hash_consteval.hpp added; hardened named_type_wrapper

Author: VioletGiraffe

cpp-template-utils.pro

@@ -22,5 +22,6 @@ HEADERS += \
 	$$files(string/*.hpp, false) \
 	$$files(tuple/*.hpp, false) \
 	$$files(utility/*.h*, false) \
+	hash/hash_consteval.hpp \
 	hash/mixers.h \
 	utility/aligned_wrapper.hpp

hash/hash_consteval.hpp

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <string_view>
+#include <stdint.h>
+
+[[nodiscard]] consteval uint32_t murmur3_32_consteval(std::string_view s, uint32_t seed = 0) noexcept
+{
+	constexpr uint32_t c1 = 0xcc9e2d51u;
+	constexpr uint32_t c2 = 0x1b873593u;
+
+	uint32_t h = seed;
+	const size_t nblocks = s.size() / 4;
+
+	for (size_t i = 0; i < nblocks; ++i)
+	{
+		// A constant expression can't reinterpret 4 bytes as a uint32_t, so build the block by hand.
+		// Fixed little-endian keeps results identical across platforms and matches the reference vectors.
+		const size_t j = i * 4;
+		uint32_t k = static_cast<uint32_t>(static_cast<uint8_t>(s[j]))
+					 | static_cast<uint32_t>(static_cast<uint8_t>(s[j + 1])) << 8
+					 | static_cast<uint32_t>(static_cast<uint8_t>(s[j + 2])) << 16
+					 | static_cast<uint32_t>(static_cast<uint8_t>(s[j + 3])) << 24;
+
+		k *= c1;
+		k = (k << 15) | (k >> 17);
+		k *= c2;
+
+		h ^= k;
+		h = (h << 13) | (h >> 19);
+		h = h * 5u + 0xe6546b64u;
+	}
+
+	uint32_t k = 0;
+	const size_t tail = nblocks * 4;
+	switch (s.size() % 4)
+	{
+	case 3: k ^= static_cast<uint32_t>(static_cast<uint8_t>(s[tail + 2])) << 16; [[fallthrough]];
+	case 2: k ^= static_cast<uint32_t>(static_cast<uint8_t>(s[tail + 1])) << 8; [[fallthrough]];
+	case 1: k ^= static_cast<uint32_t>(static_cast<uint8_t>(s[tail]));
+		k *= c1;
+		k = (k << 15) | (k >> 17);
+		k *= c2;
+		h ^= k;
+	}
+
+	h ^= static_cast<uint32_t>(s.size());
+	h ^= h >> 16;
+	h *= 0x85ebca6bu;
+	h ^= h >> 13;
+	h *= 0xc2b2ae35u;
+	h ^= h >> 16;
+
+	return h;
+}

utility/named_type_wrapper.hpp

@@ -1,10 +1,14 @@
 #pragma once
-#include <utility>
+#include "../hash/hash_consteval.hpp"
 
-template <typename T, int>
+#include <type_traits>
+
+template <typename T, uint64_t>
 struct NamedType
 {
-	explicit constexpr NamedType(T v) noexcept : _value{ std::move(v) } {}
+	static_assert(std::is_trivially_copyable_v<T> && std::is_standard_layout_v<T>); // Not a hard requirement, but right now the wrapper is not suitable for non-trivial types
+
+	explicit constexpr NamedType(T v) noexcept : _value{ v } {}
 	constexpr NamedType() noexcept = default;
 
 	constexpr operator T() const noexcept
@@ -16,5 +20,5 @@ struct NamedType
 	T _value{}; // default initialization for class types; zero initialization for primitive type: 'false' for bool, '0' for int etc.
 };
 
-#define UniqueNamedBoolType NamedType<bool, __LINE__>
-#define UniqueNamedType(T) NamedType<T, __LINE__>
+#define UniqueNamedBoolType NamedType<bool, __LINE__ + murmur3_32_consteval(__FILE__)>
+#define UniqueNamedType(T) NamedType<T, __LINE__ + murmur3_32_consteval(__FILE__)>