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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.hbase.io.util;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import org.apache.hadoop.hbase.util.ByteBufferUtils;
import org.apache.yetus.audience.InterfaceAudience;
/**
* Dictionary interface
*
* Dictionary indexes should be either bytes or shorts, only positive. (The
* first bit is reserved for detecting whether something is compressed or not).
*/
@InterfaceAudience.Private
public interface Dictionary {
byte NOT_IN_DICTIONARY = -1;
void init(int initialSize);
/**
* Gets an entry from the dictionary.
*
* @param idx index of the entry
* @return the entry, or null if non existent
*/
byte[] getEntry(short idx);
/**
* Finds the index of an entry.
* If no entry found, we add it.
*
* @param data the byte array that we're looking up
* @param offset Offset into data to add to Dictionary.
* @param length Length beyond offset that comprises entry; must be > 0.
* @return the index of the entry, or {@link #NOT_IN_DICTIONARY} if not found
*/
short findEntry(byte[] data, int offset, int length);
/**
* Finds the index of an entry.
* If no entry found, we add it.
* @param data the ByteBuffer that we're looking up
* @param offset Offset into data to add to Dictionary.
* @param length Length beyond offset that comprises entry; must be > 0.
* @return the index of the entry, or {@link #NOT_IN_DICTIONARY} if not found
*/
short findEntry(ByteBuffer data, int offset, int length);
/**
* Adds an entry to the dictionary.
* Be careful using this method. It will add an entry to the
* dictionary even if it already has an entry for the same data.
* Call {{@link #findEntry(byte[], int, int)}} to add without duplicating
* dictionary entries.
*
* @param data the entry to add
* @param offset Offset into data to add to Dictionary.
* @param length Length beyond offset that comprises entry; must be > 0.
* @return the index of the entry
*/
short addEntry(byte[] data, int offset, int length);
/**
* Flushes the dictionary, empties all values.
*/
void clear();
/**
* Helper methods to write the dictionary data to the OutputStream
* @param out the outputstream to which data needs to be written
* @param data the data to be written in byte[]
* @param offset the offset
* @param length length to be written
* @param dict the dictionary whose contents are to written
* @throws IOException
*/
public static void write(OutputStream out, byte[] data, int offset, int length, Dictionary dict)
throws IOException {
short dictIdx = Dictionary.NOT_IN_DICTIONARY;
if (dict != null) {
dictIdx = dict.findEntry(data, offset, length);
}
if (dictIdx == Dictionary.NOT_IN_DICTIONARY) {
out.write(Dictionary.NOT_IN_DICTIONARY);
StreamUtils.writeRawVInt32(out, length);
out.write(data, offset, length);
} else {
StreamUtils.writeShort(out, dictIdx);
}
}
/**
* Helper methods to write the dictionary data to the OutputStream
* @param out the outputstream to which data needs to be written
* @param data the data to be written in ByteBuffer
* @param offset the offset
* @param length length to be written
* @param dict the dictionary whose contents are to written
* @throws IOException
*/
public static void write(OutputStream out, ByteBuffer data, int offset, int length,
Dictionary dict) throws IOException {
short dictIdx = Dictionary.NOT_IN_DICTIONARY;
if (dict != null) {
dictIdx = dict.findEntry(data, offset, length);
}
if (dictIdx == Dictionary.NOT_IN_DICTIONARY) {
out.write(Dictionary.NOT_IN_DICTIONARY);
StreamUtils.writeRawVInt32(out, length);
ByteBufferUtils.copyBufferToStream(out, data, offset, length);
} else {
StreamUtils.writeShort(out, dictIdx);
}
}
}
