Remove JSON_HAS_STRING_VIEW
Instead implement @gregmarr's PR comments that perfect forwarding should be used. Also cleaned up cpp language standard detection.
This commit is contained in:
Jamie Seward
parent
d468f8c4e6
commit
33c6511dd0
2 changed files with 70 additions and 32 deletions
100
src/json.hpp
100
src/json.hpp
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@ -109,16 +109,14 @@ SOFTWARE.
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#define JSON_UNLIKELY(x) x
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#endif
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// string_view support
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#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_MSC_VER) && _MSC_VER > 1900 && defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
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#define JSON_HAS_STRING_VIEW
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// cpp language standard detection
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#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
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#define JSON_HAS_CPP_17
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#define JSON_HAS_CPP_14
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#elif (defined(__cplusplus) && __cplusplus >= 201402L) || (defined(_HAS_CXX14) && _HAS_CXX14 == 1)
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#define JSON_HAS_CPP_14
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#endif
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#if defined(JSON_HAS_STRING_VIEW)
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#include <string_view>
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#endif
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/*!
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@brief namespace for Niels Lohmann
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@see https://github.com/nlohmann
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@ -7600,26 +7598,18 @@ class basic_json
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specified "unordered" nature of JSON objects.
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*/
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#if defined(JSON_HAS_STRING_VIEW)
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// if std::string_view is to be used the object_t must
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// be declared with a transparent comparator
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// https://stackoverflow.com/questions/35525777/use-of-string-view-for-map-lookup
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using object_t = ObjectType<StringType,
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basic_json,
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std::less<>,
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AllocatorType<std::pair<const StringType,
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basic_json>>>;
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using object_comparator_key_t = std::string_view;
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#if defined(JSON_HAS_CPP_14)
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// Use transparent comparator if possible, combined with perfect forwarding
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// on find() and count() calls prevents unnecessary string construction.
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using object_comparator_t = std::less<>;
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#else
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using object_t = ObjectType<StringType,
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basic_json,
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std::less<StringType>,
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AllocatorType<std::pair<const StringType,
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basic_json>>>;
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using object_comparator_key_t = typename object_t::key_type;
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using object_comparator_t = std::less<StringType>;
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#endif
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using object_t = ObjectType<StringType,
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basic_json,
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object_comparator_t,
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AllocatorType<std::pair<const StringType,
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basic_json>>>;
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/*!
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@brief a type for an array
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@ -9868,7 +9858,7 @@ class basic_json
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#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
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and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
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#endif
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#if defined(JSON_HAS_STRING_VIEW)
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#if defined(JSON_HAS_CPP_17)
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and not std::is_same<ValueType, typename std::string_view>::value
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#endif
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, int >::type = 0 >
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@ -10906,7 +10896,7 @@ class basic_json
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@since version 1.0.0
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*/
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iterator find(object_comparator_key_t key)
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iterator find(typename object_t::key_type key)
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{
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auto result = end();
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@ -10920,9 +10910,9 @@ class basic_json
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/*!
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@brief find an element in a JSON object
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@copydoc find(object_transparent_comparator_key_t)
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@copydoc find(typename object_t::key_type)
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*/
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const_iterator find(object_comparator_key_t key) const
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const_iterator find(typename object_t::key_type key) const
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{
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auto result = cend();
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@ -10934,6 +10924,42 @@ class basic_json
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return result;
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}
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#ifdef JSON_HAS_CPP_14
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/*!
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@brief find an element in a JSON object
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@copydoc find(typename object_t::key_type)
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*/
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template<typename KeyT>
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iterator find(KeyT&& key)
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{
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auto result = end();
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if (is_object())
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{
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result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
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}
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return result;
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}
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/*!
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@brief find an element in a JSON object
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@copydoc find(typename object_t::key_type)
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*/
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template<typename KeyT>
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const_iterator find(KeyT&& key) const
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{
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auto result = cend();
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if (is_object())
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{
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result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
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}
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return result;
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}
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#endif
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/*!
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@brief returns the number of occurrences of a key in a JSON object
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@ -10955,12 +10981,24 @@ class basic_json
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@since version 1.0.0
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*/
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size_type count(object_comparator_key_t key) const
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size_type count(typename object_t::key_type key) const
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{
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// return 0 for all nonobject types
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return is_object() ? m_value.object->count(key) : 0;
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}
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#ifdef JSON_HAS_CPP_14
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/*!
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@brief returns the number of occurrences of a key in a JSON object
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@copydoc count(typename object_t::key_type)
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*/
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template<typename KeyT>
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size_type count(KeyT&& key) const
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{
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// return 0 for all nonobject types
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return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
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}
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#endif
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/// @}
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@ -82,7 +82,7 @@ if(MSVC)
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4389 /wd4309 /wd4566 /wd4996")
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if(MSVC_VERSION GREATER_EQUAL 1910)
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# Enable c++17 support in Visual Studio 2017 (for testing string_view support)
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# Enable c++17 support in Visual Studio 2017 (for testing perfect forwarding and transparent comparator in find() / count())
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++17")
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endif()
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endif()
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