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 * Additional documentation is in folly/docs/Dynamic.md.
50 * @author Jordan DeLong <delong.j@fb.com>
59 #include <type_traits>
60 #include <unordered_map>
64 #include <boost/operators.hpp>
66 #include <folly/Range.h>
67 #include <folly/Traits.h>
71 //////////////////////////////////////////////////////////////////////
76 //////////////////////////////////////////////////////////////////////
78 struct dynamic : private boost::operators<dynamic> {
88 template<class T, class Enable = void> struct NumericTypeHelper;
91 * We support direct iteration of arrays, and indirect iteration of objects.
92 * See begin(), end(), keys(), values(), and items() for more.
94 * Array iterators dereference as the elements in the array.
95 * Object key iterators dereference as the keys in the object.
96 * Object value iterators dereference as the values in the object.
97 * Object item iterators dereference as pairs of (key, value).
100 typedef std::vector<dynamic> Array;
102 typedef Array::const_iterator const_iterator;
103 typedef dynamic value_type;
104 struct const_key_iterator;
105 struct const_value_iterator;
106 struct const_item_iterator;
109 * Creation routines for making dynamic objects and arrays. Objects
110 * are maps from key to value (so named due to json-related origins
115 * // Make a fairly complex dynamic:
116 * dynamic d = dynamic::object("key", "value1")
117 * ("key2", dynamic::array("value",
122 * // Build an object in a few steps:
123 * dynamic d = dynamic::object;
125 * d["something_else"] = dynamic::array(1, 2, 3, nullptr);
128 struct EmptyArrayTag {};
132 static void array(EmptyArrayTag);
133 template <class... Args>
134 static dynamic array(Args&& ...args);
136 static ObjectMaker object();
137 static ObjectMaker object(dynamic, dynamic);
140 * Default constructor, initializes with nullptr.
145 * String compatibility constructors.
147 /* implicit */ dynamic(std::nullptr_t);
148 /* implicit */ dynamic(StringPiece val);
149 /* implicit */ dynamic(char const* val);
150 /* implicit */ dynamic(std::string val);
153 * This is part of the plumbing for array() and object(), above.
154 * Used to create a new array or object dynamic.
156 /* implicit */ dynamic(void (*)(EmptyArrayTag));
157 /* implicit */ dynamic(ObjectMaker (*)());
158 /* implicit */ dynamic(ObjectMaker const&) = delete;
159 /* implicit */ dynamic(ObjectMaker&&);
162 * Constructors for integral and float types.
163 * Other types are SFINAEd out with NumericTypeHelper.
165 template<class T, class NumericType = typename NumericTypeHelper<T>::type>
166 /* implicit */ dynamic(T t);
169 * Create a dynamic that is an array of the values from the supplied
172 template<class Iterator>
173 explicit dynamic(Iterator first, Iterator last);
175 dynamic(dynamic const&);
176 dynamic(dynamic&&) noexcept;
180 * "Deep" equality comparison. This will compare all the way down
181 * an object or array, and is potentially expensive.
183 bool operator==(dynamic const& o) const;
186 * For all types except object this returns the natural ordering on
187 * those types. For objects, we throw TypeError.
189 bool operator<(dynamic const& o) const;
194 * These throw TypeError when used with types or type combinations
195 * that don't support them.
197 * These functions may also throw if you use 64-bit integers with
198 * doubles when the integers are too big to fit in a double.
200 dynamic& operator+=(dynamic const&);
201 dynamic& operator-=(dynamic const&);
202 dynamic& operator*=(dynamic const&);
203 dynamic& operator/=(dynamic const&);
204 dynamic& operator%=(dynamic const&);
205 dynamic& operator|=(dynamic const&);
206 dynamic& operator&=(dynamic const&);
207 dynamic& operator^=(dynamic const&);
208 dynamic& operator++();
209 dynamic& operator--();
212 * Assignment from other dynamics. Because of the implicit conversion
213 * to dynamic from its potential types, you can use this to change the
214 * type pretty intuitively.
216 * Basic guarantee only.
218 dynamic& operator=(dynamic const&);
219 dynamic& operator=(dynamic&&) noexcept;
222 * For simple dynamics (not arrays or objects), this prints the
223 * value to an std::ostream in the expected way. Respects the
224 * formatting manipulators that have been sent to the stream
227 * If the dynamic holds an object or array, this prints them in a
228 * format very similar to JSON. (It will in fact actually be JSON
229 * as long as the dynamic validly represents a JSON object---i.e. it
230 * can't have non-string keys.)
