Method EncodeSelectedImp

cpp/src/arrow/compute/row/encode_internal.cc:335–378

template <class COPY_FN, class SET_NULL_FN>
void EncoderBinary::EncodeSelectedImp(uint32_t offset_within_row, RowTableImpl* rows,
                                      const KeyColumnArray& col, uint32_t num_selected,
                                      const uint16_t* selection, COPY_FN copy_fn,
                                      SET_NULL_FN set_null_fn) {
  bool is_fixed_length = rows->metadata().is_fixed_length;
  if (is_fixed_length) {
    uint32_t row_width = rows->metadata().fixed_length;
    const uint8_t* src_base = col.data(1);
    uint8_t* dst = rows->mutable_fixed_length_rows(/*row_id=*/0) + offset_within_row;
    for (uint32_t i = 0; i < num_selected; ++i) {
      copy_fn(dst, src_base, selection[i]);
      dst += row_width;
    }
    if (col.data(0)) {
      const uint8_t* non_null_bits = col.data(0);
      dst = rows->mutable_fixed_length_rows(/*row_id=*/0) + offset_within_row;
      for (uint32_t i = 0; i < num_selected; ++i) {
        bool is_null = !bit_util::GetBit(non_null_bits, selection[i] + col.bit_offset(0));
        if (is_null) {
          set_null_fn(dst);
        }
        dst += row_width;
      }
    }
  } else {
    const uint8_t* src_base = col.data(1);
    uint8_t* dst = rows->mutable_var_length_rows() + offset_within_row;
    const RowTableImpl::offset_type* offsets = rows->offsets();
    for (uint32_t i = 0; i < num_selected; ++i) {
      copy_fn(dst + offsets[i], src_base, selection[i]);
    }
    if (col.data(0)) {
      const uint8_t* non_null_bits = col.data(0);
      uint8_t* dst = rows->mutable_var_length_rows() + offset_within_row;
      const RowTableImpl::offset_type* offsets = rows->offsets();
      for (uint32_t i = 0; i < num_selected; ++i) {
        bool is_null = !bit_util::GetBit(non_null_bits, selection[i] + col.bit_offset(0));
        if (is_null) {
          set_null_fn(dst + offsets[i]);
        }
      }
    }
  }
}

void EncoderBinary::EncodeSelected(uint32_t offset_within_row, RowTableImpl* rows,
                                   const KeyColumnArray& col, uint32_t num_selected,