1 /*
2 * Copyright 2014 Google Inc. All rights reserved.
3 *
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
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16
17 #ifndef FLATBUFFERS_H_
18 #define FLATBUFFERS_H_
19
20 #include "flatbuffers/base.h"
21
22 #if defined(FLATBUFFERS_NAN_DEFAULTS)
23 # include <cmath>
24 #endif
25
26 namespace flatbuffers {
27 // Generic 'operator==' with conditional specialisations.
28 // T e - new value of a scalar field.
29 // T def - default of scalar (is known at compile-time).
IsTheSameAs(T e,T def)30 template<typename T> inline bool IsTheSameAs(T e, T def) { return e == def; }
31
32 #if defined(FLATBUFFERS_NAN_DEFAULTS) && \
33 defined(FLATBUFFERS_HAS_NEW_STRTOD) && (FLATBUFFERS_HAS_NEW_STRTOD > 0)
34 // Like `operator==(e, def)` with weak NaN if T=(float|double).
IsFloatTheSameAs(T e,T def)35 template<typename T> inline bool IsFloatTheSameAs(T e, T def) {
36 return (e == def) || ((def != def) && (e != e));
37 }
38 template<> inline bool IsTheSameAs<float>(float e, float def) {
39 return IsFloatTheSameAs(e, def);
40 }
41 template<> inline bool IsTheSameAs<double>(double e, double def) {
42 return IsFloatTheSameAs(e, def);
43 }
44 #endif
45
46 // Check 'v' is out of closed range [low; high].
47 // Workaround for GCC warning [-Werror=type-limits]:
48 // comparison is always true due to limited range of data type.
49 template<typename T>
IsOutRange(const T & v,const T & low,const T & high)50 inline bool IsOutRange(const T &v, const T &low, const T &high) {
51 return (v < low) || (high < v);
52 }
53
54 // Check 'v' is in closed range [low; high].
55 template<typename T>
IsInRange(const T & v,const T & low,const T & high)56 inline bool IsInRange(const T &v, const T &low, const T &high) {
57 return !IsOutRange(v, low, high);
58 }
59
60 // Wrapper for uoffset_t to allow safe template specialization.
61 // Value is allowed to be 0 to indicate a null object (see e.g. AddOffset).
62 template<typename T> struct Offset {
63 uoffset_t o;
OffsetOffset64 Offset() : o(0) {}
OffsetOffset65 Offset(uoffset_t _o) : o(_o) {}
UnionOffset66 Offset<void> Union() const { return Offset<void>(o); }
IsNullOffset67 bool IsNull() const { return !o; }
68 };
69
EndianCheck()70 inline void EndianCheck() {
71 int endiantest = 1;
72 // If this fails, see FLATBUFFERS_LITTLEENDIAN above.
73 FLATBUFFERS_ASSERT(*reinterpret_cast<char *>(&endiantest) ==
74 FLATBUFFERS_LITTLEENDIAN);
75 (void)endiantest;
76 }
77
AlignOf()78 template<typename T> FLATBUFFERS_CONSTEXPR size_t AlignOf() {
79 // clang-format off
80 #ifdef _MSC_VER
81 return __alignof(T);
82 #else
83 #ifndef alignof
84 return __alignof__(T);
85 #else
86 return alignof(T);
87 #endif
88 #endif
89 // clang-format on
90 }
91
92 // When we read serialized data from memory, in the case of most scalars,
93 // we want to just read T, but in the case of Offset, we want to actually
94 // perform the indirection and return a pointer.
95 // The template specialization below does just that.
96 // It is wrapped in a struct since function templates can't overload on the
97 // return type like this.
98 // The typedef is for the convenience of callers of this function
99 // (avoiding the need for a trailing return decltype)
100 template<typename T> struct IndirectHelper {
101 typedef T return_type;
102 typedef T mutable_return_type;
103 static const size_t element_stride = sizeof(T);
ReadIndirectHelper104 static return_type Read(const uint8_t *p, uoffset_t i) {
105 return EndianScalar((reinterpret_cast<const T *>(p))[i]);
106 }
107 };
108 template<typename T> struct IndirectHelper<Offset<T>> {
109 typedef const T *return_type;
110 typedef T *mutable_return_type;
111 static const size_t element_stride = sizeof(uoffset_t);
112 static return_type Read(const uint8_t *p, uoffset_t i) {
113 p += i * sizeof(uoffset_t);
114 return reinterpret_cast<return_type>(p + ReadScalar<uoffset_t>(p));
115 }
116 };
117 template<typename T> struct IndirectHelper<const T *> {
118 typedef const T *return_type;
119 typedef T *mutable_return_type;
120 static const size_t element_stride = sizeof(T);
121 static return_type Read(const uint8_t *p, uoffset_t i) {
122 return reinterpret_cast<const T *>(p + i * sizeof(T));
123 }
124 };
125
126 // An STL compatible iterator implementation for Vector below, effectively
127 // calling Get() for every element.
128 template<typename T, typename IT> struct VectorIterator {
129 typedef std::random_access_iterator_tag iterator_category;
130 typedef IT value_type;
131 typedef ptrdiff_t difference_type;
132 typedef IT *pointer;
133 typedef IT &reference;
134
135 VectorIterator(const uint8_t *data, uoffset_t i)
136 : data_(data + IndirectHelper<T>::element_stride * i) {}
137 VectorIterator(const VectorIterator &other) : data_(other.data_) {}
138 VectorIterator() : data_(nullptr) {}
139
140 VectorIterator &operator=(const VectorIterator &other) {
141 data_ = other.data_;
142 return *this;
143 }
144
145 // clang-format off
146 #if !defined(FLATBUFFERS_CPP98_STL)
147 VectorIterator &operator=(VectorIterator &&other) {
148 data_ = other.data_;
149 return *this;
150 }
151 #endif // !defined(FLATBUFFERS_CPP98_STL)
152 // clang-format on
153
154 bool operator==(const VectorIterator &other) const {
155 return data_ == other.data_;
156 }
157
158 bool operator<(const VectorIterator &other) const {
159 return data_ < other.data_;
160 }
161
162 bool operator!=(const VectorIterator &other) const {
163 return data_ != other.data_;
164 }
165
166 difference_type operator-(const VectorIterator &other) const {
167 return (data_ - other.data_) / IndirectHelper<T>::element_stride;
168 }
169
170 IT operator*() const { return IndirectHelper<T>::Read(data_, 0); }
171
172 IT operator->() const { return IndirectHelper<T>::Read(data_, 0); }
173
174 VectorIterator &operator++() {
175 data_ += IndirectHelper<T>::element_stride;
176 return *this;
177 }
178
179 VectorIterator operator++(int) {
180 VectorIterator temp(data_, 0);
181 data_ += IndirectHelper<T>::element_stride;
182 return temp;
183 }
184
185 VectorIterator operator+(const uoffset_t &offset) const {
186 return VectorIterator(data_ + offset * IndirectHelper<T>::element_stride,
187 0);
188 }
189
190 VectorIterator &operator+=(const uoffset_t &offset) {
191 data_ += offset * IndirectHelper<T>::element_stride;
192 return *this;
193 }
194
195 VectorIterator &operator--() {
196 data_ -= IndirectHelper<T>::element_stride;
197 return *this;
198 }
199
200 VectorIterator operator--(int) {
201 VectorIterator temp(data_, 0);
202 data_ -= IndirectHelper<T>::element_stride;
203 return temp;
204 }
205
206 VectorIterator operator-(const uoffset_t &offset) const {
207 return VectorIterator(data_ - offset * IndirectHelper<T>::element_stride,
208 0);
209 }
210
211 VectorIterator &operator-=(const uoffset_t &offset) {
212 data_ -= offset * IndirectHelper<T>::element_stride;
213 return *this;
214 }
215
216 private:
217 const uint8_t *data_;
218 };
219
220 template<typename Iterator>
221 struct VectorReverseIterator : public std::reverse_iterator<Iterator> {
222 explicit VectorReverseIterator(Iterator iter)
223 : std::reverse_iterator<Iterator>(iter) {}
224
225 typename Iterator::value_type operator*() const {
226 return *(std::reverse_iterator<Iterator>::current);
227 }
228
229 typename Iterator::value_type operator->() const {
230 return *(std::reverse_iterator<Iterator>::current);
231 }
232 };
233
234 struct String;
235
236 // This is used as a helper type for accessing vectors.
237 // Vector::data() assumes the vector elements start after the length field.
238 template<typename T> class Vector {
239 public:
240 typedef VectorIterator<T, typename IndirectHelper<T>::mutable_return_type>
241 iterator;
242 typedef VectorIterator<T, typename IndirectHelper<T>::return_type>
243 const_iterator;
244 typedef VectorReverseIterator<iterator> reverse_iterator;
245 typedef VectorReverseIterator<const_iterator> const_reverse_iterator;
246
247 uoffset_t size() const { return EndianScalar(length_); }
248
249 // Deprecated: use size(). Here for backwards compatibility.
250 FLATBUFFERS_ATTRIBUTE(deprecated("use size() instead"))
251 uoffset_t Length() const { return size(); }
252
253 typedef typename IndirectHelper<T>::return_type return_type;
254 typedef typename IndirectHelper<T>::mutable_return_type mutable_return_type;
255
256 return_type Get(uoffset_t i) const {
257 FLATBUFFERS_ASSERT(i < size());
258 return IndirectHelper<T>::Read(Data(), i);
259 }
260
261 return_type operator[](uoffset_t i) const { return Get(i); }
262
263 // If this is a Vector of enums, T will be its storage type, not the enum
264 // type. This function makes it convenient to retrieve value with enum
265 // type E.
266 template<typename E> E GetEnum(uoffset_t i) const {
267 return static_cast<E>(Get(i));
268 }
269
270 // If this a vector of unions, this does the cast for you. There's no check
271 // to make sure this is the right type!
272 template<typename U> const U *GetAs(uoffset_t i) const {
273 return reinterpret_cast<const U *>(Get(i));
274 }
275
276 // If this a vector of unions, this does the cast for you. There's no check
277 // to make sure this is actually a string!
278 const String *GetAsString(uoffset_t i) const {
279 return reinterpret_cast<const String *>(Get(i));
280 }
281
282 const void *GetStructFromOffset(size_t o) const {
283 return reinterpret_cast<const void *>(Data() + o);
284 }
285
286 iterator begin() { return iterator(Data(), 0); }
287 const_iterator begin() const { return const_iterator(Data(), 0); }
288
289 iterator end() { return iterator(Data(), size()); }
290 const_iterator end() const { return const_iterator(Data(), size()); }
291
292 reverse_iterator rbegin() { return reverse_iterator(end() - 1); }
293 const_reverse_iterator rbegin() const {
294 return const_reverse_iterator(end() - 1);
295 }
296
297 reverse_iterator rend() { return reverse_iterator(begin() - 1); }
298 const_reverse_iterator rend() const {
299 return const_reverse_iterator(begin() - 1);
300 }
301
302 const_iterator cbegin() const { return begin(); }
303
304 const_iterator cend() const { return end(); }
305
306 const_reverse_iterator crbegin() const { return rbegin(); }
307
308 const_reverse_iterator crend() const { return rend(); }
309
310 // Change elements if you have a non-const pointer to this object.
311 // Scalars only. See reflection.h, and the documentation.
312 void Mutate(uoffset_t i, const T &val) {
313 FLATBUFFERS_ASSERT(i < size());
314 WriteScalar(data() + i, val);
315 }
316
317 // Change an element of a vector of tables (or strings).
318 // "val" points to the new table/string, as you can obtain from
319 // e.g. reflection::AddFlatBuffer().
320 void MutateOffset(uoffset_t i, const uint8_t *val) {
321 FLATBUFFERS_ASSERT(i < size());
322 static_assert(sizeof(T) == sizeof(uoffset_t), "Unrelated types");
323 WriteScalar(data() + i,
324 static_cast<uoffset_t>(val - (Data() + i * sizeof(uoffset_t))));
325 }
326
327 // Get a mutable pointer to tables/strings inside this vector.
328 mutable_return_type GetMutableObject(uoffset_t i) const {
329 FLATBUFFERS_ASSERT(i < size());
330 return const_cast<mutable_return_type>(IndirectHelper<T>::Read(Data(), i));
331 }
332
333 // The raw data in little endian format. Use with care.
334 const uint8_t *Data() const {
335 return reinterpret_cast<const uint8_t *>(&length_ + 1);
336 }
337
338 uint8_t *Data() { return reinterpret_cast<uint8_t *>(&length_ + 1); }
339
340 // Similarly, but typed, much like std::vector::data
341 const T *data() const { return reinterpret_cast<const T *>(Data()); }
342 T *data() { return reinterpret_cast<T *>(Data()); }
343
344 template<typename K> return_type LookupByKey(K key) const {
345 void *search_result = std::bsearch(
346 &key, Data(), size(), IndirectHelper<T>::element_stride, KeyCompare<K>);
347
348 if (!search_result) {
349 return nullptr; // Key not found.
350 }
351
352 const uint8_t *element = reinterpret_cast<const uint8_t *>(search_result);
353
354 return IndirectHelper<T>::Read(element, 0);
355 }
356
357 protected:
358 // This class is only used to access pre-existing data. Don't ever
359 // try to construct these manually.
360 Vector();
361
362 uoffset_t length_;
363
364 private:
365 // This class is a pointer. Copying will therefore create an invalid object.
366 // Private and unimplemented copy constructor.
367 Vector(const Vector &);
368 Vector &operator=(const Vector &);
369
370 template<typename K> static int KeyCompare(const void *ap, const void *bp) {
371 const K *key = reinterpret_cast<const K *>(ap);
372 const uint8_t *data = reinterpret_cast<const uint8_t *>(bp);
373 auto table = IndirectHelper<T>::Read(data, 0);
374
375 // std::bsearch compares with the operands transposed, so we negate the
376 // result here.
377 return -table->KeyCompareWithValue(*key);
378 }
379 };
380
381 // Represent a vector much like the template above, but in this case we
382 // don't know what the element types are (used with reflection.h).