232 friend std::ostream& operator<<(std::ostream&, dynamic const&);
235 * Returns true if this dynamic is of the specified type.
237 bool isString() const;
238 bool isObject() const;
241 bool isArray() const;
242 bool isDouble() const;
246 * Returns: isInt() || isDouble().
248 bool isNumber() const;
251 * Returns the type of this dynamic.
256 * Returns the type of this dynamic as a printable string.
258 const char* typeName() const;
261 * Extract a value while trying to convert to the specified type.
262 * Throws exceptions if we cannot convert from the real type to the
265 * Note you can only use this to access integral types or strings,
266 * since arrays and objects are generally best dealt with as a
269 std::string asString() const;
270 double asDouble() const;
271 int64_t asInt() const;
275 * Extract the value stored in this dynamic without type conversion.
277 * These will throw a TypeError if the dynamic has a different type.
279 const std::string& getString() const&;
280 double getDouble() const&;
281 int64_t getInt() const&;
282 bool getBool() const&;
283 std::string& getString() &;
284 double& getDouble() &;
287 std::string&& getString() &&;
288 double getDouble() &&;
293 * It is occasionally useful to access a string's internal pointer
294 * directly, without the type conversion of `asString()`.
296 * These will throw a TypeError if the dynamic is not a string.
298 const char* data() const&;
299 const char* data() && = delete;
300 const char* c_str() const&;
301 const char* c_str() && = delete;
302 StringPiece stringPiece() const;
305 * Returns: true if this dynamic is null, an empty array, an empty
306 * object, or an empty string.
311 * If this is an array or an object, returns the number of elements
312 * contained. If it is a string, returns the length. Otherwise
315 std::size_t size() const;
318 * You can iterate over the values of the array. Calling these on
319 * non-arrays will throw a TypeError.
321 const_iterator begin() const;
322 const_iterator end() const;
326 * Helper object returned by keys(), values(), and items().
328 template <class T> struct IterableProxy;
332 * You can iterate over the keys, values, or items (std::pair of key and
333 * value) in an object. Calling these on non-objects will throw a TypeError.
335 IterableProxy<const_key_iterator> keys() const;
336 IterableProxy<const_value_iterator> values() const;
337 IterableProxy<const_item_iterator> items() const;
340 * AssociativeContainer-style find interface for objects. Throws if
341 * this is not an object.
343 * Returns: items().end() if the key is not present, or a
344 * const_item_iterator pointing to the item.
346 const_item_iterator find(dynamic const&) const;
349 * If this is an object, returns whether it contains a field with
350 * the given name. Otherwise throws TypeError.
352 std::size_t count(dynamic const&) const;
355 * For objects or arrays, provides access to sub-fields by index or
358 * Using these with dynamic objects that are not arrays or objects
359 * will throw a TypeError. Using an index that is out of range or
360 * object-element that's not present throws std::out_of_range.
362 dynamic const& at(dynamic const&) const&;
363 dynamic& at(dynamic const&) &;
364 dynamic&& at(dynamic const&) &&;
367 * Like 'at', above, except it returns either a pointer to the contained
368 * object or nullptr if it wasn't found. This allows a key to be tested for
369 * containment and retrieved in one operation. Example:
371 * if (auto* found = d.get_ptr(key))
374 * Using these with dynamic objects that are not arrays or objects
375 * will throw a TypeError.
377 const dynamic* get_ptr(dynamic const&) const&;
378 dynamic* get_ptr(dynamic const&) &;
379 dynamic* get_ptr(dynamic const&) && = delete;
382 * This works for access to both objects and arrays.
384 * In the case of an array, the index must be an integer, and this will throw
385 * std::out_of_range if it is less than zero or greater than size().
387 * In the case of an object, the non-const overload inserts a null
388 * value if the key isn't present. The const overload will throw
389 * std::out_of_range if the key is not present.
391 * These functions do not invalidate iterators.
393 dynamic& operator[](dynamic const&) &;
394 dynamic const& operator[](dynamic const&) const&;
395 dynamic&& operator[](dynamic const&) &&;
398 * Only defined for objects, throws TypeError otherwise.
400 * getDefault will return the value associated with the supplied key, the
401 * supplied default otherwise. setDefault will set the key to the supplied
402 * default if it is not yet set, otherwise leaving it. setDefault returns
403 * a reference to the existing value if present, the new value otherwise.
