2 * Copyright 2015 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"] = { "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", { "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>
63 #ifndef FOLLY_DYNAMIC_H_
64 #define FOLLY_DYNAMIC_H_
67 #include <initializer_list>
71 #include <type_traits>
72 #include <unordered_map>
76 #include <boost/operators.hpp>
78 #include <folly/FBString.h>
79 #include <folly/Range.h>
80 #include <folly/Traits.h>
84 //////////////////////////////////////////////////////////////////////
89 //////////////////////////////////////////////////////////////////////
91 struct dynamic : private boost::operators<dynamic> {
103 * We support direct iteration of arrays, and indirect iteration of objects.
104 * See begin(), end(), keys(), values(), and items() for more.
106 * Array iterators dereference as the elements in the array.
107 * Object key iterators dereference as the keys in the object.
108 * Object value iterators dereference as the values in the object.
109 * Object item iterators dereference as pairs of (key, value).
112 typedef std::vector<dynamic> Array;
114 typedef Array::const_iterator const_iterator;
115 typedef dynamic value_type;
116 struct const_key_iterator;
117 struct const_value_iterator;
118 struct const_item_iterator;
121 * Creation routines for making dynamic objects. Objects are maps
122 * from key to value (so named due to json-related origins here).
126 * // Make a fairly complex dynamic:
127 * dynamic d = dynamic::object("key", "value1")
128 * ("key2", { "value", "with", 4, "words" });
130 * // Build an object in a few steps:
131 * dynamic d = dynamic::object;
133 * d["something_else"] = { 1, 2, 3, nullptr };
139 static ObjectMaker object();
140 static ObjectMaker object(dynamic&&, dynamic&&);
141 static ObjectMaker object(dynamic const&, dynamic&&);
142 static ObjectMaker object(dynamic&&, dynamic const&);
143 static ObjectMaker object(dynamic const&, dynamic const&);
146 * String compatibility constructors.
148 /* implicit */ dynamic(StringPiece val);
149 /* implicit */ dynamic(char const* val);
150 /* implicit */ dynamic(std::string const& val);
151 /* implicit */ dynamic(fbstring const& val);
152 /* implicit */ dynamic(fbstring&& val);
155 * This is part of the plumbing for object(), above. Used to create
156 * a new object dynamic.
158 /* implicit */ dynamic(ObjectMaker (*)());
159 /* implicit */ dynamic(ObjectMaker const&) = delete;
160 /* implicit */ dynamic(ObjectMaker&&);
163 * Create a new array from an initializer list.
167 * dynamic v = { 1, 2, 3, "foo" };
169 /* implicit */ dynamic(std::initializer_list<dynamic> il);
170 dynamic& operator=(std::initializer_list<dynamic> il);
173 * Conversion constructors from most of the other types.
175 template<class T> /* implicit */ dynamic(T t);
178 * Create a dynamic that is an array of the values from the supplied
181 template<class Iterator> dynamic(Iterator first, Iterator last);
183 dynamic(dynamic const&);
184 dynamic(dynamic&&) noexcept;
188 * "Deep" equality comparison. This will compare all the way down
189 * an object or array, and is potentially expensive.
191 bool operator==(dynamic const& o) const;
194 * For all types except object this returns the natural ordering on
195 * those types. For objects, we throw TypeError.
197 bool operator<(dynamic const& o) const;
202 * These throw TypeError when used with types or type combinations
203 * that don't support them.
205 * These functions may also throw if you use 64-bit integers with
206 * doubles when the integers are too big to fit in a double.
208 dynamic& operator+=(dynamic const&);
209 dynamic& operator-=(dynamic const&);
210 dynamic& operator*=(dynamic const&);
211 dynamic& operator/=(dynamic const&);
212 dynamic& operator%=(dynamic const&);
213 dynamic& operator|=(dynamic const&);
214 dynamic& operator&=(dynamic const&);
215 dynamic& operator^=(dynamic const&);
216 dynamic& operator++();
217 dynamic& operator--();
220 * Assignment from other dynamics. Because of the implicit conversion
221 * to dynamic from its potential types, you can use this to change the
222 * type pretty intuitively.
224 * Basic guarantee only.
226 dynamic& operator=(dynamic const&);
227 dynamic& operator=(dynamic&&) noexcept;
230 * For simple dynamics (not arrays or objects), this prints the
231 * value to an std::ostream in the expected way. Respects the
232 * formatting manipulators that have been sent to the stream
235 * If the dynamic holds an object or array, this prints them in a
236 * format very similar to JSON. (It will in fact actually be JSON
237 * as long as the dynamic validly represents a JSON object---i.e. it
238 * can't have non-string keys.)
240 friend std::ostream& operator<<(std::ostream&, dynamic const&);
243 * Returns true if this dynamic is of the specified type.
245 bool isString() const;
246 bool isObject() const;
249 bool isArray() const;
250 bool isDouble() const;
254 * Returns: isInt() || isDouble().
256 bool isNumber() const;
259 * Returns the type of this dynamic.
264 * Returns the type of this dynamic as a printable string.
266 const char* typeName() const;
269 * Extract a value while trying to convert to the specified type.
