| /* |
| * 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.iotdb.tsfile.encoding.encoder; |
| |
| import org.apache.iotdb.tsfile.file.metadata.enums.TSEncoding; |
| import org.apache.iotdb.tsfile.utils.ReadWriteForEncodingUtils; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.io.ByteArrayOutputStream; |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.List; |
| |
| /** |
| * Encoder for int value using Zigzag . For more information, see |
| * https://gist.github.com/mfuerstenau/ba870a29e16536fdbaba |
| */ |
| public class IntZigzagEncoder extends Encoder { |
| private static final Logger logger = LoggerFactory.getLogger(IntZigzagEncoder.class); |
| private List<Integer> values; |
| byte[] buf = new byte[5]; |
| |
| public IntZigzagEncoder() { |
| super(TSEncoding.ZIGZAG); |
| this.values = new ArrayList<>(); |
| logger.debug("tsfile-encoding IntZigzagEncoder: int zigzag encoder"); |
| } |
| |
| /** encoding and bit packing. */ |
| private byte[] encodeInt(int n) { |
| n = (n << 1) ^ (n >> 31); |
| int idx = 0; |
| if ((n & ~0x7F) != 0) { |
| buf[idx++] = (byte) ((n | 0x80) & 0xFF); |
| n >>>= 7; |
| while (n > 0x7F) { |
| buf[idx++] = (byte) ((n | 0x80) & 0xFF); |
| n >>>= 7; |
| } |
| } |
| buf[idx++] = (byte) n; |
| return Arrays.copyOfRange(buf, 0, idx); |
| } |
| |
| public void encode(int value, ByteArrayOutputStream out) { |
| values.add(value); |
| } |
| |
| @Override |
| public void flush(ByteArrayOutputStream out) throws IOException { |
| // byteCache stores all <encoded-data> and we know its size |
| ByteArrayOutputStream byteCache = new ByteArrayOutputStream(); |
| final int len = values.size(); |
| if (values.size() == 0) { |
| return; |
| } |
| for (int value : values) { |
| byte[] bytes = encodeInt(value); |
| byteCache.write(bytes, 0, bytes.length); |
| } |
| // store encoded bytes size |
| ReadWriteForEncodingUtils.writeUnsignedVarInt(byteCache.size(), out); |
| // store initial list size |
| ReadWriteForEncodingUtils.writeUnsignedVarInt(len, out); |
| out.write(byteCache.toByteArray()); |
| reset(); |
| } |
| |
| private void reset() { |
| values.clear(); |
| } |
| |
| @Override |
| public long getMaxByteSize() { |
| if (values == null) { |
| return 0; |
| } |
| // try to caculate max value |
| return (long) 8 + values.size() * 4; |
| } |
| } |