1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc. All rights reserved.
3// https://developers.google.com/protocol-buffers/
4//
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18//
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30
31#ifndef GOOGLE_PROTOBUF_ARENASTRING_H__
32#define GOOGLE_PROTOBUF_ARENASTRING_H__
33
34#include <string>
35#include <type_traits>
36#include <utility>
37
38#include <google/protobuf/stubs/logging.h>
39#include <google/protobuf/stubs/common.h>
40#include <google/protobuf/stubs/fastmem.h>
41#include <google/protobuf/arena.h>
42#include <google/protobuf/port.h>
43
44#include <google/protobuf/port_def.inc>
45
46#ifdef SWIG
47#error "You cannot SWIG proto headers"
48#endif
49
50
51// This is the implementation of arena string fields written for the open-source
52// release. The ArenaStringPtr struct below is an internal implementation class
53// and *should not be used* by user code. It is used to collect string
54// operations together into one place and abstract away the underlying
55// string-field pointer representation, so that (for example) an alternate
56// implementation that knew more about ::std::string's internals could integrate
57// more closely with the arena allocator.
58
59namespace google {
60namespace protobuf {
61namespace internal {
62
63template <typename T>
64class TaggedPtr {
65 public:
66 void Set(T* p) { ptr_ = reinterpret_cast<uintptr_t>(p); }
67 T* Get() const { return reinterpret_cast<T*>(ptr_); }
68
69 bool IsNull() { return ptr_ == 0; }
70
71 private:
72 uintptr_t ptr_;
73};
74
75struct PROTOBUF_EXPORT ArenaStringPtr {
76 inline void Set(const ::std::string* default_value,
77 const ::std::string& value, Arena* arena) {
78 if (ptr_ == default_value) {
79 CreateInstance(arena, initial_value: &value);
80 } else {
81 *ptr_ = value;
82 }
83 }
84
85 inline void SetLite(const ::std::string* default_value,
86 const ::std::string& value, Arena* arena) {
87 Set(default_value, value, arena);
88 }
89
90 // Basic accessors.
91 inline const ::std::string& Get() const { return *ptr_; }
92
93 inline ::std::string* Mutable(const ::std::string* default_value,
94 Arena* arena) {
95 if (ptr_ == default_value) {
96 CreateInstance(arena, initial_value: default_value);
97 }
98 return ptr_;
99 }
100
101 // Release returns a ::std::string* instance that is heap-allocated and is not
102 // Own()'d by any arena. If the field was not set, it returns NULL. The caller
103 // retains ownership. Clears this field back to NULL state. Used to implement
104 // release_<field>() methods on generated classes.
105 inline ::std::string* Release(const ::std::string* default_value,
106 Arena* arena) {
107 if (ptr_ == default_value) {
108 return NULL;
109 }
110 return ReleaseNonDefault(default_value, arena);
111 }
112
113 // Similar to Release, but ptr_ cannot be the default_value.
114 inline ::std::string* ReleaseNonDefault(const ::std::string* default_value,
115 Arena* arena) {
116 GOOGLE_DCHECK(!IsDefault(default_value));
117 ::std::string* released = NULL;
118 if (arena != NULL) {
119 // ptr_ is owned by the arena.
120 released = new ::std::string;
121 released->swap(s&: *ptr_);
122 } else {
123 released = ptr_;
124 }
125 ptr_ = const_cast< ::std::string*>(default_value);
126 return released;
127 }
128
129 // UnsafeArenaRelease returns a ::std::string*, but it may be arena-owned
130 // (i.e. have its destructor already registered) if arena != NULL. If the
131 // field was not set, this returns NULL. This method clears this field back to
132 // NULL state. Used to implement unsafe_arena_release_<field>() methods on
133 // generated classes.
134 inline ::std::string* UnsafeArenaRelease(const ::std::string* default_value,
135 Arena* /* arena */) {
136 if (ptr_ == default_value) {
137 return NULL;
138 }
139 ::std::string* released = ptr_;
140 ptr_ = const_cast< ::std::string*>(default_value);
141 return released;
142 }
143
144 // Takes a string that is heap-allocated, and takes ownership. The string's
145 // destructor is registered with the arena. Used to implement
146 // set_allocated_<field> in generated classes.
147 inline void SetAllocated(const ::std::string* default_value,
148 ::std::string* value, Arena* arena) {
149 if (arena == NULL && ptr_ != default_value) {
150 Destroy(default_value, arena);
151 }
152 if (value != NULL) {
153 ptr_ = value;
154 if (arena != NULL) {
155 arena->Own(object: value);
156 }
157 } else {
158 ptr_ = const_cast< ::std::string*>(default_value);
159 }
160 }
161
162 // Takes a string that has lifetime equal to the arena's lifetime. The arena
163 // must be non-null. It is safe only to pass this method a value returned by
164 // UnsafeArenaRelease() on another field of a message in the same arena. Used
165 // to implement unsafe_arena_set_allocated_<field> in generated classes.
