mirror of
https://github.com/matrix-construct/construct
synced 2024-08-30 21:35:18 +02:00
401 lines
11 KiB
C++
401 lines
11 KiB
C++
/*
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* Copyright (C) 2017 Charybdis Development Team
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* Copyright (C) 2017 Jason Volk <jason@zemos.net>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice is present in all copies.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#define HAVE_IRCD_JSON_OBJECT_H
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namespace ircd {
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namespace json {
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// ircd::json::object is an extremely lightweight device for making
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// queries into a string of JSON. This is a read-only device. It is merely
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// functionality built on top of a string_view which is just a pair of
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// const char* pointers to the borders of the JSON object.
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//
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// This class computes over strings of JSON by parsing it on-the-fly
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// via forward iteration. The const_iterator is fundamental. All other member
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// functions are built from this forward iteration and have worst-case linear
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// complexity *every time you invoke them*. This is not necessarily a bad
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// thing in the appropriate use case. Our parser is pretty efficient; this
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// device conducts zero copies, zero allocations and zero indexing; instead
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// the parser provides string_views to members during the iteration.
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//
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// The returned values are character ranges (string_view's) which themselves
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// are type agnostic to their contents. The type of a value is determined at
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// the user's discretion by querying the content of the string_view using a
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// util function like json::type() etc. In other words, a value carries type
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// data from its own original content. This means the user is responsible for
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// removing prefix and suffix characters like '{' or '"' after determining the
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// type if they want a truly pure value string. Our zero-copy string_view utils
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// make this to a simple ballet of pointers.
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//
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// Other devices for dealing with strings of JSON are available: if an index
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// should be populated (ircd::json::index), or if a certain set of keys
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// should be found and extracted with a single pass (ircd::json::extract).
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//
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// Some serialization/write functions are actually provided here, these
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// are to *rewrite* JSON into our desired output form.
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//
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// Recursive traversal cannot be achieved via a single key string value; so
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// any string_view argument for a key will not be recursive. In other words,
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// due to the fact that a JS identifier can have almost any character we have
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// to use a different *type* like a vector of strings; in our common case we
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// use an initializer_list typedef'ed as `path` and those overloads will be
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// recursive.
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//
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struct object
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:string_view
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{
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struct member;
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struct const_iterator;
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using key_type = string_view;
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using mapped_type = string_view;
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using value_type = const member;
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using pointer = value_type *;
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using reference = value_type &;
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using iterator = const_iterator;
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using size_type = size_t;
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using difference_type = ptrdiff_t;
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using key_compare = std::less<member>;
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// fundamental
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const_iterator end() const;
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const_iterator begin() const;
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const_iterator find(const string_view &key) const;
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// util
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size_t count() const;
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bool has(const string_view &key) const;
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bool has(const path &) const;
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// returns value or default
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template<class T> T get(const string_view &key, const T &def = T{}) const;
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template<class T> T get(const path &, const T &def = T{}) const;
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string_view get(const string_view &key, const string_view &def = {}) const;
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string_view get(const path &, const string_view &def = {}) const;
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// returns value or throws not_found
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template<class T = string_view> T at(const string_view &key) const;
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template<class T = string_view> T at(const path &) const;
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// returns value or empty
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string_view operator[](const string_view &key) const;
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string_view operator[](const path &) const;
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// constructor. Note that you are able to construct from invalid JSON. The
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// parser is not invoked until other operations and that's when it errors.
