org.roaringbitmap.longlong.IntegerUtil Maven / Gradle / Ivy

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Roaring bitmaps are compressed bitmaps (also called bitsets) which tend to outperform conventional compressed bitmaps such as WAH or Concise.

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package org.roaringbitmap.longlong;

public class IntegerUtil {

  /**
   * convert integer to its byte array format
   * @param v an input integer value
   * @return the big endian byte array representation
   */
  public static byte[] toBDBytes(int v) {
    byte[] bytes = new byte[4];
    bytes[0] = (byte) (v >> 24);
    bytes[1] = (byte) (v >> 16);
    bytes[2] = (byte) (v >> 8);
    bytes[3] = (byte) v;
    return bytes;
  }

  /**
   * convert into its integer representation
   * @param bytes the big endian integer's byte array
   * @return a integer corresponding to input bytes
   */
  public static int fromBDBytes(byte[] bytes) {
    return (bytes[0] & 0xFF) << 24
        | (bytes[1] & 0xFF) << 16
        | (bytes[2] & 0xFF) << 8
        | bytes[3] & 0xFF;
  }

  /**
   * set a specified position byte to another value to return a fresh integer
   * @param v the input integer value
   * @param bv the byte value to insert
   * @param pos the position of an 4 byte array to replace
   * @return a fresh integer after a specified position byte been replaced
   */
  public static int setByte(int v, byte bv, int pos) {
    int i = ((3 - pos) << 3);
    v &= ~(0xFF << i);
    v |= (bv & 0xFF) << i;
    return v;
  }

  /**
   * shift the byte left from the specified position
   * @param v a integer value
   * @param pos the position from which to shift byte values left
   * @param count the shifting numbers
   * @return a fresh integer value
   */
  public static int shiftLeftFromSpecifiedPosition(int v, int pos, int count) {
    if (count != 0) {
      int shiftToLeft = (4 - count) << 3;
      int shiftToRight = shiftToLeft - (pos << 3);
      int maskShifted = 0xFFFFFFFF >>> shiftToLeft << shiftToRight;
      v = (v & ~maskShifted) | (v << 8 & maskShifted);
    }
    return v;
  }

  /**
   * fetch the first byte
   * @param v an input integer
   * @return the first byte of the big endian representation
   */
  public static byte firstByte(int v) {
    return (byte) (v >> 24);
  }
}