2 * Copyright 2014 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);
172 * Conversion constructors from most of the other types.
174 template<class T> /* implicit */ dynamic(T t);
177 * Create a dynamic that is an array of the values from the supplied
180 template<class Iterator> dynamic(Iterator first, Iterator last);
182 dynamic(dynamic const&);
183 dynamic(dynamic&&) noexcept;
187 * "Deep" equality comparison. This will compare all the way down
188 * an object or array, and is potentially expensive.
190 bool operator==(dynamic const& o) const;
193 * For all types except object this returns the natural ordering on
194 * those types. For objects, we throw TypeError.
196 bool operator<(dynamic const& o) const;
201 * These throw TypeError when used with types or type combinations
202 * that don't support them.
204 * These functions may also throw if you use 64-bit integers with
205 * doubles when the integers are too big to fit in a double.
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|=(dynamic const&);
213 dynamic& operator&=(dynamic const&);
214 dynamic& operator^=(dynamic const&);
215 dynamic& operator++();
216 dynamic& operator--();
219 * Assignment from other dynamics. Because of the implicit conversion
220 * to dynamic from its potential types, you can use this to change the
221 * type pretty intuitively.
223 * Basic guarantee only.
225 dynamic& operator=(dynamic const&);
226 dynamic& operator=(dynamic&&) noexcept;
229 * For simple dynamics (not arrays or objects), this prints the
230 * value to an std::ostream in the expected way. Respects the
231 * formatting manipulators that have been sent to the stream
234 * If the dynamic holds an object or array, this prints them in a
235 * format very similar to JSON. (It will in fact actually be JSON
236 * as long as the dynamic validly represents a JSON object---i.e. it
237 * can't have non-string keys.)
239 friend std::ostream& operator<<(std::ostream&, dynamic const&);
242 * Returns true if this dynamic is of the specified type.
244 bool isString() const;
245 bool isObject() const;
248 bool isArray() const;
249 bool isDouble() const;
253 * Returns: isInt() || isDouble().
255 bool isNumber() const;
258 * Returns the type of this dynamic.
263 * Returns the type of this dynamic as a printable string.
265 const char* typeName() const;
268 * Extract a value while trying to convert to the specified type.
269 * Throws exceptions if we cannot convert from the real type to the
272 * Note you can only use this to access integral types or strings,
273 * since arrays and objects are generally best dealt with as a
276 fbstring asString() const;
277 double asDouble() const;
278 int64_t asInt() const;
282 * Extract the value stored in this dynamic without type conversion.
284 * These will throw a TypeError if the dynamic has a different type.
286 const fbstring& getString() const;
287 double getDouble() const;
288 int64_t getInt() const;
289 bool getBool() const;
290 fbstring& getString();
296 * It is occasionally useful to access a string's internal pointer
297 * directly, without the type conversion of `asString()`.
299 * These will throw a TypeError if the dynamic is not a string.
301 const char* data() const;
302 const char* c_str() const;
303 StringPiece stringPiece() const;
306 * Returns: true if this dynamic is null, an empty array, an empty
307 * object, or an empty string.
312 * If this is an array or an object, returns the number of elements
313 * contained. If it is a string, returns the length. Otherwise
316 std::size_t size() const;
319 * You can iterate over the values of the array. Calling these on
320 * non-arrays will throw a TypeError.
322 const_iterator begin() const;
323 const_iterator end() const;
327 * Helper object returned by keys(), values(), and items().
329 template <class T> struct IterableProxy;
333 * You can iterate over the keys, values, or items (std::pair of key and
334 * value) in an object. Calling these on non-objects will throw a TypeError.
336 IterableProxy<const_key_iterator> keys() const;
337 IterableProxy<const_value_iterator> values() const;
338 IterableProxy<const_item_iterator> items() const;
341 * AssociativeContainer-style find interface for objects. Throws if
342 * this is not an object.
344 * Returns: items().end() if the key is not present, or a
345 * const_item_iterator pointing to the item.
347 const_item_iterator find(dynamic const&) const;
350 * If this is an object, returns whether it contains a field with
351 * the given name. Otherwise throws TypeError.
353 std::size_t count(dynamic const&) const;
356 * For objects or arrays, provides access to sub-fields by index or
359 * Using these with dynamic objects that are not arrays or objects
360 * will throw a TypeError. Using an index that is out of range or
361 * object-element that's not present throws std::out_of_range.
