BitWriter.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 parquet.column.values.boundedint;

import parquet.Log;
import parquet.bytes.BytesInput;
import parquet.bytes.CapacityByteArrayOutputStream;

class BitWriter {
  private static final Log LOG = Log.getLog(BitWriter.class);
  private static final boolean DEBUG = false;//Log.DEBUG;

  private CapacityByteArrayOutputStream baos;
  private int currentByte = 0;
  private int currentBytePosition = 0;
  private static final int[] byteToTrueMask = new int[8];
  private static final int[] byteToFalseMask = new int[8];
  private boolean finished = false;
  static {
    int currentMask = 1;
    for (int i = 0; i < byteToTrueMask.length; i++) {
      byteToTrueMask[i] = currentMask;
      byteToFalseMask[i] = ~currentMask;
      currentMask <<= 1;
    }
  }

  public BitWriter(int initialCapacity) {
    this.baos = new CapacityByteArrayOutputStream(initialCapacity);
  }

  public void writeBit(boolean bit) {
    if (DEBUG) LOG.debug("writing: " + (bit ? "1" : "0"));
    currentByte = setBytePosition(currentByte, currentBytePosition++, bit);
    if (currentBytePosition == 8) {
      baos.write(currentByte);
      if (DEBUG) LOG.debug("to buffer: " + toBinary(currentByte));
      currentByte = 0;
      currentBytePosition = 0;
    }
  }

  public void writeByte(int val) {
    if (DEBUG) LOG.debug("writing: " + toBinary(val) + " (" + val + ")");
    currentByte |= ((val & 0xFF) << currentBytePosition);
    baos.write(currentByte);
    if (DEBUG) LOG.debug("to buffer: " + toBinary(currentByte));
    currentByte >>>= 8;
  }

  /**
   * Write the given integer, serialized using the given number of bits.
   * It is assumed that the integer can be correctly serialized within
   * the provided bit size.
   * @param val the value to serialize
   * @param bitsToWrite the number of bits to use
   */
  public void writeNBitInteger(int val, int bitsToWrite) {
    if (DEBUG) LOG.debug("writing: " + toBinary(val, bitsToWrite) + " (" + val + ")");
    val <<= currentBytePosition;
    int upperByte = currentBytePosition + bitsToWrite;
    currentByte |= val;
    while (upperByte >= 8) {
      baos.write(currentByte); //this only writes the lowest byte
      if (DEBUG) LOG.debug("to buffer: " + toBinary(currentByte));
      upperByte -= 8;
      currentByte >>>= 8;
    }
    currentBytePosition = (currentBytePosition + bitsToWrite) % 8;
  }

  private String toBinary(int val, int alignTo) {
    String result = Integer.toBinaryString(val);
    while (result.length() < alignTo) {
      result = "0" + result;
    }
    return result;
  }

  private String toBinary(int val) {
    return toBinary(val, 8);
  }

  public BytesInput finish() {
    if (!finished) {
      if (currentBytePosition > 0) {
        baos.write(currentByte);
        if (DEBUG) LOG.debug("to buffer: " + toBinary(currentByte));
      }
    }
    finished = true;
    return BytesInput.from(baos);
  }

  public void reset() {
    baos.reset();
    currentByte = 0;
    currentBytePosition = 0;
    finished = false;
  }

  /**
   * Set or clear the given bit position in the given byte.
   * @param currentByte the byte to mutate
   * @param bitOffset the bit to set or clear
   * @param newBitValue whether to set or clear the bit
   * @return the mutated byte
   */
  private static int setBytePosition(int currentByte, int bitOffset, boolean newBitValue) {
    if (newBitValue) {
      currentByte |= byteToTrueMask[bitOffset];
    } else {
      currentByte &= byteToFalseMask[bitOffset];
    }
    return currentByte;
  }

  //This assumes you will never give it a negative value
  public void writeUnsignedVarint(int value) {
    while ((value & 0xFFFFFF80) != 0L) {
      writeByte((value & 0x7F) | 0x80);
      value >>>= 7;
    }
    writeByte(value & 0x7F);
  }

  public int getMemSize() {
    // baos = 8 bytes
    // currentByte + currentBytePosition = 8 bytes
    // the size of baos:
    //   count : 4 bytes (rounded to 8)
    //   buf : 12 bytes (8 ptr + 4 length) should technically be rounded to 8 depending on buffer size
    return 32 + (int)baos.size();
  }

  public int getCapacity() {
    return baos.getCapacity();
  }

  public String memUsageString(String prefix) {
    return baos.memUsageString(prefix);
  }
}