package net.agkn.hll.serialization;
/*
* Copyright 2013 Aggregate Knowledge, Inc.
*
* 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.
*/
import net.agkn.hll.HLLType;
/**
* A concrete {@link ISchemaVersion} representing schema version one.
*
* @author timon
*/
public class SchemaVersionOne implements ISchemaVersion {
/**
* The schema version number for this instance.
*/
public static final int SCHEMA_VERSION = 1;
// ------------------------------------------------------------------------
// Version-specific ordinals (array position) for each of the HLL types
private static final HLLType[] TYPE_ORDINALS = new HLLType[] {
HLLType.UNDEFINED,
HLLType.EMPTY,
HLLType.EXPLICIT,
HLLType.SPARSE,
HLLType.FULL
};
// ------------------------------------------------------------------------
// number of header bytes for all HLL types
private static final int HEADER_BYTE_COUNT = 3;
// sentinel values from the spec for explicit off and auto
private static final int EXPLICIT_OFF = 0;
private static final int EXPLICIT_AUTO = 63;
// ************************************************************************
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#paddingBytes(HLLType)
*/
@Override
public int paddingBytes(final HLLType type) {
return HEADER_BYTE_COUNT;
}
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#writeMetadata(byte[], IHLLMetadata)
*/
@Override
public void writeMetadata(final byte[] bytes, final IHLLMetadata metadata) {
final HLLType type = metadata.HLLType();
final int typeOrdinal = getOrdinal(type);
final int explicitCutoffValue;
if(metadata.explicitOff()) {
explicitCutoffValue = EXPLICIT_OFF;
} else if(metadata.explicitAuto()) {
explicitCutoffValue = EXPLICIT_AUTO;
} else {
explicitCutoffValue = metadata.log2ExplicitCutoff() + 1/*per spec*/;
}
bytes[0] = SerializationUtil.packVersionByte(SCHEMA_VERSION, typeOrdinal);
bytes[1] = SerializationUtil.packParametersByte(metadata.registerWidth(), metadata.registerCountLog2());
bytes[2] = SerializationUtil.packCutoffByte(explicitCutoffValue, metadata.sparseEnabled());
}
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#readMetadata(byte[])
*/
@Override
public IHLLMetadata readMetadata(final byte[] bytes) {
final byte versionByte = bytes[0];
final byte parametersByte = bytes[1];
final byte cutoffByte = bytes[2];
final int typeOrdinal = SerializationUtil.typeOrdinal(versionByte);
final int explicitCutoffValue = SerializationUtil.explicitCutoff(cutoffByte);
final boolean explicitOff = (explicitCutoffValue == EXPLICIT_OFF);
final boolean explicitAuto = (explicitCutoffValue == EXPLICIT_AUTO);
final int log2ExplicitCutoff = (explicitOff || explicitAuto) ? -1/*sentinel*/ : (explicitCutoffValue - 1/*per spec*/);
return new HLLMetadata(SCHEMA_VERSION,
getType(typeOrdinal),
SerializationUtil.registerCountLog2(parametersByte),
SerializationUtil.registerWidth(parametersByte),
log2ExplicitCutoff,
explicitOff,
explicitAuto,
SerializationUtil.sparseEnabled(cutoffByte));
}
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#getSerializer(HLLType, int, int)
*/
@Override
public IWordSerializer getSerializer(HLLType type, int wordLength, int wordCount) {
return new BigEndianAscendingWordSerializer(wordLength, wordCount, paddingBytes(type));
}
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#getDeserializer(HLLType, int, byte[])
*/
@Override
public IWordDeserializer getDeserializer(HLLType type, int wordLength, byte[] bytes) {
return new BigEndianAscendingWordDeserializer(wordLength, paddingBytes(type), bytes);
}
/* (non-Javadoc)
* @see net.agkn.hll.serialization.ISchemaVersion#schemaVersionNumber()
*/
@Override
public int schemaVersionNumber() {
return SCHEMA_VERSION;
}
// ========================================================================
// Type/Ordinal lookups
/**
* Gets the ordinal for the specified {@link HLLType}.
*
* @param type the type whose ordinal is desired
* @return the ordinal for the specified type, to be used in the version byte.
* This will always be non-negative.
*/
private static int getOrdinal(final HLLType type) {
for(int i=0; i<TYPE_ORDINALS.length; i++) {
if(TYPE_ORDINALS[i].equals(type)) return i;
}
throw new RuntimeException("Unknown HLL type " + type);
}
/**
* Gets the {@link HLLType} for the specified ordinal.
*
* @param ordinal the ordinal whose type is desired
* @return the type for the specified ordinal. This will never be <code>null</code>.
*/
private static HLLType getType(final int ordinal) {
if((ordinal < 0) || (ordinal >= TYPE_ORDINALS.length)) {
throw new IllegalArgumentException("Invalid type ordinal '" + ordinal + "'. Only 0-" + (TYPE_ORDINALS.length - 1) + " inclusive allowed.");
}
return TYPE_ORDINALS[ordinal];
}
}