java/core/src/java/org/apache/orc/impl/BitFieldWriter.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.orc.impl;

import java.io.IOException;
import java.util.function.Consumer;

public class BitFieldWriter {
  private RunLengthByteWriter output;
  private final int bitSize;
  private byte current = 0;
  private int bitsLeft = 8;

  public BitFieldWriter(PositionedOutputStream output,
                 int bitSize) throws IOException {
    this.output = new RunLengthByteWriter(output);
    this.bitSize = bitSize;
  }

  private void writeByte() throws IOException {
    output.write(current);
    current = 0;
    bitsLeft = 8;
  }

  public void flush() throws IOException {
    if (bitsLeft != 8) {
      writeByte();
    }
    output.flush();
  }

  public void write(int value) throws IOException {
    int bitsToWrite = bitSize;
    while (bitsToWrite > bitsLeft) {
      // add the bits to the bottom of the current word
      current |= value >>> (bitsToWrite - bitsLeft);
      // subtract out the bits we just added
      bitsToWrite -= bitsLeft;
      // zero out the bits above bitsToWrite
      value &= (1 << bitsToWrite) - 1;
      writeByte();
    }
    bitsLeft -= bitsToWrite;
    current |= value << bitsLeft;
    if (bitsLeft == 0) {
      writeByte();
    }
  }

  public void getPosition(PositionRecorder recorder) throws IOException {
    output.getPosition(recorder);
    recorder.addPosition(8 - bitsLeft);
  }

  public long estimateMemory() {
    return output.estimateMemory();
  }

  public void changeIv(Consumer<byte[]> modifier) {
    output.changeIv(modifier);
  }
}