fix lint

arrow-flight/src/lib.rs

@@ -452,16 +452,16 @@ mod tests {
             Field::new("c5", DataType::Timestamp(TimeUnit::Millisecond, None), true),
             Field::new("c6", DataType::Time32(TimeUnit::Second), false),
         ]);
-        // V5
+        // V5 with write_legacy_ipc_format = false
+        // this will write the continuation marker
         let option = IpcWriteOptions::default();
         let schema_ipc = SchemaAsIpc::new(&schema, &option);
         let result: SchemaResult = schema_ipc.try_into().unwrap();
-        //
         let des_schema: Schema = (&result).try_into().unwrap();
         assert_eq!(schema, des_schema);
 
         // V4 with write_legacy_ipc_format = true
-        // This will write the continuation marker
+        // this will not write the continuation marker
         let option = IpcWriteOptions::try_new(8, true, MetadataVersion::V4).unwrap();
         let schema_ipc = SchemaAsIpc::new(&schema, &option);
         let result: SchemaResult = schema_ipc.try_into().unwrap();

arrow/src/ipc/convert.rs

@@ -156,7 +156,7 @@ pub fn try_schema_from_flatbuffer_bytes(bytes: &[u8]) -> Result<Schema> {
 
 /// Try deserialize the IPC format bytes into a schema
 pub fn try_schema_from_ipc_buffer(buffer: &[u8]) -> Result<Schema> {
-    // There are two type of protocal: https://issues.apache.org/jira/browse/ARROW-6313
+    // There are two protocal types: https://issues.apache.org/jira/browse/ARROW-6313
     // The original protocal is:
     //   4 bytes - the byte length of the payload
     //   a flatbuffer Message whose header is the Schema
@@ -169,9 +169,14 @@ pub fn try_schema_from_ipc_buffer(buffer: &[u8]) -> Result<Schema> {
         // check continuation maker
         let continuation_maker = &buffer[0..4];
         let begin_offset: usize = if continuation_maker.eq(&CONTINUATION_MARKER) {
+            // 4 bytes: CONTINUATION_MARKER
+            // 4 bytes: length
+            // buffer
             4
         } else {
             // backward compatibility for buffer without the continuation maker
+            // 4 bytes: length
+            // buffer
             0
         };
         let msg =
@@ -188,9 +193,9 @@ pub fn try_schema_from_ipc_buffer(buffer: &[u8]) -> Result<Schema> {
         })?;
         Ok(fb_to_schema(ipc_schema))
     } else {
-        Err(ArrowError::ParseError(format!(
-            "The buffer length is less than 4, parser buffer to Schema"
-        )))
+        Err(ArrowError::ParseError(
+            "The buffer length is less than 4 and missing the continuation maker or length of buffer".to_string()
+        ))
     }
 }