mirror of
https://github.com/matrix-construct/construct
synced 2024-08-23 18:14:46 +02:00
266 lines
7.8 KiB
C++
266 lines
7.8 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 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. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_JSON_OBJECT_H
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namespace ircd::json
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{
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struct object;
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bool empty(const object &);
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bool operator!(const object &);
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size_t size(const object &);
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template<name_hash_t key, class T = string_view> T at(const object &);
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template<name_hash_t key, class T = string_view> T get(const object &, const T &def = {});
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bool sorted(const object &);
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size_t serialized(const object &);
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string_view stringify(mutable_buffer &, const object &);
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std::ostream &operator<<(std::ostream &, const object &);
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}
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/// Lightweight interface to a JSON object string.
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///
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/// This makes queries into a string of JSON. This is a read-only device.
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/// It is merely functionality built on top of a string_view which is just a
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/// pair of `const char*` pointers to the borders of the JSON object. The first
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/// character should be '{' and the last character should be '}' but this is
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/// not checked on construction.
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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_view. Note the contrast with
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/// with json::value which hides '"' around keys and string values: this object
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/// preserves all characters of the value for view because it carries no other
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/// type information. see: ircd::unquote().
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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.
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///
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struct ircd::json::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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static const uint max_recursion_depth;
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static const size_t max_sorted_members;
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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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const_iterator find(const name_hash_t &key) const;
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// util
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bool empty() const;
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size_t count() const;
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size_t size() const; // warns if used; use count()
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bool has(const string_view &key) 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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string_view get(const string_view &key, 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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// returns value or empty
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string_view operator[](const string_view &key) const;
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// rewrite into allocated string copy
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explicit operator std::string() 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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};
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namespace ircd::json
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{
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bool operator==(const object::member &, const object::member &);
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bool operator!=(const object::member &, const object::member &);
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bool operator<=(const object::member &, const object::member &);
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bool operator>=(const object::member &, const object::member &);
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bool operator<(const object::member &, const object::member &);
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bool operator>(const object::member &, const object::member &);
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bool sorted(const object::member *const &, const object::member *const &);
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size_t serialized(const object::member *const &, const object::member *const &);
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size_t serialized(const object::member &);
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string_view stringify(mutable_buffer &, const object::member *const &, const object::member *const &);
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string_view stringify(mutable_buffer &, const object::member &);
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std::ostream &operator<<(std::ostream &, const object::member &);
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}
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struct ircd::json::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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};
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namespace ircd::json
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{
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bool operator==(const object::const_iterator &, const object::const_iterator &);
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bool operator!=(const object::const_iterator &, const object::const_iterator &);
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bool operator<=(const object::const_iterator &, const object::const_iterator &);
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bool operator>=(const object::const_iterator &, const object::const_iterator &);
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bool operator<(const object::const_iterator &, const object::const_iterator &);
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bool operator>(const object::const_iterator &, const object::const_iterator &);
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}
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struct ircd::json::object::const_iterator
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{
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friend class object;
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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 size_type = size_t;
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using difference_type = size_t;
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using key_compare = std::less<value_type>;
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using iterator_category = std::forward_iterator_tag;
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const char *start {nullptr};
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const char *stop {nullptr};
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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
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{
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return &state;
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}
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value_type &operator*() const
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{
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return *operator->();
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}
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const_iterator &operator++();
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const_iterator() = default;
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};
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template<ircd::json::name_hash_t key,
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class T>
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T
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ircd::json::at(const object &object)
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try
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{
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const auto it(object.find(key));
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if(it == end(object))
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throw not_found
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{
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"[key hash] '%zu'", key
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};
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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
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{
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"[key hash] '%zu' 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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}
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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
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{
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"'%s'", key
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};
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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
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{
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"'%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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}
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template<ircd::json::name_hash_t key,
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class T>
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T
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ircd::json::get(const object &object,
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const T &def)
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try
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{
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const auto it{object.find(key)};
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if(it == end(object))
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return def;
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const string_view sv{it->second};
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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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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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