2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 * This is a runtime dynamically typed value. It holds types from a
19 * specific predetermined set of types (ints, bools, arrays, etc). In
20 * particular, it can be used as a convenient in-memory representation
21 * for complete json objects.
23 * In general you can try to use these objects as if they were the
24 * type they represent (although in some cases with a slightly less
25 * complete interface than the raw type), and it'll just throw a
26 * TypeError if it is used in an illegal way.
30 * dynamic twelve = 12;
31 * dynamic str = "string";
32 * dynamic map = dynamic::object;
34 * map[str + "another_str"] = dynamic::array("array", "of", 4, "elements");
35 * map.insert("null_element", nullptr);
37 * assert(map[str] == 13);
39 * // Building a complex object with a sub array inline:
40 * dynamic d = dynamic::object
42 * ("key2", dynamic::array("a", "array"))
45 * Also see folly/json.h for the serialization and deserialization
48 * Note: dynamic is not DefaultConstructible. Rationale:
50 * - The intuitive thing to initialize a defaulted dynamic to would
53 * - However, the expression dynamic d = {} is required to call the
54 * default constructor by the standard, which is confusing
55 * behavior for dynamic unless the default constructor creates an
58 * Additional documentation is in folly/docs/Dynamic.md.
60 * @author Jordan DeLong <delong.j@fb.com>
69 #include <type_traits>
70 #include <unordered_map>
74 #include <boost/operators.hpp>
76 #include <folly/Range.h>
77 #include <folly/Traits.h>
81 //////////////////////////////////////////////////////////////////////
86 //////////////////////////////////////////////////////////////////////
88 struct dynamic : private boost::operators<dynamic> {
100 * We support direct iteration of arrays, and indirect iteration of objects.
101 * See begin(), end(), keys(), values(), and items() for more.
103 * Array iterators dereference as the elements in the array.
104 * Object key iterators dereference as the keys in the object.
105 * Object value iterators dereference as the values in the object.
106 * Object item iterators dereference as pairs of (key, value).
109 typedef std::vector<dynamic> Array;
111 typedef Array::const_iterator const_iterator;
112 typedef dynamic value_type;
113 struct const_key_iterator;
114 struct const_value_iterator;
115 struct const_item_iterator;
118 * Creation routines for making dynamic objects and arrays. Objects
119 * are maps from key to value (so named due to json-related origins
124 * // Make a fairly complex dynamic:
125 * dynamic d = dynamic::object("key", "value1")
126 * ("key2", dynamic::array("value",
131 * // Build an object in a few steps:
132 * dynamic d = dynamic::object;
134 * d["something_else"] = dynamic::array(1, 2, 3, nullptr);
137 struct EmptyArrayTag {};
141 static void array(EmptyArrayTag);
142 template <class... Args>
143 static dynamic array(Args&& ...args);
145 static ObjectMaker object();
146 static ObjectMaker object(dynamic&&, dynamic&&);
147 static ObjectMaker object(dynamic const&, dynamic&&);
148 static ObjectMaker object(dynamic&&, dynamic const&);
149 static ObjectMaker object(dynamic const&, dynamic const&);
152 * String compatibility constructors.
154 /* implicit */ dynamic(StringPiece val);
155 /* implicit */ dynamic(char const* val);
156 /* implicit */ dynamic(std::string const& val);
157 /* implicit */ dynamic(std::string&& val);
160 * This is part of the plumbing for array() and object(), above.
161 * Used to create a new array or object dynamic.
163 /* implicit */ dynamic(void (*)(EmptyArrayTag));
164 /* implicit */ dynamic(ObjectMaker (*)());
165 /* implicit */ dynamic(ObjectMaker const&) = delete;
166 /* implicit */ dynamic(ObjectMaker&&);
169 * Conversion constructors from most of the other types.
171 template<class T> /* implicit */ dynamic(T t);
174 * Create a dynamic that is an array of the values from the supplied
177 template<class Iterator> dynamic(Iterator first, Iterator last);
179 dynamic(dynamic const&);
180 dynamic(dynamic&&) noexcept;
184 * "Deep" equality comparison. This will compare all the way down
185 * an object or array, and is potentially expensive.
187 bool operator==(dynamic const& o) const;
190 * For all types except object this returns the natural ordering on
191 * those types. For objects, we throw TypeError.
193 bool operator<(dynamic const& o) const;
198 * These throw TypeError when used with types or type combinations
199 * that don't support them.
201 * These functions may also throw if you use 64-bit integers with
202 * doubles when the integers are too big to fit in a double.
204 dynamic& operator+=(dynamic const&);
205 dynamic& operator-=(dynamic const&);
206 dynamic& operator*=(dynamic const&);
207 dynamic& operator/=(dynamic const&);
208 dynamic& operator%=(dynamic const&);
209 dynamic& operator|=(dynamic const&);
210 dynamic& operator&=(dynamic const&);
211 dynamic& operator^=(dynamic const&);
212 dynamic& operator++();
213 dynamic& operator--();
216 * Assignment from other dynamics. Because of the implicit conversion
217 * to dynamic from its potential types, you can use this to change the
218 * type pretty intuitively.
