commit 1.2

source/map.cxx

@@ -0,0 +1,84 @@
+module map;
+
+import std;
+
+namespace brc {
+
+map::map(std::size_t entry_count) : entries(std::make_unique<entry[]>(entry_count)), entry_count(entry_count) {}
+
+std::uint64_t map::get_key(std::string_view city) noexcept {
+	std::uint64_t raw = 0;
+	const auto data_count = std::min(static_cast<int>(city.size()), 8);
+	std::memcpy(&raw, city.data(), data_count);
+
+	raw *= 0x9E3779B97F4A7C15ULL;
+	return raw ^ (raw >> 32);
+}
+
+std::uint64_t map::get_index(std::string_view city) const noexcept {
+	const auto key = get_key(city);
+	auto index = key & (entry_count - 1);
+
+	while (true) {
+		auto& e = entries[index];
+		if (e.key_ptr == nullptr) {
+			e.key_hash = key;
+			e.key_ptr = city.data();
+			e.key_len = static_cast<std::uint16_t>(city.size());
+			break;
+		} else if (key == e.key_hash && city == std::string_view(e.key_ptr, e.key_len)) {
+			break;
+		}
+		index = (index + 1 == entry_count) ? 0 : index + 1;
+	}
+
+	return index;
+}
+
+void map::insert(std::string_view city, std::int32_t measurement) {
+	const auto index = get_index(city);
+
+	auto& entry = entries[index];
+	entry.count += 1;
+	entry.total += measurement;
+	entry.min = std::min(entry.min, measurement);
+	entry.max = std::max(entry.max, measurement);
+}
+
+void map::merge_against(const map& other) {
+	for (std::size_t i = 0; i < other.entry_count; i++) {
+		if (other.entries[i].key_ptr == nullptr) {
+			continue;
+		}
+
+		auto& other_entry = other.entries[i];
+		auto& our_entry = entries[get_index(std::string_view(other_entry.key_ptr, other_entry.key_len))];
+		our_entry.min = std::min(our_entry.min, other_entry.min);
+		our_entry.max = std::max(our_entry.max, other_entry.max);
+		our_entry.count += other_entry.count;
+		our_entry.total += other_entry.total;
+	}
+}
+
+std::vector<entry> map::collapse() const noexcept {
+	auto data = std::vector<entry>();
+	data.reserve(entry_count);
+
+	for (std::size_t i = 0; i < entry_count; i++) {
+		if (entries[i].key_ptr == nullptr) {
+			continue;
+		}
+
+		data.push_back(entries[i]);
+	}
+
+	std::sort(data.begin(), data.end(), [](const entry& a, const entry& b) {
+		const auto a_sv = std::string_view(a.key_ptr, a.key_len);
+		const auto b_sv = std::string_view(b.key_ptr, b.key_len);
+		return a_sv < b_sv;
+	});
+
+	return data;
+}
+
+}  // namespace brc