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construct/include/ircd/json/object.h
2018-11-29 13:08:37 -08:00

511 lines
13 KiB
C++

// 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_OBJECT_H
namespace ircd::json
{
struct object;
bool empty(const object &);
bool operator!(const object &);
size_t size(const object &);
template<name_hash_t key, class T = string_view> T at(const object &);
template<name_hash_t key, class T = string_view> T get(const object &, const T &def = {});
}
/// Lightweight interface to a JSON object string.
///
/// This makes queries into a string of JSON. This is a read-only device.
/// It is merely functionality built on top of a string_view which is just a
/// pair of `const char*` pointers to the borders of the JSON object. The first
/// character should be '{' and the last character should be '}' but this is
/// not checked on construction.
///
/// This class computes over strings of JSON by parsing it on-the-fly
/// via forward iteration. The const_iterator is fundamental. All other member
/// functions are built from this forward iteration and have worst-case linear
/// complexity *every time you invoke them*. This is not necessarily a bad
/// thing in the appropriate use case. Our parser is pretty efficient; this
/// device conducts zero copies, zero allocations and zero indexing; instead
/// the parser provides string_views to members during the iteration.
///
/// The returned values are character ranges (string_view's) which themselves
/// are type agnostic to their contents. The type of a value is determined at
/// the user's discretion by querying the content of the string_view using a
/// util function like json::type() etc. In other words, a value carries type
/// data from its own original content. This means the user is responsible for
/// removing prefix and suffix characters like '{' or '"' after determining the
/// type if they want a truly pure value string_view. Note the contrast with
/// with json::value which hides '"' around keys and string values: this object
/// preserves all characters of the value for view because it carries no other
/// type information. see: ircd::unquote().
///
/// Recursive traversal cannot be achieved via a single key string value; so
/// any string_view argument for a key will not be recursive. In other words,
/// due to the fact that a JS identifier can have almost any character we have
/// to use a different *type* like a vector of strings; in our common case we
/// use an initializer_list typedef'ed as `path` and those overloads will be
/// recursive.
///
struct ircd::json::object
:string_view
{
struct member;
struct const_iterator;
using key_type = string_view;
using mapped_type = string_view;
using value_type = const member;
using pointer = value_type *;
using reference = value_type &;
using iterator = const_iterator;
using size_type = size_t;
using difference_type = ptrdiff_t;
using key_compare = std::less<member>;
static const uint max_recursion_depth;
// fundamental
const_iterator end() const;
const_iterator begin() const;
const_iterator find(const string_view &key) const;
const_iterator find(const name_hash_t &key) const;
// util
bool empty() const;
size_t count() const;
size_t size() const; // warns if used; use count()
bool has(const string_view &key) const;
bool has(const path &) const;
// returns value or default
template<class T> T get(const string_view &key, const T &def = T{}) const;
template<class T> T get(const path &, const T &def = T{}) const;
string_view get(const string_view &key, const string_view &def = {}) const;
string_view get(const path &, const string_view &def = {}) const;
// returns value or throws not_found
template<class T = string_view> T at(const string_view &key) const;
template<class T = string_view> T at(const path &) const;
// returns value or empty
string_view operator[](const string_view &key) const;
string_view operator[](const path &) const;
// constructor. Note that you are able to construct from invalid JSON. The
// parser is not invoked until other operations and that's when it errors.
using string_view::string_view;
// rewrite into allocated string copy
explicit operator std::string() const;
// rewrite onto streams or buffers etc
friend bool sorted(const object &);
friend bool sorted(const member *const &, const member *const &);
friend size_t serialized(const object &);
friend size_t serialized(const member *const &, const member *const &);
friend string_view stringify(mutable_buffer &, const object &);
friend string_view stringify(mutable_buffer &, const member *const &, const member *const &);
friend std::ostream &operator<<(std::ostream &, const object &);
};
struct ircd::json::object::member
:std::pair<string_view, string_view>
{
member(const string_view &first = {}, const string_view &second = {})
:std::pair<string_view, string_view>{first, second}
{}
friend bool operator==(const object::member &, const object::member &);
friend bool operator!=(const object::member &, const object::member &);
friend bool operator<=(const object::member &, const object::member &);
friend bool operator>=(const object::member &, const object::member &);
friend bool operator<(const object::member &, const object::member &);
friend bool operator>(const object::member &, const object::member &);
// writes a single member onto stream
friend size_t serialized(const object::member &);
friend string_view stringify(mutable_buffer &, const object::member &);
friend std::ostream &operator<<(std::ostream &, const object::member &);
};
struct ircd::json::object::const_iterator
{
using key_type = string_view;
using mapped_type = string_view;
using value_type = const member;
using pointer = value_type *;
using reference = value_type &;
using size_type = size_t;
using difference_type = size_t;
using key_compare = std::less<value_type>;
using iterator_category = std::forward_iterator_tag;
protected:
friend class object;
const char *start {nullptr};
const char *stop {nullptr};
member state;
const_iterator(const char *const &start, const char *const &stop)
