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 static org.apache.arrow.util.Preconditions.checkArgument;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import org.apache.arrow.memory.ArrowBuf;
  import org.apache.arrow.memory.BufferAllocator;
  import org.apache.arrow.util.Collections2;
  import org.apache.arrow.vector.BaseVariableWidthViewVector;
  import org.apache.arrow.vector.FieldVector;
  import org.apache.arrow.vector.TypeLayout;
  import org.apache.arrow.vector.complex.StructVector;
  import org.apache.arrow.vector.compression.CompressionCodec;
  import org.apache.arrow.vector.compression.CompressionUtil;
  import org.apache.arrow.vector.compression.NoCompressionCodec;
  import org.apache.arrow.vector.ipc.message.ArrowFieldNode;
  import org.apache.arrow.vector.ipc.message.ArrowRecordBatch;
  import org.apache.arrow.vector.types.pojo.Field;
  import org.apache.arrow.vector.types.pojo.Schema;
  
  /** Loads buffers into {@link StructVector}. */
  public class StructVectorLoader {
  
    private final Schema schema;
    private final CompressionCodec.Factory factory;
  
    /**
     * A flag indicating if decompression is needed. This will affect the behavior of releasing
     * buffers.
     */
    private boolean decompressionNeeded;
  
    /**
     * Construct with a schema.
     *
     * <p>The schema referred to here can be obtained from the struct vector. The schema here should
     * be the children of a struct vector, not a schema containing the struct field itself. For
     * example: <code>
     * Schema schema = new Schema(structVector.getField().getChildren());
     * </code>
     *
     * @param schema buffers are added based on schema.
     */
    public StructVectorLoader(Schema schema) {
      this(schema, NoCompressionCodec.Factory.INSTANCE);
    }
  
    /**
     * Construct with a schema and a compression codec factory.
     *
     * @param schema buffers are added based on schema.
     * @param factory the factory to create codec.
     */
    public StructVectorLoader(Schema schema, CompressionCodec.Factory factory) {
      this.schema = schema;
      this.factory = factory;
    }
  
    /**
     * Loads the record batch into the struct vector.
     *
     * <p>This will not close the record batch.
     *
     * @param recordBatch the batch to load
     */
    public StructVector load(BufferAllocator allocator, ArrowRecordBatch recordBatch) {
      StructVector result = StructVector.emptyWithDuplicates("", allocator);
      result.initializeChildrenFromFields(this.schema.getFields());
  
      Iterator<ArrowBuf> buffers = recordBatch.getBuffers().iterator();
      Iterator<ArrowFieldNode> nodes = recordBatch.getNodes().iterator();
      CompressionUtil.CodecType codecType =
          CompressionUtil.CodecType.fromCompressionType(recordBatch.getBodyCompression().getCodec());
      decompressionNeeded = codecType != CompressionUtil.CodecType.NO_COMPRESSION;
      CompressionCodec codec =
          decompressionNeeded ? factory.createCodec(codecType) : NoCompressionCodec.INSTANCE;
      Iterator<Long> variadicBufferCounts = Collections.emptyIterator();
      if (recordBatch.getVariadicBufferCounts() != null
          && !recordBatch.getVariadicBufferCounts().isEmpty()) {
        variadicBufferCounts = recordBatch.getVariadicBufferCounts().iterator();
      }
      for (FieldVector fieldVector : result.getChildrenFromFields()) {
        loadBuffers(fieldVector, fieldVector.getField(), buffers, nodes, codec, variadicBufferCounts);
      }
      result.loadFieldBuffers(
          new ArrowFieldNode(recordBatch.getLength(), 0), Collections.singletonList(null));
      if (nodes.hasNext() || buffers.hasNext() || variadicBufferCounts.hasNext()) {
        throw new IllegalArgumentException(
            "not all nodes, buffers and variadicBufferCounts were consumed. nodes: "
                + Collections2.toString(nodes)
                + " buffers: "
                + Collections2.toString(buffers)
                + " variadicBufferCounts: "
                + Collections2.toString(variadicBufferCounts));
      }
      return result;
    }
  
    private void loadBuffers(
        FieldVector vector,
        Field field,
        Iterator<ArrowBuf> buffers,
        Iterator<ArrowFieldNode> nodes,
        CompressionCodec codec,
        Iterator<Long> variadicBufferCounts) {
      checkArgument(nodes.hasNext(), "no more field nodes for field %s and vector %s", field, vector);
      ArrowFieldNode fieldNode = nodes.next();
      // variadicBufferLayoutCount will be 0 for vectors of a type except BaseVariableWidthViewVector
      long variadicBufferLayoutCount = 0;
      if (vector instanceof BaseVariableWidthViewVector) {
        if (variadicBufferCounts.hasNext()) {
          variadicBufferLayoutCount = variadicBufferCounts.next();
        } else {
          throw new IllegalStateException(
              "No variadicBufferCounts available for BaseVariableWidthViewVector");
        }
      }
      int bufferLayoutCount =
          (int) (variadicBufferLayoutCount + TypeLayout.getTypeBufferCount(field.getType()));
      List<ArrowBuf> ownBuffers = new ArrayList<>(bufferLayoutCount);
      for (int j = 0; j < bufferLayoutCount; j++) {
        ArrowBuf nextBuf = buffers.next();
        // for vectors without nulls, the buffer is empty, so there is no need to
        // decompress it.
        ArrowBuf bufferToAdd =
            nextBuf.writerIndex() > 0 ? codec.decompress(vector.getAllocator(), nextBuf) : nextBuf;
        ownBuffers.add(bufferToAdd);
        if (decompressionNeeded) {
          // decompression performed
          nextBuf.getReferenceManager().retain();
        }
      }
      try {
        vector.loadFieldBuffers(fieldNode, ownBuffers);
        if (decompressionNeeded) {
          for (ArrowBuf buf : ownBuffers) {
            buf.close();
          }
        }
      } catch (RuntimeException e) {
        throw new IllegalArgumentException(
            "Could not load buffers for field " + field + ". error message: " + e.getMessage(), e);
      }
      List<Field> children = field.getChildren();
      if (children.size() > 0) {
        List<FieldVector> childrenFromFields = vector.getChildrenFromFields();
        checkArgument(
            children.size() == childrenFromFields.size(),
            "should have as many children as in the schema: found %s expected %s",
            childrenFromFields.size(),
            children.size());
        for (int i = 0; i < childrenFromFields.size(); i++) {
          Field child = children.get(i);
          FieldVector fieldVector = childrenFromFields.get(i);
          loadBuffers(fieldVector, child, buffers, nodes, codec, variadicBufferCounts);
        }
      }
    }
  }
  