construct/include/ircd/json/json.h

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.

#pragma once
#define HAVE_IRCD_JSON_H

/// JavaScript Object Notation: formal grammars & tools
///
namespace ircd::json
{
	IRCD_EXCEPTION(ircd::error, error);
	IRCD_EXCEPTION(error, parse_error);
	IRCD_EXCEPTION(error, print_error);
	IRCD_EXCEPTION(error, type_error);
	IRCD_EXCEPTION(error, not_found);
	IRCD_EXCEPTION(parse_error, recursion_limit);

	struct value;
	struct member;
	struct string;
	struct object;
	struct array;
	struct vector;
	struct iov;

	enum type
	{
		STRING  = 0,
		OBJECT  = 1,
		ARRAY   = 2,
		NUMBER  = 3,
		LITERAL = 4,
	};
	enum type type(const string_view &);
	enum type type(const string_view &, std::nothrow_t);
	string_view reflect(const enum type &);

	struct strung;
	template<size_t SIZE> struct buffer;
	template<class... T> string_view stringify(const mutable_buffer &&mb, T&&... t);
	template<class... T> size_t print(const mutable_buffer &buf, T&&... t);
}

/// Convenience template to allocate std::string and print() arguments to it.
struct ircd::json::strung
:std::string
{
	template<class... T> strung(T&&... t);
};

#include "util.h"
#include "array.h"
#include "object.h"
#include "vector.h"
#include "value.h"
#include "member.h"
#include "iov.h"
#include "tuple/tuple.h"

namespace ircd
{
	using json::operator ""_;
	using json::operator<<;
	using json::defined;
	using json::for_each;
	using json::until;
}

/// Strong type representing quoted strings in JSON (which may be unquoted
/// automatically when this type is encountered in a tuple etc)
struct ircd::json::string
:string_view
{
	using string_view::string_view;
};

template<size_t SIZE>
struct ircd::json::buffer
:string_view
{
	std::array<char, SIZE> b;

	template<class... T>
	buffer(T&&... t)
	:string_view{stringify(b, std::forward<T>(t)...)}
	{}
};

/// Convenience template for const rvalue mutable_buffers or basically
/// allowing a bracket initialization of a mutable_buffer in the argument
/// to stringify(). The const rvalue reference is on purpose. The stringify()
/// family of friends all use a non-const lvalue mutable_buffer as an append
/// only "stream" buffer. We don't want to modify any non-const instances of
/// the mutable_buffer you pass here by offering a `mutable_buffer &` overload
///
template<class... T>
ircd::string_view
ircd::json::stringify(const mutable_buffer &&mb,
                      T&&... t)
{
	mutable_buffer mbc{mb};
	return stringify(mbc, std::forward<T>(t)...);
}

/// Convenience template using the syntax print(mutable_buffer, ...)
/// which stringifies with null termination into buffer.
///
template<class... T>
size_t
ircd::json::print(const mutable_buffer &buf,
                  T&&... t)
{
	if(unlikely(!size(buf)))
		return 0;

	const auto sv
	{
		stringify(mutable_buffer{buf}, std::forward<T>(t)...)
	};

	assert(sv.size() < size(buf));
	assert(valid(sv, std::nothrow)); //note: false alarm when T=json::member
	buf[sv.size()] = '\0';
	return sv.size();
}

template<class... T>
ircd::json::strung::strung(T&&... t)
:std::string{[&]() -> std::string
{
	const auto size
	{
		serialized(std::forward<T>(t)...)
	};

	std::string ret(size, char{});
	const auto buf{const_cast<char *>(ret.data())};
	const auto max{ret.size() + 1};
	const auto printed
	{
		print(mutable_buffer{buf, max}, std::forward<T>(t)...)
	};

	if(unlikely(printed != ret.size()))
		throw assertive
		{
			"%zu != %zu: %s", printed, ret.size(), ret
		};

	return ret;
}()}
{
}