limit visibility of copy offload helpers to sys::unix module

library/std/src/io/copy.rs

@@ -1,9 +1,6 @@
 use crate::io::{self, ErrorKind, Read, Write};
 use crate::mem::MaybeUninit;
 
-#[cfg(all(test, unix))]
-mod tests;
-
 /// Copies the entire contents of a reader into a writer.
 ///
 /// This function will continuously read data from `reader` and then

library/std/src/sys/unix/fs.rs

@@ -1214,7 +1214,7 @@ pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
 /// if one of the files' cursor +`max_len` would exceed u64::MAX (`EOVERFLOW`).
 /// If the initial file offset was 0 then `Fallback` will only contain `0`.
 #[cfg(any(target_os = "linux", target_os = "android"))]
-pub(crate) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) -> CopyResult {
+pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) -> CopyResult {
     use crate::cmp;
     use crate::sync::atomic::{AtomicBool, Ordering};
 
@@ -1302,12 +1302,12 @@ pub(crate) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
 }
 
 #[derive(PartialEq)]
-pub(crate) enum SpliceMode {
+pub(super) enum SpliceMode {
     Sendfile,
     Splice,
 }
 
-pub(crate) enum CopyResult {
+pub(super) enum CopyResult {
     Ended(io::Result<u64>),
     Fallback(u64),
 }
@@ -1315,7 +1315,7 @@ pub(crate) enum CopyResult {
 /// performs splice or sendfile between file descriptors
 /// Does _not_ fall back to a generic copy loop.
 #[cfg(any(target_os = "linux", target_os = "android"))]
-pub(crate) fn sendfile_splice(
+pub(super) fn sendfile_splice(
     mode: SpliceMode,
     reader: RawFd,
     writer: RawFd,

library/std/src/sys/unix/kernel_copy.rs

@@ -58,6 +58,9 @@ use crate::os::unix::io::{AsRawFd, FromRawFd, RawFd};
 use crate::process::{ChildStderr, ChildStdin, ChildStdout};
 use crate::sys::fs::{copy_regular_files, sendfile_splice, CopyResult, SpliceMode};
 
+#[cfg(test)]
+mod tests;
+
 pub(crate) fn copy_spec<R: Read + ?Sized, W: Write + ?Sized>(
     read: &mut R,
     write: &mut W,