2 * Copyright 2012 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_
66 #include <unordered_map>
71 #include <type_traits>
72 #include <initializer_list>
74 #include <boost/operators.hpp>
76 #include "folly/Traits.h"
77 #include "folly/FBVector.h"
78 #include "folly/FBString.h"
82 //////////////////////////////////////////////////////////////////////
86 template<> FOLLY_ASSUME_RELOCATABLE(dynamic);
88 //////////////////////////////////////////////////////////////////////
90 struct dynamic : private boost::operators<dynamic> {
102 * We support direct iteration of arrays, and indirect iteration of objects.
103 * See begin(), end(), keys(), values(), and items() for more.
105 * Array iterators dereference as the elements in the array.
106 * Object key iterators dereference as the keys in the object.
107 * Object value iterators dereference as the values in the object.
108 * Object item iterators dereference as pairs of (key, value).
111 typedef fbvector<dynamic> Array;
113 typedef Array::const_iterator const_iterator;
114 struct const_key_iterator;
115 struct const_value_iterator;
116 struct const_item_iterator;
119 * Creation routines for making dynamic objects. Objects are maps
120 * from key to value (so named due to json-related origins here).
124 * // Make a fairly complex dynamic:
125 * dynamic d = dynamic::object("key", "value1")
126 * ("key2", { "value", "with", 4, "words" });
128 * // Build an object in a few steps:
129 * dynamic d = dynamic::object;
131 * d["something_else"] = { 1, 2, 3, nullptr };
137 template<class... Args> static ObjectMaker object(Args&&...);
140 * String compatibility constructors.
142 /* implicit */ dynamic(char const* val);
143 /* implicit */ dynamic(std::string const& val);
146 * This is part of the plumbing for object(), above. Used to create
147 * a new object dynamic.
149 /* implicit */ dynamic(ObjectMaker (*)());
150 /* implicit */ dynamic(ObjectMaker const&) = delete;
151 /* implicit */ dynamic(ObjectMaker&&);
154 * Create a new array from an initializer list.
158 * dynamic v = { 1, 2, 3, "foo" };
160 /* implicit */ dynamic(std::initializer_list<dynamic> il);
163 * Conversion constructors from most of the other types.
165 template<class T> /* implicit */ dynamic(T t);
168 * Create a dynamic that is an array of the values from the supplied
171 template<class Iterator> dynamic(Iterator first, Iterator last);
173 dynamic(dynamic const&);
178 * "Deep" equality comparison. This will compare all the way down
179 * an object or array, and is potentially expensive.
181 bool operator==(dynamic const& o) const;
184 * For all types except object this returns the natural ordering on
185 * those types. For objects, we throw TypeError.
187 bool operator<(dynamic const& o) const;
192 * These throw TypeError when used with types or type combinations
193 * that don't support them.
195 * These functions may also throw if you use 64-bit integers with
196 * doubles when the integers are too big to fit in a double.
198 dynamic& operator+=(dynamic const&);
199 dynamic& operator-=(dynamic const&);
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++();
207 dynamic& operator--();
210 * Assignment from other dynamics. Because of the implicit conversion
211 * to dynamic from its potential types, you can use this to change the
212 * type pretty intuitively.
214 * Basic guarantee only.
216 dynamic& operator=(dynamic const&);
217 dynamic& operator=(dynamic&&);
220 * For simple dynamics (not arrays or objects), this prints the
221 * value to an std::ostream in the expected way. Respects the
222 * formatting manipulators that have been sent to the stream
225 * If the dynamic holds an object or array, this prints them in a
226 * format very similar to JSON. (It will in fact actually be JSON
227 * as long as the dynamic validly represents a JSON object---i.e. it
228 * can't have non-string keys.)
230 friend std::ostream& operator<<(std::ostream&, dynamic const&);
233 * Returns true if this dynamic is of the specified type.
235 bool isString() const;
236 bool isObject() const;
239 bool isArray() const;
240 bool isDouble() const;
244 * Returns: isInt() || isDouble().
246 bool isNumber() const;
249 * Returns the type of this dynamic.
254 * Extract a value while trying to convert to the specified type.
255 * Throws exceptions if we cannot convert from the real type to the
258 * Note you can only use this to access integral types or strings,
259 * since arrays and objects are generally best delt with as a
262 fbstring asString() const;
263 double asDouble() const;
264 int64_t asInt() const;
268 * Returns: true if this dynamic is null, an empty array, an empty
269 * object, or an empty string.
274 * If this is an array or an object, returns the number of elements
275 * contained. If it is a string, returns the length. Otherwise
278 std::size_t size() const;
281 * You can iterate over the values of the array. Calling these on
282 * non-arrays will throw a TypeError.
284 const_iterator begin() const;
285 const_iterator end() const;
289 * Helper object returned by keys(), values(), and items().
291 template <class T> struct IterableProxy;
295 * You can iterate over the keys, values, or items (std::pair of key and
296 * value) in an object. Calling these on non-objects will throw a TypeError.
