252 lines
9.4 KiB
C++
252 lines
9.4 KiB
C++
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/* json11
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*
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* json11 is a tiny JSON library for C++11, providing JSON parsing and serialization.
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*
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* The core object provided by the library is json11::Json. A Json object represents any JSON
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* value: null, bool, number (int or double), string (std::string), array (std::vector), or
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* object (std::map).
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*
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* Json objects act like values: they can be assigned, copied, moved, compared for equality or
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* order, etc. There are also helper methods Json::dump, to serialize a Json to a string, and
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* Json::parse (static) to parse a std::string as a Json object.
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*
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* Internally, the various types of Json object are represented by the JsonValue class
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* hierarchy.
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*
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* A note on numbers - JSON specifies the syntax of number formatting but not its semantics,
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* so some JSON implementations distinguish between integers and floating-point numbers, while
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* some don't. In json11, we choose the latter. Because some JSON implementations (namely
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* Javascript itself) treat all numbers as the same type, distinguishing the two leads
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* to JSON that will be *silently* changed by a round-trip through those implementations.
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* Dangerous! To avoid that risk, json11 stores all numbers as double internally, but also
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* provides integer helpers.
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*
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* Fortunately, double-precision IEEE754 ('double') can precisely store any integer in the
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* range +/-2^53, which includes every 'int' on most systems. (Timestamps often use int64
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* or long long to avoid the Y2038K problem; a double storing microseconds since some epoch
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* will be exact for +/- 275 years.)
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*/
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/* Copyright (c) 2013 Dropbox, Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#pragma once
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#include <string>
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#include <vector>
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#include <map>
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#include <memory>
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#include <initializer_list>
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#ifdef _MSC_VER
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#if _MSC_VER <= 1800 // VS 2013
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#ifndef noexcept
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#define noexcept throw()
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#endif
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#ifndef snprintf
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#define snprintf _snprintf_s
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#endif
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#endif
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#endif
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namespace json11 {
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enum JsonParse
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{
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STANDARD, COMMENTS
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};
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class JsonValue;
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class Json final
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{
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public:
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// Types
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enum Type
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{
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NUL, NUMBER, BOOL, STRING, ARRAY, OBJECT
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};
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// Array and object typedefs
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typedef std::vector<Json> array;
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typedef std::map<std::string, Json> object;
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// Constructors for the various types of JSON value.
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Json() noexcept; // NUL
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Json( std::nullptr_t ) noexcept; // NUL
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Json( double value ); // NUMBER
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Json( int value ); // NUMBER
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Json( bool value ); // BOOL
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Json( const std::string& value ); // STRING
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Json( std::string&& value ); // STRING
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Json( const char* value ); // STRING
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Json( const array& values ); // ARRAY
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Json( array&& values ); // ARRAY
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Json( const object& values ); // OBJECT
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Json( object&& values ); // OBJECT
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// Implicit constructor: anything with a to_json() function.
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template <class T, class = decltype(& T::to_json)>
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Json( const T& t ) : Json( t.to_json() ) {}
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// Implicit constructor: map-like objects (std::map, std::unordered_map, etc)
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template <class M, typename std::enable_if<
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std::is_constructible<std::string,
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decltype(std::declval<M>().begin()->first)>::value
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&& std::is_constructible<Json,
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decltype(std::declval<M>().begin()->second)>::value,
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int>::type = 0>
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Json( const M& m ) : Json( object( m.begin(), m.end() ) ) {}
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// Implicit constructor: vector-like objects (std::list, std::vector, std::set, etc)
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template <class V, typename std::enable_if<
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std::is_constructible<Json, decltype( * std::declval<V>().begin() )>::value,
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int>::type = 0>
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Json( const V& v ) : Json( array( v.begin(), v.end() ) ) {}
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// This prevents Json(some_pointer) from accidentally producing a bool. Use
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// Json(bool(some_pointer)) if that behavior is desired.
