src/tint/utils/math/hash.h - tint - Git at Google

 // Copyright 2021 The Dawn & Tint Authors
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // 1. Redistributions of source code must retain the above copyright notice, this
 //    list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 //    this list of conditions and the following disclaimer in the documentation
 //    and/or other materials provided with the distribution.
 //
 // 3. Neither the name of the copyright holder nor the names of its
 //    contributors may be used to endorse or promote products derived from
 //    this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #ifndef SRC_TINT_UTILS_MATH_HASH_H_
 #define SRC_TINT_UTILS_MATH_HASH_H_

 #include <stdint.h>
 #include <cstdio>
 #include <functional>
 #include <string>
 #include <tuple>
 #include <utility>
 #include <variant>
 #include <vector>

 #include "src/tint/utils/math/crc32.h"

 namespace tint {

 namespace detail {

 template <typename T, typename = void>
 struct HasHashCodeMember : std::false_type {};

 template <typename T>
 struct HasHashCodeMember<
     T,
     std::enable_if_t<std::is_member_function_pointer_v<decltype(&T::HashCode)>>> : std::true_type {
 };

 }  // namespace detail

 /// The type of a hash code
 using HashCode = uint32_t;

 /// Forward declarations (see below)
 template <typename... ARGS>
 HashCode Hash(const ARGS&... values);

 template <typename... ARGS>
 HashCode HashCombine(HashCode hash, const ARGS&... values);

 /// A STL-compatible hasher that does a more thorough job than most implementations of std::hash.
 /// Hasher has been optimized for a better quality hash at the expense of increased computation
 /// costs.
 /// Hasher is specialized for various core Tint data types. The default implementation will use a
 /// `HashCode HashCode()` method on the `T` type, and will fallback to `std::hash<T>` if
 /// `T::HashCode` is missing.
 template <typename T>
 struct Hasher {
     /// @param value the value to hash
     /// @returns a hash of the value
     HashCode operator()(const T& value) const {
         if constexpr (detail::HasHashCodeMember<T>::value) {
             auto hash = value.HashCode();
             static_assert(std::is_same_v<decltype(hash), HashCode>,
                           "T::HashCode() must return HashCode");
             return hash;
         } else {
             return static_cast<HashCode>(std::hash<T>()(value));
         }
     }
 };

 /// Hasher specialization for pointers
 template <typename T>
 struct Hasher<T*> {
     /// @param ptr the pointer to hash
     /// @returns a hash of the pointer
     HashCode operator()(T* ptr) const {
         auto hash = reinterpret_cast<uintptr_t>(ptr);
 #ifdef TINT_HASH_SEED
         hash ^= static_cast<uint32_t>(TINT_HASH_SEED);
 #endif
         if constexpr (sizeof(hash) > 4) {
             return static_cast<HashCode>(hash >> 4 | hash >> 32);
         } else {
             return static_cast<HashCode>(hash >> 4);
         }
     }
 };

 /// Hasher specialization for std::vector
 template <typename T>
 struct Hasher<std::vector<T>> {
     /// @param vector the vector to hash
     /// @returns a hash of the vector
     HashCode operator()(const std::vector<T>& vector) const {
         auto hash = Hash(vector.size());
         for (auto& el : vector) {
             hash = HashCombine(hash, el);
         }
         return hash;
     }
 };

 /// Hasher specialization for std::tuple
 template <typename... TYPES>
 struct Hasher<std::tuple<TYPES...>> {
     /// @param tuple the tuple to hash
     /// @returns a hash of the tuple
     HashCode operator()(const std::tuple<TYPES...>& tuple) const {
         return std::apply(Hash<TYPES...>, tuple);
     }
 };

 /// Hasher specialization for std::pair
 template <typename A, typename B>
 struct Hasher<std::pair<A, B>> {
     /// @param tuple the tuple to hash
     /// @returns a hash of the tuple
     HashCode operator()(const std::pair<A, B>& tuple) const {
         return std::apply(Hash<A, B>, tuple);
     }
 };

 /// Hasher specialization for std::variant
 template <typename... TYPES>
 struct Hasher<std::variant<TYPES...>> {
     /// @param variant the variant to hash
     /// @returns a hash of the tuple
     HashCode operator()(const std::variant<TYPES...>& variant) const {
         return std::visit([](auto&& val) { return Hash(val); }, variant);
     }
 };