383 class VectorOfAny {
384 public:
385 uoffset_t size() const { return EndianScalar(length_); }
386
387 const uint8_t *Data() const {
388 return reinterpret_cast<const uint8_t *>(&length_ + 1);
389 }
390 uint8_t *Data() { return reinterpret_cast<uint8_t *>(&length_ + 1); }
391
392 protected:
393 VectorOfAny();
394
395 uoffset_t length_;
396
397 private:
398 VectorOfAny(const VectorOfAny &);
399 VectorOfAny &operator=(const VectorOfAny &);
400 };
401
402 #ifndef FLATBUFFERS_CPP98_STL
403 template<typename T, typename U>
404 Vector<Offset<T>> *VectorCast(Vector<Offset<U>> *ptr) {
405 static_assert(std::is_base_of<T, U>::value, "Unrelated types");
406 return reinterpret_cast<Vector<Offset<T>> *>(ptr);
407 }
408
409 template<typename T, typename U>
410 const Vector<Offset<T>> *VectorCast(const Vector<Offset<U>> *ptr) {
411 static_assert(std::is_base_of<T, U>::value, "Unrelated types");
412 return reinterpret_cast<const Vector<Offset<T>> *>(ptr);
413 }
414 #endif
415
416 // Convenient helper function to get the length of any vector, regardless
417 // of whether it is null or not (the field is not set).
418 template<typename T> static inline size_t VectorLength(const Vector<T> *v) {
419 return v ? v->size() : 0;
420 }
421
422 // This is used as a helper type for accessing arrays.
423 template<typename T, uint16_t length> class Array {
424 typedef
425 typename flatbuffers::integral_constant<bool,
426 flatbuffers::is_scalar<T>::value>
427 scalar_tag;
428 typedef
429 typename flatbuffers::conditional<scalar_tag::value, T, const T *>::type
430 IndirectHelperType;
431
432 public:
433 typedef typename IndirectHelper<IndirectHelperType>::return_type return_type;
434 typedef VectorIterator<T, return_type> const_iterator;
435 typedef VectorReverseIterator<const_iterator> const_reverse_iterator;
436
437 FLATBUFFERS_CONSTEXPR uint16_t size() const { return length; }
438
439 return_type Get(uoffset_t i) const {
440 FLATBUFFERS_ASSERT(i < size());
441 return IndirectHelper<IndirectHelperType>::Read(Data(), i);
442 }
443
444 return_type operator[](uoffset_t i) const { return Get(i); }
445
446 // If this is a Vector of enums, T will be its storage type, not the enum
447 // type. This function makes it convenient to retrieve value with enum
448 // type E.
449 template<typename E> E GetEnum(uoffset_t i) const {
450 return static_cast<E>(Get(i));
451 }
452
453 const_iterator begin() const { return const_iterator(Data(), 0); }
454 const_iterator end() const { return const_iterator(Data(), size()); }
455
456 const_reverse_iterator rbegin() const {
457 return const_reverse_iterator(end());
458 }
459 const_reverse_iterator rend() const { return const_reverse_iterator(end()); }
460
461 const_iterator cbegin() const { return begin(); }
462 const_iterator cend() const { return end(); }
463
464 const_reverse_iterator crbegin() const { return rbegin(); }
465 const_reverse_iterator crend() const { return rend(); }
466
467 // Get a mutable pointer to elements inside this array.
468 // This method used to mutate arrays of structs followed by a @p Mutate
469 // operation. For primitive types use @p Mutate directly.
470 // @warning Assignments and reads to/from the dereferenced pointer are not
471 // automatically converted to the correct endianness.
472 typename flatbuffers::conditional<scalar_tag::value, void, T *>::type
473 GetMutablePointer(uoffset_t i) const {
474 FLATBUFFERS_ASSERT(i < size());
475 return const_cast<T *>(&data()[i]);
476 }
477
478 // Change elements if you have a non-const pointer to this object.
479 void Mutate(uoffset_t i, const T &val) { MutateImpl(scalar_tag(), i, val); }
480
481 // The raw data in little endian format. Use with care.
482 const uint8_t *Data() const { return data_; }
483
484 uint8_t *Data() { return data_; }
485
486 // Similarly, but typed, much like std::vector::data
487 const T *data() const { return reinterpret_cast<const T *>(Data()); }
488 T *data() { return reinterpret_cast<T *>(Data()); }
489
490 protected:
491 void MutateImpl(flatbuffers::integral_constant<bool, true>, uoffset_t i,
492 const T &val) {
493 FLATBUFFERS_ASSERT(i < size());
494 WriteScalar(data() + i, val);
495 }
496
497 void MutateImpl(flatbuffers::integral_constant<bool, false>, uoffset_t i,
498 const T &val) {
499 *(GetMutablePointer(i)) = val;
500 }
501
502 // This class is only used to access pre-existing data. Don't ever
503 // try to construct these manually.
504 // 'constexpr' allows us to use 'size()' at compile time.
505 // @note Must not use 'FLATBUFFERS_CONSTEXPR' here, as const is not allowed on
506 // a constructor.
507 #if defined(__cpp_constexpr)
508 constexpr Array();
509 #else
510 Array();
511 #endif
512
513 uint8_t data_[length * sizeof(T)];
514
515 private:
516 // This class is a pointer. Copying will therefore create an invalid object.
517 // Private and unimplemented copy constructor.
518 Array(const Array &);
519 Array &operator=(const Array &);
520 };
521
522 // Specialization for Array[struct] with access using Offset<void> pointer.
523 // This specialization used by idl_gen_text.cpp.
524 template<typename T, uint16_t length> class Array<Offset<T>, length> {
525 static_assert(flatbuffers::is_same<T, void>::value, "unexpected type T");
526
527 public:
528 typedef const void *return_type;
529
530 const uint8_t *Data() const { return data_; }
531
532 // Make idl_gen_text.cpp::PrintContainer happy.
533 return_type operator[](uoffset_t) const {
534 FLATBUFFERS_ASSERT(false);
535 return nullptr;
536 }
537
538 private:
539 // This class is only used to access pre-existing data.
540 Array();
541 Array(const Array &);
542 Array &operator=(const Array &);
543
544 uint8_t data_[1];
545 };
546
547 // Lexicographically compare two strings (possibly containing nulls), and
548 // return true if the first is less than the second.
549 static inline bool StringLessThan(const char *a_data, uoffset_t a_size,
550 const char *b_data, uoffset_t b_size) {
551 const auto cmp = memcmp(a_data, b_data, (std::min)(a_size, b_size));
552 return cmp == 0 ? a_size < b_size : cmp < 0;
553 }
554
555 struct String : public Vector<char> {
556 const char *c_str() const { return reinterpret_cast<const char *>(Data()); }
557 std::string str() const { return std::string(c_str(), size()); }
558
559 // clang-format off
560 #ifdef FLATBUFFERS_HAS_STRING_VIEW
561 flatbuffers::string_view string_view() const {
562 return flatbuffers::string_view(c_str(), size());
563 }
564 #endif // FLATBUFFERS_HAS_STRING_VIEW
565 // clang-format on
566
567 bool operator<(const String &o) const {
568 return StringLessThan(this->data(), this->size(), o.data(), o.size());
569 }
570 };
571
572 // Convenience function to get std::string from a String returning an empty
573 // string on null pointer.
574 static inline std::string GetString(const String *str) {
575 return str ? str->str() : "";
576 }
577
578 // Convenience function to get char* from a String returning an empty string on
579 // null pointer.
580 static inline const char *GetCstring(const String *str) {
581 return str ? str->c_str() : "";
582 }
583
584 #ifdef FLATBUFFERS_HAS_STRING_VIEW
585 // Convenience function to get string_view from a String returning an empty
586 // string_view on null pointer.
587 static inline flatbuffers::string_view GetStringView(const String *str) {
588 return str ? str->string_view() : flatbuffers::string_view();
589 }
590 #endif // FLATBUFFERS_HAS_STRING_VIEW
591
592 // Allocator interface. This is flatbuffers-specific and meant only for
593 // `vector_downward` usage.
594 class Allocator {
595 public:
596 virtual ~Allocator() {}
597
598 // Allocate `size` bytes of memory.
599 virtual uint8_t *allocate(size_t size) = 0;
600
601 // Deallocate `size` bytes of memory at `p` allocated by this allocator.
602 virtual void deallocate(uint8_t *p, size_t size) = 0;
603
604 // Reallocate `new_size` bytes of memory, replacing the old region of size
605 // `old_size` at `p`. In contrast to a normal realloc, this grows downwards,
606 // and is intended specifcally for `vector_downward` use.
607 // `in_use_back` and `in_use_front` indicate how much of `old_size` is
608 // actually in use at each end, and needs to be copied.
609 virtual uint8_t *reallocate_downward(uint8_t *old_p, size_t old_size,
610 size_t new_size, size_t in_use_back,
611 size_t in_use_front) {
612 FLATBUFFERS_ASSERT(new_size > old_size); // vector_downward only grows
613 uint8_t *new_p = allocate(new_size);
614 memcpy_downward(old_p, old_size, new_p, new_size, in_use_back,
615 in_use_front);
616 deallocate(old_p, old_size);
617 return new_p;
618 }
619
620 protected:
621 // Called by `reallocate_downward` to copy memory from `old_p` of `old_size`
622 // to `new_p` of `new_size`. Only memory of size `in_use_front` and
623 // `in_use_back` will be copied from the front and back of the old memory
624 // allocation.
625 void memcpy_downward(uint8_t *old_p, size_t old_size, uint8_t *new_p,
626 size_t new_size, size_t in_use_back,
627 size_t in_use_front) {
628 memcpy(new_p + new_size - in_use_back, old_p + old_size - in_use_back,
629 in_use_back);
630 memcpy(new_p, old_p, in_use_front);
631 }
632 };
633
634 // DefaultAllocator uses new/delete to allocate memory regions
635 class DefaultAllocator : public Allocator {
636 public:
637 uint8_t *allocate(size_t size) FLATBUFFERS_OVERRIDE {
638 return new uint8_t[size];
639 }
640
641 void deallocate(uint8_t *p, size_t) FLATBUFFERS_OVERRIDE { delete[] p; }
642
643 static void dealloc(void *p, size_t) { delete[] static_cast<uint8_t *>(p); }
644 };
645
646 // These functions allow for a null allocator to mean use the default allocator,
647 // as used by DetachedBuffer and vector_downward below.
648 // This is to avoid having a statically or dynamically allocated default
649 // allocator, or having to move it between the classes that may own it.
650 inline uint8_t *Allocate(Allocator *allocator, size_t size) {
651 return allocator ? allocator->allocate(size)
652 : DefaultAllocator().allocate(size);
653 }
654
655 inline void Deallocate(Allocator *allocator, uint8_t *p, size_t size) {
656 if (allocator)
657 allocator->deallocate(p, size);
658 else
659 DefaultAllocator().deallocate(p, size);
660 }
661
662 inline uint8_t *ReallocateDownward(Allocator *allocator, uint8_t *old_p,
663 size_t old_size, size_t new_size,
664 size_t in_use_back, size_t in_use_front) {
665 return allocator ? allocator->reallocate_downward(old_p, old_size, new_size,
666 in_use_back, in_use_front)
667 : DefaultAllocator().reallocate_downward(
668 old_p, old_size, new_size, in_use_back, in_use_front);
669 }
670
671 // DetachedBuffer is a finished flatbuffer memory region, detached from its
672 // builder. The original memory region and allocator are also stored so that
673 // the DetachedBuffer can manage the memory lifetime.
674 class DetachedBuffer {
675 public:
676 DetachedBuffer()
677 : allocator_(nullptr),
678 own_allocator_(false),
679 buf_(nullptr),
680 reserved_(0),
681 cur_(nullptr),
682 size_(0) {}
683
684 DetachedBuffer(Allocator *allocator, bool own_allocator, uint8_t *buf,
685 size_t reserved, uint8_t *cur, size_t sz)
686 : allocator_(allocator),
687 own_allocator_(own_allocator),
688 buf_(buf),
689 reserved_(reserved),
690 cur_(cur),
691 size_(sz) {}
692
693 // clang-format off
694 #if !defined(FLATBUFFERS_CPP98_STL)
695 // clang-format on
696 DetachedBuffer(DetachedBuffer &&other)
697 : allocator_(other.allocator_),
698 own_allocator_(other.own_allocator_),
699 buf_(other.buf_),
700 reserved_(other.reserved_),
701 cur_(other.cur_),
702 size_(other.size_) {
703 other.reset();
704 }
705 // clang-format off
706 #endif // !defined(FLATBUFFERS_CPP98_STL)
707 // clang-format on
708
709 // clang-format off
710 #if !defined(FLATBUFFERS_CPP98_STL)
711 // clang-format on
712 DetachedBuffer &operator=(DetachedBuffer &&other) {
713 if (this == &other) return *this;
714
715 destroy();
716
717 allocator_ = other.allocator_;
718 own_allocator_ = other.own_allocator_;
719 buf_ = other.buf_;
720 reserved_ = other.reserved_;
721 cur_ = other.cur_;
722 size_ = other.size_;
723
724 other.reset();
725
726 return *this;
727 }
728 // clang-format off
729 #endif // !defined(FLATBUFFERS_CPP98_STL)
730 // clang-format on
731
732 ~DetachedBuffer() { destroy(); }
733
734 const uint8_t *data() const { return cur_; }
735
736 uint8_t *data() { return cur_; }
737
738 size_t size() const { return size_; }
739
740 // clang-format off
741 #if 0 // disabled for now due to the ordering of classes in this header
742 template <class T>
743 bool Verify() const {
744 Verifier verifier(data(), size());
745 return verifier.Verify<T>(nullptr);
746 }
747
748 template <class T>
749 const T* GetRoot() const {
750 return flatbuffers::GetRoot<T>(data());
751 }
752
753 template <class T>
754 T* GetRoot() {
755 return flatbuffers::GetRoot<T>(data());
756 }
757 #endif
758 // clang-format on
759
760 // clang-format off
761 #if !defined(FLATBUFFERS_CPP98_STL)
762 // clang-format on
763 // These may change access mode, leave these at end of public section
764 FLATBUFFERS_DELETE_FUNC(DetachedBuffer(const DetachedBuffer &other))
765 FLATBUFFERS_DELETE_FUNC(
766 DetachedBuffer &operator=(const DetachedBuffer &other))
767 // clang-format off
768 #endif // !defined(FLATBUFFERS_CPP98_STL)
769 // clang-format on
770
771 protected:
772 Allocator *allocator_;
773 bool own_allocator_;
774 uint8_t *buf_;
775 size_t reserved_;
776 uint8_t *cur_;
777 size_t size_;
778
779 inline void destroy() {
780 if (buf_) Deallocate(allocator_, buf_, reserved_);
781 if (own_allocator_ && allocator_) { delete allocator_; }
782 reset();
783 }
784
785 inline void reset() {
786 allocator_ = nullptr;
787 own_allocator_ = false;
788 buf_ = nullptr;
789 reserved_ = 0;
790 cur_ = nullptr;
791 size_ = 0;
792 }
793 };
794
795 // This is a minimal replication of std::vector<uint8_t> functionality,
796 // except growing from higher to lower addresses. i.e push_back() inserts data
797 // in the lowest address in the vector.