406 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const&;
407 dynamic getDefault(const dynamic& k, dynamic&& v) const&;
408 dynamic getDefault(const dynamic& k, const dynamic& v = dynamic::object) &&;
409 dynamic getDefault(const dynamic& k, dynamic&& v) &&;
410 template<class K, class V>
411 dynamic& setDefault(K&& k, V&& v);
412 // MSVC 2015 Update 3 needs these extra overloads because if V were a
413 // defaulted template parameter, it causes MSVC to consider v an rvalue
414 // reference rather than a universal reference, resulting in it not being
415 // able to find the correct overload to construct a dynamic with.
417 dynamic& setDefault(K&& k, dynamic&& v);
419 dynamic& setDefault(K&& k, const dynamic& v = dynamic::object);
422 * Resizes an array so it has at n elements, using the supplied
423 * default to fill new elements. Throws TypeError if this dynamic
426 * May invalidate iterators.
430 void resize(std::size_t n, dynamic const& = nullptr);
433 * Inserts the supplied key-value pair to an object, or throws if
434 * it's not an object.
436 * Invalidates iterators.
438 template<class K, class V> void insert(K&&, V&& val);
441 * These functions merge two folly dynamic objects.
442 * The "update" and "update_missing" functions extend the object by
443 * inserting the key/value pairs of mergeObj into the current object.
444 * For update, if key is duplicated between the two objects, it
445 * will overwrite with the value of the object being inserted (mergeObj).
446 * For "update_missing", it will prefer the value in the original object
448 * The "merge" function creates a new object consisting of the key/value
449 * pairs of both mergeObj1 and mergeObj2
450 * If the key is duplicated between the two objects,
451 * it will prefer value in the second object (mergeObj2)
453 void update(const dynamic& mergeObj);
454 void update_missing(const dynamic& other);
455 static dynamic merge(const dynamic& mergeObj1, const dynamic& mergeObj2);
458 * Erase an element from a dynamic object, by key.
460 * Invalidates iterators to the element being erased.
462 * Returns the number of elements erased (i.e. 1 or 0).
464 std::size_t erase(dynamic const& key);
467 * Erase an element from a dynamic object or array, using an
468 * iterator or an iterator range.
470 * In arrays, invalidates iterators to elements after the element
471 * being erased. In objects, invalidates iterators to the elements
474 * Returns a new iterator to the first element beyond any elements
475 * removed, or end() if there are none. (The iteration order does
478 const_iterator erase(const_iterator it);
479 const_iterator erase(const_iterator first, const_iterator last);
481 const_key_iterator erase(const_key_iterator it);
482 const_key_iterator erase(const_key_iterator first, const_key_iterator last);
484 const_value_iterator erase(const_value_iterator it);
485 const_value_iterator erase(const_value_iterator first,
486 const_value_iterator last);
488 const_item_iterator erase(const_item_iterator it);
489 const_item_iterator erase(const_item_iterator first,
490 const_item_iterator last);
492 * Append elements to an array. If this is not an array, throws
495 * Invalidates iterators.
497 void push_back(dynamic const&);
498 void push_back(dynamic&&);
501 * Remove an element from the back of an array. If this is not an array,
504 * Does not invalidate iterators.
509 * Get a hash code. This function is called by a std::hash<>
510 * specialization, also.
512 * Throws TypeError if this is an object, array, or null.
514 std::size_t hash() const;
517 friend struct TypeError;
519 template<class T> struct TypeInfo;
520 template<class T> struct CompareOp;
521 template<class T> struct GetAddrImpl;
522 template<class T> struct PrintImpl;
524 explicit dynamic(Array&& array);
526 template<class T> T const& get() const;
527 template<class T> T& get();
528 template<class T> T* get_nothrow() & noexcept;
529 template<class T> T const* get_nothrow() const& noexcept;
530 template<class T> T* get_nothrow() && noexcept = delete;
531 template<class T> T* getAddress() noexcept;
532 template<class T> T const* getAddress() const noexcept;
534 template<class T> T asImpl() const;
536 static char const* typeName(Type);
537 void destroy() noexcept;
538 void print(std::ostream&) const;
539 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
544 explicit Data() : nul(nullptr) {}
547 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
548 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
557 * Objects are placement new'd here. We have to use a char buffer
558 * because we don't know the type here (std::unordered_map<> with
559 * dynamic would be parameterizing a std:: template with an
560 * incomplete type right now). (Note that in contrast we know it
561 * is ok to do this with fbvector because we own it.)
563 std::aligned_storage<
564 sizeof(std::unordered_map<int,int>),
565 alignof(std::unordered_map<int,int>)
566 >::type objectBuffer;
570 //////////////////////////////////////////////////////////////////////
574 #include <folly/dynamic-inl.h>