Method PropagateSingle

cpp/src/arrow/compute/exec.cc:579–611

  }

  Status PropagateSingle() {
    // One array
    const ArraySpan& arr = *arrays_with_nulls_[0];
    const uint8_t* arr_bitmap = arr.buffers[0].data;

    // Reuse the null count if it's known
    output_->null_count = arr.null_count;

    if (bitmap_preallocated_) {
      CopyBitmap(arr_bitmap, arr.offset, arr.length, bitmap_, output_->offset);
      return Status::OK();
    }

    // Two cases when memory was not pre-allocated:
    //
    // * Offset is zero: we reuse the bitmap as is
    // * Offset is nonzero but a multiple of 8: we can slice the bitmap
    // * Offset is not a multiple of 8: we must allocate and use CopyBitmap
    //
    // Keep in mind that output_->offset is not permitted to be nonzero when
    // the bitmap is not preallocated, and that precondition is asserted
    // higher in the call stack.
    if (arr.offset == 0) {
      output_->buffers[0] = arr.GetBuffer(0);
    } else if (arr.offset % 8 == 0) {
      output_->buffers[0] = SliceBuffer(arr.GetBuffer(0), arr.offset / 8,
                                        bit_util::BytesForBits(arr.length));
    } else {
      RETURN_NOT_OK(EnsureAllocated());
      CopyBitmap(arr_bitmap, arr.offset, arr.length, bitmap_, /*dst_offset=*/0);
    }
    return Status::OK();
  }

  Status PropagateMultiple() {
    // More than one array. We use BitmapAnd to intersect their bitmaps