798 // Since this vector leaves the lower part unused, we support a "scratch-pad"
799 // that can be stored there for temporary data, to share the allocated space.
800 // Essentially, this supports 2 std::vectors in a single buffer.
801 class vector_downward {
802 public:
803 explicit vector_downward(size_t initial_size, Allocator *allocator,
804 bool own_allocator, size_t buffer_minalign)
805 : allocator_(allocator),
806 own_allocator_(own_allocator),
807 initial_size_(initial_size),
808 buffer_minalign_(buffer_minalign),
809 reserved_(0),
810 buf_(nullptr),
811 cur_(nullptr),
812 scratch_(nullptr) {}
813
814 // clang-format off
815 #if !defined(FLATBUFFERS_CPP98_STL)
816 vector_downward(vector_downward &&other)
817 #else
818 vector_downward(vector_downward &other)
819 #endif // defined(FLATBUFFERS_CPP98_STL)
820 // clang-format on
821 : allocator_(other.allocator_),
822 own_allocator_(other.own_allocator_),
823 initial_size_(other.initial_size_),
824 buffer_minalign_(other.buffer_minalign_),
825 reserved_(other.reserved_),
826 buf_(other.buf_),
827 cur_(other.cur_),
828 scratch_(other.scratch_) {
829 // No change in other.allocator_
830 // No change in other.initial_size_
831 // No change in other.buffer_minalign_
832 other.own_allocator_ = false;
833 other.reserved_ = 0;
834 other.buf_ = nullptr;
835 other.cur_ = nullptr;
836 other.scratch_ = nullptr;
837 }
838
839 // clang-format off
840 #if !defined(FLATBUFFERS_CPP98_STL)
841 // clang-format on
842 vector_downward &operator=(vector_downward &&other) {
843 // Move construct a temporary and swap idiom
844 vector_downward temp(std::move(other));
845 swap(temp);
846 return *this;
847 }
848 // clang-format off
849 #endif // defined(FLATBUFFERS_CPP98_STL)
850 // clang-format on
851
852 ~vector_downward() {
853 clear_buffer();
854 clear_allocator();
855 }
856
857 void reset() {
858 clear_buffer();
859 clear();
860 }
861
862 void clear() {
863 if (buf_) {
864 cur_ = buf_ + reserved_;
865 } else {
866 reserved_ = 0;
867 cur_ = nullptr;
868 }
869 clear_scratch();
870 }
871
872 void clear_scratch() { scratch_ = buf_; }
873
874 void clear_allocator() {
875 if (own_allocator_ && allocator_) { delete allocator_; }
876 allocator_ = nullptr;
877 own_allocator_ = false;
878 }
879
880 void clear_buffer() {
881 if (buf_) Deallocate(allocator_, buf_, reserved_);
882 buf_ = nullptr;
883 }
884
885 // Relinquish the pointer to the caller.
886 uint8_t *release_raw(size_t &allocated_bytes, size_t &offset) {
887 auto *buf = buf_;
888 allocated_bytes = reserved_;
889 offset = static_cast<size_t>(cur_ - buf_);
890
891 // release_raw only relinquishes the buffer ownership.
892 // Does not deallocate or reset the allocator. Destructor will do that.
893 buf_ = nullptr;
894 clear();
895 return buf;
896 }
897
898 // Relinquish the pointer to the caller.
899 DetachedBuffer release() {
900 // allocator ownership (if any) is transferred to DetachedBuffer.
901 DetachedBuffer fb(allocator_, own_allocator_, buf_, reserved_, cur_,
902 size());
903 if (own_allocator_) {
904 allocator_ = nullptr;
905 own_allocator_ = false;
906 }
907 buf_ = nullptr;
908 clear();
909 return fb;
910 }
911
912 size_t ensure_space(size_t len) {
913 FLATBUFFERS_ASSERT(cur_ >= scratch_ && scratch_ >= buf_);
914 if (len > static_cast<size_t>(cur_ - scratch_)) { reallocate(len); }
915 // Beyond this, signed offsets may not have enough range:
916 // (FlatBuffers > 2GB not supported).
917 FLATBUFFERS_ASSERT(size() < FLATBUFFERS_MAX_BUFFER_SIZE);
918 return len;
919 }
920
921 inline uint8_t *make_space(size_t len) {
922 size_t space = ensure_space(len);
923 cur_ -= space;
924 return cur_;
925 }
926
927 // Returns nullptr if using the DefaultAllocator.
928 Allocator *get_custom_allocator() { return allocator_; }
929
930 uoffset_t size() const {
931 return static_cast<uoffset_t>(reserved_ - (cur_ - buf_));
932 }
933
934 uoffset_t scratch_size() const {
935 return static_cast<uoffset_t>(scratch_ - buf_);
936 }
937
938 size_t capacity() const { return reserved_; }
939
940 uint8_t *data() const {
941 FLATBUFFERS_ASSERT(cur_);
942 return cur_;
943 }
944
945 uint8_t *scratch_data() const {
946 FLATBUFFERS_ASSERT(buf_);
947 return buf_;
948 }
949
950 uint8_t *scratch_end() const {
951 FLATBUFFERS_ASSERT(scratch_);
952 return scratch_;
953 }
954
955 uint8_t *data_at(size_t offset) const { return buf_ + reserved_ - offset; }
956
957 void push(const uint8_t *bytes, size_t num) {
958 if (num > 0) { memcpy(make_space(num), bytes, num); }
959 }
960
961 // Specialized version of push() that avoids memcpy call for small data.
962 template<typename T> void push_small(const T &little_endian_t) {
963 make_space(sizeof(T));
964 *reinterpret_cast<T *>(cur_) = little_endian_t;
965 }
966
967 template<typename T> void scratch_push_small(const T &t) {
968 ensure_space(sizeof(T));
969 *reinterpret_cast<T *>(scratch_) = t;
970 scratch_ += sizeof(T);
971 }
972
973 // fill() is most frequently called with small byte counts (<= 4),
974 // which is why we're using loops rather than calling memset.
975 void fill(size_t zero_pad_bytes) {
976 make_space(zero_pad_bytes);
977 for (size_t i = 0; i < zero_pad_bytes; i++) cur_[i] = 0;
978 }
979
980 // Version for when we know the size is larger.
981 // Precondition: zero_pad_bytes > 0
982 void fill_big(size_t zero_pad_bytes) {
983 memset(make_space(zero_pad_bytes), 0, zero_pad_bytes);
984 }
985
986 void pop(size_t bytes_to_remove) { cur_ += bytes_to_remove; }
987 void scratch_pop(size_t bytes_to_remove) { scratch_ -= bytes_to_remove; }
988
989 void swap(vector_downward &other) {
990 using std::swap;
991 swap(allocator_, other.allocator_);
992 swap(own_allocator_, other.own_allocator_);
993 swap(initial_size_, other.initial_size_);
994 swap(buffer_minalign_, other.buffer_minalign_);
995 swap(reserved_, other.reserved_);
996 swap(buf_, other.buf_);
997 swap(cur_, other.cur_);
998 swap(scratch_, other.scratch_);
999 }
1000
1001 void swap_allocator(vector_downward &other) {
1002 using std::swap;
1003 swap(allocator_, other.allocator_);
1004 swap(own_allocator_, other.own_allocator_);
1005 }
1006
1007 private:
1008 // You shouldn't really be copying instances of this class.
1009 FLATBUFFERS_DELETE_FUNC(vector_downward(const vector_downward &))
1010 FLATBUFFERS_DELETE_FUNC(vector_downward &operator=(const vector_downward &))
1011
1012 Allocator *allocator_;
1013 bool own_allocator_;
1014 size_t initial_size_;
1015 size_t buffer_minalign_;
1016 size_t reserved_;
1017 uint8_t *buf_;
1018 uint8_t *cur_; // Points at location between empty (below) and used (above).
1019 uint8_t *scratch_; // Points to the end of the scratchpad in use.
1020
1021 void reallocate(size_t len) {
1022 auto old_reserved = reserved_;
1023 auto old_size = size();
1024 auto old_scratch_size = scratch_size();
1025 reserved_ +=
1026 (std::max)(len, old_reserved ? old_reserved / 2 : initial_size_);
1027 reserved_ = (reserved_ + buffer_minalign_ - 1) & ~(buffer_minalign_ - 1);
1028 if (buf_) {
1029 buf_ = ReallocateDownward(allocator_, buf_, old_reserved, reserved_,
1030 old_size, old_scratch_size);
1031 } else {
1032 buf_ = Allocate(allocator_, reserved_);
1033 }
1034 cur_ = buf_ + reserved_ - old_size;
1035 scratch_ = buf_ + old_scratch_size;
1036 }
1037 };
1038
1039 // Converts a Field ID to a virtual table offset.
1040 inline voffset_t FieldIndexToOffset(voffset_t field_id) {
1041 // Should correspond to what EndTable() below builds up.
1042 const int fixed_fields = 2; // Vtable size and Object Size.
1043 return static_cast<voffset_t>((field_id + fixed_fields) * sizeof(voffset_t));
1044 }
1045
1046 template<typename T, typename Alloc>
1047 const T *data(const std::vector<T, Alloc> &v) {
1048 // Eventually the returned pointer gets passed down to memcpy, so
1049 // we need it to be non-null to avoid undefined behavior.
1050 static uint8_t t;
1051 return v.empty() ? reinterpret_cast<const T *>(&t) : &v.front();
1052 }
1053 template<typename T, typename Alloc> T *data(std::vector<T, Alloc> &v) {
1054 // Eventually the returned pointer gets passed down to memcpy, so
1055 // we need it to be non-null to avoid undefined behavior.
1056 static uint8_t t;
1057 return v.empty() ? reinterpret_cast<T *>(&t) : &v.front();
1058 }
1059
1060 /// @endcond
1061
1062 /// @addtogroup flatbuffers_cpp_api
1063 /// @{
1064 /// @class FlatBufferBuilder
1065 /// @brief Helper class to hold data needed in creation of a FlatBuffer.
1066 /// To serialize data, you typically call one of the `Create*()` functions in
1067 /// the generated code, which in turn call a sequence of `StartTable`/
1068 /// `PushElement`/`AddElement`/`EndTable`, or the builtin `CreateString`/
1069 /// `CreateVector` functions. Do this is depth-first order to build up a tree to
1070 /// the root. `Finish()` wraps up the buffer ready for transport.
1071 class FlatBufferBuilder {
1072 public:
1073 /// @brief Default constructor for FlatBufferBuilder.
1074 /// @param[in] initial_size The initial size of the buffer, in bytes. Defaults
1075 /// to `1024`.
1076 /// @param[in] allocator An `Allocator` to use. If null will use
1077 /// `DefaultAllocator`.
1078 /// @param[in] own_allocator Whether the builder/vector should own the
1079 /// allocator. Defaults to / `false`.
1080 /// @param[in] buffer_minalign Force the buffer to be aligned to the given
1081 /// minimum alignment upon reallocation. Only needed if you intend to store
1082 /// types with custom alignment AND you wish to read the buffer in-place
1083 /// directly after creation.
1084 explicit FlatBufferBuilder(
1085 size_t initial_size = 1024, Allocator *allocator = nullptr,
1086 bool own_allocator = false,
1087 size_t buffer_minalign = AlignOf<largest_scalar_t>())
1088 : buf_(initial_size, allocator, own_allocator, buffer_minalign),
1089 num_field_loc(0),
1090 max_voffset_(0),
1091 nested(false),
1092 finished(false),
1093 minalign_(1),
1094 force_defaults_(false),
1095 dedup_vtables_(true),
1096 string_pool(nullptr) {
1097 EndianCheck();
1098 }
1099
1100 // clang-format off
1101 /// @brief Move constructor for FlatBufferBuilder.
1102 #if !defined(FLATBUFFERS_CPP98_STL)
1103 FlatBufferBuilder(FlatBufferBuilder &&other)
1104 #else
1105 FlatBufferBuilder(FlatBufferBuilder &other)
1106 #endif // #if !defined(FLATBUFFERS_CPP98_STL)
1107 : buf_(1024, nullptr, false, AlignOf<largest_scalar_t>()),
1108 num_field_loc(0),
1109 max_voffset_(0),
1110 nested(false),
1111 finished(false),
1112 minalign_(1),
1113 force_defaults_(false),
1114 dedup_vtables_(true),
1115 string_pool(nullptr) {
1116 EndianCheck();
1117 // Default construct and swap idiom.
1118 // Lack of delegating constructors in vs2010 makes it more verbose than needed.
1119 Swap(other);
1120 }
1121 // clang-format on
1122
1123 // clang-format off
1124 #if !defined(FLATBUFFERS_CPP98_STL)
1125 // clang-format on
1126 /// @brief Move assignment operator for FlatBufferBuilder.
1127 FlatBufferBuilder &operator=(FlatBufferBuilder &&other) {
1128 // Move construct a temporary and swap idiom
1129 FlatBufferBuilder temp(std::move(other));
1130 Swap(temp);
1131 return *this;
1132 }
1133 // clang-format off
1134 #endif // defined(FLATBUFFERS_CPP98_STL)
1135 // clang-format on
1136
1137 void Swap(FlatBufferBuilder &other) {
1138 using std::swap;
1139 buf_.swap(other.buf_);
1140 swap(num_field_loc, other.num_field_loc);
1141 swap(max_voffset_, other.max_voffset_);
1142 swap(nested, other.nested);
1143 swap(finished, other.finished);
1144 swap(minalign_, other.minalign_);
1145 swap(force_defaults_, other.force_defaults_);
1146 swap(dedup_vtables_, other.dedup_vtables_);
1147 swap(string_pool, other.string_pool);
1148 }
1149
1150 ~FlatBufferBuilder() {
1151 if (string_pool) delete string_pool;
1152 }
1153
1154 void Reset() {
1155 Clear(); // clear builder state
1156 buf_.reset(); // deallocate buffer
1157 }
1158
1159 /// @brief Reset all the state in this FlatBufferBuilder so it can be reused
1160 /// to construct another buffer.
1161 void Clear() {
1162 ClearOffsets();
1163 buf_.clear();
1164 nested = false;
1165 finished = false;
1166 minalign_ = 1;
1167 if (string_pool) string_pool->clear();
1168 }
1169
1170 /// @brief The current size of the serialized buffer, counting from the end.
1171 /// @return Returns an `uoffset_t` with the current size of the buffer.
1172 uoffset_t GetSize() const { return buf_.size(); }
1173
1174 /// @brief Get the serialized buffer (after you call `Finish()`).
1175 /// @return Returns an `uint8_t` pointer to the FlatBuffer data inside the
1176 /// buffer.
1177 uint8_t *GetBufferPointer() const {
1178 Finished();
1179 return buf_.data();
1180 }
1181
1182 /// @brief Get a pointer to an unfinished buffer.
