1 files changed, 254 insertions, 2 deletions

diff --git a/include/openvic-dataloader/detail/SymbolIntern.hpp b/include/openvic-dataloader/detail/SymbolIntern.hpp
index 8755887..d72a0ba 100644
--- a/include/openvic-dataloader/detail/SymbolIntern.hpp
+++ b/include/openvic-dataloader/detail/SymbolIntern.hpp
@@ -1,14 +1,266 @@
 #pragma once
 
 #include <cstdint>
+#include <iterator>
+#include <string_view>
+
+#include <openvic-dataloader/detail/pinned_vector.hpp>
 
 #include <dryad/symbol.hpp>
 
 namespace ovdl {
+	// Contains all unique symbols, null-terminated, in memory one after the other.
+	template<typename CharT>
+	struct symbol_buffer {
+		static constexpr auto min_buffer_size = 16 * 1024;
+
+		constexpr symbol_buffer() : _data_buffer(ovdl::detail::max_elements(min_buffer_size + 1)) {}
+		explicit symbol_buffer(std::size_t max_elements)
+			: _data_buffer(ovdl::detail::max_elements(std::max<std::size_t>(max_elements, min_buffer_size + 1))) {
+			_data_buffer.reserve(min_buffer_size);
+		}
+
+		void free() {
+		}
+
+		bool reserve(std::size_t new_capacity) {
+			if (new_capacity <= _data_buffer.capacity())
+				return true;
+
+			if (new_capacity >= _data_buffer.max_size()) {
+				_data_buffer.reserve(_data_buffer.max_size());
+				return false;
+			}
+
+			_data_buffer.reserve(new_capacity * sizeof(CharT));
+
+			return true;
+		}
+
+		bool reserve_new_string(std::size_t new_string_length) {
+			// +1 for null-terminator.
+			auto new_size = _data_buffer.size() + new_string_length + 1;
+			if (new_size <= _data_buffer.capacity())
+				return true;
+
+			auto new_capacity = new_size * 2;
+			if (new_capacity < min_buffer_size)
+				new_capacity = min_buffer_size;
+
+			if (!reserve(new_capacity)) {
+				return _data_buffer.capacity() >= new_size;
+			}
+
+			return true;
+		}
+
+		const CharT* insert(const CharT* str, std::size_t length) {
+			DRYAD_PRECONDITION(_data_buffer.capacity() - _data_buffer.size() >= length + 1);
+
+			auto index = _data_buffer.cend();
+
+			_data_buffer.insert(_data_buffer.cend(), str, str + (length * sizeof(CharT)));
+			_data_buffer.push_back(CharT(0));
+
+			return index;
+		}
+
+		const CharT* c_str(std::size_t index) const {
+			DRYAD_PRECONDITION(index < _data_buffer.size());
+			return _data_buffer.data() + index;
+		}
+
+		std::size_t size() const {
+			return _data_buffer.size();
+		}
+
+		std::size_t capacity() const {
+			return _data_buffer.capacity();
+		}
+
+		std::size_t max_size() const {
+			return _data_buffer.max_size();
+		}
+
+	private:
+		detail::pinned_vector<CharT> _data_buffer;
+	};
+
+	template<typename IndexType, typename CharT>
+	struct symbol_index_hash_traits {
+		const symbol_buffer<CharT>* buffer;
+
+		using value_type = IndexType;
+
+		struct string_view {
+			const CharT* ptr;
+			std::size_t length;
+		};
+
+		static constexpr bool is_unoccupied(IndexType index) {
+			return index == IndexType(-1);
+		}
+		static void fill_unoccupied(IndexType* data, std::size_t size) {
+			// It has all bits set to 1, so we can do it per-byte.
+			std::memset(data, static_cast<unsigned char>(-1), size * sizeof(IndexType));
+		}
+
+		static constexpr bool is_equal(IndexType entry, IndexType value) {
+			return entry == value;
+		}
+		bool is_equal(IndexType entry, string_view str) const {
+			auto existing_str = buffer->c_str(entry);
+			return std::strncmp(existing_str, str.ptr, str.length) == 0 && *(existing_str + str.length) == CharT(0);
+		}
+
+		std::size_t hash(IndexType entry) const {
+			auto str = buffer->c_str(entry);
+			return dryad::default_hash_algorithm().hash_c_str(str).finish();
+		}
+		static constexpr std::size_t hash(string_view str) {
+			return dryad::default_hash_algorithm()
+				.hash_bytes(reinterpret_cast<const unsigned char*>(str.ptr), str.length * sizeof(CharT))
+				.finish();
+		}
+	};
+
+	template<typename CharT = char>
+	class symbol;
+
+	template<typename Id, typename CharT = char, typename IndexType = std::size_t,
+		typename MemoryResource = void>
+	class symbol_interner {
+		static_assert(std::is_trivial_v<CharT>);
+		static_assert(std::is_unsigned_v<IndexType>);
+
+		using resource_ptr = dryad::_detail::memory_resource_ptr<MemoryResource>;
