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/**
* 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.HadoopIllegalArgumentException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.erasurecode.ErasureCoderOptions;
import org.apache.hadoop.io.erasurecode.rawcoder.util.DumpUtil;
import org.apache.hadoop.io.erasurecode.rawcoder.util.GF256;
import org.apache.hadoop.io.erasurecode.rawcoder.util.RSUtil;
import java.nio.ByteBuffer;
import java.util.Arrays;
/**
* A raw erasure decoder in RS code scheme in pure Java in case native one
* isn't available in some environment. Please always use native implementations
* when possible. This new Java coder is about 5X faster than the one originated
* from HDFS-RAID, and also compatible with the native/ISA-L coder.
*/
@InterfaceAudience.Private
public class RSRawDecoder extends RawErasureDecoder {
//relevant to schema and won't change during decode calls
private byte[] encodeMatrix;
/**
* Below are relevant to schema and erased indexes, thus may change during
* decode calls.
*/
private byte[] decodeMatrix;
private byte[] invertMatrix;
/**
* Array of input tables generated from coding coefficients previously.
* Must be of size 32*k*rows
*/
private byte[] gfTables;
private int[] cachedErasedIndexes;
private int[] validIndexes;
private int numErasedDataUnits;
private boolean[] erasureFlags;
public RSRawDecoder(ErasureCoderOptions coderOptions) {
super(coderOptions);
int numAllUnits = getNumAllUnits();
if (getNumAllUnits() >= RSUtil.GF.getFieldSize()) {
throw new HadoopIllegalArgumentException(
"Invalid getNumDataUnits() and numParityUnits");
}
encodeMatrix = new byte[numAllUnits * getNumDataUnits()];
RSUtil.genCauchyMatrix(encodeMatrix, numAllUnits, getNumDataUnits());
if (allowVerboseDump()) {
DumpUtil.dumpMatrix(encodeMatrix, getNumDataUnits(), numAllUnits);
}
}
@Override
protected void doDecode(ByteBufferDecodingState decodingState) {
CoderUtil.resetOutputBuffers(decodingState.outputs,
decodingState.decodeLength);
prepareDecoding(decodingState.inputs, decodingState.erasedIndexes);
ByteBuffer[] realInputs = new ByteBuffer[getNumDataUnits()];
for (int i = 0; i < getNumDataUnits(); i++) {
realInputs[i] = decodingState.inputs[validIndexes[i]];
}
RSUtil.encodeData(gfTables, realInputs, decodingState.outputs);
}
@Override
protected void doDecode(ByteArrayDecodingState decodingState) {
int dataLen = decodingState.decodeLength;
CoderUtil.resetOutputBuffers(decodingState.outputs,
decodingState.outputOffsets, dataLen);
prepareDecoding(decodingState.inputs, decodingState.erasedIndexes);
byte[][] realInputs = new byte[getNumDataUnits()][];
int[] realInputOffsets = new int[getNumDataUnits()];
for (int i = 0; i < getNumDataUnits(); i++) {
realInputs[i] = decodingState.inputs[validIndexes[i]];
realInputOffsets[i] = decodingState.inputOffsets[validIndexes[i]];
}
RSUtil.encodeData(gfTables, dataLen, realInputs, realInputOffsets,
decodingState.outputs, decodingState.outputOffsets);
}
private void prepareDecoding(T[] inputs, int[] erasedIndexes) {
int[] tmpValidIndexes = CoderUtil.getValidIndexes(inputs);
if (Arrays.equals(this.cachedErasedIndexes, erasedIndexes) &&
Arrays.equals(this.validIndexes, tmpValidIndexes)) {
return; // Optimization. Nothing to do
}
this.cachedErasedIndexes =
Arrays.copyOf(erasedIndexes, erasedIndexes.length);
this.validIndexes =
Arrays.copyOf(tmpValidIndexes, tmpValidIndexes.length);
processErasures(erasedIndexes);
}
private void processErasures(int[] erasedIndexes) {
this.decodeMatrix = new byte[getNumAllUnits() * getNumDataUnits()];
this.invertMatrix = new byte[getNumAllUnits() * getNumDataUnits()];
this.gfTables = new byte[getNumAllUnits() * getNumDataUnits() * 32];
this.erasureFlags = new boolean[getNumAllUnits()];
this.numErasedDataUnits = 0;
for (int i = 0; i < erasedIndexes.length; i++) {
int index = erasedIndexes[i];
erasureFlags[index] = true;
if (index < getNumDataUnits()) {
numErasedDataUnits++;
}
}
generateDecodeMatrix(erasedIndexes);
RSUtil.initTables(getNumDataUnits(), erasedIndexes.length,
decodeMatrix, 0, gfTables);
if (allowVerboseDump()) {
System.out.println(DumpUtil.bytesToHex(gfTables, -1));
}
}
// Generate decode matrix from encode matrix
private void generateDecodeMatrix(int[] erasedIndexes) {
int i, j, r, p;
byte s;
byte[] tmpMatrix = new byte[getNumAllUnits() * getNumDataUnits()];
// Construct matrix tmpMatrix by removing error rows
for (i = 0; i < getNumDataUnits(); i++) {
r = validIndexes[i];
for (j = 0; j < getNumDataUnits(); j++) {
tmpMatrix[getNumDataUnits() * i + j] =
encodeMatrix[getNumDataUnits() * r + j];
}
}
GF256.gfInvertMatrix(tmpMatrix, invertMatrix, getNumDataUnits());
for (i = 0; i < numErasedDataUnits; i++) {
for (j = 0; j < getNumDataUnits(); j++) {
decodeMatrix[getNumDataUnits() * i + j] =
invertMatrix[getNumDataUnits() * erasedIndexes[i] + j];
}
}
for (p = numErasedDataUnits; p < erasedIndexes.length; p++) {
for (i = 0; i < getNumDataUnits(); i++) {
s = 0;
for (j = 0; j < getNumDataUnits(); j++) {
s ^= GF256.gfMul(invertMatrix[j * getNumDataUnits() + i],
encodeMatrix[getNumDataUnits() * erasedIndexes[p] + j]);
}
decodeMatrix[getNumDataUnits() * p + i] = s;
}
}
}
}