1183 /// @return Returns a `uint8_t` pointer to the unfinished buffer.
1184 uint8_t *GetCurrentBufferPointer() const { return buf_.data(); }
1185
1186 /// @brief Get the released pointer to the serialized buffer.
1187 /// @warning Do NOT attempt to use this FlatBufferBuilder afterwards!
1188 /// @return A `FlatBuffer` that owns the buffer and its allocator and
1189 /// behaves similar to a `unique_ptr` with a deleter.
1190 FLATBUFFERS_ATTRIBUTE(deprecated("use Release() instead"))
1191 DetachedBuffer ReleaseBufferPointer() {
1192 Finished();
1193 return buf_.release();
1194 }
1195
1196 /// @brief Get the released DetachedBuffer.
1197 /// @return A `DetachedBuffer` that owns the buffer and its allocator.
1198 DetachedBuffer Release() {
1199 Finished();
1200 return buf_.release();
1201 }
1202
1203 /// @brief Get the released pointer to the serialized buffer.
1204 /// @param size The size of the memory block containing
1205 /// the serialized `FlatBuffer`.
1206 /// @param offset The offset from the released pointer where the finished
1207 /// `FlatBuffer` starts.
1208 /// @return A raw pointer to the start of the memory block containing
1209 /// the serialized `FlatBuffer`.
1210 /// @remark If the allocator is owned, it gets deleted when the destructor is
1211 /// called..
1212 uint8_t *ReleaseRaw(size_t &size, size_t &offset) {
1213 Finished();
1214 return buf_.release_raw(size, offset);
1215 }
1216
1217 /// @brief get the minimum alignment this buffer needs to be accessed
1218 /// properly. This is only known once all elements have been written (after
1219 /// you call Finish()). You can use this information if you need to embed
1220 /// a FlatBuffer in some other buffer, such that you can later read it
1221 /// without first having to copy it into its own buffer.
1222 size_t GetBufferMinAlignment() {
1223 Finished();
1224 return minalign_;
1225 }
1226
1227 /// @cond FLATBUFFERS_INTERNAL
1228 void Finished() const {
1229 // If you get this assert, you're attempting to get access a buffer
1230 // which hasn't been finished yet. Be sure to call
1231 // FlatBufferBuilder::Finish with your root table.
1232 // If you really need to access an unfinished buffer, call
1233 // GetCurrentBufferPointer instead.
1234 FLATBUFFERS_ASSERT(finished);
1235 }
1236 /// @endcond
1237
1238 /// @brief In order to save space, fields that are set to their default value
1239 /// don't get serialized into the buffer.
1240 /// @param[in] fd When set to `true`, always serializes default values that
1241 /// are set. Optional fields which are not set explicitly, will still not be
1242 /// serialized.
1243 void ForceDefaults(bool fd) { force_defaults_ = fd; }
1244
1245 /// @brief By default vtables are deduped in order to save space.
1246 /// @param[in] dedup When set to `true`, dedup vtables.
1247 void DedupVtables(bool dedup) { dedup_vtables_ = dedup; }
1248
1249 /// @cond FLATBUFFERS_INTERNAL
1250 void Pad(size_t num_bytes) { buf_.fill(num_bytes); }
1251
1252 void TrackMinAlign(size_t elem_size) {
1253 if (elem_size > minalign_) minalign_ = elem_size;
1254 }
1255
1256 void Align(size_t elem_size) {
1257 TrackMinAlign(elem_size);
1258 buf_.fill(PaddingBytes(buf_.size(), elem_size));
1259 }
1260
1261 void PushFlatBuffer(const uint8_t *bytes, size_t size) {
1262 PushBytes(bytes, size);
1263 finished = true;
1264 }
1265
1266 void PushBytes(const uint8_t *bytes, size_t size) { buf_.push(bytes, size); }
1267
1268 void PopBytes(size_t amount) { buf_.pop(amount); }
1269
1270 template<typename T> void AssertScalarT() {
1271 // The code assumes power of 2 sizes and endian-swap-ability.
1272 static_assert(flatbuffers::is_scalar<T>::value, "T must be a scalar type");
1273 }
1274
1275 // Write a single aligned scalar to the buffer
1276 template<typename T> uoffset_t PushElement(T element) {
1277 AssertScalarT<T>();
1278 T litle_endian_element = EndianScalar(element);
1279 Align(sizeof(T));
1280 buf_.push_small(litle_endian_element);
1281 return GetSize();
1282 }
1283
1284 template<typename T> uoffset_t PushElement(Offset<T> off) {
1285 // Special case for offsets: see ReferTo below.
1286 return PushElement(ReferTo(off.o));
1287 }
1288
1289 // When writing fields, we track where they are, so we can create correct
1290 // vtables later.
1291 void TrackField(voffset_t field, uoffset_t off) {
1292 FieldLoc fl = { off, field };
1293 buf_.scratch_push_small(fl);
1294 num_field_loc++;
1295 max_voffset_ = (std::max)(max_voffset_, field);
1296 }
1297
1298 // Like PushElement, but additionally tracks the field this represents.
1299 template<typename T> void AddElement(voffset_t field, T e, T def) {
1300 // We don't serialize values equal to the default.
1301 if (IsTheSameAs(e, def) && !force_defaults_) return;
1302 auto off = PushElement(e);
1303 TrackField(field, off);
1304 }
1305
1306 template<typename T> void AddOffset(voffset_t field, Offset<T> off) {
1307 if (off.IsNull()) return; // Don't store.
1308 AddElement(field, ReferTo(off.o), static_cast<uoffset_t>(0));
1309 }
1310
1311 template<typename T> void AddStruct(voffset_t field, const T *structptr) {
1312 if (!structptr) return; // Default, don't store.
1313 Align(AlignOf<T>());
1314 buf_.push_small(*structptr);
1315 TrackField(field, GetSize());
1316 }
1317
1318 void AddStructOffset(voffset_t field, uoffset_t off) {
1319 TrackField(field, off);
1320 }
1321
1322 // Offsets initially are relative to the end of the buffer (downwards).
1323 // This function converts them to be relative to the current location
1324 // in the buffer (when stored here), pointing upwards.
1325 uoffset_t ReferTo(uoffset_t off) {
1326 // Align to ensure GetSize() below is correct.
1327 Align(sizeof(uoffset_t));
1328 // Offset must refer to something already in buffer.
1329 FLATBUFFERS_ASSERT(off && off <= GetSize());
1330 return GetSize() - off + static_cast<uoffset_t>(sizeof(uoffset_t));
1331 }
1332
1333 void NotNested() {
1334 // If you hit this, you're trying to construct a Table/Vector/String
1335 // during the construction of its parent table (between the MyTableBuilder
1336 // and table.Finish().
1337 // Move the creation of these sub-objects to above the MyTableBuilder to
1338 // not get this assert.
1339 // Ignoring this assert may appear to work in simple cases, but the reason
1340 // it is here is that storing objects in-line may cause vtable offsets
1341 // to not fit anymore. It also leads to vtable duplication.
1342 FLATBUFFERS_ASSERT(!nested);
1343 // If you hit this, fields were added outside the scope of a table.
1344 FLATBUFFERS_ASSERT(!num_field_loc);
1345 }
1346
1347 // From generated code (or from the parser), we call StartTable/EndTable
1348 // with a sequence of AddElement calls in between.
1349 uoffset_t StartTable() {
1350 NotNested();
1351 nested = true;
1352 return GetSize();
1353 }
1354
1355 // This finishes one serialized object by generating the vtable if it's a
1356 // table, comparing it against existing vtables, and writing the
1357 // resulting vtable offset.
1358 uoffset_t EndTable(uoffset_t start) {
1359 // If you get this assert, a corresponding StartTable wasn't called.
1360 FLATBUFFERS_ASSERT(nested);
1361 // Write the vtable offset, which is the start of any Table.
1362 // We fill it's value later.
1363 auto vtableoffsetloc = PushElement<soffset_t>(0);
1364 // Write a vtable, which consists entirely of voffset_t elements.
1365 // It starts with the number of offsets, followed by a type id, followed
1366 // by the offsets themselves. In reverse:
1367 // Include space for the last offset and ensure empty tables have a
1368 // minimum size.
1369 max_voffset_ =
1370 (std::max)(static_cast<voffset_t>(max_voffset_ + sizeof(voffset_t)),
1371 FieldIndexToOffset(0));
1372 buf_.fill_big(max_voffset_);
1373 auto table_object_size = vtableoffsetloc - start;
1374 // Vtable use 16bit offsets.
1375 FLATBUFFERS_ASSERT(table_object_size < 0x10000);
1376 WriteScalar<voffset_t>(buf_.data() + sizeof(voffset_t),
1377 static_cast<voffset_t>(table_object_size));
1378 WriteScalar<voffset_t>(buf_.data(), max_voffset_);
1379 // Write the offsets into the table
1380 for (auto it = buf_.scratch_end() - num_field_loc * sizeof(FieldLoc);
1381 it < buf_.scratch_end(); it += sizeof(FieldLoc)) {
1382 auto field_location = reinterpret_cast<FieldLoc *>(it);
1383 auto pos = static_cast<voffset_t>(vtableoffsetloc - field_location->off);
1384 // If this asserts, it means you've set a field twice.
1385 FLATBUFFERS_ASSERT(
1386 !ReadScalar<voffset_t>(buf_.data() + field_location->id));
1387 WriteScalar<voffset_t>(buf_.data() + field_location->id, pos);
1388 }
1389 ClearOffsets();
1390 auto vt1 = reinterpret_cast<voffset_t *>(buf_.data());
1391 auto vt1_size = ReadScalar<voffset_t>(vt1);
1392 auto vt_use = GetSize();
1393 // See if we already have generated a vtable with this exact same
1394 // layout before. If so, make it point to the old one, remove this one.
1395 if (dedup_vtables_) {
1396 for (auto it = buf_.scratch_data(); it < buf_.scratch_end();
1397 it += sizeof(uoffset_t)) {
1398 auto vt_offset_ptr = reinterpret_cast<uoffset_t *>(it);
1399 auto vt2 = reinterpret_cast<voffset_t *>(buf_.data_at(*vt_offset_ptr));
1400 auto vt2_size = ReadScalar<voffset_t>(vt2);
1401 if (vt1_size != vt2_size || 0 != memcmp(vt2, vt1, vt1_size)) continue;
1402 vt_use = *vt_offset_ptr;
1403 buf_.pop(GetSize() - vtableoffsetloc);
1404 break;
1405 }
1406 }
1407 // If this is a new vtable, remember it.
1408 if (vt_use == GetSize()) { buf_.scratch_push_small(vt_use); }
1409 // Fill the vtable offset we created above.
1410 // The offset points from the beginning of the object to where the
1411 // vtable is stored.
1412 // Offsets default direction is downward in memory for future format
1413 // flexibility (storing all vtables at the start of the file).
1414 WriteScalar(buf_.data_at(vtableoffsetloc),
1415 static_cast<soffset_t>(vt_use) -
1416 static_cast<soffset_t>(vtableoffsetloc));
1417
1418 nested = false;
1419 return vtableoffsetloc;
1420 }
1421
1422 FLATBUFFERS_ATTRIBUTE(deprecated("call the version above instead"))
1423 uoffset_t EndTable(uoffset_t start, voffset_t /*numfields*/) {
1424 return EndTable(start);
1425 }
1426
1427 // This checks a required field has been set in a given table that has
1428 // just been constructed.
1429 template<typename T> void Required(Offset<T> table, voffset_t field);
1430
1431 uoffset_t StartStruct(size_t alignment) {
1432 Align(alignment);
1433 return GetSize();
1434 }
1435
1436 uoffset_t EndStruct() { return GetSize(); }
1437
1438 void ClearOffsets() {
1439 buf_.scratch_pop(num_field_loc * sizeof(FieldLoc));
1440 num_field_loc = 0;
1441 max_voffset_ = 0;
1442 }
1443
1444 // Aligns such that when "len" bytes are written, an object can be written
1445 // after it with "alignment" without padding.
1446 void PreAlign(size_t len, size_t alignment) {
1447 TrackMinAlign(alignment);
1448 buf_.fill(PaddingBytes(GetSize() + len, alignment));
1449 }
1450 template<typename T> void PreAlign(size_t len) {
1451 AssertScalarT<T>();
1452 PreAlign(len, sizeof(T));
1453 }
1454 /// @endcond
1455
1456 /// @brief Store a string in the buffer, which can contain any binary data.
1457 /// @param[in] str A const char pointer to the data to be stored as a string.
1458 /// @param[in] len The number of bytes that should be stored from `str`.
1459 /// @return Returns the offset in the buffer where the string starts.
1460 Offset<String> CreateString(const char *str, size_t len) {
1461 NotNested();
1462 PreAlign<uoffset_t>(len + 1); // Always 0-terminated.
1463 buf_.fill(1);
1464 PushBytes(reinterpret_cast<const uint8_t *>(str), len);
1465 PushElement(static_cast<uoffset_t>(len));
1466 return Offset<String>(GetSize());
1467 }
1468
1469 /// @brief Store a string in the buffer, which is null-terminated.
1470 /// @param[in] str A const char pointer to a C-string to add to the buffer.
1471 /// @return Returns the offset in the buffer where the string starts.
1472 Offset<String> CreateString(const char *str) {
1473 return CreateString(str, strlen(str));
1474 }
1475
1476 /// @brief Store a string in the buffer, which is null-terminated.
1477 /// @param[in] str A char pointer to a C-string to add to the buffer.
1478 /// @return Returns the offset in the buffer where the string starts.
1479 Offset<String> CreateString(char *str) {
1480 return CreateString(str, strlen(str));
1481 }
1482
1483 /// @brief Store a string in the buffer, which can contain any binary data.
1484 /// @param[in] str A const reference to a std::string to store in the buffer.
1485 /// @return Returns the offset in the buffer where the string starts.
1486 Offset<String> CreateString(const std::string &str) {
1487 return CreateString(str.c_str(), str.length());
1488 }
1489
1490 // clang-format off
1491 #ifdef FLATBUFFERS_HAS_STRING_VIEW
1492 /// @brief Store a string in the buffer, which can contain any binary data.
1493 /// @param[in] str A const string_view to copy in to the buffer.
1494 /// @return Returns the offset in the buffer where the string starts.
1495 Offset<String> CreateString(flatbuffers::string_view str) {
1496 return CreateString(str.data(), str.size());
1497 }
1498 #endif // FLATBUFFERS_HAS_STRING_VIEW
1499 // clang-format on
1500
1501 /// @brief Store a string in the buffer, which can contain any binary data.