+		using traits = symbol_index_hash_traits<IndexType, CharT>;
+
+	public:
+		using symbol = ovdl::symbol<CharT>;
+
+		//=== construction ===//
+		constexpr symbol_interner() : _resource(dryad::_detail::get_memory_resource<MemoryResource>()) {}
+		constexpr explicit symbol_interner(std::size_t max_elements)
+			: _buffer(max_elements),
+			  _resource(dryad::_detail::get_memory_resource<MemoryResource>()) {}
+		constexpr explicit symbol_interner(std::size_t max_elements, MemoryResource* resource)
+			: _buffer(max_elements),
+			  _resource(resource) {}
+
+		~symbol_interner() noexcept {
+			_buffer.free();
+			_map.free(_resource);
+		}
+
+		symbol_interner(symbol_interner&& other) noexcept
+			: _buffer(other._buffer), _map(other._map), _resource(other._resource) {
+			other._buffer = {};
+			other._map = {};
+		}
+
+		symbol_interner& operator=(symbol_interner&& other) noexcept {
+			dryad::_detail::swap(_buffer, other._buffer);
+			dryad::_detail::swap(_map, other._map);
+			dryad::_detail::swap(_resource, other._resource);
+			return *this;
+		}
+
+		//=== interning ===//
+		bool reserve(std::size_t number_of_symbols, std::size_t average_symbol_length) {
+			auto success = _buffer.reserve(number_of_symbols * average_symbol_length);
+			_map.rehash(_resource, _map.to_table_capacity(number_of_symbols), traits { &_buffer });
+			return success;
+		}
+
+		symbol intern(const CharT* str, std::size_t length) {
+			if (_map.should_rehash())
+				_map.rehash(_resource, traits { &_buffer });
+
+			auto entry = _map.lookup_entry(typename traits::string_view { str, length }, traits { &_buffer });
+			if (entry)
+				// Already interned, return index.
+				return symbol(_buffer.c_str(entry.get()));
+
+			// Copy string data to buffer, as we don't have it yet.
+			if (!_buffer.reserve_new_string(length)) // Ran out of virtual memory space
+				return symbol();
+
+			auto begin = _buffer.insert(str, length);
+			auto idx = std::distance(_buffer.c_str(0), begin);
+			DRYAD_PRECONDITION(idx == IndexType(idx)); // Overflow of index type.
+
+			// Store index in map.
+			entry.create(IndexType(idx));
+
+			// Return new symbol.
+			return symbol(begin);
+		}
+		template<std::size_t N>
+		symbol intern(const CharT (&literal)[N]) {
+			DRYAD_PRECONDITION(literal[N - 1] == CharT(0));
+			return intern(literal, N - 1);
+		}
+
+	private:
+		symbol_buffer<CharT> _buffer;
+		dryad::_detail::hash_table<traits, 1024> _map;
+		DRYAD_EMPTY_MEMBER resource_ptr _resource;
+
+		friend symbol;
+	};
+
+	template<typename CharT>
+	struct symbol {
+		using char_type = CharT;
+
+		constexpr symbol() = default;
+		constexpr explicit symbol(const CharT* begin) : _begin(begin) {}
+
+		constexpr explicit operator bool() const {
+			return _begin != nullptr;
+		}
+
+		constexpr const CharT* c_str() const {
+			return _begin;
+		}
+
+		constexpr const std::basic_string_view<CharT> view() const {
+			return _begin;
+		}
+
+		//=== comparison ===//
+		friend constexpr bool operator==(symbol lhs, symbol rhs) {
+			return lhs._begin == rhs._begin;
+		}
+		friend constexpr bool operator!=(symbol lhs, symbol rhs) {
+			return lhs._begin != rhs._begin;
+		}
+
+		friend constexpr bool operator<(symbol lhs, symbol rhs) {
+			return lhs._begin < rhs._begin;
+		}
+		friend constexpr bool operator<=(symbol lhs, symbol rhs) {
+			return lhs._begin <= rhs._begin;
+		}
+		friend constexpr bool operator>(symbol lhs, symbol rhs) {
+			return lhs._begin > rhs._begin;
+		}
+		friend constexpr bool operator>=(symbol lhs, symbol rhs) {
+			return lhs._begin >= rhs._begin;
+		}
+
+	private:
+		const CharT* _begin = nullptr;
+
+		template<typename, typename, typename, typename>
+		friend class symbol_interner;
+	};
+
 	struct SymbolIntern {
 		struct SymbolId;
 		using index_type = std::uint32_t;
-		using symbol_type = dryad::symbol<SymbolId, index_type>;
-		using symbol_interner_type = dryad::symbol_interner<SymbolId, char, index_type>;
+		using symbol_type = symbol<char>;
+		using symbol_interner_type = symbol_interner<SymbolId, symbol_type::char_type, index_type>;
 	};
 }
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