org.apache.pig.PigStreamingBase Maven / Gradle / Ivy
/*
* 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.pig;
import java.io.IOException;
import org.apache.pig.classification.InterfaceAudience;
import org.apache.pig.classification.InterfaceStability;
import org.apache.pig.data.WritableByteArray;
import org.apache.pig.data.Tuple;
/**
* The interface is used for the custom mapping of
* - a {@link Tuple} to a byte array. The byte array is fed to the stdin
* of the streaming process.
* - a byte array, received from the stdout of the streaming process,
* to a {@link Tuple}.
*
* This interface is designed to provide a common protocol for data exchange
* between Pig runtime and streaming executables.
*
* Typically, a user implements this interface for a particular type of stream
* command and specifies the implementation class in the Pig DEFINE statement.
*
* @since Pig 0.12
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public abstract class PigStreamingBase implements PigToStream, StreamToPig {
@Override
@Deprecated
public final byte[] serialize(Tuple t) throws IOException {
WritableByteArray data = serializeToBytes(t);
if (data.getLength() == data.getData().length) {
return data.getData();
} else {
byte[] buf = new byte[data.getLength()];
System.arraycopy(data.getData(), 0, buf, 0, data.getLength());
return buf;
}
}
/**
* Given a tuple, produce an array of bytes to be passed to the streaming
* executable.
* @param t Tuple to serialize
* @return Serialized form of the tuple
* @throws IOException
*/
public abstract WritableByteArray serializeToBytes(Tuple t) throws IOException;
@Override
@Deprecated
public final Tuple deserialize(byte[] bytes) throws IOException {
return deserialize(bytes, 0, bytes.length);
}
/**
* Given a byte array from a streaming executable, produce a tuple.
* @param bytes bytes to deserialize.
* @param offset the offset in the byte array from which to deserialize.
* @param length the number of bytes from the offset of the byte array to deserialize.
* @return Data as a Pig Tuple.
* @throws IOException
*/
public abstract Tuple deserialize(byte[] bytes, int offset, int length) throws IOException;
/**
* This will be called on the front end during planning and not on the back
* end during execution.
*
* @return the {@link LoadCaster} associated with this object, or null if
* there is no such LoadCaster.
* @throws IOException if there is an exception during LoadCaster
*/
@Override
public abstract LoadCaster getLoadCaster() throws IOException;
}