220 * Basic guarantee only.
222 dynamic& operator=(dynamic const&);
223 dynamic& operator=(dynamic&&) noexcept;
226 * For simple dynamics (not arrays or objects), this prints the
227 * value to an std::ostream in the expected way. Respects the
228 * formatting manipulators that have been sent to the stream
231 * If the dynamic holds an object or array, this prints them in a
232 * format very similar to JSON. (It will in fact actually be JSON
233 * as long as the dynamic validly represents a JSON object---i.e. it
234 * can't have non-string keys.)
236 friend std::ostream& operator<<(std::ostream&, dynamic const&);
239 * Returns true if this dynamic is of the specified type.
241 bool isString() const;
242 bool isObject() const;
245 bool isArray() const;
246 bool isDouble() const;
250 * Returns: isInt() || isDouble().
252 bool isNumber() const;
255 * Returns the type of this dynamic.
260 * Returns the type of this dynamic as a printable string.
262 const char* typeName() const;
265 * Extract a value while trying to convert to the specified type.
266 * Throws exceptions if we cannot convert from the real type to the
269 * Note you can only use this to access integral types or strings,
270 * since arrays and objects are generally best dealt with as a
273 std::string asString() const;
274 double asDouble() const;
275 int64_t asInt() const;
279 * Extract the value stored in this dynamic without type conversion.
281 * These will throw a TypeError if the dynamic has a different type.
283 const std::string& getString() const&;
284 double getDouble() const&;
285 int64_t getInt() const&;
286 bool getBool() const&;
287 std::string& getString() &;
288 double& getDouble() &;
291 std::string&& getString() &&;
292 double getDouble() &&;
297 * It is occasionally useful to access a string's internal pointer
298 * directly, without the type conversion of `asString()`.
300 * These will throw a TypeError if the dynamic is not a string.
302 const char* data() const&;
303 const char* data() && = delete;
304 const char* c_str() const&;
305 const char* c_str() && = delete;
306 StringPiece stringPiece() const;
309 * Returns: true if this dynamic is null, an empty array, an empty
310 * object, or an empty string.
315 * If this is an array or an object, returns the number of elements
316 * contained. If it is a string, returns the length. Otherwise
319 std::size_t size() const;
322 * You can iterate over the values of the array. Calling these on
323 * non-arrays will throw a TypeError.
325 const_iterator begin() const;
326 const_iterator end() const;
330 * Helper object returned by keys(), values(), and items().
332 template <class T> struct IterableProxy;
336 * You can iterate over the keys, values, or items (std::pair of key and
337 * value) in an object. Calling these on non-objects will throw a TypeError.
339 IterableProxy<const_key_iterator> keys() const;
340 IterableProxy<const_value_iterator> values() const;
341 IterableProxy<const_item_iterator> items() const;
344 * AssociativeContainer-style find interface for objects. Throws if
345 * this is not an object.
347 * Returns: items().end() if the key is not present, or a
348 * const_item_iterator pointing to the item.
350 const_item_iterator find(dynamic const&) const;
353 * If this is an object, returns whether it contains a field with
354 * the given name. Otherwise throws TypeError.
356 std::size_t count(dynamic const&) const;
359 * For objects or arrays, provides access to sub-fields by index or
362 * Using these with dynamic objects that are not arrays or objects
363 * will throw a TypeError. Using an index that is out of range or
364 * object-element that's not present throws std::out_of_range.
366 dynamic const& at(dynamic const&) const&;
367 dynamic& at(dynamic const&) &;
368 dynamic&& at(dynamic const&) &&;
371 * Like 'at', above, except it returns either a pointer to the contained
372 * object or nullptr if it wasn't found. This allows a key to be tested for
373 * containment and retrieved in one operation. Example:
375 * if (auto* found = d.get_ptr(key))
378 * Using these with dynamic objects that are not arrays or objects
379 * will throw a TypeError.
381 const dynamic* get_ptr(dynamic const&) const&;
382 dynamic* get_ptr(dynamic const&) &;
383 dynamic* get_ptr(dynamic const&) && = delete;
386 * This works for access to both objects and arrays.
388 * In the case of an array, the index must be an integer, and this will throw
389 * std::out_of_range if it is less than zero or greater than size().
391 * In the case of an object, the non-const overload inserts a null
392 * value if the key isn't present. The const overload will throw
393 * std::out_of_range if the key is not present.
395 * These functions do not invalidate iterators.
397 dynamic& operator[](dynamic const&) &;
398 dynamic const& operator[](dynamic const&) const&;
399 dynamic&& operator[](dynamic const&) &&;
402 * Only defined for objects, throws TypeError otherwise.