1502 /// @param[in] str A const pointer to a `String` struct to add to the buffer.
1503 /// @return Returns the offset in the buffer where the string starts
1504 Offset<String> CreateString(const String *str) {
1505 return str ? CreateString(str->c_str(), str->size()) : 0;
1506 }
1507
1508 /// @brief Store a string in the buffer, which can contain any binary data.
1509 /// @param[in] str A const reference to a std::string like type with support
1510 /// of T::c_str() and T::length() to store in the buffer.
1511 /// @return Returns the offset in the buffer where the string starts.
1512 template<typename T> Offset<String> CreateString(const T &str) {
1513 return CreateString(str.c_str(), str.length());
1514 }
1515
1516 /// @brief Store a string in the buffer, which can contain any binary data.
1517 /// If a string with this exact contents has already been serialized before,
1518 /// instead simply returns the offset of the existing string.
1519 /// @param[in] str A const char pointer to the data to be stored as a string.
1520 /// @param[in] len The number of bytes that should be stored from `str`.
1521 /// @return Returns the offset in the buffer where the string starts.
1522 Offset<String> CreateSharedString(const char *str, size_t len) {
1523 if (!string_pool)
1524 string_pool = new StringOffsetMap(StringOffsetCompare(buf_));
1525 auto size_before_string = buf_.size();
1526 // Must first serialize the string, since the set is all offsets into
1527 // buffer.
1528 auto off = CreateString(str, len);
1529 auto it = string_pool->find(off);
1530 // If it exists we reuse existing serialized data!
1531 if (it != string_pool->end()) {
1532 // We can remove the string we serialized.
1533 buf_.pop(buf_.size() - size_before_string);
1534 return *it;
1535 }
1536 // Record this string for future use.
1537 string_pool->insert(off);
1538 return off;
1539 }
1540
1541 /// @brief Store a string in the buffer, which null-terminated.
1542 /// If a string with this exact contents has already been serialized before,
1543 /// instead simply returns the offset of the existing string.
1544 /// @param[in] str A const char pointer to a C-string to add to the buffer.
1545 /// @return Returns the offset in the buffer where the string starts.
1546 Offset<String> CreateSharedString(const char *str) {
1547 return CreateSharedString(str, strlen(str));
1548 }
1549
1550 /// @brief Store a string in the buffer, which can contain any binary data.
1551 /// If a string with this exact contents has already been serialized before,
1552 /// instead simply returns the offset of the existing string.
1553 /// @param[in] str A const reference to a std::string to store in the buffer.
1554 /// @return Returns the offset in the buffer where the string starts.
1555 Offset<String> CreateSharedString(const std::string &str) {
1556 return CreateSharedString(str.c_str(), str.length());
1557 }
1558
1559 /// @brief Store a string in the buffer, which can contain any binary data.
1560 /// If a string with this exact contents has already been serialized before,
1561 /// instead simply returns the offset of the existing string.
1562 /// @param[in] str A const pointer to a `String` struct to add to the buffer.
1563 /// @return Returns the offset in the buffer where the string starts
1564 Offset<String> CreateSharedString(const String *str) {
1565 return CreateSharedString(str->c_str(), str->size());
1566 }
1567
1568 /// @cond FLATBUFFERS_INTERNAL
1569 uoffset_t EndVector(size_t len) {
1570 FLATBUFFERS_ASSERT(nested); // Hit if no corresponding StartVector.
1571 nested = false;
1572 return PushElement(static_cast<uoffset_t>(len));
1573 }
1574
1575 void StartVector(size_t len, size_t elemsize) {
1576 NotNested();
1577 nested = true;
1578 PreAlign<uoffset_t>(len * elemsize);
1579 PreAlign(len * elemsize, elemsize); // Just in case elemsize > uoffset_t.
1580 }
1581
1582 // Call this right before StartVector/CreateVector if you want to force the
1583 // alignment to be something different than what the element size would
1584 // normally dictate.
1585 // This is useful when storing a nested_flatbuffer in a vector of bytes,
1586 // or when storing SIMD floats, etc.
1587 void ForceVectorAlignment(size_t len, size_t elemsize, size_t alignment) {
1588 PreAlign(len * elemsize, alignment);
1589 }
1590
1591 // Similar to ForceVectorAlignment but for String fields.
1592 void ForceStringAlignment(size_t len, size_t alignment) {
1593 PreAlign((len + 1) * sizeof(char), alignment);
1594 }
1595
1596 /// @endcond
1597
1598 /// @brief Serialize an array into a FlatBuffer `vector`.
1599 /// @tparam T The data type of the array elements.
1600 /// @param[in] v A pointer to the array of type `T` to serialize into the
1601 /// buffer as a `vector`.
1602 /// @param[in] len The number of elements to serialize.
1603 /// @return Returns a typed `Offset` into the serialized data indicating
1604 /// where the vector is stored.
1605 template<typename T> Offset<Vector<T>> CreateVector(const T *v, size_t len) {
1606 // If this assert hits, you're specifying a template argument that is
1607 // causing the wrong overload to be selected, remove it.
1608 AssertScalarT<T>();
1609 StartVector(len, sizeof(T));
1610 // clang-format off
1611 #if FLATBUFFERS_LITTLEENDIAN
1612 PushBytes(reinterpret_cast<const uint8_t *>(v), len * sizeof(T));
1613 #else
1614 if (sizeof(T) == 1) {
1615 PushBytes(reinterpret_cast<const uint8_t *>(v), len);
1616 } else {
1617 for (auto i = len; i > 0; ) {
1618 PushElement(v[--i]);
1619 }
1620 }
1621 #endif
1622 // clang-format on
1623 return Offset<Vector<T>>(EndVector(len));
1624 }
1625
1626 template<typename T>
1627 Offset<Vector<Offset<T>>> CreateVector(const Offset<T> *v, size_t len) {
1628 StartVector(len, sizeof(Offset<T>));
1629 for (auto i = len; i > 0;) { PushElement(v[--i]); }
1630 return Offset<Vector<Offset<T>>>(EndVector(len));
1631 }
1632
1633 /// @brief Serialize a `std::vector` into a FlatBuffer `vector`.
1634 /// @tparam T The data type of the `std::vector` elements.
1635 /// @param v A const reference to the `std::vector` to serialize into the
1636 /// buffer as a `vector`.
1637 /// @return Returns a typed `Offset` into the serialized data indicating
1638 /// where the vector is stored.
1639 template<typename T> Offset<Vector<T>> CreateVector(const std::vector<T> &v) {
1640 return CreateVector(data(v), v.size());
1641 }
1642
1643 // vector<bool> may be implemented using a bit-set, so we can't access it as
1644 // an array. Instead, read elements manually.
1645 // Background: https://isocpp.org/blog/2012/11/on-vectorbool
1646 Offset<Vector<uint8_t>> CreateVector(const std::vector<bool> &v) {
1647 StartVector(v.size(), sizeof(uint8_t));
1648 for (auto i = v.size(); i > 0;) {
1649 PushElement(static_cast<uint8_t>(v[--i]));
1650 }
1651 return Offset<Vector<uint8_t>>(EndVector(v.size()));
1652 }
1653
1654 // clang-format off
1655 #ifndef FLATBUFFERS_CPP98_STL
1656 /// @brief Serialize values returned by a function into a FlatBuffer `vector`.
1657 /// This is a convenience function that takes care of iteration for you.
1658 /// @tparam T The data type of the `std::vector` elements.
1659 /// @param f A function that takes the current iteration 0..vector_size-1 and
1660 /// returns any type that you can construct a FlatBuffers vector out of.
1661 /// @return Returns a typed `Offset` into the serialized data indicating
1662 /// where the vector is stored.
1663 template<typename T> Offset<Vector<T>> CreateVector(size_t vector_size,
1664 const std::function<T (size_t i)> &f) {
1665 std::vector<T> elems(vector_size);
1666 for (size_t i = 0; i < vector_size; i++) elems[i] = f(i);
1667 return CreateVector(elems);
1668 }
1669 #endif
1670 // clang-format on
1671
1672 /// @brief Serialize values returned by a function into a FlatBuffer `vector`.
1673 /// This is a convenience function that takes care of iteration for you.
1674 /// @tparam T The data type of the `std::vector` elements.
1675 /// @param f A function that takes the current iteration 0..vector_size-1,
1676 /// and the state parameter returning any type that you can construct a
1677 /// FlatBuffers vector out of.
1678 /// @param state State passed to f.
1679 /// @return Returns a typed `Offset` into the serialized data indicating
1680 /// where the vector is stored.
1681 template<typename T, typename F, typename S>
1682 Offset<Vector<T>> CreateVector(size_t vector_size, F f, S *state) {
1683 std::vector<T> elems(vector_size);
1684 for (size_t i = 0; i < vector_size; i++) elems[i] = f(i, state);
1685 return CreateVector(elems);
1686 }
1687
1688 /// @brief Serialize a `std::vector<std::string>` into a FlatBuffer `vector`.
1689 /// This is a convenience function for a common case.
1690 /// @param v A const reference to the `std::vector` to serialize into the
1691 /// buffer as a `vector`.
1692 /// @return Returns a typed `Offset` into the serialized data indicating
1693 /// where the vector is stored.
1694 Offset<Vector<Offset<String>>> CreateVectorOfStrings(
1695 const std::vector<std::string> &v) {
1696 std::vector<Offset<String>> offsets(v.size());
1697 for (size_t i = 0; i < v.size(); i++) offsets[i] = CreateString(v[i]);
1698 return CreateVector(offsets);
1699 }
1700
1701 /// @brief Serialize an array of structs into a FlatBuffer `vector`.
1702 /// @tparam T The data type of the struct array elements.
1703 /// @param[in] v A pointer to the array of type `T` to serialize into the
1704 /// buffer as a `vector`.
1705 /// @param[in] len The number of elements to serialize.
1706 /// @return Returns a typed `Offset` into the serialized data indicating
1707 /// where the vector is stored.
1708 template<typename T>
1709 Offset<Vector<const T *>> CreateVectorOfStructs(const T *v, size_t len) {
1710 StartVector(len * sizeof(T) / AlignOf<T>(), AlignOf<T>());
1711 PushBytes(reinterpret_cast<const uint8_t *>(v), sizeof(T) * len);
1712 return Offset<Vector<const T *>>(EndVector(len));
1713 }
1714
1715 /// @brief Serialize an array of native structs into a FlatBuffer `vector`.
1716 /// @tparam T The data type of the struct array elements.
1717 /// @tparam S The data type of the native struct array elements.
1718 /// @param[in] v A pointer to the array of type `S` to serialize into the
1719 /// buffer as a `vector`.
1720 /// @param[in] len The number of elements to serialize.
1721 /// @return Returns a typed `Offset` into the serialized data indicating
1722 /// where the vector is stored.
1723 template<typename T, typename S>
1724 Offset<Vector<const T *>> CreateVectorOfNativeStructs(const S *v,
1725 size_t len) {
1726 extern T Pack(const S &);
1727 std::vector<T> vv(len);
1728 std::transform(v, v + len, vv.begin(), Pack);
1729 return CreateVectorOfStructs<T>(data(vv), vv.size());
1730 }
1731
1732 // clang-format off
1733 #ifndef FLATBUFFERS_CPP98_STL
1734 /// @brief Serialize an array of structs into a FlatBuffer `vector`.
1735 /// @tparam T The data type of the struct array elements.
1736 /// @param[in] filler A function that takes the current iteration 0..vector_size-1
1737 /// and a pointer to the struct that must be filled.
1738 /// @return Returns a typed `Offset` into the serialized data indicating
1739 /// where the vector is stored.
1740 /// This is mostly useful when flatbuffers are generated with mutation
1741 /// accessors.
1742 template<typename T> Offset<Vector<const T *>> CreateVectorOfStructs(
1743 size_t vector_size, const std::function<void(size_t i, T *)> &filler) {
1744 T* structs = StartVectorOfStructs<T>(vector_size);
1745 for (size_t i = 0; i < vector_size; i++) {
1746 filler(i, structs);
1747 structs++;
1748 }
1749 return EndVectorOfStructs<T>(vector_size);
1750 }
1751 #endif
1752 // clang-format on
1753
1754 /// @brief Serialize an array of structs into a FlatBuffer `vector`.
1755 /// @tparam T The data type of the struct array elements.
1756 /// @param[in] f A function that takes the current iteration 0..vector_size-1,
1757 /// a pointer to the struct that must be filled and the state argument.
1758 /// @param[in] state Arbitrary state to pass to f.
1759 /// @return Returns a typed `Offset` into the serialized data indicating
1760 /// where the vector is stored.
1761 /// This is mostly useful when flatbuffers are generated with mutation
1762 /// accessors.
1763 template<typename T, typename F, typename S>
1764 Offset<Vector<const T *>> CreateVectorOfStructs(size_t vector_size, F f,
1765 S *state) {
1766 T *structs = StartVectorOfStructs<T>(vector_size);
1767 for (size_t i = 0; i < vector_size; i++) {
1768 f(i, structs, state);
1769 structs++;
1770 }
1771 return EndVectorOfStructs<T>(vector_size);
1772 }
1773
1774 /// @brief Serialize a `std::vector` of structs into a FlatBuffer `vector`.
1775 /// @tparam T The data type of the `std::vector` struct elements.
1776 /// @param[in] v A const reference to the `std::vector` of structs to
1777 /// serialize into the buffer as a `vector`.
1778 /// @return Returns a typed `Offset` into the serialized data indicating
1779 /// where the vector is stored.
1780 template<typename T, typename Alloc>
1781 Offset<Vector<const T *>> CreateVectorOfStructs(
1782 const std::vector<T, Alloc> &v) {
1783 return CreateVectorOfStructs(data(v), v.size());
1784 }
1785
1786 /// @brief Serialize a `std::vector` of native structs into a FlatBuffer
1787 /// `vector`.
1788 /// @tparam T The data type of the `std::vector` struct elements.
1789 /// @tparam S The data type of the `std::vector` native struct elements.
1790 /// @param[in] v A const reference to the `std::vector` of structs to
1791 /// serialize into the buffer as a `vector`.
1792 /// @return Returns a typed `Offset` into the serialized data indicating
1793 /// where the vector is stored.
1794 template<typename T, typename S>
1795 Offset<Vector<const T *>> CreateVectorOfNativeStructs(
1796 const std::vector<S> &v) {
1797 return CreateVectorOfNativeStructs<T, S>(data(v), v.size());
1798 }
1799
1800 /// @cond FLATBUFFERS_INTERNAL
1801 template<typename T> struct StructKeyComparator {
1802 bool operator()(const T &a, const T &b) const {
1803 return a.KeyCompareLessThan(&b);
1804 }
1805
1806 FLATBUFFERS_DELETE_FUNC(
1807 StructKeyComparator &operator=(const StructKeyComparator &))
1808 };
1809 /// @endcond
1810
1811 /// @brief Serialize a `std::vector` of structs into a FlatBuffer `vector`
1812 /// in sorted order.
