mirror of
https://github.com/nlohmann/json.git
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121 lines
3.5 KiB
C++
121 lines
3.5 KiB
C++
#pragma once
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#include <cstddef> // size_t, uint8_t
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#include <functional> // hash
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#include <nlohmann/detail/macro_scope.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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// boost::hash_combine
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inline std::size_t combine(std::size_t seed, std::size_t h) noexcept
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{
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seed ^= h + 0x9e3779b9 + (seed << 6U) + (seed >> 2U);
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return seed;
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}
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/*!
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@brief hash a JSON value
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The hash function tries to rely on std::hash where possible. Furthermore, the
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type of the JSON value is taken into account to have different hash values for
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null, 0, 0U, and false, etc.
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@tparam BasicJsonType basic_json specialization
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@param j JSON value to hash
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@return hash value of j
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*/
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template<typename BasicJsonType>
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std::size_t hash(const BasicJsonType& j)
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{
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using string_t = typename BasicJsonType::string_t;
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using number_integer_t = typename BasicJsonType::number_integer_t;
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using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
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using number_float_t = typename BasicJsonType::number_float_t;
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const auto type = static_cast<std::size_t>(j.type());
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switch (j.type())
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{
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case BasicJsonType::value_t::null:
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case BasicJsonType::value_t::discarded:
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{
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return combine(type, 0);
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}
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case BasicJsonType::value_t::object:
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{
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auto seed = combine(type, j.size());
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for (const auto& element : j.items())
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{
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const auto h = std::hash<string_t> {}(element.key());
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seed = combine(seed, h);
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seed = combine(seed, hash(element.value()));
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}
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return seed;
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}
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case BasicJsonType::value_t::array:
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{
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auto seed = combine(type, j.size());
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for (const auto& element : j)
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{
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seed = combine(seed, hash(element));
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}
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return seed;
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}
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case BasicJsonType::value_t::string:
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{
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const auto h = std::hash<string_t> {}(j.template get_ref<const string_t&>());
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return combine(type, h);
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}
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case BasicJsonType::value_t::boolean:
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{
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const auto h = std::hash<bool> {}(j.template get<bool>());
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return combine(type, h);
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}
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case BasicJsonType::value_t::number_integer:
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{
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const auto h = std::hash<number_integer_t> {}(j.template get<number_integer_t>());
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return combine(type, h);
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}
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case BasicJsonType::value_t::number_unsigned:
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{
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const auto h = std::hash<number_unsigned_t> {}(j.template get<number_unsigned_t>());
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return combine(type, h);
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}
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case BasicJsonType::value_t::number_float:
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{
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const auto h = std::hash<number_float_t> {}(j.template get<number_float_t>());
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return combine(type, h);
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}
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case BasicJsonType::value_t::binary:
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{
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auto seed = combine(type, j.get_binary().size());
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const auto h = std::hash<bool> {}(j.get_binary().has_subtype());
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seed = combine(seed, h);
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seed = combine(seed, j.get_binary().subtype());
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for (const auto byte : j.get_binary())
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{
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seed = combine(seed, std::hash<std::uint8_t> {}(byte));
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}
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return seed;
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}
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default: // LCOV_EXCL_LINE
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JSON_ASSERT(false); // LCOV_EXCL_LINE
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return 0; // LCOV_EXCL_LINE
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}
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}
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} // namespace detail
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} // namespace nlohmann
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