Parse nlohmann/json with our SAX handler and the PEGTL

Author: d-frey

src/test/json/nlohmann.cc

@@ -0,0 +1,138 @@
+// Copyright (c) 2015-2016 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#include "test.hh"
+
+#include "nlohmann/json.hpp"
+
+namespace tao
+{
+   namespace json
+   {
+      namespace
+      {
+         // SAX consumer to build a NLohmann/JSON value
+         class to_nlohmann
+         {
+         private:
+            std::vector< nlohmann::json > stack_;
+            std::vector< std::string > keys_;
+
+         public:
+            nlohmann::json value;
+
+            void null()
+            {
+               value = nullptr;
+            }
+
+            void boolean( const bool v )
+            {
+               value = v;
+            }
+
+            void number( const std::int64_t v )
+            {
+               value = v;
+            }
+
+            void number( const std::uint64_t v )
+            {
+               value = v;
+            }
+
+            void number( const double v )
+            {
+               value = v;
+            }
+
+            void string( const std::string & v )
+            {
+               value = v;
+            }
+
+            void string( std::string && v )
+            {
+               value = std::move( v );
+            }
+
+            // array
+            void begin_array()
+            {
+               stack_.push_back( nlohmann::json::array() );
+            }
+
+            void element()
+            {
+               stack_.back().push_back( std::move( value ) );
+            }
+
+            void end_array()
+            {
+               value = std::move( stack_.back() );
+               stack_.pop_back();
+            }
+
+            // object
+            void begin_object()
+            {
+               stack_.push_back( nlohmann::json::object() );
+            }
+
+            void key( const std::string & v )
+            {
+               keys_.push_back( v );
+            }
+
+            void key( std::string && v )
+            {
+               keys_.push_back( std::move( v ) );
+            }
+
+            void member()
+            {
+               stack_.back().push_back( nlohmann::json::object_t::value_type( std::move( keys_.back() ), std::move( value ) ) );
+               keys_.pop_back();
+            }
+
+            void end_object()
+            {
+               value = std::move( stack_.back() );
+               stack_.pop_back();
+            }
+         };
+
+      } //
+
+      void unit_test()
+      {
+         // combine a taocpp/json SAX parser (using the PEGTL) with the above
+         to_nlohmann handler;
+         sax::from_string( "[ null, true, false, 42, 43.0, \"foo\", [ 1, 2, 3 ], { \"a\" : \"b\", \"c\" : \"d\" } ]", handler );
+
+         const auto & v = handler.value;
+
+         TEST_ASSERT( v.type() == nlohmann::json::value_t::array );
+         TEST_ASSERT( v.size() == 8 );
+         TEST_ASSERT( v[ 0 ] == nullptr );
+         TEST_ASSERT( v[ 1 ].get< bool >() == true );
+         TEST_ASSERT( v[ 2 ].get< bool >() == false );
+         TEST_ASSERT( v[ 3 ] == 42 );
+         TEST_ASSERT( v[ 4 ] == 43.0 );
+         TEST_ASSERT( v[ 5 ] == "foo" );
+         TEST_ASSERT( v[ 6 ].type() == nlohmann::json::value_t::array );
+         TEST_ASSERT( v[ 6 ].size() == 3 );
+         TEST_ASSERT( v[ 6 ][ 0 ] == 1 );
+         TEST_ASSERT( v[ 6 ][ 1 ] == 2 );
+         TEST_ASSERT( v[ 6 ][ 2 ] == 3 );
+         TEST_ASSERT( v[ 7 ].type() == nlohmann::json::value_t::object );
+         TEST_ASSERT( v[ 7 ].size() == 2 );
+         TEST_ASSERT( v[ 7 ].at( "a" ) == "b" );
+         TEST_ASSERT( v[ 7 ].at( "c" ) == "d" );
+      }
+
+   } // json
+
+} // tao
+
+#include "main.hh"