asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/LenDescriptor.java

package edu.uci.ics.asterix.runtime.evaluators.functions;

import java.io.DataOutput;
import java.io.IOException;

import edu.uci.ics.asterix.common.functions.FunctionConstants;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AOrderedListSerializerDeserializer;
import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AUnorderedListSerializerDeserializer;
import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
import edu.uci.ics.asterix.om.base.AInt32;
import edu.uci.ics.asterix.om.base.AMutableInt32;
import edu.uci.ics.asterix.om.base.ANull;
import edu.uci.ics.asterix.om.types.ATypeTag;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
import edu.uci.ics.hyracks.algebricks.runtime.base.IEvaluator;
import edu.uci.ics.hyracks.algebricks.runtime.base.IEvaluatorFactory;
import edu.uci.ics.hyracks.api.dataflow.value.ISerializerDeserializer;
import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.ArrayBackedValueStorage;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IDataOutputProvider;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

public class LenDescriptor extends AbstractScalarFunctionDynamicDescriptor {

    private static final long serialVersionUID = 1L;
    private final static FunctionIdentifier FID = new FunctionIdentifier(FunctionConstants.ASTERIX_NS, "len", 1, true);
    private final static byte SER_ORDEREDLIST_TYPE_TAG = ATypeTag.ORDEREDLIST.serialize();
    private final static byte SER_UNORDEREDLIST_TYPE_TAG = ATypeTag.UNORDEREDLIST.serialize();
    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();

    @Override
    public IEvaluatorFactory createEvaluatorFactory(final IEvaluatorFactory[] args) throws AlgebricksException {

        return new IEvaluatorFactory() {
            private static final long serialVersionUID = 1L;

            @Override
            public IEvaluator createEvaluator(final IDataOutputProvider output) throws AlgebricksException {

                return new IEvaluator() {

                    private final DataOutput out = output.getDataOutput();
                    private final ArrayBackedValueStorage inputVal = new ArrayBackedValueStorage();
                    private final IEvaluator evalList = args[0].createEvaluator(inputVal);

                    // result
                    private final AMutableInt32 res = new AMutableInt32(0);
                    @SuppressWarnings("unchecked")
                    private final ISerializerDeserializer<AInt32> int32Serde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.AINT32);
                    @SuppressWarnings("unchecked")
                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
                            .getSerializerDeserializer(BuiltinType.ANULL);

                    @Override
                    public void evaluate(IFrameTupleReference tuple) throws AlgebricksException {
                        inputVal.reset();
                        evalList.evaluate(tuple);

                        byte[] serList = inputVal.getBytes();

                        if (serList[0] == SER_NULL_TYPE_TAG) {
                            try {
                                nullSerde.serialize(ANull.NULL, out);
                            } catch (HyracksDataException e) {
                                throw new AlgebricksException(e);
                            }
                            return;
                        }

                        if (serList[0] != SER_ORDEREDLIST_TYPE_TAG && serList[0] != SER_UNORDEREDLIST_TYPE_TAG) {
                            throw new AlgebricksException("len() can only be called on ordered or unordered lists.");
                        }

                        int numberOfitems = 0;
                        if (serList[0] == SER_ORDEREDLIST_TYPE_TAG)
                            numberOfitems = AOrderedListSerializerDeserializer.getNumberOfItems(serList);
                        else
                            numberOfitems = AUnorderedListSerializerDeserializer.getNumberOfItems(serList);

                        res.setValue(numberOfitems);
                        try {
                            int32Serde.serialize(res, out);
                        } catch (IOException e) {
                            throw new AlgebricksException(e);
                        }
                    }
                };
            }
        };
    }

    @Override
    public FunctionIdentifier getIdentifier() {
        return FID;
    }

}