vector/src/main/java/org/apache/arrow/vector/BaseFixedWidthVector.java [679:740]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      } else {
        /* Copy data
         * When the first bit starts from the middle of a byte (offset != 0),
         * copy data from src BitVector.
         * Each byte in the target is composed by a part in i-th byte,
         * another part in (i+1)-th byte.
         */
        target.allocateValidityBuffer(byteSizeTarget);

        for (int i = 0; i < byteSizeTarget - 1; i++) {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + i, offset);
          byte b2 =
              BitVectorHelper.getBitsFromNextByte(
                  this.validityBuffer, firstByteSource + i + 1, offset);

          target.validityBuffer.setByte(i, (b1 + b2));
        }

        /* Copying the last piece is done in the following manner:
         * if the source vector has 1 or more bytes remaining, we copy
         * the last piece as a byte formed by shifting data
         * from the current byte and the next byte.
         *
         * if the source vector has no more bytes remaining
         * (we are at the last byte), we copy the last piece as a byte
         * by shifting data from the current byte.
         */
        if ((firstByteSource + byteSizeTarget - 1) < lastByteSource) {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget - 1, offset);
          byte b2 =
              BitVectorHelper.getBitsFromNextByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget, offset);

          target.validityBuffer.setByte(byteSizeTarget - 1, b1 + b2);
        } else {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget - 1, offset);
          target.validityBuffer.setByte(byteSizeTarget - 1, b1);
        }
      }
    }
  }

  /*----------------------------------------------------------------*
  |                                                                |
  |          common getters and setters                            |
  |                                                                |
  *----------------------------------------------------------------*/

  /**
   * Get the number of elements that are null in the vector.
   *
   * @return the number of null elements.
   */
  @Override
  public int getNullCount() {
    return BitVectorHelper.getNullCount(validityBuffer, valueCount);
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



vector/src/main/java/org/apache/arrow/vector/BaseLargeVariableWidthVector.java [830:890]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      } else {
        /* Copy data
         * When the first bit starts from the middle of a byte (offset != 0),
         * copy data from src BitVector.
         * Each byte in the target is composed by a part in i-th byte,
         * another part in (i+1)-th byte.
         */
        target.allocateValidityBuffer(byteSizeTarget);

        for (int i = 0; i < byteSizeTarget - 1; i++) {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + i, offset);
          byte b2 =
              BitVectorHelper.getBitsFromNextByte(
                  this.validityBuffer, firstByteSource + i + 1, offset);

          target.validityBuffer.setByte(i, (b1 + b2));
        }
        /* Copying the last piece is done in the following manner:
         * if the source vector has 1 or more bytes remaining, we copy
         * the last piece as a byte formed by shifting data
         * from the current byte and the next byte.
         *
         * if the source vector has no more bytes remaining
         * (we are at the last byte), we copy the last piece as a byte
         * by shifting data from the current byte.
         */
        if ((firstByteSource + byteSizeTarget - 1) < lastByteSource) {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget - 1, offset);
          byte b2 =
              BitVectorHelper.getBitsFromNextByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget, offset);

          target.validityBuffer.setByte(byteSizeTarget - 1, b1 + b2);
        } else {
          byte b1 =
              BitVectorHelper.getBitsFromCurrentByte(
                  this.validityBuffer, firstByteSource + byteSizeTarget - 1, offset);
          target.validityBuffer.setByte(byteSizeTarget - 1, b1);
        }
      }
    }
  }

  /*----------------------------------------------------------------*
  |                                                                |
  |                common getters and setters                      |
  |                                                                |
  *----------------------------------------------------------------*/

  /**
   * Get the number of elements that are null in the vector.
   *
   * @return the number of null elements.
   */
  @Override
  public int getNullCount() {
    return BitVectorHelper.getNullCount(validityBuffer, valueCount);
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -