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Add transparent comparator and perfect forwarding support to find() and count() #795

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merged 9 commits into from
Oct 27, 2017
Merged

Add transparent comparator and perfect forwarding support to find() and count() #795

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1a66679
Add string_view support
jseward Oct 21, 2017
59cde1a
Fix for _HAS_CXX17 == 0
jseward Oct 21, 2017
d468f8c
Use consistent logic to determine if string_view exists
jseward Oct 21, 2017
33c6511
Remove JSON_HAS_STRING_VIEW
jseward Oct 23, 2017
73b1629
Remove tabs for spaces
jseward Oct 24, 2017
16ffdbc
Remove c++17 support flag in cmake
jseward Oct 24, 2017
6c9a401
Remove old non-perfect forwarding find and count
jseward Oct 24, 2017
715c98b
Remove extra spaces
jseward Oct 24, 2017
992c836
Add missing spaces
jseward Oct 24, 2017
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39 changes: 29 additions & 10 deletions src/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,14 @@ SOFTWARE.
#define JSON_UNLIKELY(x) x
#endif

// cpp language standard detection
#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
#define JSON_HAS_CPP_17
#define JSON_HAS_CPP_14
#elif (defined(__cplusplus) && __cplusplus >= 201402L) || (defined(_HAS_CXX14) && _HAS_CXX14 == 1)
#define JSON_HAS_CPP_14
#endif

/*!
@brief namespace for Niels Lohmann
@see https://github.com/nlohmann
Expand Down Expand Up @@ -7589,9 +7597,17 @@ class basic_json
7159](http://rfc7159.net/rfc7159), because any order implements the
specified "unordered" nature of JSON objects.
*/

#if defined(JSON_HAS_CPP_14)
// Use transparent comparator if possible, combined with perfect forwarding
// on find() and count() calls prevents unnecessary string construction.
using object_comparator_t = std::less<>;
#else
using object_comparator_t = std::less<StringType>;
#endif
using object_t = ObjectType<StringType,
basic_json,
std::less<StringType>,
object_comparator_t,
AllocatorType<std::pair<const StringType,
basic_json>>>;

Expand Down Expand Up @@ -9842,7 +9858,7 @@ class basic_json
#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif
#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_MSC_VER) && _MSC_VER >1900 && defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
#if defined(JSON_HAS_CPP_17)
and not std::is_same<ValueType, typename std::string_view>::value
#endif
, int >::type = 0 >
Expand Down Expand Up @@ -10868,7 +10884,7 @@ class basic_json
@note This method always returns @ref end() when executed on a JSON type
that is not an object.

@param[in] key key value of the element to search for
@param[in] key key value of the element to search for.

@return Iterator to an element with key equivalent to @a key. If no such
element is found or the JSON value is not an object, past-the-end (see
Expand All @@ -10880,29 +10896,31 @@ class basic_json

@since version 1.0.0
*/
iterator find(typename object_t::key_type key)
template<typename KeyT>
iterator find(KeyT&& key)
{
auto result = end();

if (is_object())
{
result.m_it.object_iterator = m_value.object->find(key);
result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
}

return result;
}

/*!
@brief find an element in a JSON object
@copydoc find(typename object_t::key_type)
@copydoc find(KeyT&&)
*/
const_iterator find(typename object_t::key_type key) const
template<typename KeyT>
const_iterator find(KeyT&& key) const
{
auto result = cend();

if (is_object())
{
result.m_it.object_iterator = m_value.object->find(key);
result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
}

return result;
Expand All @@ -10929,10 +10947,11 @@ class basic_json

@since version 1.0.0
*/
size_type count(typename object_t::key_type key) const
template<typename KeyT>
size_type count(KeyT&& key) const
{
// return 0 for all nonobject types
return is_object() ? m_value.object->count(key) : 0;
return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
}

/// @}
Expand Down