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>
66 #include <initializer_list>
70 #include <type_traits>
71 #include <unordered_map>
75 #include <boost/operators.hpp>
77 #include <folly/Range.h>
78 #include <folly/Traits.h>
82 //////////////////////////////////////////////////////////////////////
87 //////////////////////////////////////////////////////////////////////
89 struct dynamic : private boost::operators<dynamic> {
101 * We support direct iteration of arrays, and indirect iteration of objects.
102 * See begin(), end(), keys(), values(), and items() for more.
104 * Array iterators dereference as the elements in the array.
105 * Object key iterators dereference as the keys in the object.
106 * Object value iterators dereference as the values in the object.
107 * Object item iterators dereference as pairs of (key, value).
110 typedef std::vector<dynamic> Array;
112 typedef Array::const_iterator const_iterator;
113 typedef dynamic value_type;
114 struct const_key_iterator;
115 struct const_value_iterator;
116 struct const_item_iterator;
119 * Creation routines for making dynamic objects and arrays. Objects
120 * are maps from key to value (so named due to json-related origins
125 * // Make a fairly complex dynamic:
126 * dynamic d = dynamic::object("key", "value1")
127 * ("key2", dynamic::array("value",
132 * // Build an object in a few steps:
133 * dynamic d = dynamic::object;
135 * d["something_else"] = dynamic::array(1, 2, 3, nullptr);
138 struct PrivateTag {};
139 struct EmptyArrayTag {};
143 static void array(EmptyArrayTag);
144 template <class... Args>
145 static dynamic array(Args&& ...args);
147 static ObjectMaker object();
148 static ObjectMaker object(dynamic&&, dynamic&&);
149 static ObjectMaker object(dynamic const&, dynamic&&);
150 static ObjectMaker object(dynamic&&, dynamic const&);
151 static ObjectMaker object(dynamic const&, dynamic const&);
154 * String compatibility constructors.
156 /* implicit */ dynamic(StringPiece val);
157 /* implicit */ dynamic(char const* val);
158 /* implicit */ dynamic(std::string const& val);
159 /* implicit */ dynamic(std::string&& val);
162 * This is part of the plumbing for array() and object(), above.
163 * Used to create a new array or object dynamic.
165 /* implicit */ dynamic(void (*)(EmptyArrayTag));
166 /* implicit */ dynamic(ObjectMaker (*)());
167 /* implicit */ dynamic(ObjectMaker const&) = delete;
168 /* implicit */ dynamic(ObjectMaker&&);
171 * Create a new array from an initializer list.
175 * dynamic v = { 1, 2, 3, "foo" };
177 // TODO(ott, 10300209): Remove once all uses have been eradicated.
180 "Initializer list syntax is deprecated (#10300209). Use dynamic::array.")
181 /* implicit */ dynamic(std::initializer_list<dynamic> il);
182 dynamic(std::initializer_list<dynamic> il, PrivateTag);
184 "Initializer list syntax is deprecated (#10300209). Use dynamic::array.")
185 dynamic& operator=(std::initializer_list<dynamic> il);
188 * Conversion constructors from most of the other types.
190 template<class T> /* implicit */ dynamic(T t);
193 * Create a dynamic that is an array of the values from the supplied
196 template<class Iterator> dynamic(Iterator first, Iterator last);
198 dynamic(dynamic const&);
199 dynamic(dynamic&&) noexcept;
203 * "Deep" equality comparison. This will compare all the way down
204 * an object or array, and is potentially expensive.
206 bool operator==(dynamic const& o) const;
209 * For all types except object this returns the natural ordering on
210 * those types. For objects, we throw TypeError.
212 bool operator<(dynamic const& o) const;
217 * These throw TypeError when used with types or type combinations
218 * that don't support them.
220 * These functions may also throw if you use 64-bit integers with
221 * doubles when the integers are too big to fit in a double.
223 dynamic& operator+=(dynamic const&);
224 dynamic& operator-=(dynamic const&);
225 dynamic& operator*=(dynamic const&);
226 dynamic& operator/=(dynamic const&);
227 dynamic& operator%=(dynamic const&);
228 dynamic& operator|=(dynamic const&);
229 dynamic& operator&=(dynamic const&);
230 dynamic& operator^=(dynamic const&);
231 dynamic& operator++();
232 dynamic& operator--();
235 * Assignment from other dynamics. Because of the implicit conversion
236 * to dynamic from its potential types, you can use this to change the
237 * type pretty intuitively.
239 * Basic guarantee only.
