jansson/janssonxx.h

// janssonxx - C++ wrapper for jansson
//
// author: Sean Middleditch <sean@middleditch.us>
//
// janssonxx is free software; you can redistribute it and/or modify
// it under the terms of the MIT license. See LICENSE for details.


#if !defined(JANSSONXX_H)
#define JANSSONXX_H 1

#include <string>
#include <ostream>
#include <istream>
#include <sstream>
#include <cstdlib>

namespace jansson {
	// include in the jansson namespace
#	include <jansson.h>

	class Iterator;
	class Value;
	class _ArrayProxy;

	// base class for JSON value interface
	template <typename _Base>
	class _ValueBase : public _Base {
	public:
		// empty constructor
		_ValueBase() : _Base() {}

		// copy constructor
		_ValueBase(const _Base& base) : _Base(base) {}

		// create reference to value
		_ValueBase(json_t* json) : _Base(json) {}

		// assignment operator
		_ValueBase& operator=(const Value& value) { _Base::operator=(value); return *this; }

		// check value type
		bool is_undefined() const { return _Base::as_json() == 0; }
		bool is_object() const { return json_is_object(_Base::as_json()); }
		bool is_array() const { return json_is_array(_Base::as_json()); }
		bool is_string() const { return json_is_string(_Base::as_json()); }
		bool is_integer() const { return json_is_integer(_Base::as_json()); }
		bool is_real() const { return json_is_real(_Base::as_json()); }
		bool is_number() const { return json_is_number(_Base::as_json()); }
		bool is_true() const { return json_is_true(_Base::as_json()); }
		bool is_false() const { return json_is_false(_Base::as_json()); }
		bool is_boolean() const { return json_is_boolean(_Base::as_json()); }
		bool is_null() const { return json_is_null(_Base::as_json()); }

		// get size of array or object
		inline unsigned int size() const;

		// get value at array index (const version)
		inline const Value at(unsigned int index) const;

		inline const Value operator[](signed int index) const;
		inline const Value operator[](unsigned int index) const;
		inline const Value operator[](signed short index) const;
		inline const Value operator[](unsigned short index) const;
		inline const Value operator[](signed long index) const;
		inline const Value operator[](unsigned long index) const;

		// get value at array index (non-const version)
		inline _ValueBase<_ArrayProxy> at(unsigned int index);

		inline _ValueBase<_ArrayProxy> operator[](signed int index);
		inline _ValueBase<_ArrayProxy> operator[](unsigned int index);
		inline _ValueBase<_ArrayProxy> operator[](signed short index);
		inline _ValueBase<_ArrayProxy> operator[](unsigned short index);
		inline _ValueBase<_ArrayProxy> operator[](signed long index);
		inline _ValueBase<_ArrayProxy> operator[](unsigned long index);

		// get object property
		inline const Value get(const char* key) const;

		inline const Value get(const std::string& key) const;
		inline const Value operator[](const char* key) const;
		inline const Value operator[](const std::string& key) const;

		// clear all array/object values
		inline void clear();

		// get value cast to specified type
		inline const char* as_cstring() const;
		inline std::string as_string() const;
		inline int as_integer() const;
		inline double as_real() const;
		inline double as_number() const;
		inline bool as_boolean() const;

		// set an object property (converts value to object is not one already)
		inline _Base& set_key(const char* key, const Value& value);

		inline _Base& set_key(const std::string& key, const Value& value);

		// set an array index (converts value to object is not one already)
		inline _Base& set_at(unsigned int index, const Value& value);

		// delete an object key
		inline _Base& del_key(const char* key);

		inline _Base& del_key(const std::string& key);

		// delete an item from an array by index
		inline _Base& del_at(unsigned int index);

		// insert an item into an array at a given index
		inline _Base& insert_at(unsigned int index, const Value& value);
	};

	// represents any JSON value, private base
	class _Value {
	public:
		// construct new Value with an undefined value
		_Value() : _value(0) {}

		// copy constructor
		_Value(const _Value& value) : _value(json_incref(value._value)) {}

		// make a reference to an existing json_t value
		explicit _Value(json_t* value) : _value(json_incref(value)) {}

		// free Value resources
		~_Value() { json_decref(_value); }

		// copy an existing Value
		_Value& operator=(const _Value& e) {
			if (&e != this) {
				json_decref(_value);
				_value = json_incref(e._value);
			}
			return *this;
		}

