Improve decode code of read_non_compressed_block()

src/deflate/decode.rs

@@ -82,18 +82,23 @@ where
                 nlen
             ))
         } else {
-            let old_len = self.buffer.len();
-            // We cannot use `self.buffer.set_len()` here because that would
-            // pass uninitialized memory to .read_exact(), which does
-            // NOT guarantee that it will never read from the buffer.
-            // See https://github.com/rust-lang/rust/pull/62102/
-            // Surprisingly, zero-initializing the buffer here
-            // makes decoding 5% **faster** than using reserve() + set_len()
-            self.buffer.resize(old_len + len as usize, 0);
             self.bit_reader
                 .as_inner_mut()
-                .read_exact(&mut self.buffer[old_len..])?;
-            Ok(())
+                .take(len.into())
+                .read_to_end(&mut self.buffer)
+                .and_then(|used| {
+                    if used != len.into() {
+                        Err(io::Error::new(
+                            io::ErrorKind::UnexpectedEof,
+                            format!(
+                                "The reader has incorrect length: expected {}, read {}",
+                                len, used
+                            ),
+                        ))
+                    } else {
+                        Ok(())
+                    }
+                })
         }
     }
     fn read_compressed_block<H>(&mut self, huffman: &H) -> io::Result<()>