diff --git a/include/nlohmann/detail/hash.hpp b/include/nlohmann/detail/hash.hpp new file mode 100644 index 00000000..d3313e96 --- /dev/null +++ b/include/nlohmann/detail/hash.hpp @@ -0,0 +1,117 @@ +#pragma once + +#include // size_t, uint8_t +#include // hash + +namespace nlohmann +{ +namespace detail +{ + +// boost::hash_combine +std::size_t combine(std::size_t seed, std::size_t h) noexcept +{ + seed ^= h + 0x9e3779b9 + (seed << 6U) + (seed >> 2U); + return seed; +} + +/*! +@brief hash a JSON value + +The hash function tries to rely on std::hash where possible. Furthermore, the +type of the JSON value is taken into account to have different hash values for +null, 0, 0U, and false, etc. + +@tparam BasicJsonType basic_json specialization +@param j JSON value to hash +@return hash value of j +*/ +template +std::size_t hash(const BasicJsonType& j) +{ + using string_t = typename BasicJsonType::string_t; + using number_integer_t = typename BasicJsonType::number_integer_t; + using number_unsigned_t = typename BasicJsonType::number_unsigned_t; + using number_float_t = typename BasicJsonType::number_float_t; + + const auto type = static_cast(j.type()); + switch (j.type()) + { + case BasicJsonType::value_t::null: + case BasicJsonType::value_t::discarded: + { + return combine(type, 0); + } + + case BasicJsonType::value_t::object: + { + auto seed = combine(type, j.size()); + for (const auto& element : j.items()) + { + const auto h = std::hash {}(element.key()); + seed = combine(seed, h); + seed = combine(seed, hash(element.value())); + } + return seed; + } + + case BasicJsonType::value_t::array: + { + auto seed = combine(type, j.size()); + for (const auto& element : j) + { + seed = combine(seed, hash(element)); + } + return seed; + } + + case BasicJsonType::value_t::string: + { + const auto h = std::hash {}(j.template get_ref()); + return combine(type, h); + } + + case BasicJsonType::value_t::boolean: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case BasicJsonType::value_t::number_integer: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::number_unsigned: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::number_float: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::binary: + { + auto seed = combine(type, j.get_binary().size()); + const auto h = std::hash {}(j.get_binary().has_subtype()); + seed = combine(seed, h); + seed = combine(seed, j.get_binary().subtype()); + for (const auto byte : j.get_binary()) + { + seed = combine(seed, std::hash {}(byte)); + } + return seed; + } + + default: // LCOV_EXCL_LINE + JSON_ASSERT(false); // LCOV_EXCL_LINE + } +} + +} // namespace detail +} // namespace nlohmann diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp index 7c2cf2b1..1a45b776 100644 --- a/include/nlohmann/json.hpp +++ b/include/nlohmann/json.hpp @@ -51,6 +51,7 @@ SOFTWARE. #include #include #include +#include #include #include #include @@ -8698,9 +8699,7 @@ struct hash */ std::size_t operator()(const nlohmann::json& j) const { - // a naive hashing via the string representation - const auto& h = hash(); - return h(j.dump()); + return nlohmann::detail::hash(j); } }; diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp index 32986cb6..7f59aca2 100644 --- a/single_include/nlohmann/json.hpp +++ b/single_include/nlohmann/json.hpp @@ -4442,6 +4442,125 @@ class byte_container_with_subtype : public BinaryType // #include +// #include + + +#include // size_t, uint8_t +#include // hash + +namespace nlohmann +{ +namespace detail +{ + +// boost::hash_combine +std::size_t combine(std::size_t seed, std::size_t h) noexcept +{ + seed ^= h + 0x9e3779b9 + (seed << 6U) + (seed >> 2U); + return seed; +} + +/*! +@brief hash a JSON value + +The hash function tries to rely on std::hash where possible. Furthermore, the +type of the JSON value is taken into account to have different hash values for +null, 0, 0U, and false, etc. + +@tparam BasicJsonType basic_json specialization +@param j JSON value to hash +@return hash value of j +*/ +template +std::size_t hash(const BasicJsonType& j) +{ + using string_t = typename BasicJsonType::string_t; + using number_integer_t = typename BasicJsonType::number_integer_t; + using number_unsigned_t = typename BasicJsonType::number_unsigned_t; + using number_float_t = typename BasicJsonType::number_float_t; + + const auto type = static_cast(j.type()); + switch (j.type()) + { + case BasicJsonType::value_t::null: + case BasicJsonType::value_t::discarded: + { + return combine(type, 0); + } + + case BasicJsonType::value_t::object: + { + auto seed = combine(type, j.size()); + for (const auto& element : j.items()) + { + const auto h = std::hash {}(element.key()); + seed = combine(seed, h); + seed = combine(seed, hash(element.value())); + } + return seed; + } + + case BasicJsonType::value_t::array: + { + auto seed = combine(type, j.size()); + for (const auto& element : j) + { + seed = combine(seed, hash(element)); + } + return seed; + } + + case BasicJsonType::value_t::string: + { + const auto h = std::hash {}(j.template get_ref()); + return combine(type, h); + } + + case BasicJsonType::value_t::boolean: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case BasicJsonType::value_t::number_integer: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::number_unsigned: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::number_float: + { + const auto h = std::hash {}(j.template get()); + return combine(type, h); + } + + case nlohmann::detail::value_t::binary: + { + auto seed = combine(type, j.get_binary().size()); + const auto h = std::hash {}(j.get_binary().has_subtype()); + seed = combine(seed, h); + seed = combine(seed, j.get_binary().subtype()); + for (const auto byte : j.get_binary()) + { + seed = combine(seed, std::hash {}(byte)); + } + return seed; + } + + default: // LCOV_EXCL_LINE + JSON_ASSERT(false); // LCOV_EXCL_LINE + } +} + +} // namespace detail +} // namespace nlohmann + // #include @@ -24653,9 +24772,7 @@ struct hash */ std::size_t operator()(const nlohmann::json& j) const { - // a naive hashing via the string representation - const auto& h = hash(); - return h(j.dump()); + return nlohmann::detail::hash(j); } }; diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt index 9146d43b..91ff5a21 100644 --- a/test/CMakeLists.txt +++ b/test/CMakeLists.txt @@ -112,6 +112,7 @@ set(files src/unit-deserialization.cpp src/unit-element_access1.cpp src/unit-element_access2.cpp + src/unit-hash.cpp src/unit-inspection.cpp src/unit-items.cpp src/unit-iterators1.cpp diff --git a/test/src/unit-hash.cpp b/test/src/unit-hash.cpp new file mode 100644 index 00000000..186cad88 --- /dev/null +++ b/test/src/unit-hash.cpp @@ -0,0 +1,84 @@ +/* + __ _____ _____ _____ + __| | __| | | | JSON for Modern C++ (test suite) +| | |__ | | | | | | version 3.8.0 +|_____|_____|_____|_|___| https://github.com/nlohmann/json + +Licensed under the MIT License . +SPDX-License-Identifier: MIT +Copyright (c) 2013-2019 Niels Lohmann . + +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. +*/ + +#include "doctest_compatibility.h" + +#include +using json = nlohmann::json; + +#include + +TEST_CASE("hash") +{ + // Collect hashes for different JSON values and make sure that they are distinct + // We cannot compare against fixed values, because the implementation of + // std::hash may differ between compilers. + + std::set hashes; + + // null + hashes.insert(std::hash {}(json(nullptr))); + + // boolean + hashes.insert(std::hash {}(json(true))); + hashes.insert(std::hash {}(json(false))); + + // string + hashes.insert(std::hash {}(json(""))); + hashes.insert(std::hash {}(json("foo"))); + + // number + hashes.insert(std::hash {}(json(0))); + hashes.insert(std::hash {}(json(unsigned(0)))); + + hashes.insert(std::hash {}(json(-1))); + hashes.insert(std::hash {}(json(0.0))); + hashes.insert(std::hash {}(json(42.23))); + + // array + hashes.insert(std::hash {}(json::array())); + hashes.insert(std::hash {}(json::array({1, 2, 3}))); + + // object + hashes.insert(std::hash {}(json::object())); + hashes.insert(std::hash {}(json::object({{"foo", "bar"}}))); + + // binary + hashes.insert(std::hash {}(json::binary({}))); + hashes.insert(std::hash {}(json::binary({}, 0))); + hashes.insert(std::hash {}(json::binary({}, 42))); + hashes.insert(std::hash {}(json::binary({1, 2, 3}))); + hashes.insert(std::hash {}(json::binary({1, 2, 3}, 0))); + hashes.insert(std::hash {}(json::binary({1, 2, 3}, 42))); + + // discarded + hashes.insert(std::hash {}(json(json::value_t::discarded))); + + CHECK(hashes.size() == 21); +}