		// get the underlying json_t
		json_t* as_json() const { return _value; }

	protected:
		// take ownership of a json_t (does not increase reference count)
		static _Value _take(json_t* json) {
			_Value v;
			v._value = json;
			return v;
		}

	private:
		// internal value pointer
		json_t* _value;
	};

	// proxies an array element
	class _ArrayProxy {
	public:
		// construct new Value with an undefined value
		_ArrayProxy() : _array(0), _index(0) {}

		// constructor
		_ArrayProxy(json_t* array, unsigned int index) : _array(array), _index(index) {}

		// assign to the proxied element
		inline _ArrayProxy& operator=(const Value& value);

		// get the proxied element
		json_t* as_json() const { return json_array_get(_array, _index); }

	private:
		// array object we wrap
		json_t* _array;

		// index of property
		unsigned int _index;
	};

	// represents any JSON value
	class Value : public _ValueBase<_Value> {
	public:
		// empty constructor
		Value() : _ValueBase<_Value>() {}

		// copy constructor for base
		Value(const _Value& value) : _ValueBase<_Value>(value) {}
	
		// copy constructor for base
		Value(const _ValueBase<_Value>& value) : _ValueBase<_Value>(value) {}

		// copy constructor
		Value(const Value& value) : _ValueBase<_Value>(value) {}

		// create reference to value
		explicit Value(json_t* json) : _ValueBase<_Value>(json) {}

		// construct Value from input
		static inline Value from(const char* value) { return Value::_take(json_string(value)); }
		static inline Value from(const std::string& value) { return from(value.c_str()); }
		static inline Value from(bool value) { return Value::_take(value ? json_true() : json_false()); }
		static inline Value from(signed int value) { return Value::_take(json_integer(value)); }
		static inline Value from(unsigned int value) { return Value::_take(json_integer(value)); }
		static inline Value from(signed short value) { return Value::_take(json_integer(value)); }
		static inline Value from(unsigned short value) { return Value::_take(json_integer(value)); }
		static inline Value from(signed long value) { return Value::_take(json_integer(value)); }
		static inline Value from(unsigned long value) { return Value::_take(json_integer(value)); }
		static inline Value from(float value) { return Value::_take(json_real(value)); }
		static inline Value from(double value) { return Value::_take(json_real(value)); }

		// create a new empty object
		static inline Value object() { return Value::_take(json_object()); }

		// create a new empty array
		static inline Value array() { return Value::_take(json_array()); }

		// create a new null value
		static inline Value null() { return Value::_take(json_null()); }

		// load a file as a JSON value
		static Value load_file(const char* path, json_error_t* error = 0) {
			return Value::_take(json_load_file(path, error));
		}

		// load a string as a JSON value
		static Value load_string(const char* string, json_error_t* error = 0) {
			return Value::_take(json_loads(string, error));
		}

		// write the value to a file
		int save_file(const char* path, int flags = 0) const {
			return json_dump_file(as_json(), path, flags);
		}

		// write the value to a string (caller must deallocate with free()!)
		char* save_string(int flags = 0) const {
			return json_dumps(as_json(), flags);
		}
	};

	// iterators over a JSON object
	class Iterator {
	public:
		// construct a new iterator for a given object
		Iterator(const Value& value) : _object(value), _iter(0) {
			_iter = json_object_iter(_object.as_json());
		}

		// increment iterator
		void next() {
			_iter = json_object_iter_next(_object.as_json(), _iter);
		}

		Iterator& operator++() { next(); return *this; }

		// test if iterator is still valid
		bool valid() const { return _iter != 0; }
		operator bool() const { return valid(); }

		// get key
		const char* ckey() const {
			return json_object_iter_key(_iter);
		}

		std::string key() const { return ckey(); }

		// get value
		const Value value() const {
			return Value(json_object_iter_value(_iter));
		}

		// dereference value
		const Value operator*() const { return value(); }

	private:
		// disallow copying
		Iterator(const Iterator&);
		Iterator& operator=(const Iterator&);

		// object being iterated over
		Value _object;

		// iterator value
		void* _iter;
	};

} // namespace jansson

// stream JSON value out
std::ostream& operator<<(std::ostream& os, const jansson::Value& value) {
	char* tmp = value.save_string();
	if (tmp != 0) {
		os << tmp;
		free(tmp);
	}
	return os;
}

// read JSON value
std::istream& operator>>(std::istream& is, jansson::Value& value) {
	std::stringstream tmp;
	while (is)
		tmp << static_cast<char>(is.get());
	value = jansson::Value::load_string(tmp.str().c_str());
	return is;
}

#include "janssonxx.tcc"

#endif