270 * Throws exceptions if we cannot convert from the real type to the
273 * Note you can only use this to access integral types or strings,
274 * since arrays and objects are generally best dealt with as a
277 fbstring asString() const;
278 double asDouble() const;
279 int64_t asInt() const;
283 * Extract the value stored in this dynamic without type conversion.
285 * These will throw a TypeError if the dynamic has a different type.
287 const fbstring& getString() const&;
288 double getDouble() const&;
289 int64_t getInt() const&;
290 bool getBool() const&;
291 fbstring& getString() &;
292 double& getDouble() &;
295 fbstring getString() &&;
296 double getDouble() &&;
301 * It is occasionally useful to access a string's internal pointer
302 * directly, without the type conversion of `asString()`.
304 * These will throw a TypeError if the dynamic is not a string.
306 const char* data() const&;
307 const char* data() && = delete;
308 const char* c_str() const&;
309 const char* c_str() && = delete;
310 StringPiece stringPiece() const;
313 * Returns: true if this dynamic is null, an empty array, an empty
314 * object, or an empty string.
319 * If this is an array or an object, returns the number of elements
320 * contained. If it is a string, returns the length. Otherwise
323 std::size_t size() const;
326 * You can iterate over the values of the array. Calling these on
327 * non-arrays will throw a TypeError.
329 const_iterator begin() const;
330 const_iterator end() const;
334 * Helper object returned by keys(), values(), and items().
336 template <class T> struct IterableProxy;
340 * You can iterate over the keys, values, or items (std::pair of key and
341 * value) in an object. Calling these on non-objects will throw a TypeError.
343 IterableProxy<const_key_iterator> keys() const;
344 IterableProxy<const_value_iterator> values() const;
345 IterableProxy<const_item_iterator> items() const;
348 * AssociativeContainer-style find interface for objects. Throws if
349 * this is not an object.
351 * Returns: items().end() if the key is not present, or a
352 * const_item_iterator pointing to the item.
354 const_item_iterator find(dynamic const&) const;
357 * If this is an object, returns whether it contains a field with
358 * the given name. Otherwise throws TypeError.
360 std::size_t count(dynamic const&) const;
363 * For objects or arrays, provides access to sub-fields by index or
366 * Using these with dynamic objects that are not arrays or objects
367 * will throw a TypeError. Using an index that is out of range or
368 * object-element that's not present throws std::out_of_range.
370 dynamic const& at(dynamic const&) const&;
371 dynamic& at(dynamic const&) &;
372 dynamic at(dynamic const&) &&;
375 * Like 'at', above, except it returns either a pointer to the contained
376 * object or nullptr if it wasn't found. This allows a key to be tested for
377 * containment and retrieved in one operation. Example:
379 * if (auto* found = d.get_ptr(key))
382 * Using these with dynamic objects that are not arrays or objects
383 * will throw a TypeError.
385 const dynamic* get_ptr(dynamic const&) const&;
386 dynamic* get_ptr(dynamic const&) &;
387 dynamic* get_ptr(dynamic const&) && = delete;
390 * This works for access to both objects and arrays.
392 * In the case of an array, the index must be an integer, and this will throw
393 * std::out_of_range if it is less than zero or greater than size().
395 * In the case of an object, the non-const overload inserts a null
396 * value if the key isn't present. The const overload will throw
397 * std::out_of_range if the key is not present.
399 * These functions do not invalidate iterators.
401 dynamic& operator[](dynamic const&) &;
402 dynamic const& operator[](dynamic const&) const&;
403 dynamic operator[](dynamic const&) &&;
406 * Only defined for objects, throws TypeError otherwise.
408 * getDefault will return the value associated with the supplied key, the
409 * supplied default otherwise. setDefault will set the key to the supplied
410 * default if it is not yet set, otherwise leaving it. setDefault returns
411 * a reference to the existing value if present, the new value otherwise.
414 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const&;
415 dynamic getDefault(const dynamic& k, dynamic&& v) const&;
416 dynamic getDefault(const dynamic& k, const dynamic& v = dynamic::object) &&;
417 dynamic getDefault(const dynamic& k, dynamic&& v) &&;
418 template<class K, class V = dynamic>
419 dynamic& setDefault(K&& k, V&& 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 template<class T> T const& get() const;
525 template<class T> T& get();
526 template<class T> T* get_nothrow() & noexcept;
527 template<class T> T const* get_nothrow() const& noexcept;
528 template<class T> T* get_nothrow() && noexcept = delete;
529 template<class T> T* getAddress() noexcept;
530 template<class T> T const* getAddress() const noexcept;
532 template<class T> T asImpl() const;
534 static char const* typeName(Type);
535 void destroy() noexcept;
536 void print(std::ostream&) const;
537 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
542 explicit Data() : nul(nullptr) {}
545 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
546 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
555 * Objects are placement new'd here. We have to use a char buffer
556 * because we don't know the type here (std::unordered_map<> with
557 * dynamic would be parameterizing a std:: template with an
558 * incomplete type right now). (Note that in contrast we know it
559 * is ok to do this with fbvector because we own it.)
561 std::aligned_storage<
562 sizeof(std::unordered_map<int,int>),
563 alignof(std::unordered_map<int,int>)
564 >::type objectBuffer;
568 //////////////////////////////////////////////////////////////////////
572 #include <folly/dynamic-inl.h>