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Diffstat (limited to 'src/contrib/SDL-3.2.20/include/SDL3/SDL_atomic.h')
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diff --git a/src/contrib/SDL-3.2.20/include/SDL3/SDL_atomic.h b/src/contrib/SDL-3.2.20/include/SDL3/SDL_atomic.h new file mode 100644 index 0000000..78b5e0f --- /dev/null +++ b/src/contrib/SDL-3.2.20/include/SDL3/SDL_atomic.h | |||
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1 | /* | ||
2 | Simple DirectMedia Layer | ||
3 | Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org> | ||
4 | |||
5 | This software is provided 'as-is', without any express or implied | ||
6 | warranty. In no event will the authors be held liable for any damages | ||
7 | arising from the use of this software. | ||
8 | |||
9 | Permission is granted to anyone to use this software for any purpose, | ||
10 | including commercial applications, and to alter it and redistribute it | ||
11 | freely, subject to the following restrictions: | ||
12 | |||
13 | 1. The origin of this software must not be misrepresented; you must not | ||
14 | claim that you wrote the original software. If you use this software | ||
15 | in a product, an acknowledgment in the product documentation would be | ||
16 | appreciated but is not required. | ||
17 | 2. Altered source versions must be plainly marked as such, and must not be | ||
18 | misrepresented as being the original software. | ||
19 | 3. This notice may not be removed or altered from any source distribution. | ||
20 | */ | ||
21 | |||
22 | /** | ||
23 | * # CategoryAtomic | ||
24 | * | ||
25 | * Atomic operations. | ||
26 | * | ||
27 | * IMPORTANT: If you are not an expert in concurrent lockless programming, you | ||
28 | * should not be using any functions in this file. You should be protecting | ||
29 | * your data structures with full mutexes instead. | ||
30 | * | ||
31 | * ***Seriously, here be dragons!*** | ||
32 | * | ||
33 | * You can find out a little more about lockless programming and the subtle | ||
34 | * issues that can arise here: | ||
35 | * https://learn.microsoft.com/en-us/windows/win32/dxtecharts/lockless-programming | ||
36 | * | ||
37 | * There's also lots of good information here: | ||
38 | * | ||
39 | * - https://www.1024cores.net/home/lock-free-algorithms | ||
40 | * - https://preshing.com/ | ||
41 | * | ||
42 | * These operations may or may not actually be implemented using processor | ||
43 | * specific atomic operations. When possible they are implemented as true | ||
44 | * processor specific atomic operations. When that is not possible the are | ||
45 | * implemented using locks that *do* use the available atomic operations. | ||
46 | * | ||
47 | * All of the atomic operations that modify memory are full memory barriers. | ||
48 | */ | ||
49 | |||
50 | #ifndef SDL_atomic_h_ | ||
51 | #define SDL_atomic_h_ | ||
52 | |||
53 | #include <SDL3/SDL_stdinc.h> | ||
54 | #include <SDL3/SDL_platform_defines.h> | ||
55 | |||
56 | #include <SDL3/SDL_begin_code.h> | ||
57 | |||
58 | /* Set up for C function definitions, even when using C++ */ | ||
59 | #ifdef __cplusplus | ||
60 | extern "C" { | ||
61 | #endif | ||
62 | |||
63 | /** | ||
64 | * An atomic spinlock. | ||
65 | * | ||
66 | * The atomic locks are efficient spinlocks using CPU instructions, but are | ||
67 | * vulnerable to starvation and can spin forever if a thread holding a lock | ||
68 | * has been terminated. For this reason you should minimize the code executed | ||
69 | * inside an atomic lock and never do expensive things like API or system | ||
70 | * calls while holding them. | ||
71 | * | ||
72 | * They are also vulnerable to starvation if the thread holding the lock is | ||
73 | * lower priority than other threads and doesn't get scheduled. In general you | ||
74 | * should use mutexes instead, since they have better performance and | ||
75 | * contention behavior. | ||
76 | * | ||
77 | * The atomic locks are not safe to lock recursively. | ||
78 | * | ||