1813 /// @tparam T The data type of the `std::vector` struct elements.
1814 /// @param[in] v A const reference to the `std::vector` of structs to
1815 /// serialize into the buffer as a `vector`.
1816 /// @return Returns a typed `Offset` into the serialized data indicating
1817 /// where the vector is stored.
1818 template<typename T>
1819 Offset<Vector<const T *>> CreateVectorOfSortedStructs(std::vector<T> *v) {
1820 return CreateVectorOfSortedStructs(data(*v), v->size());
1821 }
1822
1823 /// @brief Serialize a `std::vector` of native structs into a FlatBuffer
1824 /// `vector` in sorted order.
1825 /// @tparam T The data type of the `std::vector` struct elements.
1826 /// @tparam S The data type of the `std::vector` native struct elements.
1827 /// @param[in] v A const reference to the `std::vector` of structs to
1828 /// serialize into the buffer as a `vector`.
1829 /// @return Returns a typed `Offset` into the serialized data indicating
1830 /// where the vector is stored.
1831 template<typename T, typename S>
1832 Offset<Vector<const T *>> CreateVectorOfSortedNativeStructs(
1833 std::vector<S> *v) {
1834 return CreateVectorOfSortedNativeStructs<T, S>(data(*v), v->size());
1835 }
1836
1837 /// @brief Serialize an array of structs into a FlatBuffer `vector` in sorted
1838 /// order.
1839 /// @tparam T The data type of the struct array elements.
1840 /// @param[in] v A pointer to the array of type `T` to serialize into the
1841 /// buffer as a `vector`.
1842 /// @param[in] len The number of elements to serialize.
1843 /// @return Returns a typed `Offset` into the serialized data indicating
1844 /// where the vector is stored.
1845 template<typename T>
1846 Offset<Vector<const T *>> CreateVectorOfSortedStructs(T *v, size_t len) {
1847 std::sort(v, v + len, StructKeyComparator<T>());
1848 return CreateVectorOfStructs(v, len);
1849 }
1850
1851 /// @brief Serialize an array of native structs into a FlatBuffer `vector` in
1852 /// sorted order.
1853 /// @tparam T The data type of the struct array elements.
1854 /// @tparam S The data type of the native struct array elements.
1855 /// @param[in] v A pointer to the array of type `S` to serialize into the
1856 /// buffer as a `vector`.
1857 /// @param[in] len The number of elements to serialize.
1858 /// @return Returns a typed `Offset` into the serialized data indicating
1859 /// where the vector is stored.
1860 template<typename T, typename S>
1861 Offset<Vector<const T *>> CreateVectorOfSortedNativeStructs(S *v,
1862 size_t len) {
1863 extern T Pack(const S &);
1864 typedef T (*Pack_t)(const S &);
1865 std::vector<T> vv(len);
1866 std::transform(v, v + len, vv.begin(), static_cast<Pack_t &>(Pack));
1867 return CreateVectorOfSortedStructs<T>(vv, len);
1868 }
1869
1870 /// @cond FLATBUFFERS_INTERNAL
1871 template<typename T> struct TableKeyComparator {
1872 TableKeyComparator(vector_downward &buf) : buf_(buf) {}
1873 TableKeyComparator(const TableKeyComparator &other) : buf_(other.buf_) {}
1874 bool operator()(const Offset<T> &a, const Offset<T> &b) const {
1875 auto table_a = reinterpret_cast<T *>(buf_.data_at(a.o));
1876 auto table_b = reinterpret_cast<T *>(buf_.data_at(b.o));
1877 return table_a->KeyCompareLessThan(table_b);
1878 }
1879 vector_downward &buf_;
1880
1881 private:
1882 TableKeyComparator &operator=(const TableKeyComparator &other) {
1883 buf_ = other.buf_;
1884 return *this;
1885 }
1886 };
1887 /// @endcond
1888
1889 /// @brief Serialize an array of `table` offsets as a `vector` in the buffer
1890 /// in sorted order.
1891 /// @tparam T The data type that the offset refers to.
1892 /// @param[in] v An array of type `Offset<T>` that contains the `table`
1893 /// offsets to store in the buffer in sorted order.
1894 /// @param[in] len The number of elements to store in the `vector`.
1895 /// @return Returns a typed `Offset` into the serialized data indicating
1896 /// where the vector is stored.
1897 template<typename T>
1898 Offset<Vector<Offset<T>>> CreateVectorOfSortedTables(Offset<T> *v,
1899 size_t len) {
1900 std::sort(v, v + len, TableKeyComparator<T>(buf_));
1901 return CreateVector(v, len);
1902 }
1903
1904 /// @brief Serialize an array of `table` offsets as a `vector` in the buffer
1905 /// in sorted order.
1906 /// @tparam T The data type that the offset refers to.
1907 /// @param[in] v An array of type `Offset<T>` that contains the `table`
1908 /// offsets to store in the buffer in sorted order.
1909 /// @return Returns a typed `Offset` into the serialized data indicating
1910 /// where the vector is stored.
1911 template<typename T>
1912 Offset<Vector<Offset<T>>> CreateVectorOfSortedTables(
1913 std::vector<Offset<T>> *v) {
1914 return CreateVectorOfSortedTables(data(*v), v->size());
1915 }
1916
1917 /// @brief Specialized version of `CreateVector` for non-copying use cases.
1918 /// Write the data any time later to the returned buffer pointer `buf`.
1919 /// @param[in] len The number of elements to store in the `vector`.
1920 /// @param[in] elemsize The size of each element in the `vector`.
1921 /// @param[out] buf A pointer to a `uint8_t` pointer that can be
1922 /// written to at a later time to serialize the data into a `vector`
1923 /// in the buffer.
1924 uoffset_t CreateUninitializedVector(size_t len, size_t elemsize,
1925 uint8_t **buf) {
1926 NotNested();
1927 StartVector(len, elemsize);
1928 buf_.make_space(len * elemsize);
1929 auto vec_start = GetSize();
1930 auto vec_end = EndVector(len);
1931 *buf = buf_.data_at(vec_start);
1932 return vec_end;
1933 }
1934
1935 /// @brief Specialized version of `CreateVector` for non-copying use cases.
1936 /// Write the data any time later to the returned buffer pointer `buf`.
1937 /// @tparam T The data type of the data that will be stored in the buffer
1938 /// as a `vector`.
1939 /// @param[in] len The number of elements to store in the `vector`.
1940 /// @param[out] buf A pointer to a pointer of type `T` that can be
1941 /// written to at a later time to serialize the data into a `vector`
1942 /// in the buffer.
1943 template<typename T>
1944 Offset<Vector<T>> CreateUninitializedVector(size_t len, T **buf) {
1945 AssertScalarT<T>();
1946 return CreateUninitializedVector(len, sizeof(T),
1947 reinterpret_cast<uint8_t **>(buf));
1948 }
1949
1950 template<typename T>
1951 Offset<Vector<const T *>> CreateUninitializedVectorOfStructs(size_t len,
1952 T **buf) {
1953 return CreateUninitializedVector(len, sizeof(T),
1954 reinterpret_cast<uint8_t **>(buf));
1955 }
1956
1957 // @brief Create a vector of scalar type T given as input a vector of scalar
1958 // type U, useful with e.g. pre "enum class" enums, or any existing scalar
1959 // data of the wrong type.
1960 template<typename T, typename U>
1961 Offset<Vector<T>> CreateVectorScalarCast(const U *v, size_t len) {
1962 AssertScalarT<T>();
1963 AssertScalarT<U>();
1964 StartVector(len, sizeof(T));
1965 for (auto i = len; i > 0;) { PushElement(static_cast<T>(v[--i])); }
1966 return Offset<Vector<T>>(EndVector(len));
1967 }
1968
1969 /// @brief Write a struct by itself, typically to be part of a union.
1970 template<typename T> Offset<const T *> CreateStruct(const T &structobj) {
1971 NotNested();
1972 Align(AlignOf<T>());
1973 buf_.push_small(structobj);
1974 return Offset<const T *>(GetSize());
1975 }
1976
1977 /// @brief The length of a FlatBuffer file header.
1978 static const size_t kFileIdentifierLength = 4;
1979
1980 /// @brief Finish serializing a buffer by writing the root offset.
1981 /// @param[in] file_identifier If a `file_identifier` is given, the buffer
1982 /// will be prefixed with a standard FlatBuffers file header.
1983 template<typename T>
1984 void Finish(Offset<T> root, const char *file_identifier = nullptr) {
1985 Finish(root.o, file_identifier, false);
1986 }
1987
1988 /// @brief Finish a buffer with a 32 bit size field pre-fixed (size of the
1989 /// buffer following the size field). These buffers are NOT compatible
1990 /// with standard buffers created by Finish, i.e. you can't call GetRoot
1991 /// on them, you have to use GetSizePrefixedRoot instead.
1992 /// All >32 bit quantities in this buffer will be aligned when the whole
1993 /// size pre-fixed buffer is aligned.
1994 /// These kinds of buffers are useful for creating a stream of FlatBuffers.
1995 template<typename T>
1996 void FinishSizePrefixed(Offset<T> root,
1997 const char *file_identifier = nullptr) {
1998 Finish(root.o, file_identifier, true);
1999 }
2000
2001 void SwapBufAllocator(FlatBufferBuilder &other) {
2002 buf_.swap_allocator(other.buf_);
2003 }
2004
2005 protected:
2006 // You shouldn't really be copying instances of this class.
2007 FlatBufferBuilder(const FlatBufferBuilder &);
2008 FlatBufferBuilder &operator=(const FlatBufferBuilder &);
2009
2010 void Finish(uoffset_t root, const char *file_identifier, bool size_prefix) {
2011 NotNested();
2012 buf_.clear_scratch();
2013 // This will cause the whole buffer to be aligned.
2014 PreAlign((size_prefix ? sizeof(uoffset_t) : 0) + sizeof(uoffset_t) +
2015 (file_identifier ? kFileIdentifierLength : 0),
2016 minalign_);
2017 if (file_identifier) {
2018 FLATBUFFERS_ASSERT(strlen(file_identifier) == kFileIdentifierLength);
2019 PushBytes(reinterpret_cast<const uint8_t *>(file_identifier),
2020 kFileIdentifierLength);
2021 }
2022 PushElement(ReferTo(root)); // Location of root.
2023 if (size_prefix) { PushElement(GetSize()); }
2024 finished = true;
2025 }
2026
2027 struct FieldLoc {
2028 uoffset_t off;
2029 voffset_t id;
2030 };
2031
2032 vector_downward buf_;
2033
2034 // Accumulating offsets of table members while it is being built.
2035 // We store these in the scratch pad of buf_, after the vtable offsets.
2036 uoffset_t num_field_loc;
2037 // Track how much of the vtable is in use, so we can output the most compact
2038 // possible vtable.
2039 voffset_t max_voffset_;
2040
2041 // Ensure objects are not nested.
2042 bool nested;
2043
2044 // Ensure the buffer is finished before it is being accessed.
2045 bool finished;
2046
2047 size_t minalign_;
2048
2049 bool force_defaults_; // Serialize values equal to their defaults anyway.
2050
2051 bool dedup_vtables_;
2052
2053 struct StringOffsetCompare {
2054 StringOffsetCompare(const vector_downward &buf) : buf_(&buf) {}
2055 bool operator()(const Offset<String> &a, const Offset<String> &b) const {
2056 auto stra = reinterpret_cast<const String *>(buf_->data_at(a.o));
2057 auto strb = reinterpret_cast<const String *>(buf_->data_at(b.o));
2058 return StringLessThan(stra->data(), stra->size(), strb->data(),
2059 strb->size());
2060 }
2061 const vector_downward *buf_;
2062 };
2063
2064 // For use with CreateSharedString. Instantiated on first use only.
2065 typedef std::set<Offset<String>, StringOffsetCompare> StringOffsetMap;
2066 StringOffsetMap *string_pool;
2067
2068 private:
2069 // Allocates space for a vector of structures.
2070 // Must be completed with EndVectorOfStructs().
2071 template<typename T> T *StartVectorOfStructs(size_t vector_size) {
2072 StartVector(vector_size * sizeof(T) / AlignOf<T>(), AlignOf<T>());
2073 return reinterpret_cast<T *>(buf_.make_space(vector_size * sizeof(T)));
2074 }
2075
2076 // End the vector of structues in the flatbuffers.
2077 // Vector should have previously be started with StartVectorOfStructs().
2078 template<typename T>
2079 Offset<Vector<const T *>> EndVectorOfStructs(size_t vector_size) {
2080 return Offset<Vector<const T *>>(EndVector(vector_size));
2081 }
2082 };
2083 /// @}
2084
2085 /// @cond FLATBUFFERS_INTERNAL
2086 // Helpers to get a typed pointer to the root object contained in the buffer.
2087 template<typename T> T *GetMutableRoot(void *buf) {
2088 EndianCheck();
2089 return reinterpret_cast<T *>(
2090 reinterpret_cast<uint8_t *>(buf) +
2091 EndianScalar(*reinterpret_cast<uoffset_t *>(buf)));
2092 }
2093
2094 template<typename T> const T *GetRoot(const void *buf) {
2095 return GetMutableRoot<T>(const_cast<void *>(buf));
2096 }
2097
2098 template<typename T> const T *GetSizePrefixedRoot(const void *buf) {
2099 return GetRoot<T>(reinterpret_cast<const uint8_t *>(buf) + sizeof(uoffset_t));
2100 }
2101
2102 /// Helpers to get a typed pointer to objects that are currently being built.
2103 /// @warning Creating new objects will lead to reallocations and invalidates
2104 /// the pointer!
2105 template<typename T>
2106 T *GetMutableTemporaryPointer(FlatBufferBuilder &fbb, Offset<T> offset) {
2107 return reinterpret_cast<T *>(fbb.GetCurrentBufferPointer() + fbb.GetSize() -
2108 offset.o);
2109 }
2110
2111 template<typename T>
2112 const T *GetTemporaryPointer(FlatBufferBuilder &fbb, Offset<T> offset) {
2113 return GetMutableTemporaryPointer<T>(fbb, offset);
2114 }
2115
2116 /// @brief Get a pointer to the the file_identifier section of the buffer.
2117 /// @return Returns a const char pointer to the start of the file_identifier
2118 /// characters in the buffer. The returned char * has length
2119 /// 'flatbuffers::FlatBufferBuilder::kFileIdentifierLength'.
