std: Standardize (input, output) param orderings

This functions swaps the order of arguments to a few functions that previously
took (output, input) parameters, but now take (input, output) parameters (in
that order).

The affected functions are:

* ptr::copy
* ptr::copy_nonoverlapping
* slice::bytes::copy_memory
* intrinsics::copy
* intrinsics::copy_nonoverlapping

Closes #22890
[breaking-change]

3 files changed, 5 insertions, 5 deletions

diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs
index 98581fc43f8..8eea06bf6b0 100644
--- a/src/libstd/io/buffered.rs
+++ b/src/libstd/io/buffered.rs
@@ -177,8 +177,8 @@ impl<W: Write> BufWriter<W> {
         if written > 0 {
             // NB: would be better expressed as .remove(0..n) if it existed
             unsafe {
-                ptr::copy(self.buf.as_mut_ptr(),
-                          self.buf.as_ptr().offset(written as isize),
+                ptr::copy(self.buf.as_ptr().offset(written as isize),
+                          self.buf.as_mut_ptr(),
                           len - written);
             }
         }
diff --git a/src/libstd/io/cursor.rs b/src/libstd/io/cursor.rs
index 79f0af670b4..c8a41beecbc 100644
--- a/src/libstd/io/cursor.rs
+++ b/src/libstd/io/cursor.rs
@@ -151,7 +151,7 @@ impl Write for Cursor<Vec<u8>> {
         // there (left), and what will be appended on the end (right)
         let space = self.inner.len() - pos as usize;
         let (left, right) = buf.split_at(cmp::min(space, buf.len()));
-        slice::bytes::copy_memory(&mut self.inner[(pos as usize)..], left);
+        slice::bytes::copy_memory(left, &mut self.inner[(pos as usize)..]);
         self.inner.push_all(right);
 
         // Bump us forward
diff --git a/src/libstd/io/impls.rs b/src/libstd/io/impls.rs
index ce03e26866b..52daba36213 100644
--- a/src/libstd/io/impls.rs
+++ b/src/libstd/io/impls.rs
@@ -149,7 +149,7 @@ impl<'a> Read for &'a [u8] {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         let amt = cmp::min(buf.len(), self.len());
         let (a, b) = self.split_at(amt);
-        slice::bytes::copy_memory(buf, a);
+        slice::bytes::copy_memory(a, buf);
         *self = b;
         Ok(amt)
     }
@@ -170,7 +170,7 @@ impl<'a> Write for &'a mut [u8] {
     fn write(&mut self, data: &[u8]) -> io::Result<usize> {
         let amt = cmp::min(data.len(), self.len());
         let (a, b) = mem::replace(self, &mut []).split_at_mut(amt);
-        slice::bytes::copy_memory(a, &data[..amt]);
+        slice::bytes::copy_memory(&data[..amt], a);
         *self = b;
         Ok(amt)
     }