Mercurial > repos > rliterman > csp2
diff CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/include/kj/hash.h @ 69:33d812a61356
planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author | jpayne |
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date | Tue, 18 Mar 2025 17:55:14 -0400 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/include/kj/hash.h Tue Mar 18 17:55:14 2025 -0400 @@ -0,0 +1,196 @@ +// Copyright (c) 2018 Kenton Varda and contributors +// Licensed under the MIT License: +// +// Permission is hereby granted, free of charge, to any person obtaining a copy +// of this software and associated documentation files (the "Software"), to deal +// in the Software without restriction, including without limitation the rights +// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +// copies of the Software, and to permit persons to whom the Software is +// furnished to do so, subject to the following conditions: +// +// The above copyright notice and this permission notice shall be included in +// all copies or substantial portions of the Software. +// +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +// THE SOFTWARE. + +#pragma once + +#include "string.h" + +KJ_BEGIN_HEADER + +namespace kj { +namespace _ { // private + +struct HashCoder { + // This is a dummy type with only one instance: HASHCODER (below). To make an arbitrary type + // hashable, define `operator*(HashCoder, T)` to return any other type that is already hashable. + // Be sure to declare the operator in the same namespace as `T` **or** in the global scope. + // You can use the KJ_HASHCODE() macro as syntax sugar for this. + // + // A more usual way to accomplish what we're doing here would be to require that you define + // a function like `hashCode(T)` and then rely on argument-dependent lookup. However, this has + // the problem that it pollutes other people's namespaces and even the global namespace. For + // example, some other project may already have functions called `hashCode` which do something + // different. Declaring `operator*` with `HashCoder` as the left operand cannot conflict with + // anything. + + uint operator*(ArrayPtr<const byte> s) const; + inline uint operator*(ArrayPtr<byte> s) const { return operator*(s.asConst()); } + + inline uint operator*(ArrayPtr<const char> s) const { return operator*(s.asBytes()); } + inline uint operator*(ArrayPtr<char> s) const { return operator*(s.asBytes()); } + inline uint operator*(const Array<const char>& s) const { return operator*(s.asBytes()); } + inline uint operator*(const Array<char>& s) const { return operator*(s.asBytes()); } + inline uint operator*(const String& s) const { return operator*(s.asBytes()); } + inline uint operator*(const StringPtr& s) const { return operator*(s.asBytes()); } + inline uint operator*(const ConstString& s) const { return operator*(s.asBytes()); } + + inline uint operator*(decltype(nullptr)) const { return 0; } + inline uint operator*(bool b) const { return b; } + inline uint operator*(char i) const { return i; } + inline uint operator*(signed char i) const { return i; } + inline uint operator*(unsigned char i) const { return i; } + inline uint operator*(signed short i) const { return i; } + inline uint operator*(unsigned short i) const { return i; } + inline uint operator*(signed int i) const { return i; } + inline uint operator*(unsigned int i) const { return i; } + + inline uint operator*(signed long i) const { + if (sizeof(i) == sizeof(uint)) { + return operator*(static_cast<uint>(i)); + } else { + return operator*(static_cast<unsigned long long>(i)); + } + } + inline uint operator*(unsigned long i) const { + if (sizeof(i) == sizeof(uint)) { + return operator*(static_cast<uint>(i)); + } else { + return operator*(static_cast<unsigned long long>(i)); + } + } + inline uint operator*(signed long long i) const { + return operator*(static_cast<unsigned long long>(i)); + } + inline uint operator*(unsigned long long i) const { + // Mix 64 bits to 32 bits in such a way that if our input values