commit 1.2

source/map.ixx

@@ -0,0 +1,38 @@
+export module map;
+
+import std;
+
+namespace brc {
+
+export struct entry {
+	std::uint64_t key_hash = 0;
+	const char* key_ptr = nullptr;								  // 8, 8
+	std::int64_t total = 0;										  // 8, 26
+	std::int32_t min = std::numeric_limits<std::int32_t>::max();  // 4, 12
+	std::int32_t max = std::numeric_limits<std::int32_t>::min();  // 4, 16
+	std::uint32_t count = 0;									  // 4, 30
+	std::uint16_t key_len = 0;									  // 2, 32
+};
+
+export class map {
+private:
+	std::size_t entry_count;
+	std::unique_ptr<entry[]> entries;
+
+	[[nodiscard]] static std::uint64_t get_key(std::string_view city) noexcept;
+
+	[[nodiscard]] std::uint64_t get_index(std::string_view city) const noexcept;
+
+public:
+	explicit map(std::size_t entry_count);
+
+	void insert(std::string_view city, std::int32_t measurement);
+
+	[[nodiscard]] entry& operator[](std::string_view city);
+
+	void merge_against(const map& other);
+
+	[[nodiscard]] std::vector<entry> collapse() const noexcept;
+};
+
+}  // namespace brc