/*
* Copyright © 2014 Cask Data, Inc.
*
* Licensed 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 co.cask.cdap.api.data.batch;
/**
* Defines a reader of a dataset {@link Split}.
* @param <KEY> The key type.
* @param <VALUE> The value type.
*/
public abstract class SplitReader<KEY, VALUE> {
/**
* Called once at initialization.
* @param split The split that defines the range of records to read.
* @throws InterruptedException
*/
public abstract void initialize(Split split) throws InterruptedException;
/**
* Read the next key, value pair.
* @return true if a key/value pair was read.
* @throws InterruptedException
*/
public abstract boolean nextKeyValue() throws InterruptedException;
/**
* Get the current key.
* @return The current key, or null if there is no current key.
* @throws InterruptedException
*/
public abstract KEY getCurrentKey() throws InterruptedException;
/**
* Get the current value.
* @return The current value of the object that was read.
* @throws InterruptedException
*/
public abstract VALUE getCurrentValue() throws InterruptedException;
/**
* The current progress of the record reader through its data.
* By default progress is not reported in the middle of split reading.
* @return A number between 0.0 and 1.0 that is the fraction of the data that has been read.
* @throws InterruptedException
*/
public float getProgress() throws InterruptedException {
return 0;
}
/**
* Close the record reader.
*/
public abstract void close();
}