differ primarily in the upper + // 32 bits, we still get good diffusion. (I.e. we cannot just truncate!) + // + // 49123 is an arbitrarily-chosen prime that is vaguely close to 2^16. + // + // TODO(perf): I just made this up. Is it OK? + return static_cast<uint>(i) + static_cast<uint>(i >> 32) * 49123; + } + + template <typename T> + uint operator*(T* ptr) const { + static_assert(!isSameType<Decay<T>, char>(), "Wrap in StringPtr if you want to hash string " + "contents. If you want to hash the pointer, cast to void*"); + if (sizeof(ptr) == sizeof(uint)) { + // TODO(cleanup): In C++17, make the if() above be `if constexpr ()`, then change this to + // reinterpret_cast<uint>(ptr). + return reinterpret_cast<unsigned long long>(ptr); + } else { + return operator*(reinterpret_cast<unsigned long long>(ptr)); + } + } + + template <typename T, typename = decltype(instance<const HashCoder&>() * instance<const T&>())> + uint operator*(ArrayPtr<T> arr) const; + template <typename T, typename = decltype(instance<const HashCoder&>() * instance<const T&>())> + uint operator*(const Array<T>& arr) const; + template <typename T, typename = EnableIf<__is_enum(T)>> + inline uint operator*(T e) const; + + template <typename T, typename Result = decltype(instance<T>().hashCode())> + inline Result operator*(T&& value) const { return kj::fwd<T>(value).hashCode(); } +}; +static KJ_CONSTEXPR(const) HashCoder HASHCODER = HashCoder(); + +} // namespace _ (private) + +#define KJ_HASHCODE(...) operator*(::kj::_::HashCoder, __VA_ARGS__) +// Defines a hash function for a custom type. Example: +// +// class Foo {...}; +// inline uint KJ_HASHCODE(const Foo& foo) { return kj::hashCode(foo.x, foo.y); } +// +// This allows Foo to be passed to hashCode(). +// +// The function should be declared either in the same namespace as the target type or in the global +// namespace. It can return any type which itself is hashable -- that value will be hashed in turn +// until a `uint` comes out. + +inline uint hashCode(uint value) { return value; } +template <typename T> +inline uint hashCode(T&& value) { return hashCode(_::HASHCODER * kj::fwd<T>(value)); } +template <typename T, size_t N> +inline uint hashCode(T (&arr)[N]) { + static_assert(!isSameType<Decay<T>, char>(), "Wrap in StringPtr if you want to hash string " + "contents. If you want to hash the pointer, cast to void*"); + static_assert(isSameType<Decay<T>, char>(), "Wrap in ArrayPtr if you want to hash a C array. " + "If you want to hash the pointer, cast to void*"); + return 0; +} +template <typename... T> +inline uint hashCode(T&&... values) { + uint hashes[] = { hashCode(kj::fwd<T>(values))... }; + return hashCode(kj::ArrayPtr<uint>(hashes).asBytes()); +} +// kj::hashCode() is a universal hashing function, like kj::str() is a universal stringification +// function. Throw stuff in, get a hash code. +// +// Hash codes may differ between different processes, even running exactly the same code. +// +// NOT SUITABLE FOR CRYPTOGRAPHY. This is for hash tables, not crypto. + +// ======================================================================================= +// inline implementation details + +namespace _ { // private + +template <typename T, typename> +inline uint HashCoder::operator*(ArrayPtr<T> arr) const { + // Hash each array element to create a string of hashes, then murmur2 over those. + // + // TODO(perf): Choose a more-modern hash. (See hash.c++.) + + constexpr uint m = 0x5bd1e995; + constexpr uint r = 24; + uint h = arr.size() * sizeof(uint); + + for (auto& e: arr) { + uint k = kj::hashCode(e); + k *= m; + k ^= k >> r; + k *= m; + h *= m; + h ^= k; + } + + h ^= h >> 13; + h *= m; + h ^= h >> 15; + return h; +} +template <typename T, typename> +inline uint HashCoder::operator*(const Array<T>& arr) const { + return operator*(arr.asPtr()); +} + +template <typename T, typename> +inline uint HashCoder::operator*(T e) const { + return operator*(static_cast<__underlying_type(T)>(e)); +} + +} // namespace _ (private) +} // namespace kj + +KJ_END_HEADER