 /// Hasher specialization for std::string, which also supports hashing of const char* and
 /// std::string_view without first constructing a std::string.
 template <>
 struct Hasher<std::string> {
     /// @param str the string to hash
     /// @returns a hash of the string
     HashCode operator()(const std::string& str) const {
         return static_cast<HashCode>(std::hash<std::string_view>()(std::string_view(str)));
     }

     /// @param str the string to hash
     /// @returns a hash of the string
     HashCode operator()(const char* str) const {
         return static_cast<HashCode>(std::hash<std::string_view>()(std::string_view(str)));
     }

     /// @param str the string to hash
     /// @returns a hash of the string
     HashCode operator()(const std::string_view& str) const {
         return static_cast<HashCode>(std::hash<std::string_view>()(str));
     }
 };

 /// @param args the arguments to hash
 /// @returns a hash of the variadic list of arguments.
 ///          The returned hash is dependent on the order of the arguments.
 template <typename... ARGS>
 HashCode Hash(const ARGS&... args) {
     if constexpr (sizeof...(ARGS) == 0) {
         return 0;
     } else if constexpr (sizeof...(ARGS) == 1) {
         using T = std::tuple_element_t<0, std::tuple<ARGS...>>;
         return Hasher<T>()(args...);
     } else {
         HashCode hash = 102931;  // seed with an arbitrary prime
         return HashCombine(hash, args...);
     }
 }

 /// @param hash the hash value to combine with
 /// @param values the values to hash
 /// @returns a hash of the variadic list of arguments.
 ///          The returned hash is dependent on the order of the arguments.
 template <typename... ARGS>
 HashCode HashCombine(HashCode hash, const ARGS&... values) {
 #ifdef TINT_HASH_SEED
     constexpr uint32_t offset = 0x7f4a7c16 ^ static_cast<uint32_t>(TINT_HASH_SEED);
 #else
     constexpr uint32_t offset = 0x7f4a7c16;
 #endif

     ((hash ^= Hash(values) + (offset ^ (hash >> 2))), ...);
     return hash;
 }

 /// A STL-compatible equal_to implementation that specializes for types.
 template <typename T>
 struct EqualTo {
     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     constexpr bool operator()(const T& lhs, const T& rhs) const {
         return std::equal_to<T>()(lhs, rhs);
     }
 };

 /// A specialization for EqualTo for std::string, which supports additional comparision with
 /// std::string_view and const char*.
 template <>
 struct EqualTo<std::string> {
     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     bool operator()(const std::string& lhs, const std::string& rhs) const { return lhs == rhs; }

     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     bool operator()(const std::string& lhs, const char* rhs) const { return lhs == rhs; }

     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     bool operator()(const std::string& lhs, std::string_view rhs) const { return lhs == rhs; }

     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     bool operator()(const char* lhs, const std::string& rhs) const { return lhs == rhs; }

     /// @param lhs the left hand side value
     /// @param rhs the right hand side value
     /// @returns true if the two values are equal
     bool operator()(std::string_view lhs, const std::string& rhs) const { return lhs == rhs; }
 };

 /// Wrapper for a hashable type enabling the wrapped value to be used as a key
 /// for an unordered_map or unordered_set.
 template <typename T>
 struct UnorderedKeyWrapper {
     /// The wrapped value
     T value;
     /// The hash of value
     HashCode hash;

     /// Constructor
     /// @param v the value to wrap
     explicit UnorderedKeyWrapper(const T& v) : value(v), hash(Hash(v)) {}

     /// Move constructor
     /// @param v the value to wrap
     explicit UnorderedKeyWrapper(T&& v) : value(std::move(v)), hash(Hash(value)) {}

     /// @returns true if this wrapper comes before other
     /// @param other the RHS of the operator
     bool operator<(const UnorderedKeyWrapper& other) const { return hash < other.hash; }

     /// @returns true if this wrapped value is equal to the other wrapped value
     /// @param other the RHS of the operator
     bool operator==(const UnorderedKeyWrapper& other) const { return value == other.value; }
 };

 }  // namespace tint

 namespace std {

 /// Custom std::hash specialization for tint::UnorderedKeyWrapper
 template <typename T>
 class hash<tint::UnorderedKeyWrapper<T>> {
   public:
     /// @param w the UnorderedKeyWrapper
     /// @return the hash value
     inline std::size_t operator()(const tint::UnorderedKeyWrapper<T>& w) const { return w.hash; }
 };