:start{start}
,stop{stop}
{}
public:
value_type *operator->() const { return &state; }
value_type &operator*() const { return *operator->(); }
const_iterator &operator++();
const_iterator() = default;
friend bool operator==(const const_iterator &, const const_iterator &);
friend bool operator!=(const const_iterator &, const const_iterator &);
friend bool operator<=(const const_iterator &, const const_iterator &);
friend bool operator>=(const const_iterator &, const const_iterator &);
friend bool operator<(const const_iterator &, const const_iterator &);
friend bool operator>(const const_iterator &, const const_iterator &);
};
inline ircd::string_view
ircd::json::object::operator[](const path &path)
const
{
return get(path);
}
inline ircd::string_view
ircd::json::object::operator[](const string_view &key)
const
{
const auto it(find(key));
return it != end()? it->second : string_view{};
}
template<class T>
T
ircd::json::object::at(const path &path)
const try
{
object object(*this);
const auto it(std::find_if(std::begin(path), std::end(path), [&object]
(const string_view &key)
{
const auto it(object.find(key));
if(it == std::end(object))
throw not_found
{
"'%s'", key
};
object = it->second;
return false;
}));
return lex_cast<T>(object);
}
catch(const bad_lex_cast &e)
{
throw type_error
{
"'%s' must cast to type %s",
ircd::string(path),
typeid(T).name()
};
}
template<ircd::json::name_hash_t key,
class T>
T
ircd::json::at(const object &object)
try
{
const auto it(object.find(key));
if(it == end(object))
throw not_found
{
"[key hash] '%zu'", key
};
return lex_cast<T>(it->second);
}
catch(const bad_lex_cast &e)
{
throw type_error
{
"[key hash] '%zu' must cast to type %s",
key,
typeid(T).name()
};
}
template<class T>
T
ircd::json::object::at(const string_view &key)
const try
{
const auto it(find(key));
if(it == end())
throw not_found
{
"'%s'", key
};
return lex_cast<T>(it->second);
}
catch(const bad_lex_cast &e)
{
throw type_error
{
"'%s' must cast to type %s",
key,
typeid(T).name()
};
}
inline ircd::string_view
ircd::json::object::get(const path &path,
const string_view &def)
const
{
return get<string_view>(path, def);
}
inline ircd::string_view
ircd::json::object::get(const string_view &key,
const string_view &def)
const
{
return get<string_view>(key, def);
}
template<class T>
T
ircd::json::object::get(const path &path,
const T &def)
const try
{
object object(*this);
const auto it(std::find_if(std::begin(path), std::end(path), [&object]
(const string_view &key)
{
const auto it(object.find(key));
if(it == std::end(object))
return true;
object = it->second;
return false;
}));
return it == std::end(path)? lex_cast<T>(object) : def;
}
catch(const bad_lex_cast &e)
{
return def;
}
template<ircd::json::name_hash_t key,
class T>
ircd::string_view
ircd::json::get(const object &object,
const T &def)
try
{
const auto it{object.find(key)};
if(it == end(object))
return def;
const string_view sv{it->second};
return !sv.empty()? lex_cast<T>(sv) : def;
}
catch(const bad_lex_cast &e)
{
return def;
}
template<class T>
T
ircd::json::object::get(const string_view &key,
const T &def)
const try
{
const string_view sv(operator[](key));
return !sv.empty()? lex_cast<T>(sv) : def;
}
catch(const bad_lex_cast &e)
{
return def;
}
inline size_t
ircd::json::size(const object &object)
{
return object.size();
}
inline size_t
ircd::json::object::size()
const
{
return count();
}
inline size_t
ircd::json::object::count()
const
{
return std::distance(begin(), end());
}
inline bool
ircd::json::operator!(const object &object)
{
return empty(object);
}
inline bool
ircd::json::empty(const object &object)
{
return object.empty();
}
inline bool
ircd::json::object::empty()
const
{
const string_view &sv{*this};
assert(sv.size() > 2 || (sv.empty() || sv == empty_object));
return sv.size() <= 2;
}
inline bool
ircd::json::object::has(const path &path)
const
{
object object(*this);
const auto it(std::find_if(std::begin(path), std::end(path), [&object]
(const string_view &key)
{
const auto val(object[key]);
if(val.empty())
return true;
object = val;
return false;
}));
// && path.size() ensures false for empty path.
return it == std::end(path) && path.size();
}
inline bool
ircd::json::object::has(const string_view &key)
const
{
return find(key) != end();
}
inline ircd::json::object::const_iterator
ircd::json::object::find(const name_hash_t &key)
const
{
return std::find_if(begin(), end(), [&key]
(const auto &member)
{
return name_hash(member.first) == key;
});
}
inline ircd::json::object::const_iterator
ircd::json::object::find(const string_view &key)
const
{
return std::find_if(begin(), end(), [&key]
(const auto &member)
{
return member.first == key;
});
}
inline bool
ircd::json::operator==(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start == b.start;
}
inline bool
ircd::json::operator!=(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start != b.start;
}
inline bool
ircd::json::operator<=(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start <= b.start;
}
inline bool
ircd::json::operator>=(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start >= b.start;
}
inline bool
ircd::json::operator<(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start < b.start;
}
inline bool
ircd::json::operator>(const object::const_iterator &a, const object::const_iterator &b)
{
return a.start > b.start;
}
inline bool
ircd::json::operator==(const object::member &a, const object::member &b)
{
return a.first == b.first;
}
inline bool
ircd::json::operator!=(const object::member &a, const object::member &b)
{
return a.first != b.first;
}
inline bool
ircd::json::operator<=(const object::member &a, const object::member &b)
{
return a.first <= b.first;
}
inline bool
ircd::json::operator>=(const object::member &a, const object::member &b)
{
return a.first >= b.first;
}
inline bool
ircd::json::operator<(const object::member &a, const object::member &b)
{
return a.first < b.first;
}
inline bool
ircd::json::operator>(const object::member &a, const object::member &b)
{
return a.first > b.first;
}