iotdb-core/tsfile/src/main/java/org/apache/iotdb/tsfile/encoding/encoder/LongRleEncoder.java

/*
 * 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.common.conf.TSFileConfig;
import org.apache.iotdb.tsfile.encoding.bitpacking.LongPacker;
import org.apache.iotdb.tsfile.utils.ReadWriteForEncodingUtils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;

/** Encoder for long value using rle or bit-packing. */
public class LongRleEncoder extends RleEncoder<Long> {

  /** Packer for packing long value. */
  private LongPacker packer;

  /** Constructor of LongRleEncoder. */
  public LongRleEncoder() {
    super();
    bufferedValues = new Long[TSFileConfig.RLE_MIN_REPEATED_NUM];
    preValue = (long) 0;
    values = new ArrayList<Long>();
  }

  @Override
  public void encode(long value, ByteArrayOutputStream out) {
    values.add(value);
  }

  /**
   * write all values buffered in cache to OutputStream.
   *
   * @param out - byteArrayOutputStream
   * @throws IOException cannot flush to OutputStream
   */
  @Override
  public void flush(ByteArrayOutputStream out) throws IOException {
    // we get bit width after receiving all data
    this.bitWidth = ReadWriteForEncodingUtils.getLongMaxBitWidth(values);
    packer = new LongPacker(bitWidth);
    for (Long value : values) {
      encodeValue(value);
    }
    super.flush(out);
  }

  @Override
  protected void reset() {
    super.reset();
    preValue = (long) 0;
  }

  /**
   * write bytes to OutputStream using rle rle format: [header][value].
   *
   * @throws IOException cannot write rle run
   */
  @Override
  protected void writeRleRun() throws IOException {
    endPreviousBitPackedRun(TSFileConfig.RLE_MIN_REPEATED_NUM);
    ReadWriteForEncodingUtils.writeUnsignedVarInt(repeatCount << 1, byteCache);
    ReadWriteForEncodingUtils.writeLongLittleEndianPaddedOnBitWidth(preValue, byteCache, bitWidth);
    repeatCount = 0;
    numBufferedValues = 0;
  }

  @Override
  protected void clearBuffer() {
    for (int i = numBufferedValues; i < TSFileConfig.RLE_MIN_REPEATED_NUM; i++) {
      bufferedValues[i] = (long) 0;
    }
  }

  @Override
  protected void convertBuffer() {
    byte[] bytes = new byte[bitWidth];
    long[] tmpBuffer = new long[TSFileConfig.RLE_MIN_REPEATED_NUM];
    for (int i = 0; i < TSFileConfig.RLE_MIN_REPEATED_NUM; i++) {
      tmpBuffer[i] = bufferedValues[i];
    }
    packer.pack8Values(tmpBuffer, 0, bytes);
    // we'll not write bit-packing group to OutputStream immediately
    // we buffer them in list
    bytesBuffer.add(bytes);
  }

  @Override
  public int getOneItemMaxSize() {
    // 4 + 4 + max(4+8,1 + 4 + 8 * 8)
    // length + bitwidth + max(rle-header + num, bit-header + lastNum + 8packer)
    return 77;
  }

  @Override
  public long getMaxByteSize() {
    if (values == null) {
      return 0;
    }
    // try to caculate max value
    int groupNum = (values.size() / 8 + 1) / 63 + 1;
    return (long) 8 + groupNum * 5 + values.size() * 8;
  }
}