2120 /// This function is UNDEFINED for FlatBuffers whose schema does not include
2121 /// a file_identifier (likely points at padding or the start of a the root
2122 /// vtable).
2123 inline const char *GetBufferIdentifier(const void *buf,
2124 bool size_prefixed = false) {
2125 return reinterpret_cast<const char *>(buf) +
2126 ((size_prefixed) ? 2 * sizeof(uoffset_t) : sizeof(uoffset_t));
2127 }
2128
2129 // Helper to see if the identifier in a buffer has the expected value.
2130 inline bool BufferHasIdentifier(const void *buf, const char *identifier,
2131 bool size_prefixed = false) {
2132 return strncmp(GetBufferIdentifier(buf, size_prefixed), identifier,
2133 FlatBufferBuilder::kFileIdentifierLength) == 0;
2134 }
2135
2136 // Helper class to verify the integrity of a FlatBuffer
2137 class Verifier FLATBUFFERS_FINAL_CLASS {
2138 public:
2139 Verifier(const uint8_t *buf, size_t buf_len, uoffset_t _max_depth = 64,
2140 uoffset_t _max_tables = 1000000, bool _check_alignment = true)
2141 : buf_(buf),
2142 size_(buf_len),
2143 depth_(0),
2144 max_depth_(_max_depth),
2145 num_tables_(0),
2146 max_tables_(_max_tables),
2147 upper_bound_(0),
2148 check_alignment_(_check_alignment) {
2149 FLATBUFFERS_ASSERT(size_ < FLATBUFFERS_MAX_BUFFER_SIZE);
2150 }
2151
2152 // Central location where any verification failures register.
2153 bool Check(bool ok) const {
2154 // clang-format off
2155 #ifdef FLATBUFFERS_DEBUG_VERIFICATION_FAILURE
2156 FLATBUFFERS_ASSERT(ok);
2157 #endif
2158 #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
2159 if (!ok)
2160 upper_bound_ = 0;
2161 #endif
2162 // clang-format on
2163 return ok;
2164 }
2165
2166 // Verify any range within the buffer.
2167 bool Verify(size_t elem, size_t elem_len) const {
2168 // clang-format off
2169 #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
2170 auto upper_bound = elem + elem_len;
2171 if (upper_bound_ < upper_bound)
2172 upper_bound_ = upper_bound;
2173 #endif
2174 // clang-format on
2175 return Check(elem_len < size_ && elem <= size_ - elem_len);
2176 }
2177
2178 template<typename T> bool VerifyAlignment(size_t elem) const {
2179 return Check((elem & (sizeof(T) - 1)) == 0 || !check_alignment_);
2180 }
2181
2182 // Verify a range indicated by sizeof(T).
2183 template<typename T> bool Verify(size_t elem) const {
2184 return VerifyAlignment<T>(elem) && Verify(elem, sizeof(T));
2185 }
2186
2187 bool VerifyFromPointer(const uint8_t *p, size_t len) {
2188 auto o = static_cast<size_t>(p - buf_);
2189 return Verify(o, len);
2190 }
2191
2192 // Verify relative to a known-good base pointer.
2193 bool Verify(const uint8_t *base, voffset_t elem_off, size_t elem_len) const {
2194 return Verify(static_cast<size_t>(base - buf_) + elem_off, elem_len);
2195 }
2196
2197 template<typename T>
2198 bool Verify(const uint8_t *base, voffset_t elem_off) const {
2199 return Verify(static_cast<size_t>(base - buf_) + elem_off, sizeof(T));
2200 }
2201
2202 // Verify a pointer (may be NULL) of a table type.
2203 template<typename T> bool VerifyTable(const T *table) {
2204 return !table || table->Verify(*this);
2205 }
2206
2207 // Verify a pointer (may be NULL) of any vector type.
2208 template<typename T> bool VerifyVector(const Vector<T> *vec) const {
2209 return !vec || VerifyVectorOrString(reinterpret_cast<const uint8_t *>(vec),
2210 sizeof(T));
2211 }
2212
2213 // Verify a pointer (may be NULL) of a vector to struct.
2214 template<typename T> bool VerifyVector(const Vector<const T *> *vec) const {
2215 return VerifyVector(reinterpret_cast<const Vector<T> *>(vec));
2216 }
2217
2218 // Verify a pointer (may be NULL) to string.
2219 bool VerifyString(const String *str) const {
2220 size_t end;
2221 return !str || (VerifyVectorOrString(reinterpret_cast<const uint8_t *>(str),
2222 1, &end) &&
2223 Verify(end, 1) && // Must have terminator
2224 Check(buf_[end] == '\0')); // Terminating byte must be 0.
2225 }
2226
2227 // Common code between vectors and strings.
2228 bool VerifyVectorOrString(const uint8_t *vec, size_t elem_size,
2229 size_t *end = nullptr) const {
2230 auto veco = static_cast<size_t>(vec - buf_);
2231 // Check we can read the size field.
2232 if (!Verify<uoffset_t>(veco)) return false;
2233 // Check the whole array. If this is a string, the byte past the array
2234 // must be 0.
2235 auto size = ReadScalar<uoffset_t>(vec);
2236 auto max_elems = FLATBUFFERS_MAX_BUFFER_SIZE / elem_size;
2237 if (!Check(size < max_elems))
2238 return false; // Protect against byte_size overflowing.
2239 auto byte_size = sizeof(size) + elem_size * size;
2240 if (end) *end = veco + byte_size;
2241 return Verify(veco, byte_size);
2242 }
2243
2244 // Special case for string contents, after the above has been called.
2245 bool VerifyVectorOfStrings(const Vector<Offset<String>> *vec) const {
2246 if (vec) {
2247 for (uoffset_t i = 0; i < vec->size(); i++) {
2248 if (!VerifyString(vec->Get(i))) return false;
2249 }
2250 }
2251 return true;
2252 }
2253
2254 // Special case for table contents, after the above has been called.
2255 template<typename T> bool VerifyVectorOfTables(const Vector<Offset<T>> *vec) {
2256 if (vec) {
2257 for (uoffset_t i = 0; i < vec->size(); i++) {
2258 if (!vec->Get(i)->Verify(*this)) return false;
2259 }
2260 }
2261 return true;
2262 }
2263
2264 __supress_ubsan__("unsigned-integer-overflow") bool VerifyTableStart(
2265 const uint8_t *table) {
2266 // Check the vtable offset.
2267 auto tableo = static_cast<size_t>(table - buf_);
2268 if (!Verify<soffset_t>(tableo)) return false;
2269 // This offset may be signed, but doing the subtraction unsigned always
2270 // gives the result we want.
2271 auto vtableo = tableo - static_cast<size_t>(ReadScalar<soffset_t>(table));
2272 // Check the vtable size field, then check vtable fits in its entirety.
2273 return VerifyComplexity() && Verify<voffset_t>(vtableo) &&
2274 VerifyAlignment<voffset_t>(ReadScalar<voffset_t>(buf_ + vtableo)) &&
2275 Verify(vtableo, ReadScalar<voffset_t>(buf_ + vtableo));
2276 }
2277
2278 template<typename T>
2279 bool VerifyBufferFromStart(const char *identifier, size_t start) {
2280 if (identifier && (size_ < 2 * sizeof(flatbuffers::uoffset_t) ||
2281 !BufferHasIdentifier(buf_ + start, identifier))) {
2282 return false;
2283 }
2284
2285 // Call T::Verify, which must be in the generated code for this type.
2286 auto o = VerifyOffset(start);
2287 return o && reinterpret_cast<const T *>(buf_ + start + o)->Verify(*this)
2288 // clang-format off
2289 #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
2290 && GetComputedSize()
2291 #endif
2292 ;
2293 // clang-format on
2294 }
2295
2296 // Verify this whole buffer, starting with root type T.
2297 template<typename T> bool VerifyBuffer() { return VerifyBuffer<T>(nullptr); }
2298
2299 template<typename T> bool VerifyBuffer(const char *identifier) {
2300 return VerifyBufferFromStart<T>(identifier, 0);
2301 }
2302
2303 template<typename T> bool VerifySizePrefixedBuffer(const char *identifier) {
2304 return Verify<uoffset_t>(0U) &&
2305 ReadScalar<uoffset_t>(buf_) == size_ - sizeof(uoffset_t) &&
2306 VerifyBufferFromStart<T>(identifier, sizeof(uoffset_t));
2307 }
2308
2309 uoffset_t VerifyOffset(size_t start) const {
2310 if (!Verify<uoffset_t>(start)) return 0;
2311 auto o = ReadScalar<uoffset_t>(buf_ + start);
2312 // May not point to itself.
2313 if (!Check(o != 0)) return 0;
2314 // Can't wrap around / buffers are max 2GB.
2315 if (!Check(static_cast<soffset_t>(o) >= 0)) return 0;
2316 // Must be inside the buffer to create a pointer from it (pointer outside
2317 // buffer is UB).
2318 if (!Verify(start + o, 1)) return 0;
2319 return o;
2320 }
2321
2322 uoffset_t VerifyOffset(const uint8_t *base, voffset_t start) const {
2323 return VerifyOffset(static_cast<size_t>(base - buf_) + start);
2324 }
2325
2326 // Called at the start of a table to increase counters measuring data
2327 // structure depth and amount, and possibly bails out with false if
2328 // limits set by the constructor have been hit. Needs to be balanced
2329 // with EndTable().
2330 bool VerifyComplexity() {
2331 depth_++;
2332 num_tables_++;
2333 return Check(depth_ <= max_depth_ && num_tables_ <= max_tables_);
2334 }
2335
2336 // Called at the end of a table to pop the depth count.
2337 bool EndTable() {
2338 depth_--;
2339 return true;
2340 }
2341
2342 // Returns the message size in bytes
2343 size_t GetComputedSize() const {
2344 // clang-format off
2345 #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
2346 uintptr_t size = upper_bound_;
2347 // Align the size to uoffset_t
2348 size = (size - 1 + sizeof(uoffset_t)) & ~(sizeof(uoffset_t) - 1);
2349 return (size > size_) ? 0 : size;
2350 #else
2351 // Must turn on FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE for this to work.
2352 (void)upper_bound_;
2353 FLATBUFFERS_ASSERT(false);
2354 return 0;
2355 #endif
2356 // clang-format on
2357 }
2358
2359 private:
2360 const uint8_t *buf_;
2361 size_t size_;
2362 uoffset_t depth_;
2363 uoffset_t max_depth_;
2364 uoffset_t num_tables_;
2365 uoffset_t max_tables_;
2366 mutable size_t upper_bound_;
2367 bool check_alignment_;
2368 };
2369
2370 // Convenient way to bundle a buffer and its length, to pass it around
2371 // typed by its root.
2372 // A BufferRef does not own its buffer.
2373 struct BufferRefBase {}; // for std::is_base_of
2374 template<typename T> struct BufferRef : BufferRefBase {
2375 BufferRef() : buf(nullptr), len(0), must_free(false) {}
2376 BufferRef(uint8_t *_buf, uoffset_t _len)
2377 : buf(_buf), len(_len), must_free(false) {}
2378
2379 ~BufferRef() {
2380 if (must_free) free(buf);
2381 }
2382
2383 const T *GetRoot() const { return flatbuffers::GetRoot<T>(buf); }
2384
2385 bool Verify() {
2386 Verifier verifier(buf, len);
2387 return verifier.VerifyBuffer<T>(nullptr);
2388 }
2389
2390 uint8_t *buf;
2391 uoffset_t len;
2392 bool must_free;
2393 };
2394
2395 // "structs" are flat structures that do not have an offset table, thus
2396 // always have all members present and do not support forwards/backwards
2397 // compatible extensions.
2398
2399 class Struct FLATBUFFERS_FINAL_CLASS {
2400 public:
2401 template<typename T> T GetField(uoffset_t o) const {
2402 return ReadScalar<T>(&data_[o]);
2403 }
2404
2405 template<typename T> T GetStruct(uoffset_t o) const {
2406 return reinterpret_cast<T>(&data_[o]);
2407 }
2408
2409 const uint8_t *GetAddressOf(uoffset_t o) const { return &data_[o]; }
2410 uint8_t *GetAddressOf(uoffset_t o) { return &data_[o]; }
2411
2412 private:
2413 // private constructor & copy constructor: you obtain instances of this
2414 // class by pointing to existing data only
2415 Struct();
2416 Struct(const Struct &);
2417 Struct &operator=(const Struct &);
2418
2419 uint8_t data_[1];
2420 };
2421
2422 // "tables" use an offset table (possibly shared) that allows fields to be
2423 // omitted and added at will, but uses an extra indirection to read.
2424 class Table {
2425 public:
2426 const uint8_t *GetVTable() const {
2427 return data_ - ReadScalar<soffset_t>(data_);
2428 }
2429
2430 // This gets the field offset for any of the functions below it, or 0
2431 // if the field was not present.
2432 voffset_t GetOptionalFieldOffset(voffset_t field) const {
2433 // The vtable offset is always at the start.
2434 auto vtable = GetVTable();
2435 // The first element is the size of the vtable (fields + type id + itself).
2436 auto vtsize = ReadScalar<voffset_t>(vtable);
2437 // If the field we're accessing is outside the vtable, we're reading older
2438 // data, so it's the same as if the offset was 0 (not present).
2439 return field < vtsize ? ReadScalar<voffset_t>(vtable + field) : 0;
2440 }
2441
2442 template<typename T> T GetField(voffset_t field, T defaultval) const {
2443 auto field_offset = GetOptionalFieldOffset(field);
2444 return field_offset ? ReadScalar<T>(data_ + field_offset) : defaultval;
2445 }
2446
2447 template<typename P> P GetPointer(voffset_t field) {
2448 auto field_offset = GetOptionalFieldOffset(field);
2449 auto p = data_ + field_offset;
2450 return field_offset ? reinterpret_cast<P>(p + ReadScalar<uoffset_t>(p))
2451 : nullptr;
2452 }
2453 template<typename P> P GetPointer(voffset_t field) const {
2454 return const_cast<Table *>(this)->GetPointer<P>(field);
2455 }
2456
2457 template<typename P> P GetStruct(voffset_t field) const {
2458 auto field_offset = GetOptionalFieldOffset(field);
2459 auto p = const_cast<uint8_t *>(data_ + field_offset);
2460 return field_offset ? reinterpret_cast<P>(p) : nullptr;
2461 }
2462
2463 template<typename T> bool SetField(voffset_t field, T val, T def) {
2464 auto field_offset = GetOptionalFieldOffset(field);
2465 if (!field_offset) return IsTheSameAs(val, def);
2466 WriteScalar(data_ + field_offset, val);
2467 return true;
2468 }
2469
2470 bool SetPointer(voffset_t field, const uint8_t *val) {
2471 auto field_offset = GetOptionalFieldOffset(field);
2472 if (!field_offset) return false;
2473 WriteScalar(data_ + field_offset,
2474 static_cast<uoffset_t>(val - (data_ + field_offset)));
2475 return true;
2476 }
2477
2478 uint8_t *GetAddressOf(voffset_t field) {
2479 auto field_offset = GetOptionalFieldOffset(field);
2480 return field_offset ? data_ + field_offset : nullptr;
2481 }
2482 const uint8_t *GetAddressOf(voffset_t field) const {
2483 return const_cast<Table *>(this)->GetAddressOf(field);
2484 }
2485
2486 bool CheckField(voffset_t field) const {
2487 return GetOptionalFieldOffset(field) != 0;
2488 }
2489
2490 // Verify the vtable of this table.
