[GitHub] [arrow-rs] alamb commented on a diff in pull request #1804: Add public API for decoding parquet footer

[GitBox <gi...@apache.org>]

alamb commented on code in PR #1804:
URL: https://github.com/apache/arrow-rs/pull/1804#discussion_r891423381


##########
parquet/src/arrow/async_reader.rs:
##########
@@ -140,24 +138,13 @@ impl<T: AsyncRead + AsyncSeek + Unpin + Send> AsyncFileReader for T {
             let mut buf = [0_u8; 8];
             self.read_exact(&mut buf).await?;
 
-            if buf[4..] != PARQUET_MAGIC {
-                return Err(general_err!("Invalid Parquet file. Corrupt footer"));
-            }
-
-            let metadata_len = LittleEndian::read_i32(&buf[..4]) as i64;
-            if metadata_len < 0 {
-                return Err(general_err!(
-                    "Invalid Parquet file. Metadata length is less than zero ({})",
-                    metadata_len
-                ));
-            }
-
-            self.seek(SeekFrom::End(-8 - metadata_len)).await?;
+            let metadata_len = decode_footer(&buf)?;
+            self.seek(SeekFrom::End(-8 - metadata_len as i64)).await?;

Review Comment:
   I wonder if we can make this magic `8` a `const` somewhere to help readablility -- or maybe it is already `FOOTER_SIZE`



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