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Json( void* ) = delete;
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// Accessors
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Type type() const;
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bool is_null() const { return type() == NUL; }
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bool is_number() const { return type() == NUMBER; }
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bool is_bool() const { return type() == BOOL; }
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bool is_string() const { return type() == STRING; }
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bool is_array() const { return type() == ARRAY; }
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bool is_object() const { return type() == OBJECT; }
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// Return the enclosed value if this is a number, 0 otherwise. Note that json11 does not
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// distinguish between integer and non-integer numbers - number_value() and int_value()
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// can both be applied to a NUMBER-typed object.
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double number_value() const;
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int int_value() const;
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// Return the enclosed value if this is a boolean, false otherwise.
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bool bool_value() const;
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// Return the enclosed string if this is a string, "" otherwise.
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const std::string& string_value() const;
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// Return the enclosed std::vector if this is an array, or an empty vector otherwise.
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const array& array_items() const;
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// Return the enclosed std::map if this is an object, or an empty map otherwise.
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const object& object_items() const;
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// Return a reference to arr[i] if this is an array, Json() otherwise.
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const Json& operator[]( size_t i ) const;
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// Return a reference to obj[key] if this is an object, Json() otherwise.
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const Json& operator[]( const std::string& key ) const;
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// Serialize.
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void dump( std::string& out ) const;
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std::string dump() const
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{
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std::string out;
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dump( out );
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return out;
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}
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// Parse. If parse fails, return Json() and assign an error message to err.
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static Json parse( const std::string& in,
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std::string& err,
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JsonParse strategy = JsonParse::STANDARD );
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static Json parse( const char* in,
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std::string& err,
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JsonParse strategy = JsonParse::STANDARD )
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{
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if( in )
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{
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return parse( std::string( in ), err, strategy );
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}
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else
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{
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err = "null input";
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return nullptr;
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}
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}
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// Parse multiple objects, concatenated or separated by whitespace
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static std::vector<Json> parse_multi( const std::string& in,
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std::string::size_type& parser_stop_pos,
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std::string& err,
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JsonParse strategy = JsonParse::STANDARD );
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static inline std::vector<Json> parse_multi( const std::string& in,
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std::string& err,
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JsonParse strategy = JsonParse::STANDARD )
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{
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std::string::size_type parser_stop_pos;
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return parse_multi( in, parser_stop_pos, err, strategy );
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}
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bool operator==( const Json& rhs ) const;
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bool operator<( const Json& rhs ) const;
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bool operator!=( const Json& rhs ) const { return !(*this == rhs); }
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bool operator<=( const Json& rhs ) const { return !(rhs < *this); }
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bool operator>( const Json& rhs ) const { return rhs < *this; }
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bool operator>=( const Json& rhs ) const { return !(*this < rhs); }
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/* has_shape(types, err)
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*
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* Return true if this is a JSON object and, for each item in types, has a field of
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* the given type. If not, return false and set err to a descriptive message.
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*/
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typedef std::initializer_list<std::pair<std::string, Type> > shape;
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bool has_shape( const shape& types, std::string& err ) const;
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private:
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std::shared_ptr<JsonValue> m_ptr;
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};
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// Internal class hierarchy - JsonValue objects are not exposed to users of this API.
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class JsonValue
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{
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protected:
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friend class Json;
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friend class JsonInt;
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friend class JsonDouble;
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virtual Json::Type type() const = 0;
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virtual bool equals( const JsonValue* other ) const = 0;
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virtual bool less( const JsonValue* other ) const = 0;
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virtual void dump( std::string& out ) const = 0;
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virtual double number_value() const;
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virtual int int_value() const;
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virtual bool bool_value() const;
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virtual const std::string& string_value() const;
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virtual const Json::array& array_items() const;
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virtual const Json& operator[]( size_t i ) const;
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virtual const Json::object& object_items() const;
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virtual const Json& operator[]( const std::string& key ) const;
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virtual ~JsonValue() {}
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};
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} // namespace json11
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