/*
* Copyright 2016 Naver Corp.
*
* 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 com.navercorp.pinpoint.common.server.bo.codec.strategy.impl;
import com.navercorp.pinpoint.common.buffer.Buffer;
import com.navercorp.pinpoint.common.server.bo.codec.ArithmeticOperation;
import com.navercorp.pinpoint.common.server.bo.codec.TypedBufferHandler;
import com.navercorp.pinpoint.common.server.bo.codec.strategy.EncodingStrategy;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* @author HyunGil Jeong
*/
public abstract class DeltaEncodingStrategy<T extends Number> implements EncodingStrategy<T> {
private static final byte CODE = 2;
protected final TypedBufferHandler<T> bufferHandler;
protected final ArithmeticOperation<T> operation;
protected DeltaEncodingStrategy(TypedBufferHandler<T> bufferHandler, ArithmeticOperation<T> operation) {
this.bufferHandler = bufferHandler;
this.operation = operation;
}
@Override
public byte getCode() {
return CODE;
}
public static class Unsigned<T extends Number> extends DeltaEncodingStrategy<T> {
public Unsigned(TypedBufferHandler<T> bufferHandler, ArithmeticOperation<T> operation) {
super(bufferHandler, operation);
}
@Override
public void encodeValues(Buffer buffer, List<T> values) {
if (values.isEmpty()) {
return;
}
T initialValue = values.get(0);
this.bufferHandler.putV(buffer, initialValue);
T previousValue = initialValue;
// skip first value as this value is stored without compression
for (int i = 1; i < values.size(); ++i) {
T value = values.get(i);
this.bufferHandler.putV(buffer, this.operation.xor(value, previousValue));
previousValue = value;
}
}
@Override
public List<T> decodeValues(Buffer buffer, int numValues) {
if (numValues < 1) {
return Collections.emptyList();
}
List<T> values = new ArrayList<T>(numValues);
T initialValue = this.bufferHandler.readV(buffer);
values.add(initialValue);
T previousValue = initialValue;
// loop through numValues - 1 as the first value is simply read from buffer
for (int i = 0; i < numValues - 1; ++i) {
T value = this.operation.xor(previousValue, this.bufferHandler.readV(buffer));
values.add(value);
previousValue = value;
}
return values;
}
}
}