add write_all to AsyncWrite

and use it to implement io::copy

Author: pchickey

src/io/copy.rs

@@ -12,14 +12,6 @@ where
         if bytes_read == 0 {
             break 'read Ok(());
         }
-        let mut slice = &buf[0..bytes_read];
-
-        'write: loop {
-            let bytes_written = writer.write(slice).await?;
-            slice = &slice[bytes_written..];
-            if slice.is_empty() {
-                break 'write;
-            }
-        }
+        writer.write_all(&buf[0..bytes_read]).await?;
     }
 }

src/io/write.rs

@@ -5,4 +5,15 @@ pub trait AsyncWrite {
     // Required methods
     async fn write(&mut self, buf: &[u8]) -> io::Result<usize>;
     async fn flush(&mut self) -> io::Result<()>;
+
+    async fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        let mut to_write = &buf[0..];
+        loop {
+            let bytes_written = self.write(to_write).await?;
+            to_write = &to_write[bytes_written..];
+            if to_write.is_empty() {
+                return Ok(());
+            }
+        }
+    }
 }