2491 // Call this once per table, followed by VerifyField once per field.
2492 bool VerifyTableStart(Verifier &verifier) const {
2493 return verifier.VerifyTableStart(data_);
2494 }
2495
2496 // Verify a particular field.
2497 template<typename T>
2498 bool VerifyField(const Verifier &verifier, voffset_t field) const {
2499 // Calling GetOptionalFieldOffset should be safe now thanks to
2500 // VerifyTable().
2501 auto field_offset = GetOptionalFieldOffset(field);
2502 // Check the actual field.
2503 return !field_offset || verifier.Verify<T>(data_, field_offset);
2504 }
2505
2506 // VerifyField for required fields.
2507 template<typename T>
2508 bool VerifyFieldRequired(const Verifier &verifier, voffset_t field) const {
2509 auto field_offset = GetOptionalFieldOffset(field);
2510 return verifier.Check(field_offset != 0) &&
2511 verifier.Verify<T>(data_, field_offset);
2512 }
2513
2514 // Versions for offsets.
2515 bool VerifyOffset(const Verifier &verifier, voffset_t field) const {
2516 auto field_offset = GetOptionalFieldOffset(field);
2517 return !field_offset || verifier.VerifyOffset(data_, field_offset);
2518 }
2519
2520 bool VerifyOffsetRequired(const Verifier &verifier, voffset_t field) const {
2521 auto field_offset = GetOptionalFieldOffset(field);
2522 return verifier.Check(field_offset != 0) &&
2523 verifier.VerifyOffset(data_, field_offset);
2524 }
2525
2526 private:
2527 // private constructor & copy constructor: you obtain instances of this
2528 // class by pointing to existing data only
2529 Table();
2530 Table(const Table &other);
2531 Table &operator=(const Table &);
2532
2533 uint8_t data_[1];
2534 };
2535
2536 template<typename T>
2537 void FlatBufferBuilder::Required(Offset<T> table, voffset_t field) {
2538 auto table_ptr = reinterpret_cast<const Table *>(buf_.data_at(table.o));
2539 bool ok = table_ptr->GetOptionalFieldOffset(field) != 0;
2540 // If this fails, the caller will show what field needs to be set.
2541 FLATBUFFERS_ASSERT(ok);
2542 (void)ok;
2543 }
2544
2545 /// @brief This can compute the start of a FlatBuffer from a root pointer, i.e.
2546 /// it is the opposite transformation of GetRoot().
2547 /// This may be useful if you want to pass on a root and have the recipient
2548 /// delete the buffer afterwards.
2549 inline const uint8_t *GetBufferStartFromRootPointer(const void *root) {
2550 auto table = reinterpret_cast<const Table *>(root);
2551 auto vtable = table->GetVTable();
2552 // Either the vtable is before the root or after the root.
2553 auto start = (std::min)(vtable, reinterpret_cast<const uint8_t *>(root));
2554 // Align to at least sizeof(uoffset_t).
2555 start = reinterpret_cast<const uint8_t *>(reinterpret_cast<uintptr_t>(start) &
2556 ~(sizeof(uoffset_t) - 1));
2557 // Additionally, there may be a file_identifier in the buffer, and the root
2558 // offset. The buffer may have been aligned to any size between
2559 // sizeof(uoffset_t) and FLATBUFFERS_MAX_ALIGNMENT (see "force_align").
2560 // Sadly, the exact alignment is only known when constructing the buffer,
2561 // since it depends on the presence of values with said alignment properties.
2562 // So instead, we simply look at the next uoffset_t values (root,
2563 // file_identifier, and alignment padding) to see which points to the root.
2564 // None of the other values can "impersonate" the root since they will either
2565 // be 0 or four ASCII characters.
2566 static_assert(FlatBufferBuilder::kFileIdentifierLength == sizeof(uoffset_t),
2567 "file_identifier is assumed to be the same size as uoffset_t");
2568 for (auto possible_roots = FLATBUFFERS_MAX_ALIGNMENT / sizeof(uoffset_t) + 1;
2569 possible_roots; possible_roots--) {
2570 start -= sizeof(uoffset_t);
2571 if (ReadScalar<uoffset_t>(start) + start ==
2572 reinterpret_cast<const uint8_t *>(root))
2573 return start;
2574 }
2575 // We didn't find the root, either the "root" passed isn't really a root,
2576 // or the buffer is corrupt.
2577 // Assert, because calling this function with bad data may cause reads
2578 // outside of buffer boundaries.
2579 FLATBUFFERS_ASSERT(false);
2580 return nullptr;
2581 }
2582
2583 /// @brief This return the prefixed size of a FlatBuffer.
2584 inline uoffset_t GetPrefixedSize(const uint8_t *buf) {
2585 return ReadScalar<uoffset_t>(buf);
2586 }
2587
2588 // Base class for native objects (FlatBuffer data de-serialized into native
2589 // C++ data structures).
2590 // Contains no functionality, purely documentative.
2591 struct NativeTable {};
2592
2593 /// @brief Function types to be used with resolving hashes into objects and
2594 /// back again. The resolver gets a pointer to a field inside an object API
2595 /// object that is of the type specified in the schema using the attribute
2596 /// `cpp_type` (it is thus important whatever you write to this address
2597 /// matches that type). The value of this field is initially null, so you
2598 /// may choose to implement a delayed binding lookup using this function
2599 /// if you wish. The resolver does the opposite lookup, for when the object
2600 /// is being serialized again.
2601 typedef uint64_t hash_value_t;
2602 // clang-format off
2603 #ifdef FLATBUFFERS_CPP98_STL
2604 typedef void (*resolver_function_t)(void **pointer_adr, hash_value_t hash);
2605 typedef hash_value_t (*rehasher_function_t)(void *pointer);
2606 #else
2607 typedef std::function<void (void **pointer_adr, hash_value_t hash)>
2608 resolver_function_t;
2609 typedef std::function<hash_value_t (void *pointer)> rehasher_function_t;
2610 #endif
2611 // clang-format on
2612
2613 // Helper function to test if a field is present, using any of the field
2614 // enums in the generated code.
2615 // `table` must be a generated table type. Since this is a template parameter,
2616 // this is not typechecked to be a subclass of Table, so beware!
2617 // Note: this function will return false for fields equal to the default
2618 // value, since they're not stored in the buffer (unless force_defaults was
2619 // used).
2620 template<typename T>
2621 bool IsFieldPresent(const T *table, typename T::FlatBuffersVTableOffset field) {
2622 // Cast, since Table is a private baseclass of any table types.
2623 return reinterpret_cast<const Table *>(table)->CheckField(
2624 static_cast<voffset_t>(field));
2625 }
2626
2627 // Utility function for reverse lookups on the EnumNames*() functions
2628 // (in the generated C++ code)
2629 // names must be NULL terminated.
2630 inline int LookupEnum(const char **names, const char *name) {
2631 for (const char **p = names; *p; p++)
2632 if (!strcmp(*p, name)) return static_cast<int>(p - names);
2633 return -1;
2634 }
2635
2636 // These macros allow us to layout a struct with a guarantee that they'll end
2637 // up looking the same on different compilers and platforms.
2638 // It does this by disallowing the compiler to do any padding, and then
2639 // does padding itself by inserting extra padding fields that make every
2640 // element aligned to its own size.
2641 // Additionally, it manually sets the alignment of the struct as a whole,
2642 // which is typically its largest element, or a custom size set in the schema
2643 // by the force_align attribute.
2644 // These are used in the generated code only.
2645
2646 // clang-format off
2647 #if defined(_MSC_VER)
2648 #define FLATBUFFERS_MANUALLY_ALIGNED_STRUCT(alignment) \
2649 __pragma(pack(1)) \
2650 struct __declspec(align(alignment))
2651 #define FLATBUFFERS_STRUCT_END(name, size) \
2652 __pragma(pack()) \
2653 static_assert(sizeof(name) == size, "compiler breaks packing rules")
2654 #elif defined(__GNUC__) || defined(__clang__) || defined(__ICCARM__)
2655 #define FLATBUFFERS_MANUALLY_ALIGNED_STRUCT(alignment) \
2656 _Pragma("pack(1)") \
2657 struct __attribute__((aligned(alignment)))
2658 #define FLATBUFFERS_STRUCT_END(name, size) \
2659 _Pragma("pack()") \
2660 static_assert(sizeof(name) == size, "compiler breaks packing rules")
2661 #else
2662 #error Unknown compiler, please define structure alignment macros
2663 #endif
2664 // clang-format on
2665
2666 // Minimal reflection via code generation.
2667 // Besides full-fat reflection (see reflection.h) and parsing/printing by
2668 // loading schemas (see idl.h), we can also have code generation for mimimal
2669 // reflection data which allows pretty-printing and other uses without needing
2670 // a schema or a parser.
2671 // Generate code with --reflect-types (types only) or --reflect-names (names
2672 // also) to enable.
2673 // See minireflect.h for utilities using this functionality.
2674
2675 // These types are organized slightly differently as the ones in idl.h.
2676 enum SequenceType { ST_TABLE, ST_STRUCT, ST_UNION, ST_ENUM };
2677
2678 // Scalars have the same order as in idl.h
2679 // clang-format off
2680 #define FLATBUFFERS_GEN_ELEMENTARY_TYPES(ET) \
2681 ET(ET_UTYPE) \
2682 ET(ET_BOOL) \
2683 ET(ET_CHAR) \
2684 ET(ET_UCHAR) \
2685 ET(ET_SHORT) \
2686 ET(ET_USHORT) \
2687 ET(ET_INT) \
2688 ET(ET_UINT) \
2689 ET(ET_LONG) \
2690 ET(ET_ULONG) \
2691 ET(ET_FLOAT) \
2692 ET(ET_DOUBLE) \
2693 ET(ET_STRING) \
2694 ET(ET_SEQUENCE) // See SequenceType.
2695
2696 enum ElementaryType {
2697 #define FLATBUFFERS_ET(E) E,
2698 FLATBUFFERS_GEN_ELEMENTARY_TYPES(FLATBUFFERS_ET)
2699 #undef FLATBUFFERS_ET
2700 };
2701
2702 inline const char * const *ElementaryTypeNames() {
2703 static const char * const names[] = {
2704 #define FLATBUFFERS_ET(E) #E,
2705 FLATBUFFERS_GEN_ELEMENTARY_TYPES(FLATBUFFERS_ET)
2706 #undef FLATBUFFERS_ET
2707 };
2708 return names;
2709 }
2710 // clang-format on
2711
2712 // Basic type info cost just 16bits per field!
2713 struct TypeCode {
2714 uint16_t base_type : 4; // ElementaryType
2715 uint16_t is_vector : 1;
2716 int16_t sequence_ref : 11; // Index into type_refs below, or -1 for none.
2717 };
2718
2719 static_assert(sizeof(TypeCode) == 2, "TypeCode");
2720
2721 struct TypeTable;
2722
2723 // Signature of the static method present in each type.
2724 typedef const TypeTable *(*TypeFunction)();
2725
2726 struct TypeTable {
2727 SequenceType st;
2728 size_t num_elems; // of type_codes, values, names (but not type_refs).
2729 const TypeCode *type_codes; // num_elems count
2730 const TypeFunction *type_refs; // less than num_elems entries (see TypeCode).
2731 const int64_t *values; // Only set for non-consecutive enum/union or structs.
2732 const char *const *names; // Only set if compiled with --reflect-names.
2733 };
2734
2735 // String which identifies the current version of FlatBuffers.
2736 // flatbuffer_version_string is used by Google developers to identify which
2737 // applications uploaded to Google Play are using this library. This allows
2738 // the development team at Google to determine the popularity of the library.
2739 // How it works: Applications that are uploaded to the Google Play Store are
2740 // scanned for this version string. We track which applications are using it
2741 // to measure popularity. You are free to remove it (of course) but we would
2742 // appreciate if you left it in.
2743
2744 // Weak linkage is culled by VS & doesn't work on cygwin.
2745 // clang-format off
2746 #if !defined(_WIN32) && !defined(__CYGWIN__)
2747
2748 extern volatile __attribute__((weak)) const char *flatbuffer_version_string;
2749 volatile __attribute__((weak)) const char *flatbuffer_version_string =
2750 "FlatBuffers "
2751 FLATBUFFERS_STRING(FLATBUFFERS_VERSION_MAJOR) "."
2752 FLATBUFFERS_STRING(FLATBUFFERS_VERSION_MINOR) "."
2753 FLATBUFFERS_STRING(FLATBUFFERS_VERSION_REVISION);
2754
2755 #endif // !defined(_WIN32) && !defined(__CYGWIN__)
2756
2757 #define FLATBUFFERS_DEFINE_BITMASK_OPERATORS(E, T)\
2758 inline E operator | (E lhs, E rhs){\
2759 return E(T(lhs) | T(rhs));\
2760 }\
2761 inline E operator & (E lhs, E rhs){\
2762 return E(T(lhs) & T(rhs));\
2763 }\
2764 inline E operator ^ (E lhs, E rhs){\
2765 return E(T(lhs) ^ T(rhs));\
2766 }\
2767 inline E operator ~ (E lhs){\
2768 return E(~T(lhs));\
2769 }\
2770 inline E operator |= (E &lhs, E rhs){\
2771 lhs = lhs | rhs;\
2772 return lhs;\
2773 }\
2774 inline E operator &= (E &lhs, E rhs){\
2775 lhs = lhs & rhs;\
2776 return lhs;\
2777 }\
2778 inline E operator ^= (E &lhs, E rhs){\
2779 lhs = lhs ^ rhs;\
2780 return lhs;\
2781 }\
2782 inline bool operator !(E rhs) \
2783 {\
2784 return !bool(T(rhs)); \
2785 }
2786 /// @endcond
2787 } // namespace flatbuffers
2788
2789 // clang-format on
2790
2791 #endif // FLATBUFFERS_H_
2792