241 dynamic& operator=(dynamic const&);
242 dynamic& operator=(dynamic&&) noexcept;
245 * For simple dynamics (not arrays or objects), this prints the
246 * value to an std::ostream in the expected way. Respects the
247 * formatting manipulators that have been sent to the stream
250 * If the dynamic holds an object or array, this prints them in a
251 * format very similar to JSON. (It will in fact actually be JSON
252 * as long as the dynamic validly represents a JSON object---i.e. it
253 * can't have non-string keys.)
255 friend std::ostream& operator<<(std::ostream&, dynamic const&);
258 * Returns true if this dynamic is of the specified type.
260 bool isString() const;
261 bool isObject() const;
264 bool isArray() const;
265 bool isDouble() const;
269 * Returns: isInt() || isDouble().
271 bool isNumber() const;
274 * Returns the type of this dynamic.
279 * Returns the type of this dynamic as a printable string.
281 const char* typeName() const;
284 * Extract a value while trying to convert to the specified type.
285 * Throws exceptions if we cannot convert from the real type to the
288 * Note you can only use this to access integral types or strings,
289 * since arrays and objects are generally best dealt with as a
292 std::string asString() const;
293 double asDouble() const;
294 int64_t asInt() const;
298 * Extract the value stored in this dynamic without type conversion.
300 * These will throw a TypeError if the dynamic has a different type.
302 const std::string& getString() const&;
303 double getDouble() const&;
304 int64_t getInt() const&;
305 bool getBool() const&;
306 std::string& getString() &;
307 double& getDouble() &;
310 std::string getString() &&;
311 double getDouble() &&;
316 * It is occasionally useful to access a string's internal pointer
317 * directly, without the type conversion of `asString()`.
319 * These will throw a TypeError if the dynamic is not a string.
321 const char* data() const&;
322 const char* data() && = delete;
323 const char* c_str() const&;
324 const char* c_str() && = delete;
325 StringPiece stringPiece() const;
328 * Returns: true if this dynamic is null, an empty array, an empty
329 * object, or an empty string.
334 * If this is an array or an object, returns the number of elements
335 * contained. If it is a string, returns the length. Otherwise
338 std::size_t size() const;
341 * You can iterate over the values of the array. Calling these on
342 * non-arrays will throw a TypeError.
344 const_iterator begin() const;
345 const_iterator end() const;
349 * Helper object returned by keys(), values(), and items().
351 template <class T> struct IterableProxy;
355 * You can iterate over the keys, values, or items (std::pair of key and
356 * value) in an object. Calling these on non-objects will throw a TypeError.
358 IterableProxy<const_key_iterator> keys() const;
359 IterableProxy<const_value_iterator> values() const;
360 IterableProxy<const_item_iterator> items() const;
363 * AssociativeContainer-style find interface for objects. Throws if
364 * this is not an object.
366 * Returns: items().end() if the key is not present, or a
367 * const_item_iterator pointing to the item.
369 const_item_iterator find(dynamic const&) const;
372 * If this is an object, returns whether it contains a field with
373 * the given name. Otherwise throws TypeError.
375 std::size_t count(dynamic const&) const;
378 * For objects or arrays, provides access to sub-fields by index or
381 * Using these with dynamic objects that are not arrays or objects
382 * will throw a TypeError. Using an index that is out of range or
383 * object-element that's not present throws std::out_of_range.
385 dynamic const& at(dynamic const&) const&;
386 dynamic& at(dynamic const&) &;
387 dynamic at(dynamic const&) &&;
390 * Like 'at', above, except it returns either a pointer to the contained
391 * object or nullptr if it wasn't found. This allows a key to be tested for
392 * containment and retrieved in one operation. Example:
394 * if (auto* found = d.get_ptr(key))
397 * Using these with dynamic objects that are not arrays or objects
398 * will throw a TypeError.
400 const dynamic* get_ptr(dynamic const&) const&;
401 dynamic* get_ptr(dynamic const&) &;
402 dynamic* get_ptr(dynamic const&) && = delete;
405 * This works for access to both objects and arrays.
407 * In the case of an array, the index must be an integer, and this will throw
408 * std::out_of_range if it is less than zero or greater than size().
410 * In the case of an object, the non-const overload inserts a null
411 * value if the key isn't present. The const overload will throw
412 * std::out_of_range if the key is not present.
414 * These functions do not invalidate iterators.
416 dynamic& operator[](dynamic const&) &;
417 dynamic const& operator[](dynamic const&) const&;
418 dynamic operator[](dynamic const&) &&;
421 * Only defined for objects, throws TypeError otherwise.