 }  // namespace std

 #endif  // SRC_TINT_UTILS_MATH_HASH_H_
	// Copyright 2021 The Dawn & Tint Authors
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// 1. Redistributions of source code must retain the above copyright notice, this
	// list of conditions and the following disclaimer.
	//
	// 2. Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	//
	// 3. Neither the name of the copyright holder nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#ifndef SRC_TINT_UTILS_MATH_HASH_H_
	#define SRC_TINT_UTILS_MATH_HASH_H_

	#include <stdint.h>
	#include <cstdio>
	#include <functional>
	#include <string>
	#include <tuple>
	#include <utility>
	#include <variant>
	#include <vector>

	#include "src/tint/utils/math/crc32.h"

	namespace tint {

	namespace detail {

	template <typename T, typename = void>
	struct HasHashCodeMember : std::false_type {};

	template <typename T>
	struct HasHashCodeMember<
	T,
	std::enable_if_t<std::is_member_function_pointer_v<decltype(&T::HashCode)>>> : std::true_type {
	};

	} // namespace detail

	/// The type of a hash code
	using HashCode = uint32_t;

	/// Forward declarations (see below)
	template <typename... ARGS>
	HashCode Hash(const ARGS&... values);

	template <typename... ARGS>
	HashCode HashCombine(HashCode hash, const ARGS&... values);

	/// A STL-compatible hasher that does a more thorough job than most implementations of std::hash.
	/// Hasher has been optimized for a better quality hash at the expense of increased computation
	/// costs.
	/// Hasher is specialized for various core Tint data types. The default implementation will use a
	/// `HashCode HashCode()` method on the `T` type, and will fallback to `std::hash<T>` if
	/// `T::HashCode` is missing.
	template <typename T>
	struct Hasher {
	/// @param value the value to hash
	/// @returns a hash of the value
	HashCode operator()(const T& value) const {
	if constexpr (detail::HasHashCodeMember<T>::value) {
	auto hash = value.HashCode();
	static_assert(std::is_same_v<decltype(hash), HashCode>,
	"T::HashCode() must return HashCode");
	return hash;
	} else {
	return static_cast<HashCode>(std::hash<T>()(value));
	}
	}
	};

	/// Hasher specialization for pointers
	template <typename T>
	struct Hasher<T*> {
	/// @param ptr the pointer to hash
	/// @returns a hash of the pointer
	HashCode operator()(T* ptr) const {
	auto hash = reinterpret_cast<uintptr_t>(ptr);
	#ifdef TINT_HASH_SEED
	hash ^= static_cast<uint32_t>(TINT_HASH_SEED);
	#endif
	if constexpr (sizeof(hash) > 4) {
	return static_cast<HashCode>(hash >> 4 \| hash >> 32);
	} else {
	return static_cast<HashCode>(hash >> 4);
	}
	}
	};

	/// Hasher specialization for std::vector
	template <typename T>
	struct Hasher<std::vector<T>> {
	/// @param vector the vector to hash
	/// @returns a hash of the vector
	HashCode operator()(const std::vector<T>& vector) const {
	auto hash = Hash(vector.size());
	for (auto& el : vector) {
	hash = HashCombine(hash, el);
	}
	return hash;
	}
	};

	/// Hasher specialization for std::tuple
	template <typename... TYPES>
	struct Hasher<std::tuple<TYPES...>> {
	/// @param tuple the tuple to hash
	/// @returns a hash of the tuple
	HashCode operator()(const std::tuple<TYPES...>& tuple) const {
	return std::apply(Hash<TYPES...>, tuple);
	}
	};

	/// Hasher specialization for std::pair
	template <typename A, typename B>
	struct Hasher<std::pair<A, B>> {
	/// @param tuple the tuple to hash
	/// @returns a hash of the tuple
	HashCode operator()(const std::pair<A, B>& tuple) const {
	return std::apply(Hash<A, B>, tuple);
	}
	};

	/// Hasher specialization for std::variant
	template <typename... TYPES>
	struct Hasher<std::variant<TYPES...>> {
	/// @param variant the variant to hash
	/// @returns a hash of the tuple
	HashCode operator()(const std::variant<TYPES...>& variant) const {
	return std::visit([](auto&& val) { return Hash(val); }, variant);
	}
	};

