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/*-
 * Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle NoSQL
 * Database made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle NoSQL Database for a copy of the license and
 * additional information.
 */

package oracle.kv.impl.api.ops;

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

import oracle.kv.Value;
import oracle.kv.impl.util.FastExternalizable;
import oracle.kv.impl.util.UserDataControl;

/**
 * Holds a Value for a result, optimized to avoid array allocations/copies.
 * Value is serialized on the service from a byte array and deserialized on
 * the client into a Value object.
 *
 * @see #writeFastExternal FastExternalizable format
 */
public class ResultValue implements FastExternalizable {

    /* The value field is non-null on the client and null on the service. */
    private final Value value;
    /* The bytes field is non-null on the service and null on the client. */
    private final byte[] bytes;
    /* A byte array to represent an empty record on the wire to the client */
    private static final byte[] EMPTY_BYTES = new byte[] {0};

    /**
     * Used by the service.
     */
    ResultValue(byte[] bytes) {
        this.value = null;
        if (bytes == null || bytes.length == 0) {
            this.bytes = EMPTY_BYTES;
        } else {
            this.bytes = bytes;
        }
    }

    /**
     * Deserialize into byte array.
     * Used by the client when deserializing a response.
     */
    public ResultValue(DataInput in, short serialVersion)
        throws IOException {

        bytes = null;
        value = new Value(in, serialVersion);
    }

    /**
     * FastExternalizable writer.  Used by both the client and the server when
     * serializing a response.  Format:
     * 
     *  [Choice] ({@link Value}) value // on client
     * 
 [Choice] On server:
     *    
     *     {@link Value#writeFastExternal(DataOutput, short, byte[])
     *         Value.writeFastExternal(} {@link #getBytes bytes)}
     *    
     * 
     */
    @Override
    public void writeFastExternal(DataOutput out,
                                  short serialVersion)
        throws IOException {

        if (value != null) {
            value.writeFastExternal(out, serialVersion);
        } else {
            Value.writeFastExternal(out, serialVersion, bytes);
        }
    }

    /**
     * Used by the client.
     */
    Value getValue() {
        if (value == null) {
            /* Only occurs in tests when RMI is bypassed. */
            return Value.fromByteArray(bytes);
        }
        return value;
    }

    byte[] getBytes() {
        return bytes;
    }

    @Override
    public String toString() {
        return UserDataControl.displayValue(value, bytes);
    }
}