wjones127 commented on code in PR #34133: URL: https://github.com/apache/arrow/pull/34133#discussion_r1148720269
########## csharp/src/Apache.Arrow/C/CArrowSchemaExporter.cs: ########## @@ -0,0 +1,278 @@ +// 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.Collections.Generic; +using System.IO; +using System.Linq; +using System.Runtime.InteropServices; +using Apache.Arrow.Types; + +namespace Apache.Arrow.C +{ + public static class CArrowSchemaExporter + { + /// <summary> + /// Export a type to a <see cref="CArrowSchema"/>. + /// </summary> + /// <param name="datatype">The datatype to export</param> + /// <param name="schema">An allocated but uninitialized CArrowSchema pointer.</param> + /// <example> + /// <code> + /// CArrowSchema* exportPtr = CArrowSchema.Create(); + /// CArrowSchemaExporter.ExportType(dataType, exportPtr); + /// foreign_import_function(exportPtr); + /// CArrowSchema.Free(exportPtr); + /// </code> + /// </example> + public static unsafe void ExportType(IArrowType datatype, CArrowSchema* schema) + { + if (datatype == null) + { + throw new ArgumentNullException(nameof(datatype)); + } + if (schema == null) + { + throw new ArgumentNullException(nameof(schema)); + } + if (schema->release != null) + { + throw new ArgumentException("Cannot export schema to a struct that is already initialized."); + } + + schema->format = StringUtil.ToCStringUtf8(GetFormat(datatype)); + schema->name = null; + schema->metadata = null; + schema->flags = GetFlags(datatype); + + schema->children = ConstructChildren(datatype, out var numChildren); + schema->n_children = numChildren; + + schema->dictionary = ConstructDictionary(datatype); + + schema->release = (delegate* unmanaged[Stdcall]<CArrowSchema*, void>)Marshal.GetFunctionPointerForDelegate( + ReleaseCArrowSchema); + + schema->private_data = null; + } + + /// <summary> + /// Export a field to a <see cref="CArrowSchema"/>. + /// </summary> + /// <param name="field">The field to export</param> + /// <param name="schema">An allocated but uninitialized CArrowSchema pointer.</param> + /// <example> + /// <code> + /// CArrowSchema* exportPtr = CArrowSchema.Create(); + /// CArrowSchemaExporter.ExportType(field, exportPtr); + /// foreign_import_function(exportPtr); + /// CArrowSchema.Free(exportPtr); + /// </code> + /// </example> + public static unsafe void ExportField(Field field, CArrowSchema* schema) + { + ExportType(field.DataType, schema); + schema->name = StringUtil.ToCStringUtf8(field.Name); + // TODO: field metadata Review Comment: I've created an umbrella issue to track the remaining C data interface tasks (https://github.com/apache/arrow/issues/33856) and another one to track remaining data types to implement (https://github.com/apache/arrow/issues/34736). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