	/// Hasher specialization for std::string, which also supports hashing of const char* and
	/// std::string_view without first constructing a std::string.
	template <>
	struct Hasher<std::string> {
	/// @param str the string to hash
	/// @returns a hash of the string
	HashCode operator()(const std::string& str) const {
	return static_cast<HashCode>(std::hash<std::string_view>()(std::string_view(str)));
	}

	/// @param str the string to hash
	/// @returns a hash of the string
	HashCode operator()(const char* str) const {
	return static_cast<HashCode>(std::hash<std::string_view>()(std::string_view(str)));
	}

	/// @param str the string to hash
	/// @returns a hash of the string
	HashCode operator()(const std::string_view& str) const {
	return static_cast<HashCode>(std::hash<std::string_view>()(str));
	}
	};

	/// @param args the arguments to hash
	/// @returns a hash of the variadic list of arguments.
	/// The returned hash is dependent on the order of the arguments.
	template <typename... ARGS>
	HashCode Hash(const ARGS&... args) {
	if constexpr (sizeof...(ARGS) == 0) {
	return 0;
	} else if constexpr (sizeof...(ARGS) == 1) {
	using T = std::tuple_element_t<0, std::tuple<ARGS...>>;
	return Hasher<T>()(args...);
	} else {
	HashCode hash = 102931; // seed with an arbitrary prime
	return HashCombine(hash, args...);
	}
	}

	/// @param hash the hash value to combine with
	/// @param values the values to hash
	/// @returns a hash of the variadic list of arguments.
	/// The returned hash is dependent on the order of the arguments.
	template <typename... ARGS>
	HashCode HashCombine(HashCode hash, const ARGS&... values) {
	#ifdef TINT_HASH_SEED
	constexpr uint32_t offset = 0x7f4a7c16 ^ static_cast<uint32_t>(TINT_HASH_SEED);
	#else
	constexpr uint32_t offset = 0x7f4a7c16;
	#endif

	((hash ^= Hash(values) + (offset ^ (hash >> 2))), ...);
	return hash;
	}

	/// A STL-compatible equal_to implementation that specializes for types.
	template <typename T>
	struct EqualTo {
	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	constexpr bool operator()(const T& lhs, const T& rhs) const {
	return std::equal_to<T>()(lhs, rhs);
	}
	};

	/// A specialization for EqualTo for std::string, which supports additional comparision with
	/// std::string_view and const char*.
	template <>
	struct EqualTo<std::string> {
	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	bool operator()(const std::string& lhs, const std::string& rhs) const { return lhs == rhs; }

	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	bool operator()(const std::string& lhs, const char* rhs) const { return lhs == rhs; }

	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	bool operator()(const std::string& lhs, std::string_view rhs) const { return lhs == rhs; }

	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	bool operator()(const char* lhs, const std::string& rhs) const { return lhs == rhs; }

	/// @param lhs the left hand side value
	/// @param rhs the right hand side value
	/// @returns true if the two values are equal
	bool operator()(std::string_view lhs, const std::string& rhs) const { return lhs == rhs; }
	};

	/// Wrapper for a hashable type enabling the wrapped value to be used as a key
	/// for an unordered_map or unordered_set.
	template <typename T>
	struct UnorderedKeyWrapper {
	/// The wrapped value
	T value;
	/// The hash of value
	HashCode hash;

	/// Constructor
	/// @param v the value to wrap
	explicit UnorderedKeyWrapper(const T& v) : value(v), hash(Hash(v)) {}

	/// Move constructor
	/// @param v the value to wrap
	explicit UnorderedKeyWrapper(T&& v) : value(std::move(v)), hash(Hash(value)) {}

	/// @returns true if this wrapper comes before other
	/// @param other the RHS of the operator
	bool operator<(const UnorderedKeyWrapper& other) const { return hash < other.hash; }

	/// @returns true if this wrapped value is equal to the other wrapped value
	/// @param other the RHS of the operator
	bool operator==(const UnorderedKeyWrapper& other) const { return value == other.value; }
	};

	} // namespace tint

	namespace std {

	/// Custom std::hash specialization for tint::UnorderedKeyWrapper
	template <typename T>
	class hash<tint::UnorderedKeyWrapper<T>> {
	public:
	/// @param w the UnorderedKeyWrapper
	/// @return the hash value
	inline std::size_t operator()(const tint::UnorderedKeyWrapper<T>& w) const { return w.hash; }
	};

	} // namespace std

	#endif // SRC_TINT_UTILS_MATH_HASH_H_