vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java [864:921]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    if (length <= 0) {
      return;
    }

    final int firstByteSource = BitVectorHelper.byteIndex(startIndex);
    final int lastByteSource = BitVectorHelper.byteIndex(valueCount - 1);
    final int byteSizeTarget = getValidityBufferSizeFromCount(length);
    final int offset = startIndex % 8;

    if (offset == 0) {
      // slice
      if (target.validityBuffer != null) {
        target.validityBuffer.getReferenceManager().release();
      }
      final ArrowBuf slicedValidityBuffer = validityBuffer.slice(firstByteSource, byteSizeTarget);
      target.validityBuffer = transferBuffer(slicedValidityBuffer, target.allocator);
      return;
    }

    /* 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);
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthViewVector.java [869:926]:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    if (length <= 0) {
      return;
    }

    final int firstByteSource = BitVectorHelper.byteIndex(startIndex);
    final int lastByteSource = BitVectorHelper.byteIndex(valueCount - 1);
    final int byteSizeTarget = getValidityBufferSizeFromCount(length);
    final int offset = startIndex % 8;

    if (offset == 0) {
      // slice
      if (target.validityBuffer != null) {
        target.validityBuffer.getReferenceManager().release();
      }
      final ArrowBuf slicedValidityBuffer = validityBuffer.slice(firstByteSource, byteSizeTarget);
      target.validityBuffer = transferBuffer(slicedValidityBuffer, target.allocator);
      return;
    }

    /* 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);
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -