Method insert_into_empty_slot

cpp/src/arrow/compute/key_map_internal.h:322–347

};

void SwissTable::insert_into_empty_slot(uint32_t global_slot_id, uint32_t hash,
                                        uint32_t group_id) {
  const int num_groupid_bits = num_groupid_bits_from_log_blocks(log_blocks_);

  // We assume here that the number of bits is rounded up to 8, 16, 32 or 64.
  // In that case we can insert group id value using aligned 64-bit word access.
  assert(num_groupid_bits == 8 || num_groupid_bits == 16 || num_groupid_bits == 32 ||
         num_groupid_bits == 64);

  const int num_block_bytes = num_block_bytes_from_num_groupid_bits(num_groupid_bits);
  constexpr uint32_t stamp_mask = 0x7f;

  int start_slot = (global_slot_id & kLocalSlotMask);
  int stamp = (hash >> bits_shift_for_block_and_stamp_) & stamp_mask;
  uint32_t block_id = global_slot_id >> kLogSlotsPerBlock;
  uint8_t* blockbase = mutable_block_data(block_id, num_block_bytes);

  blockbase[kMaxLocalSlot - start_slot] = static_cast<uint8_t>(stamp);
  int groupid_bit_offset = start_slot * num_groupid_bits;

  // Block status bytes should start at an address aligned to 8 bytes
  assert((reinterpret_cast<uint64_t>(blockbase) & 7) == 0);
  uint64_t* ptr = reinterpret_cast<uint64_t*>(blockbase + bytes_status_in_block_) +
                  (groupid_bit_offset >> 6);
  *ptr |= (static_cast<uint64_t>(group_id) << (groupid_bit_offset & 63));
}

}  // namespace compute
}  // namespace arrow