[GitHub] [arrow] CurtHagenlocher commented on a diff in pull request #35496: GH-33856: [C#] Implement C Data Interface for C#

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

CurtHagenlocher commented on code in PR #35496:
URL: https://github.com/apache/arrow/pull/35496#discussion_r1222376209


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csharp/src/Apache.Arrow/C/CArrowArrayStreamImporter.cs:
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@@ -0,0 +1,137 @@
+// 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.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Apache.Arrow.Ipc;
+
+namespace Apache.Arrow.C
+{
+    public static class CArrowArrayStreamImporter
+    {
+        /// <summary>
+        /// Import C pointer as an <see cref="IArrowArrayStream"/>.
+        /// </summary>
+        /// <remarks>
+        /// This will call the release callback on the passed struct if the function fails.
+        /// Otherwise, the release callback is called when the IArrowArrayStream is disposed.
+        /// </remarks>
+        /// <examples>
+        /// Typically, you will allocate an uninitialized CArrowArrayStream pointer,
+        /// pass that to external function, and then use this method to import
+        /// the result.
+        /// 
+        /// <code>
+        /// CArrowArrayStream* importedPtr = CArrowArrayStream.Create();
+        /// foreign_export_function(importedPtr);
+        /// IArrowArrayStream importedStream = CArrowArrayStreamImporter.ImportStream(importedPtr);
+        /// </code>
+        /// </examples>
+        public static unsafe IArrowArrayStream ImportArrayStream(CArrowArrayStream* ptr)
+        {
+            return new ImportedArrowArrayStream(ptr);
+        }
+
+        private sealed unsafe class ImportedArrowArrayStream : IArrowArrayStream
+        {
+            private readonly CArrowArrayStream* _cArrayStream;
+            private readonly Schema _schema;
+            private bool _disposed;
+
+            public ImportedArrowArrayStream(CArrowArrayStream* cArrayStream)
+            {
+                if (cArrayStream == null)
+                {
+                    throw new ArgumentNullException(nameof(cArrayStream));
+                }
+                _cArrayStream = cArrayStream;
+                if (_cArrayStream->release == null)
+                {
+                    throw new ArgumentException("Tried to import an array stream that has already been released.", nameof(cArrayStream));
+                }
+
+                CArrowSchema* cSchema = CArrowSchema.Create();
+                try
+                {
+                    int errno = _cArrayStream->get_schema(_cArrayStream, cSchema);
+                    if (errno != 0)
+                    {
+                        throw new Exception($"Unexpected error recieved from external stream. Errno: {errno}");
+                    }
+                    _schema = CArrowSchemaImporter.ImportSchema(cSchema);
+                }
+                finally
+                {
+                    if (_schema == null)
+                    {
+                        CArrowSchema.Free(cSchema);
+                    }
+                }
+            }
+
+            ~ImportedArrowArrayStream()
+            {
+                Dispose();
+            }
+
+            public Schema Schema => _schema;
+
+            public ValueTask<RecordBatch> ReadNextRecordBatchAsync(CancellationToken cancellationToken = default)
+            {
+                if (_disposed)
+                {
+                    throw new ObjectDisposedException(typeof(ImportedArrowArrayStream).Name);
+                }
+
+                RecordBatch result = null;
+                CArrowArray* cArray = CArrowArray.Create();

Review Comment:
   Yes, this has already been discovered and there's a PR out for fixing it: https://github.com/apache/arrow/pull/35810



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