as SpecCopy>::copy(reader, writer)
+    }
+}
+
+impl<T: SpecCopy> SpecCopy for Take<T> {
+    fn copy<R: Read + ?Sized, W: Write + ?Sized>(
+        reader: &mut R,
+        writer: &mut W,
+    ) -> Result<CopyState> {
+        <T as SpecCopy>::copy(reader, writer)
+    }
+}
+
+impl<T: ?Sized + SpecCopy> SpecCopy for BufReader<T> {
+    fn copy<R: Read + ?Sized, W: Write + ?Sized>(
+        reader: &mut R,
+        writer: &mut W,
+    ) -> Result<CopyState> {
+        <T as SpecCopy>::copy(reader, writer)
+    }
+}