166 inline void UnsafeArenaSetAllocated(const ::std::string* default_value,
167 ::std::string* value,
168 Arena* /* arena */) {
169 if (value != NULL) {
170 ptr_ = value;
171 } else {
172 ptr_ = const_cast< ::std::string*>(default_value);
173 }
174 }
175
176 // Swaps internal pointers. Arena-safety semantics: this is guarded by the
177 // logic in Swap()/UnsafeArenaSwap() at the message level, so this method is
178 // 'unsafe' if called directly.
179 PROTOBUF_ALWAYS_INLINE void Swap(ArenaStringPtr* other) {
180 std::swap(a&: ptr_, b&: other->ptr_);
181 }
182 PROTOBUF_ALWAYS_INLINE void Swap(ArenaStringPtr* other,
183 const ::std::string* default_value,
184 Arena* arena) {
185#ifndef NDEBUG
186 // For debug builds, we swap the contents of the string, rather than the
187 // string instances themselves. This invalidates previously taken const
188 // references that are (per our documentation) invalidated by calling Swap()
189 // on the message.
190 //
191 // If both strings are the default_value, swapping is uninteresting.
192 // Otherwise, we use ArenaStringPtr::Mutable() to access the string, to
193 // ensure that we do not try to mutate default_value itself.
194 if (IsDefault(default_value) && other->IsDefault(default_value)) {
195 return;
196 }
197
198 ::std::string* this_ptr = Mutable(default_value, arena);
199 ::std::string* other_ptr = other->Mutable(default_value, arena);
200
201 this_ptr->swap(s&: *other_ptr);
202#else
203 std::swap(ptr_, other->ptr_);
204 (void)default_value;
205 (void)arena;
206#endif
207 }
208
209 // Frees storage (if not on an arena).
210 inline void Destroy(const ::std::string* default_value, Arena* arena) {
211 if (arena == NULL && ptr_ != default_value) {
212 delete ptr_;
213 }
214 }
215
216 // Clears content, but keeps allocated string if arena != NULL, to avoid the
217 // overhead of heap operations. After this returns, the content (as seen by
218 // the user) will always be the empty string. Assumes that |default_value|
219 // is an empty string.
220 inline void ClearToEmpty(const ::std::string* default_value,
221 Arena* /* arena */) {
222 if (ptr_ == default_value) {
223 // Already set to default (which is empty) -- do nothing.
224 } else {
225 ptr_->clear();
226 }
227 }
228
229 // Clears content, assuming that the current value is not the empty string
230 // default.
231 inline void ClearNonDefaultToEmpty() { ptr_->clear(); }
232 inline void ClearNonDefaultToEmptyNoArena() { ptr_->clear(); }
233
234 // Clears content, but keeps allocated string if arena != NULL, to avoid the
235 // overhead of heap operations. After this returns, the content (as seen by
236 // the user) will always be equal to |default_value|.
237 inline void ClearToDefault(const ::std::string* default_value,
238 Arena* /* arena */) {
239 if (ptr_ == default_value) {
240 // Already set to default -- do nothing.
241 } else {
242 // Have another allocated string -- rather than throwing this away and
243 // resetting ptr_ to the canonical default string instance, we just reuse
244 // this instance.
245 *ptr_ = *default_value;
246 }
247 }
248
249 // Called from generated code / reflection runtime only. Resets value to point
250 // to a default string pointer, with the semantics that this ArenaStringPtr
251 // does not own the pointed-to memory. Disregards initial value of ptr_ (so
252 // this is the *ONLY* safe method to call after construction or when
253 // reinitializing after becoming the active field in a oneof union).
254 inline void UnsafeSetDefault(const ::std::string* default_value) {
255 // Casting away 'const' is safe here: accessors ensure that ptr_ is only
256 // returned as a const if it is equal to default_value.
257 ptr_ = const_cast< ::std::string*>(default_value);
258 }
259
260 // The 'NoArena' variants of methods below assume arena == NULL and are
261 // optimized to provide very little overhead relative to a raw string pointer
262 // (while still being in-memory compatible with other code that assumes
263 // ArenaStringPtr). Note the invariant that a class instance that has only
264 // ever been mutated by NoArena methods must *only* be in the String state
265 // (i.e., tag bits are not used), *NEVER* ArenaString. This allows all
266 // tagged-pointer manipulations to be avoided.