404 * getDefault will return the value associated with the supplied key, the
405 * supplied default otherwise. setDefault will set the key to the supplied
406 * default if it is not yet set, otherwise leaving it. setDefault returns
407 * a reference to the existing value if present, the new value otherwise.
410 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const&;
411 dynamic getDefault(const dynamic& k, dynamic&& v) const&;
412 dynamic getDefault(const dynamic& k, const dynamic& v = dynamic::object) &&;
413 dynamic getDefault(const dynamic& k, dynamic&& v) &&;
414 template<class K, class V>
415 dynamic& setDefault(K&& k, V&& v);
416 // MSVC 2015 Update 3 needs these extra overloads because if V were a
417 // defaulted template parameter, it causes MSVC to consider v an rvalue
418 // reference rather than a universal reference, resulting in it not being
419 // able to find the correct overload to construct a dynamic with.
421 dynamic& setDefault(K&& k, dynamic&& v);
423 dynamic& setDefault(K&& k, const dynamic& v = dynamic::object);
426 * Resizes an array so it has at n elements, using the supplied
427 * default to fill new elements. Throws TypeError if this dynamic
430 * May invalidate iterators.
434 void resize(std::size_t n, dynamic const& = nullptr);
437 * Inserts the supplied key-value pair to an object, or throws if
438 * it's not an object.
440 * Invalidates iterators.
442 template<class K, class V> void insert(K&&, V&& val);
445 * These functions merge two folly dynamic objects.
446 * The "update" and "update_missing" functions extend the object by
447 * inserting the key/value pairs of mergeObj into the current object.
448 * For update, if key is duplicated between the two objects, it
449 * will overwrite with the value of the object being inserted (mergeObj).
450 * For "update_missing", it will prefer the value in the original object
452 * The "merge" function creates a new object consisting of the key/value
453 * pairs of both mergeObj1 and mergeObj2
454 * If the key is duplicated between the two objects,
455 * it will prefer value in the second object (mergeObj2)
457 void update(const dynamic& mergeObj);
458 void update_missing(const dynamic& other);
459 static dynamic merge(const dynamic& mergeObj1, const dynamic& mergeObj2);
462 * Erase an element from a dynamic object, by key.
464 * Invalidates iterators to the element being erased.
466 * Returns the number of elements erased (i.e. 1 or 0).
468 std::size_t erase(dynamic const& key);
471 * Erase an element from a dynamic object or array, using an
472 * iterator or an iterator range.
474 * In arrays, invalidates iterators to elements after the element
475 * being erased. In objects, invalidates iterators to the elements
478 * Returns a new iterator to the first element beyond any elements
479 * removed, or end() if there are none. (The iteration order does
482 const_iterator erase(const_iterator it);
483 const_iterator erase(const_iterator first, const_iterator last);
485 const_key_iterator erase(const_key_iterator it);
486 const_key_iterator erase(const_key_iterator first, const_key_iterator last);
488 const_value_iterator erase(const_value_iterator it);
489 const_value_iterator erase(const_value_iterator first,
490 const_value_iterator last);
492 const_item_iterator erase(const_item_iterator it);
493 const_item_iterator erase(const_item_iterator first,
494 const_item_iterator last);
496 * Append elements to an array. If this is not an array, throws
499 * Invalidates iterators.
501 void push_back(dynamic const&);
502 void push_back(dynamic&&);
505 * Remove an element from the back of an array. If this is not an array,
508 * Does not invalidate iterators.
513 * Get a hash code. This function is called by a std::hash<>
514 * specialization, also.
516 * Throws TypeError if this is an object, array, or null.
518 std::size_t hash() const;
521 friend struct TypeError;
523 template<class T> struct TypeInfo;
524 template<class T> struct CompareOp;
525 template<class T> struct GetAddrImpl;
526 template<class T> struct PrintImpl;
528 explicit dynamic(Array&& array);
530 template<class T> T const& get() const;
531 template<class T> T& get();
532 template<class T> T* get_nothrow() & noexcept;
533 template<class T> T const* get_nothrow() const& noexcept;
534 template<class T> T* get_nothrow() && noexcept = delete;
535 template<class T> T* getAddress() noexcept;
536 template<class T> T const* getAddress() const noexcept;
538 template<class T> T asImpl() const;
540 static char const* typeName(Type);
541 void destroy() noexcept;
542 void print(std::ostream&) const;
543 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
548 explicit Data() : nul(nullptr) {}
551 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
552 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
561 * Objects are placement new'd here. We have to use a char buffer
562 * because we don't know the type here (std::unordered_map<> with
563 * dynamic would be parameterizing a std:: template with an
564 * incomplete type right now). (Note that in contrast we know it
565 * is ok to do this with fbvector because we own it.)
567 std::aligned_storage<
568 sizeof(std::unordered_map<int,int>),
569 alignof(std::unordered_map<int,int>)
570 >::type objectBuffer;
574 //////////////////////////////////////////////////////////////////////
578 #include <folly/dynamic-inl.h>