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using string_view::string_view;
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// rewrite into allocated string copy
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explicit operator std::string() const;
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// rewrite onto streams or buffers etc
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friend std::ostream &operator<<(std::ostream &, const object &);
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friend object serialize(const object &, char *&buf, char *const &stop);
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friend size_t print(char *const &buf, const size_t &max, const object &);
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};
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struct object::member
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:std::pair<string_view, string_view>
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{
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member(const string_view &first = {}, const string_view &second = {})
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:std::pair<string_view, string_view>{first, second}
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{}
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friend bool operator==(const member &, const member &);
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friend bool operator!=(const member &, const member &);
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friend bool operator<=(const member &, const member &);
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friend bool operator>=(const member &, const member &);
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friend bool operator<(const member &, const member &);
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friend bool operator>(const member &, const member &);
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// writes a single member onto stream
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friend std::ostream &operator<<(std::ostream &, const object::member &);
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};
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struct object::const_iterator
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{
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using value_type = const member;
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using pointer = value_type *;
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using reference = value_type &;
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using difference_type = size_t;
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using iterator_category = std::forward_iterator_tag;
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protected:
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friend class object;
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const char *start;
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const char *stop;
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member state;
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const_iterator(const char *const &start, const char *const &stop)
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:start{start}
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,stop{stop}
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{}
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public:
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value_type *operator->() const { return &state; }
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value_type &operator*() const { return *operator->(); }
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const_iterator &operator++();
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friend bool operator==(const const_iterator &, const const_iterator &);
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friend bool operator!=(const const_iterator &, const const_iterator &);
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friend bool operator<=(const const_iterator &, const const_iterator &);
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friend bool operator>=(const const_iterator &, const const_iterator &);
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friend bool operator<(const const_iterator &, const const_iterator &);
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friend bool operator>(const const_iterator &, const const_iterator &);
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};
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} // namespace json
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} // namespace ircd
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inline ircd::string_view
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ircd::json::object::operator[](const path &path)
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const
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{
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return get(path);
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}
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inline ircd::string_view
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ircd::json::object::operator[](const string_view &key)
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const
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{
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const auto it(find(key));
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return it != end()? it->second : string_view{};
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}
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template<class T>
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T
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ircd::json::object::at(const path &path)
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const try
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{
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object object(*this);
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const auto it(std::find_if(std::begin(path), std::end(path), [&object]
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(const string_view &key)
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{
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const auto it(object.find(key));
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if(it == std::end(object))
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throw not_found("'%s'", key);
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object = it->second;
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return false;
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}));
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return lex_cast<T>(object);
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}
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catch(const bad_lex_cast &e)
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{
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throw type_error("'%s' must cast to type %s",
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string(path),
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typeid(T).name());
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}
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template<class T>
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T
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ircd::json::object::at(const string_view &key)
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const try
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{
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const auto it(find(key));
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if(it == end())
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throw not_found("'%s'", key);
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return lex_cast<T>(it->second);
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}
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catch(const bad_lex_cast &e)
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{
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throw type_error("'%s' must cast to type %s",
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key,
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typeid(T).name());
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}
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inline ircd::string_view
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ircd::json::object::get(const path &path,
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const string_view &def)
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const
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{
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return get<string_view>(path, def);
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}
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inline ircd::string_view
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ircd::json::object::get(const string_view &key,
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const string_view &def)
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const
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{
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return get<string_view>(key, def);
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}
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template<class T>
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T
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ircd::json::object::get(const path &path,
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const T &def)
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const try
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{
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object object(*this);
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const auto it(std::find_if(std::begin(path), std::end(path), [&object]
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(const string_view &key)
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{
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const auto it(object.find(key));
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if(it == std::end(object))
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return true;
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object = it->second;
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return false;
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}));
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return it == std::end(path)? lex_cast<T>(object) : def;
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}
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catch(const bad_lex_cast &e)
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{
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return def;
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}
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template<class T>
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T
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ircd::json::object::get(const string_view &key,
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const T &def)
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const try
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{
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const string_view sv(operator[](key));
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return !sv.empty()? lex_cast<T>(sv) : def;
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}
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catch(const bad_lex_cast &e)
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{
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return def;
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}
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inline size_t
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ircd::json::object::count()
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const
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{
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return std::distance(begin(), end());
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}
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inline bool
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ircd::json::object::has(const path &path)
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const
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{
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object object(*this);
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const auto it(std::find_if(std::begin(path), std::end(path), [&object]
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(const string_view &key)
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{
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const auto val(object[key]);
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if(val.empty())
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return true;
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object = val;
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return false;
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}));
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// && path.size() ensures false for empty path.
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return it == std::end(path) && path.size();
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}
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inline bool
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ircd::json::object::has(const string_view &key)
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const
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{
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return find(key) != end();
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}
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inline ircd::json::object::const_iterator
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ircd::json::object::find(const string_view &key)
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const
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{
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return std::find_if(begin(), end(), [&key]
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(const auto &member)
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{
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return member.first == key;
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});
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}
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inline bool
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ircd::json::operator==(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start == b.start;
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}
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inline bool
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ircd::json::operator!=(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start != b.start;
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}
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inline bool
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ircd::json::operator<=(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start <= b.start;
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}
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inline bool
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ircd::json::operator>=(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start >= b.start;
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}
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inline bool
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ircd::json::operator<(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start < b.start;
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}
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inline bool
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ircd::json::operator>(const object::const_iterator &a, const object::const_iterator &b)
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{
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return a.start > b.start;
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}
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inline bool
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ircd::json::operator==(const object::member &a, const object::member &b)
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{
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return a.first == b.first;
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}
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inline bool
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ircd::json::operator!=(const object::member &a, const object::member &b)
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{
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return a.first != b.first;
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}
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inline bool
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ircd::json::operator<=(const object::member &a, const object::member &b)
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{
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return a.first <= b.first;
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}
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inline bool
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ircd::json::operator>=(const object::member &a, const object::member &b)
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{
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return a.first >= b.first;
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}
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inline bool
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ircd::json::operator<(const object::member &a, const object::member &b)
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{
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return a.first < b.first;
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}
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inline bool
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ircd::json::operator>(const object::member &a, const object::member &b)
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{
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return a.first > b.first;
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}
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