Refactor bufread::decoder: Extract poll ready check (#418)

Move the check into the generic implementation,
instead of repeating

Author: NobodyXu

crates/async-compression/src/futures/bufread/generic/decoder.rs

@@ -23,10 +23,8 @@ impl<R: AsyncBufRead, D: DecodeV2> AsyncRead for Decoder<R, D> {
         }
 
         let mut output = WriteBuffer::new_initialized(buf);
-        match self.do_poll_read(cx, &mut output)? {
-            Poll::Pending if output.written().is_empty() => Poll::Pending,
-            _ => Poll::Ready(Ok(output.written_len())),
-        }
+        self.do_poll_read(cx, &mut output)
+            .map_ok(|()| output.written_len())
     }
 }
 

crates/async-compression/src/futures/bufread/generic/encoder.rs

@@ -23,10 +23,8 @@ impl<R: AsyncBufRead, E: EncodeV2> AsyncRead for Encoder<R, E> {
         }
 
         let mut output = WriteBuffer::new_initialized(buf);
-        match self.do_poll_read(cx, &mut output)? {
-            Poll::Pending if output.written().is_empty() => Poll::Pending,
-            _ => Poll::Ready(Ok(output.written_len())),
-        }
+        self.do_poll_read(cx, &mut output)
+            .map_ok(|()| output.written_len())
     }
 }
 

crates/async-compression/src/generic/bufread/decoder.rs

@@ -175,7 +175,11 @@ macro_rules! impl_decoder {
             }
 
             loop {
-                let mut input = PartialBuffer::new(ready!(reader.as_mut().poll_fill_buf(cx))?);
+                let mut input = PartialBuffer::new(match reader.as_mut().poll_fill_buf(cx)? {
+                    Poll::Ready(input) => input,
+                    Poll::Pending if output.written().is_empty() => return Poll::Pending,
+                    _ => return Poll::Ready(Ok(())),
+                });
 
                 let control_flow = inner.do_poll_read(output, decoder, &mut input, false);
 

crates/async-compression/src/tokio/bufread/generic/mod.rs

@@ -30,8 +30,5 @@ fn poll_read(
     unsafe { buf.assume_init(initialized) };
     buf.advance(written);
 
-    match res? {
-        Poll::Pending if written == 0 => Poll::Pending,
-        _ => Poll::Ready(Ok(())),
-    }
+    res
 }