private static void writeValue()

in vector/src/main/codegen/templates/ComplexCopier.java [48:134]
82 lines of code
21 McCabe index (conditional complexity)

  private static void writeValue(FieldReader reader, FieldWriter writer) {
    final MinorType mt = reader.getMinorType();

      switch (mt) {

      case LIST:
      case LISTVIEW:
      case LARGELIST:
      case LARGELISTVIEW:
      case FIXED_SIZE_LIST:
        if (reader.isSet()) {
          writer.startList();
          while (reader.next()) {
            FieldReader childReader = reader.reader();
            FieldWriter childWriter = getListWriterForReader(childReader, writer);
            if (childReader.isSet()) {
              writeValue(childReader, childWriter);
            } else {
              childWriter.writeNull();
            }
          }
          writer.endList();
        } else {
          writer.writeNull();
        }
        break;
      case MAP:
        if (reader.isSet()) {
          UnionMapReader mapReader = (UnionMapReader) reader;
          writer.startMap();
          while (mapReader.next()) {
            FieldReader structReader = reader.reader();
            if (structReader.isSet()) {
              writer.startEntry();
              writeValue(mapReader.key(), getMapWriterForReader(mapReader.key(), writer.key()));
              writeValue(mapReader.value(), getMapWriterForReader(mapReader.value(), writer.value()));
              writer.endEntry();
            } else {
              writer.writeNull();
            }
          }
          writer.endMap();
        } else {
          writer.writeNull();
        }
        break;
      case STRUCT:
        if (reader.isSet()) {
          writer.start();
          for(String name : reader){
            FieldReader childReader = reader.reader(name);
            if (childReader.getMinorType() != Types.MinorType.NULL) {
              FieldWriter childWriter = getStructWriterForReader(childReader, writer, name);
              if (childReader.isSet()) {
                writeValue(childReader, childWriter);
              } else {
                childWriter.writeNull();
              }
            }
          }
          writer.end();
        } else {
          writer.writeNull();
        }
        break;
  <#list vv.types as type><#list type.minor as minor><#assign name = minor.class?cap_first />
  <#assign fields = minor.fields!type.fields />
  <#assign uncappedName = name?uncap_first/>

  <#if !minor.typeParams?? || minor.class?starts_with("Decimal") >

      case ${name?upper_case}:
        if (reader.isSet()) {
          Nullable${name}Holder ${uncappedName}Holder = new Nullable${name}Holder();
          reader.read(${uncappedName}Holder);
          if (${uncappedName}Holder.isSet == 1) {
            writer.write${name}(<#list fields as field>${uncappedName}Holder.${field.name}<#if field_has_next>, </#if></#list><#if minor.class?starts_with("Decimal")>, new ArrowType.Decimal(${uncappedName}Holder.precision, ${uncappedName}Holder.scale, ${name}Holder.WIDTH * 8)</#if>);
          }
        } else {
          writer.writeNull();
        }
        break;

  </#if>
  </#list></#list>
      }
 }