write::BzDecoder: Fix infinite loop on drop when no data is read or written

src/write.rs

@@ -204,7 +204,13 @@ impl<W: Write> BzDecoder<W> {
     /// [`write`]: Self::write
     pub fn try_finish(&mut self) -> io::Result<()> {
         while !self.done {
-            let _ = self.write(&[])?;
+            // The write is effectively a `self.flush()`, but we want to know how many
+            // bytes were written. exit if no input was read and no output was written
+            if self.write(&[])? == 0 {
+                // finishing the output stream is effectively EOF of the input
+                let msg = "Input EOF reached before logical stream end";
+                return Err(io::Error::new(io::ErrorKind::UnexpectedEof, msg));
+            }
         }
         self.dump()
     }
@@ -311,6 +317,14 @@ mod tests {
         assert_eq!(&data[..], b"");
     }
 
+    #[test]
+    fn write_empty_drop() {
+        // the drop implementation used to loop infinitely for empty input
+        // see https://github.com/trifectatechfoundation/bzip2-rs/pull/118
+        let d = BzDecoder::new(Vec::new());
+        drop(d);
+    }
+
     #[test]
     fn write_invalid() {
         // see https://github.com/trifectatechfoundation/bzip2-rs/issues/98