content: /*
   * 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.
   */
  package org.apache.arrow.c;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.io.StringWriter;
  import java.nio.charset.StandardCharsets;
  import org.apache.arrow.c.jni.JniWrapper;
  import org.apache.arrow.c.jni.PrivateData;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.vector.ipc.ArrowReader;
  import org.apache.arrow.vector.types.pojo.Schema;
  
  /** Utility to export an {@link ArrowReader} as an ArrowArrayStream. */
  final class ArrayStreamExporter {
    private final BufferAllocator allocator;
  
    ArrayStreamExporter(BufferAllocator allocator) {
      this.allocator = allocator;
    }
  
    /** Java-side state for the exported stream. */
    static class ExportedArrayStreamPrivateData implements PrivateData {
      final BufferAllocator allocator;
      final ArrowReader reader;
      // Read by the JNI side for get_last_error
      byte[] lastError;
  
      ExportedArrayStreamPrivateData(BufferAllocator allocator, ArrowReader reader) {
        this.allocator = allocator;
        this.reader = reader;
      }
  
      private int setLastError(Throwable err) {
        // Do not let exceptions propagate up to JNI
        try {
          StringWriter buf = new StringWriter();
          PrintWriter writer = new PrintWriter(buf);
          err.printStackTrace(writer);
          lastError = buf.toString().getBytes(StandardCharsets.UTF_8);
        } catch (Throwable e) {
          // Bail out of setting the error message - we'll still return an error code
          lastError = null;
        }
        return 5; // = EIO
      }
  
      @SuppressWarnings("unused") // Used by JNI
      int getNext(long arrayAddress) {
        try (ArrowArray out = ArrowArray.wrap(arrayAddress)) {
          if (reader.loadNextBatch()) {
            Data.exportVectorSchemaRoot(allocator, reader.getVectorSchemaRoot(), reader, out);
          } else {
            out.markReleased();
          }
          return 0;
        } catch (Throwable e) {
          return setLastError(e);
        }
      }
  
      @SuppressWarnings("unused") // Used by JNI
      int getSchema(long schemaAddress) {
        try (ArrowSchema out = ArrowSchema.wrap(schemaAddress)) {
          final Schema schema = reader.getVectorSchemaRoot().getSchema();
          Data.exportSchema(allocator, schema, reader, out);
          return 0;
        } catch (Throwable e) {
          return setLastError(e);
        }
      }
  
      @Override
      public void close() {
        try {
          reader.close();
        } catch (IOException e) {
          // XXX: C Data Interface gives us no way to signal errors to the caller,
          // but the JNI side will catch this and log an error.
          throw new RuntimeException(e);
        }
      }
    }
  
    void export(ArrowArrayStream stream, ArrowReader reader) {
      ExportedArrayStreamPrivateData data = new ExportedArrayStreamPrivateData(allocator, reader);
      try {
        JniWrapper.get().exportArrayStream(stream.memoryAddress(), data);
      } catch (Exception e) {
        data.close();
        throw e;
      }
    }
  }
  