/**
* 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.hadoop.io.erasurecode.coder;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.io.erasurecode.ECBlockGroup;
/**
* An erasure coder to perform encoding or decoding given a group. Generally it
* involves calculating necessary internal steps according to codec logic. For
* each step,it calculates necessary input blocks to read chunks from and output
* parity blocks to write parity chunks into from the group. It also takes care
* of appropriate raw coder to use for the step. And encapsulates all the
* necessary info (input blocks, output blocks and raw coder) into a step
* represented by {@link ErasureCodingStep}. ErasureCoder callers can use the
* step to do the real work with retrieved input and output chunks.
*
* Note, currently only one coding step is supported. Will support complex cases
* of multiple coding steps.
*
*/
@InterfaceAudience.Private
public interface ErasureCoder extends Configurable {
/**
* The number of data input units for the coding. A unit can be a byte,
* chunk or buffer or even a block.
* @return count of data input units
*/
public int getNumDataUnits();
/**
* The number of parity output units for the coding. A unit can be a byte,
* chunk, buffer or even a block.
* @return count of parity output units
*/
public int getNumParityUnits();
/**
* Calculate the encoding or decoding steps given a block blockGroup.
*
* Note, currently only one coding step is supported. Will support complex
* cases of multiple coding steps.
*
* @param blockGroup the erasure coding block group containing all necessary
* information for codec calculation
*/
public ErasureCodingStep calculateCoding(ECBlockGroup blockGroup);
/**
* Tell if direct or off-heap buffer is preferred or not. It's for callers to
* decide how to allocate coding chunk buffers, either on heap or off heap.
* It will return false by default.
* @return true if direct buffer is preferred for performance consideration,
* otherwise false.
*/
public boolean preferDirectBuffer();
/**
* Release the resources if any. Good chance to invoke RawErasureCoder#release.
*/
public void release();
}