org.apache.hadoop.io.erasurecode.rawcoder.XORRawEncoder 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.hadoop.io.erasurecode.rawcoder;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.erasurecode.ErasureCoderOptions;
import java.nio.ByteBuffer;
/**
* A raw encoder in XOR code scheme in pure Java, adapted from HDFS-RAID.
*
* XOR code is an important primitive code scheme in erasure coding and often
* used in advanced codes, like HitchHiker and LRC, though itself is rarely
* deployed independently.
*/
@InterfaceAudience.Private
public class XORRawEncoder extends RawErasureEncoder {
public XORRawEncoder(ErasureCoderOptions coderOptions) {
super(coderOptions);
}
protected void doEncode(ByteBufferEncodingState encodingState) {
CoderUtil.resetOutputBuffers(encodingState.outputs,
encodingState.encodeLength);
ByteBuffer output = encodingState.outputs[0];
// Get the first buffer's data.
int iIdx, oIdx;
for (iIdx = encodingState.inputs[0].position(), oIdx = output.position();
iIdx < encodingState.inputs[0].limit(); iIdx++, oIdx++) {
output.put(oIdx, encodingState.inputs[0].get(iIdx));
}
// XOR with everything else.
for (int i = 1; i < encodingState.inputs.length; i++) {
for (iIdx = encodingState.inputs[i].position(), oIdx = output.position();
iIdx < encodingState.inputs[i].limit();
iIdx++, oIdx++) {
output.put(oIdx, (byte) (output.get(oIdx) ^
encodingState.inputs[i].get(iIdx)));
}
}
}
@Override
protected void doEncode(ByteArrayEncodingState encodingState) {
int dataLen = encodingState.encodeLength;
CoderUtil.resetOutputBuffers(encodingState.outputs,
encodingState.outputOffsets, dataLen);
byte[] output = encodingState.outputs[0];
// Get the first buffer's data.
int iIdx, oIdx;
for (iIdx = encodingState.inputOffsets[0],
oIdx = encodingState.outputOffsets[0];
iIdx < encodingState.inputOffsets[0] + dataLen; iIdx++, oIdx++) {
output[oIdx] = encodingState.inputs[0][iIdx];
}
// XOR with everything else.
for (int i = 1; i < encodingState.inputs.length; i++) {
for (iIdx = encodingState.inputOffsets[i],
oIdx = encodingState.outputOffsets[0];
iIdx < encodingState.inputOffsets[i] + dataLen; iIdx++, oIdx++) {
output[oIdx] ^= encodingState.inputs[i][iIdx];
}
}
}
}