Function pack

matlab/src/cpp/arrow/matlab/bit/pack.cc:46–74

Pack an unpacked MATLAB logical array into a bit-packed arrow::Buffer.

// Pack an unpacked MATLAB logical array into a bit-packed arrow::Buffer.
arrow::Result<std::shared_ptr<arrow::Buffer>> pack(
    const ::matlab::data::TypedArray<bool> matlab_logical_array) {
  // Validate that the input arrow::Buffer has sufficient size to store a full bit-packed
  // representation of the input MATLAB logical array.
  const auto unpacked_buffer_length = matlab_logical_array.getNumberOfElements();

  // Compute the bit packed length from the unpacked length.
  const auto packed_buffer_length = packedLength(unpacked_buffer_length);

  ARROW_ASSIGN_OR_RAISE(auto packed_validity_bitmap_buffer,
                        arrow::AllocateResizableBuffer(packed_buffer_length));

  // Get pointers to the internal uint8_t arrays behind arrow::Buffer and mxArray
  // Get raw bool array pointer from MATLAB logical array.
  // Get an iterator to the raw bool data behind the MATLAB logical array.
  auto unpacked_bool_data_iterator = matlab_logical_array.cbegin();

  // Iterate over the mxLogical array and write bit-packed bools to the arrow::Buffer.
  // Call into a loop-unrolled Arrow utility for better performance when bit-packing.
  auto generator = [&]() -> bool { return *(unpacked_bool_data_iterator++); };
  const int64_t start_offset = 0;

  auto mutable_data = packed_validity_bitmap_buffer->mutable_data();

  arrow::internal::GenerateBitsUnrolled(mutable_data, start_offset,
                                        unpacked_buffer_length, generator);

  return packed_validity_bitmap_buffer;
}

}  // namespace arrow::matlab::bit