423 * getDefault will return the value associated with the supplied key, the
424 * supplied default otherwise. setDefault will set the key to the supplied
425 * default if it is not yet set, otherwise leaving it. setDefault returns
426 * a reference to the existing value if present, the new value otherwise.
429 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const&;
430 dynamic getDefault(const dynamic& k, dynamic&& v) const&;
431 dynamic getDefault(const dynamic& k, const dynamic& v = dynamic::object) &&;
432 dynamic getDefault(const dynamic& k, dynamic&& v) &&;
433 template<class K, class V = dynamic>
434 dynamic& setDefault(K&& k, V&& v = dynamic::object);
437 * Resizes an array so it has at n elements, using the supplied
438 * default to fill new elements. Throws TypeError if this dynamic
441 * May invalidate iterators.
445 void resize(std::size_t n, dynamic const& = nullptr);
448 * Inserts the supplied key-value pair to an object, or throws if
449 * it's not an object.
451 * Invalidates iterators.
453 template<class K, class V> void insert(K&&, V&& val);
456 * These functions merge two folly dynamic objects.
457 * The "update" and "update_missing" functions extend the object by
458 * inserting the key/value pairs of mergeObj into the current object.
459 * For update, if key is duplicated between the two objects, it
460 * will overwrite with the value of the object being inserted (mergeObj).
461 * For "update_missing", it will prefer the value in the original object
463 * The "merge" function creates a new object consisting of the key/value
464 * pairs of both mergeObj1 and mergeObj2
465 * If the key is duplicated between the two objects,
466 * it will prefer value in the second object (mergeObj2)
468 void update(const dynamic& mergeObj);
469 void update_missing(const dynamic& other);
470 static dynamic merge(const dynamic& mergeObj1, const dynamic& mergeObj2);
473 * Erase an element from a dynamic object, by key.
475 * Invalidates iterators to the element being erased.
477 * Returns the number of elements erased (i.e. 1 or 0).
479 std::size_t erase(dynamic const& key);
482 * Erase an element from a dynamic object or array, using an
483 * iterator or an iterator range.
485 * In arrays, invalidates iterators to elements after the element
486 * being erased. In objects, invalidates iterators to the elements
489 * Returns a new iterator to the first element beyond any elements
490 * removed, or end() if there are none. (The iteration order does
493 const_iterator erase(const_iterator it);
494 const_iterator erase(const_iterator first, const_iterator last);
496 const_key_iterator erase(const_key_iterator it);
497 const_key_iterator erase(const_key_iterator first, const_key_iterator last);
499 const_value_iterator erase(const_value_iterator it);
500 const_value_iterator erase(const_value_iterator first,
501 const_value_iterator last);
503 const_item_iterator erase(const_item_iterator it);
504 const_item_iterator erase(const_item_iterator first,
505 const_item_iterator last);
507 * Append elements to an array. If this is not an array, throws
510 * Invalidates iterators.
512 void push_back(dynamic const&);
513 void push_back(dynamic&&);
516 * Remove an element from the back of an array. If this is not an array,
519 * Does not invalidate iterators.
524 * Get a hash code. This function is called by a std::hash<>
525 * specialization, also.
527 * Throws TypeError if this is an object, array, or null.
529 std::size_t hash() const;
532 friend struct TypeError;
534 template<class T> struct TypeInfo;
535 template<class T> struct CompareOp;
536 template<class T> struct GetAddrImpl;
537 template<class T> struct PrintImpl;
539 template<class T> T const& get() const;
540 template<class T> T& get();
541 template<class T> T* get_nothrow() & noexcept;
542 template<class T> T const* get_nothrow() const& noexcept;
543 template<class T> T* get_nothrow() && noexcept = delete;
544 template<class T> T* getAddress() noexcept;
545 template<class T> T const* getAddress() const noexcept;
547 template<class T> T asImpl() const;
549 static char const* typeName(Type);
550 void destroy() noexcept;
551 void print(std::ostream&) const;
552 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
557 explicit Data() : nul(nullptr) {}
560 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
561 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
570 * Objects are placement new'd here. We have to use a char buffer
571 * because we don't know the type here (std::unordered_map<> with
572 * dynamic would be parameterizing a std:: template with an
573 * incomplete type right now). (Note that in contrast we know it
574 * is ok to do this with fbvector because we own it.)
576 std::aligned_storage<
577 sizeof(std::unordered_map<int,int>),
578 alignof(std::unordered_map<int,int>)
579 >::type objectBuffer;
583 //////////////////////////////////////////////////////////////////////
587 #include <folly/dynamic-inl.h>