compact_theta_sketch_alloc compact_theta_sketch_alloc::deserialize_v2()

in theta/include/theta_sketch_impl.hpp [581:619]

• 39 lines of code
• 11 McCabe index (conditional complexity)

compact_theta_sketch_alloc<A> compact_theta_sketch_alloc<A>::deserialize_v2(
    uint8_t preamble_longs, std::istream& is, uint64_t seed, const A& allocator)
{
  read<uint8_t>(is); // unused
  read<uint16_t>(is); // unused
  const uint16_t seed_hash = read<uint16_t>(is);
  checker<true>::check_seed_hash(seed_hash, compute_seed_hash(seed));
  if (preamble_longs == 1) {
    if (!is.good()) throw std::runtime_error("error reading from std::istream");
    std::vector<uint64_t, A> entries(0, 0, allocator);
    return compact_theta_sketch_alloc(true, true, seed_hash, theta_constants::MAX_THETA, std::move(entries));
  } else if (preamble_longs == 2) {
    const uint32_t num_entries = read<uint32_t>(is);
    read<uint32_t>(is); // unused
    std::vector<uint64_t, A> entries(num_entries, 0, allocator);
    if (num_entries == 0) {
      return compact_theta_sketch_alloc(true, true, seed_hash, theta_constants::MAX_THETA, std::move(entries));
    }
    read(is, entries.data(), entries.size() * sizeof(uint64_t));
    if (!is.good()) throw std::runtime_error("error reading from std::istream");
    return compact_theta_sketch_alloc(false, true, seed_hash, theta_constants::MAX_THETA, std::move(entries));
  } else if (preamble_longs == 3) {
    const uint32_t num_entries = read<uint32_t>(is);
    read<uint32_t>(is); // unused
    const auto theta = read<uint64_t>(is);
    bool is_empty = (num_entries == 0) && (theta == theta_constants::MAX_THETA);
    std::vector<uint64_t, A> entries(num_entries, 0, allocator);
    if (is_empty) {
      if (!is.good()) throw std::runtime_error("error reading from std::istream");
      return compact_theta_sketch_alloc(true, true, seed_hash, theta, std::move(entries));
    } else {
      read(is, entries.data(), sizeof(uint64_t) * entries.size());
      if (!is.good()) throw std::runtime_error("error reading from std::istream");
      return compact_theta_sketch_alloc(false, true, seed_hash, theta, std::move(entries));
    }
  } else {
    throw std::invalid_argument(std::to_string(preamble_longs) + " longs of premable, but expected 1, 2, or 3");
  }
}