363 dynamic const& at(dynamic const&) 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&);
381 * This works for access to both objects and arrays.
383 * In the case of an array, the index must be an integer, and this will throw
384 * std::out_of_range if it is less than zero or greater than size().
386 * In the case of an object, the non-const overload inserts a null
387 * value if the key isn't present. The const overload will throw
388 * std::out_of_range if the key is not present.
390 * These functions do not invalidate iterators.
392 dynamic& operator[](dynamic const&);
393 dynamic const& operator[](dynamic const&) const;
396 * Only defined for objects, throws TypeError otherwise.
398 * getDefault will return the value associated with the supplied key, the
399 * supplied default otherwise. setDefault will set the key to the supplied
400 * default if it is not yet set, otherwise leaving it. setDefault returns
401 * a reference to the existing value if present, the new value otherwise.
404 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const;
405 dynamic&& getDefault(const dynamic& k, dynamic&& v) const;
406 template<class K, class V = dynamic>
407 dynamic& setDefault(K&& k, V&& v = dynamic::object);
410 * Resizes an array so it has at n elements, using the supplied
411 * default to fill new elements. Throws TypeError if this dynamic
414 * May invalidate iterators.
418 void resize(std::size_t n, dynamic const& = nullptr);
421 * Inserts the supplied key-value pair to an object, or throws if
422 * it's not an object.
424 * Invalidates iterators.
426 template<class K, class V> void insert(K&&, V&& val);
429 * Erase an element from a dynamic object, by key.
431 * Invalidates iterators to the element being erased.
433 * Returns the number of elements erased (i.e. 1 or 0).
435 std::size_t erase(dynamic const& key);
438 * Erase an element from a dynamic object or array, using an
439 * iterator or an iterator range.
441 * In arrays, invalidates iterators to elements after the element
442 * being erased. In objects, invalidates iterators to the elements
445 * Returns a new iterator to the first element beyond any elements
446 * removed, or end() if there are none. (The iteration order does
449 const_iterator erase(const_iterator it);
450 const_iterator erase(const_iterator first, const_iterator last);
452 const_key_iterator erase(const_key_iterator it);
453 const_key_iterator erase(const_key_iterator first, const_key_iterator last);
455 const_value_iterator erase(const_value_iterator it);
456 const_value_iterator erase(const_value_iterator first,
457 const_value_iterator last);
459 const_item_iterator erase(const_item_iterator it);
460 const_item_iterator erase(const_item_iterator first,
461 const_item_iterator last);
463 * Append elements to an array. If this is not an array, throws
466 * Invalidates iterators.
468 void push_back(dynamic const&);
469 void push_back(dynamic&&);
472 * Remove an element from the back of an array. If this is not an array,
475 * Does not invalidate iterators.
480 * Get a hash code. This function is called by a std::hash<>
481 * specialization, also.
483 * Throws TypeError if this is an object, array, or null.
485 std::size_t hash() const;
488 friend struct TypeError;
490 template<class T> struct TypeInfo;
491 template<class T> struct CompareOp;
492 template<class T> struct GetAddrImpl;
493 template<class T> struct PrintImpl;
495 template<class T> T const& get() const;
496 template<class T> T& get();
497 template<class T> T* get_nothrow() noexcept;
498 template<class T> T const* get_nothrow() const noexcept;
499 template<class T> T* getAddress() noexcept;
500 template<class T> T const* getAddress() const noexcept;
502 template<class T> T asImpl() const;
504 static char const* typeName(Type);
505 void destroy() noexcept;
506 void print(std::ostream&) const;
507 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
512 explicit Data() : nul(nullptr) {}
515 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
516 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
525 * Objects are placement new'd here. We have to use a char buffer
526 * because we don't know the type here (std::unordered_map<> with
527 * dynamic would be parameterizing a std:: template with an
528 * incomplete type right now). (Note that in contrast we know it
529 * is ok to do this with fbvector because we own it.)
531 typename std::aligned_storage<
532 sizeof(std::unordered_map<int,int>),
533 alignof(std::unordered_map<int,int>)
534 >::type objectBuffer;
538 //////////////////////////////////////////////////////////////////////
542 #include <folly/dynamic-inl.h>