ARROW-550: [Format] Draft experimental Tensor flatbuffer message type

cpp/src/arrow/ipc/CMakeLists.txt

@@ -114,6 +114,7 @@ set(FBS_SRC
   ${CMAKE_SOURCE_DIR}/../format/Message.fbs
   ${CMAKE_SOURCE_DIR}/../format/File.fbs
   ${CMAKE_SOURCE_DIR}/../format/Schema.fbs
+  ${CMAKE_SOURCE_DIR}/../format/Tensor.fbs
   ${CMAKE_CURRENT_SOURCE_DIR}/feather.fbs)
 
 foreach(FIL ${FBS_SRC})

format/Message.fbs

@@ -16,6 +16,7 @@
 // under the License.
 
 include "Schema.fbs";
+include "Tensor.fbs";
 
 namespace org.apache.arrow.flatbuf;
 
@@ -82,7 +83,7 @@ table DictionaryBatch {
 /// which may include experimental metadata types. For maximum compatibility,
 /// it is best to send data using RecordBatch
 union MessageHeader {
-  Schema, DictionaryBatch, RecordBatch
+  Schema, DictionaryBatch, RecordBatch, Tensor
 }
 
 table Message {

format/Tensor.fbs

@@ -0,0 +1,60 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+/// EXPERIMENTAL: Metadata for n-dimensional arrays, aka "tensors" or
+/// "ndarrays". Arrow implementations in general are not required to implement
+/// this type
+
+include "Schema.fbs";
+
+namespace org.apache.arrow.flatbuf;
+
+/// Shape data for a single axis in a tensor
+table TensorDim {
+  /// Length of dimension
+  size: long;
+
+  /// Name of the dimension, optional
+  name: string;
+}
+
+enum TensorOrder : byte {
+  /// Higher dimensions vary first when traversing data in byte-contiguous
+  /// order, aka "C order"
+  ROW_MAJOR,
+
+  /// Lower dimensions vary first when traversing data in byte-contiguous
+  /// order, aka "Fortran order"
+  COLUMN_MAJOR
+}
+
+table Tensor {
+  /// The type of data contained in a value cell. Currently only fixed-width
+  /// value types are supported, no strings or nested types
+  type: Type;
+
+  /// The dimensions of the tensor, optionally named
+  shape: [TensorDim];
+
+  /// The memory order of the tensor's data
+  order: TensorOrder;
+
+  /// The location and size of the tensor's data
+  data: Buffer;
+}
+
+root_type Tensor;

java/format/pom.xml

@@ -110,8 +110,9 @@
               <argument>-o</argument>
               <argument>${flatc.generated.files}</argument>
               <argument>../../format/Schema.fbs</argument>
-              <argument>../../format/Message.fbs</argument>
+              <argument>../../format/Tensor.fbs</argument>
               <argument>../../format/File.fbs</argument>
+              <argument>../../format/Message.fbs</argument>
             </arguments>
           </configuration>
         </execution>