267 inline void SetNoArena(const ::std::string* default_value,
268 const ::std::string& value) {
269 if (ptr_ == default_value) {
270 CreateInstanceNoArena(initial_value: &value);
271 } else {
272 *ptr_ = value;
273 }
274 }
275
276 void SetNoArena(const ::std::string* default_value, ::std::string&& value) {
277 if (IsDefault(default_value)) {
278 ptr_ = new ::std::string(std::move(value));
279 } else {
280 *ptr_ = std::move(value);
281 }
282 }
283
284 void AssignWithDefault(const ::std::string* default_value,
285 ArenaStringPtr value);
286
287 inline const ::std::string& GetNoArena() const { return *ptr_; }
288
289 inline ::std::string* MutableNoArena(const ::std::string* default_value) {
290 if (ptr_ == default_value) {
291 CreateInstanceNoArena(initial_value: default_value);
292 }
293 return ptr_;
294 }
295
296 inline ::std::string* ReleaseNoArena(const ::std::string* default_value) {
297 if (ptr_ == default_value) {
298 return NULL;
299 } else {
300 return ReleaseNonDefaultNoArena(default_value);
301 }
302 }
303
304 inline ::std::string* ReleaseNonDefaultNoArena(
305 const ::std::string* default_value) {
306 GOOGLE_DCHECK(!IsDefault(default_value));
307 ::std::string* released = ptr_;
308 ptr_ = const_cast< ::std::string*>(default_value);
309 return released;
310 }
311
312 inline void SetAllocatedNoArena(const ::std::string* default_value,
313 ::std::string* value) {
314 if (ptr_ != default_value) {
315 delete ptr_;
316 }
317 if (value != NULL) {
318 ptr_ = value;
319 } else {
320 ptr_ = const_cast< ::std::string*>(default_value);
321 }
322 }
323
324 inline void DestroyNoArena(const ::std::string* default_value) {
325 if (ptr_ != default_value) {
326 delete ptr_;
327 }
328 }
329
330 inline void ClearToEmptyNoArena(const ::std::string* default_value) {
331 if (ptr_ == default_value) {
332 // Nothing: already equal to default (which is the empty string).
333 } else {
334 ptr_->clear();
335 }
336 }
337
338 inline void ClearToDefaultNoArena(const ::std::string* default_value) {
339 if (ptr_ == default_value) {
340 // Nothing: already set to default.
341 } else {
342 // Reuse existing allocated instance.
343 *ptr_ = *default_value;
344 }
345 }
346
347 // Internal accessor used only at parse time to provide direct access to the
348 // raw pointer from the shared parse routine (in the non-arenas case). The
349 // parse routine does the string allocation in order to save code size in the
350 // generated parsing code.
351 inline ::std::string** UnsafeRawStringPointer() { return &ptr_; }
352
353 inline bool IsDefault(const ::std::string* default_value) const {
354 return ptr_ == default_value;
355 }
356
357 // Internal accessors!!!!
358 void UnsafeSetTaggedPointer(TaggedPtr< ::std::string> value) {
359 ptr_ = value.Get();
360 }
361 // Generated code only! An optimization, in certain cases the generated
362 // code is certain we can obtain a string with no default checks and
363 // tag tests.
364 ::std::string* UnsafeMutablePointer() { return ptr_; }
365
366 private:
367 ::std::string* ptr_;
368
369 PROTOBUF_NOINLINE
370 void CreateInstance(Arena* arena, const ::std::string* initial_value) {
371 GOOGLE_DCHECK(initial_value != NULL);
372 // uses "new ::std::string" when arena is nullptr
373 ptr_ = Arena::Create< ::std::string>(arena, args: *initial_value);
374 }
375 PROTOBUF_NOINLINE
376 void CreateInstanceNoArena(const ::std::string* initial_value) {
377 GOOGLE_DCHECK(initial_value != NULL);
378 ptr_ = new ::std::string(*initial_value);
379 }
380};
381
382} // namespace internal
383} // namespace protobuf
384
385namespace protobuf {
386namespace internal {
387
388inline void ArenaStringPtr::AssignWithDefault(
389 const ::std::string* default_value, ArenaStringPtr value) {
390 const ::std::string* me = *UnsafeRawStringPointer();
391 const ::std::string* other = *value.UnsafeRawStringPointer();
392 // If the pointers are the same then do nothing.
393 if (me != other) {
394 SetNoArena(default_value, value: value.GetNoArena());
395 }
396}
397
398} // namespace internal
399} // namespace protobuf
400} // namespace google
401
402
403#include <google/protobuf/port_undef.inc>
404
405#endif // GOOGLE_PROTOBUF_ARENASTRING_H__
406

source code of include/google/protobuf/arenastring.h