Add AsyncBufRead implementation for ProgressBarIter (#315)

src/iter.rs

@@ -200,6 +200,24 @@ impl<W: tokio::io::AsyncSeek + Unpin> tokio::io::AsyncSeek for ProgressBarIter<W
     }
 }
 
+#[cfg(feature = "tokio")]
+impl<W: tokio::io::AsyncBufRead + Unpin + tokio::io::AsyncRead> tokio::io::AsyncBufRead
+    for ProgressBarIter<W>
+{
+    fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
+        let this = self.get_mut();
+        let result = Pin::new(&mut this.it).poll_fill_buf(cx);
+        if let Poll::Ready(Ok(buf)) = &result {
+            this.progress.inc(buf.len() as u64);
+        }
+        result
+    }
+
+    fn consume(mut self: Pin<&mut Self>, amt: usize) {
+        Pin::new(&mut self.it).consume(amt);
+    }
+}
+
 impl<W: io::Write> io::Write for ProgressBarIter<W> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         self.it.write(buf).map(|inc| {