[GitHub] [arrow] kou commented on a diff in pull request #34842: GH-34858: [Swift] Initial reader impl

["kou (via GitHub)" <gi...@apache.org>]

kou commented on code in PR #34842:
URL: https://github.com/apache/arrow/pull/34842#discussion_r1156400638


##########
swift/Arrow/Sources/Arrow/File_generated.swift:
##########


Review Comment:
   Should we add these generated files to this repository?
   Can we generate them in build time instead of adding them?



##########
swift/Arrow/Tests/ArrowTests/testdata.arrow:
##########


Review Comment:
   How did you create these test data?
   If you created them by using other Apache Arrow implementation such as C++ implementation, how about adding a program that generates them and generating them in test time instead of adding these test data?



##########
swift/Arrow/Sources/Arrow/ChunkedArray.swift:
##########
@@ -42,8 +45,32 @@ public class ChunkedArray<T> {
         self.nullCount = nullCount
     }
     
-    subscript(_ index: UInt) -> ArrowArray<T> {
-        return arrays[Int(index)]
+    public subscript(_ index: UInt) -> T? {
+        if arrays.count == 0 {
+            return nil
+        }
+        
+        var localIndex = index
+        var arrayIndex = 0;
+        var len: UInt = arrays[arrayIndex].length
+        while(localIndex > len) {

Review Comment:
   Is a space missing here?
   
   ```suggestion
           while (localIndex > len) {
   ```



##########
swift/Arrow/Sources/Arrow/ArrowReader.swift:
##########
@@ -0,0 +1,163 @@
+// 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.
+
+import FlatBuffers
+import Foundation
+
+public enum ArrowError: Error {
+    case runtimeError(String)
+}
+
+let FILEMARKER = "ARROW1"
+let CONTINUATIONMARKER = -1
+
+public class ArrowReader {

Review Comment:
   We have "streaming format" https://arrow.apache.org/docs/format/Columnar.html#ipc-streaming-format and "file format" https://arrow.apache.org/docs/format/Columnar.html#ipc-file-format .
   It seems that this is a reader for "file format".
   We may want to add "file" to this class name such as `ArrowFileReader`.



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