hadoop XORRawDecoder 源码
haddop XORRawDecoder 代码
文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java
/**
* 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 decoder 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 XORRawDecoder extends RawErasureDecoder {
public XORRawDecoder(ErasureCoderOptions coderOptions) {
super(coderOptions);
}
@Override
protected void doDecode(ByteBufferDecodingState decodingState) {
CoderUtil.resetOutputBuffers(decodingState.outputs,
decodingState.decodeLength);
ByteBuffer output = decodingState.outputs[0];
int erasedIdx = decodingState.erasedIndexes[0];
// Process the inputs.
int iIdx, oIdx;
for (int i = 0; i < decodingState.inputs.length; i++) {
// Skip the erased location.
if (i == erasedIdx) {
continue;
}
for (iIdx = decodingState.inputs[i].position(), oIdx = output.position();
iIdx < decodingState.inputs[i].limit();
iIdx++, oIdx++) {
output.put(oIdx, (byte) (output.get(oIdx) ^
decodingState.inputs[i].get(iIdx)));
}
}
}
@Override
protected void doDecode(ByteArrayDecodingState decodingState) {
byte[] output = decodingState.outputs[0];
int dataLen = decodingState.decodeLength;
CoderUtil.resetOutputBuffers(decodingState.outputs,
decodingState.outputOffsets, dataLen);
int erasedIdx = decodingState.erasedIndexes[0];
// Process the inputs.
int iIdx, oIdx;
for (int i = 0; i < decodingState.inputs.length; i++) {
// Skip the erased location.
if (i == erasedIdx) {
continue;
}
for (iIdx = decodingState.inputOffsets[i],
oIdx = decodingState.outputOffsets[0];
iIdx < decodingState.inputOffsets[i] + dataLen; iIdx++, oIdx++) {
output[oIdx] ^= decodingState.inputs[i][iIdx];
}
}
}
}
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