298 IterableProxy<const_key_iterator> keys() const;
299 IterableProxy<const_value_iterator> values() const;
300 IterableProxy<const_item_iterator> items() const;
303 * AssociativeContainer-style find interface for objects. Throws if
304 * this is not an object.
306 * Returns: end() if the key is not present, or an iterator pointing
309 const_item_iterator find(dynamic const&) const;
312 * If this is an object, returns whether it contains a field with
313 * the given name. Otherwise throws TypeError.
315 std::size_t count(dynamic const&) const;
318 * For objects or arrays, provides access to sub-fields by index or
321 * Using these with dynamic objects that are not arrays or objects
322 * will throw a TypeError. Using an index that is out of range or
323 * object-element that's not present throws std::out_of_range.
325 dynamic const& at(dynamic const&) const;
326 dynamic& at(dynamic const&);
329 * This works for access to both objects and arrays.
331 * In the case of an array, the index must be an integer, and this will throw
332 * std::out_of_range if it is less than zero or greater than size().
334 * In the case of an object, the non-const overload inserts a null
335 * value if the key isn't present. The const overload will throw
336 * std::out_of_range if the key is not present.
338 * These functions do not invalidate iterators.
340 dynamic& operator[](dynamic const&);
341 dynamic const& operator[](dynamic const&) const;
344 * Only defined for objects, throws TypeError otherwise.
346 * getDefault will return the value associated with the supplied key, the
347 * supplied default otherwise. setDefault will set the key to the supplied
348 * default if it is not yet set, otherwise leaving it. setDefault returns
349 * a reference to the existing value if present, the new value otherwise.
352 getDefault(const dynamic& k, const dynamic& v = dynamic::object) const;
353 dynamic&& getDefault(const dynamic& k, dynamic&& v) const;
354 template<class K, class V = dynamic>
355 dynamic& setDefault(K&& k, V&& v = dynamic::object);
358 * Resizes an array so it has at n elements, using the supplied
359 * default to fill new elements. Throws TypeError if this dynamic
362 * May invalidate iterators.
366 void resize(std::size_t n, dynamic const& = nullptr);
369 * Inserts the supplied key-value pair to an object, or throws if
370 * it's not an object.
372 * Invalidates iterators.
374 template<class K, class V> void insert(K&&, V&& val);
377 * Erase an element from a dynamic object, by key.
379 * Invalidates iterators to the element being erased.
381 * Returns the number of elements erased (i.e. 1 or 0).
383 std::size_t erase(dynamic const& key);
386 * Erase an element from a dynamic object or array, using an
387 * iterator or an iterator range.
389 * In arrays, invalidates iterators to elements after the element
390 * being erased. In objects, invalidates iterators to the elements
393 * Returns a new iterator to the first element beyond any elements
394 * removed, or end() if there are none. (The iteration order does
397 const_iterator erase(const_iterator it);
398 const_iterator erase(const_iterator first, const_iterator last);
400 const_key_iterator erase(const_key_iterator it);
401 const_key_iterator erase(const_key_iterator first, const_key_iterator last);
403 const_value_iterator erase(const_value_iterator it);
404 const_value_iterator erase(const_value_iterator first,
405 const_value_iterator last);
407 const_item_iterator erase(const_item_iterator it);
408 const_item_iterator erase(const_item_iterator first,
409 const_item_iterator last);
411 * Append elements to an array. If this is not an array, throws
414 * Invalidates iterators.
416 void push_back(dynamic const&);
417 void push_back(dynamic&&);
420 * Get a hash code. This function is called by a std::hash<>
421 * specialization, also.
423 * Throws TypeError if this is an object, array, or null.
425 std::size_t hash() const;
428 friend struct TypeError;
431 template<class T> struct TypeInfo;
432 template<class T> struct CompareOp;
433 template<class T> struct GetAddrImpl;
434 template<class T> struct PrintImpl;
436 template<class T> T const& get() const;
437 template<class T> T& get();
438 template<class T> T* get_nothrow();
439 template<class T> T const* get_nothrow() const;
440 template<class T> T* getAddress();
441 template<class T> T const* getAddress() const;
443 template<class T> T asImpl() const;
445 static char const* typeName(Type);
447 void print(std::ostream&) const;
448 void print_as_pseudo_json(std::ostream&) const; // see json.cpp
453 explicit Data() : nul(nullptr) {}
456 // XXX: gcc does an ICE if we use std::nullptr_t instead of void*
457 // here. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50361
466 * Objects are placement new'd here. We have to use a char buffer
467 * because we don't know the type here (std::unordered_map<> with
468 * dynamic would be parameterizing a std:: template with an
469 * incomplete type right now). (Note that in contrast we know it
470 * is ok to do this with fbvector because we own it.)
472 typename std::aligned_storage<
473 sizeof(std::unordered_map<int,int>),
474 alignof(std::unordered_map<int,int>)
475 >::type objectBuffer;
479 //////////////////////////////////////////////////////////////////////
483 #include "folly/dynamic-inl.h"