79 | * Porting Note: The spin lock functions and type are required and can not be | ||
80 | * emulated because they are used in the atomic emulation code. | ||
81 | */ | ||
82 | typedef int SDL_SpinLock; | ||
83 | |||
84 | /** | ||
85 | * Try to lock a spin lock by setting it to a non-zero value. | ||
86 | * | ||
87 | * ***Please note that spinlocks are dangerous if you don't know what you're | ||
88 | * doing. Please be careful using any sort of spinlock!*** | ||
89 | * | ||
90 | * \param lock a pointer to a lock variable. | ||
91 | * \returns true if the lock succeeded, false if the lock is already held. | ||
92 | * | ||
93 | * \threadsafety It is safe to call this function from any thread. | ||
94 | * | ||
95 | * \since This function is available since SDL 3.2.0. | ||
96 | * | ||
97 | * \sa SDL_LockSpinlock | ||
98 | * \sa SDL_UnlockSpinlock | ||
99 | */ | ||
100 | extern SDL_DECLSPEC bool SDLCALL SDL_TryLockSpinlock(SDL_SpinLock *lock); | ||
101 | |||
102 | /** | ||
103 | * Lock a spin lock by setting it to a non-zero value. | ||
104 | * | ||
105 | * ***Please note that spinlocks are dangerous if you don't know what you're | ||
106 | * doing. Please be careful using any sort of spinlock!*** | ||
107 | * | ||
108 | * \param lock a pointer to a lock variable. | ||
109 | * | ||
110 | * \threadsafety It is safe to call this function from any thread. | ||
111 | * | ||
112 | * \since This function is available since SDL 3.2.0. | ||
113 | * | ||
114 | * \sa SDL_TryLockSpinlock | ||
115 | * \sa SDL_UnlockSpinlock | ||
116 | */ | ||
117 | extern SDL_DECLSPEC void SDLCALL SDL_LockSpinlock(SDL_SpinLock *lock); | ||
118 | |||
119 | /** | ||
120 | * Unlock a spin lock by setting it to 0. | ||
121 | * | ||
122 | * Always returns immediately. | ||
123 | * | ||
124 | * ***Please note that spinlocks are dangerous if you don't know what you're | ||
125 | * doing. Please be careful using any sort of spinlock!*** | ||
126 | * | ||
127 | * \param lock a pointer to a lock variable. | ||
128 | * | ||
129 | * \threadsafety It is safe to call this function from any thread. | ||
130 | * | ||
131 | * \since This function is available since SDL 3.2.0. | ||
132 | * | ||
133 | * \sa SDL_LockSpinlock | ||
134 | * \sa SDL_TryLockSpinlock | ||
135 | */ | ||
136 | extern SDL_DECLSPEC void SDLCALL SDL_UnlockSpinlock(SDL_SpinLock *lock); | ||
137 | |||
138 | |||
139 | #ifdef SDL_WIKI_DOCUMENTATION_SECTION | ||
140 | |||
141 | /** | ||
142 | * Mark a compiler barrier. | ||
143 | * | ||
144 | * A compiler barrier prevents the compiler from reordering reads and writes | ||
145 | * to globally visible variables across the call. | ||
146 | * | ||
147 | * This macro only prevents the compiler from reordering reads and writes, it | ||
148 | * does not prevent the CPU from reordering reads and writes. However, all of | ||
149 | * the atomic operations that modify memory are full memory barriers. | ||
150 | * | ||
151 | * \threadsafety Obviously this macro is safe to use from any thread at any | ||
152 | * time, but if you find yourself needing this, you are probably | ||
153 | * dealing with some very sensitive code; be careful! | ||
154 | * | ||
155 | * \since This macro is available since SDL 3.2.0. | ||
156 | */ | ||
157 | #define SDL_CompilerBarrier() DoCompilerSpecificReadWriteBarrier() | ||
158 | |||
159 | #elif defined(_MSC_VER) && (_MSC_VER > 1200) && !defined(__clang__) | ||
160 | void _ReadWriteBarrier(void); | ||
161 | #pragma intrinsic(_ReadWriteBarrier) | ||
162 | #define SDL_CompilerBarrier() _ReadWriteBarrier() | ||
163 | #elif (defined(__GNUC__) && !defined(SDL_PLATFORM_EMSCRIPTEN)) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120)) | ||
164 | /* This is correct for all CPUs when using GCC or Solaris Studio 12.1+. */ | ||
165 | #define SDL_CompilerBarrier() __asm__ __volatile__ ("" : : : "memory") | ||
166 | #elif defined(__WATCOMC__) | ||
167 | extern __inline void SDL_CompilerBarrier(void); | ||
168 | #pragma aux SDL_CompilerBarrier = "" parm [] modify exact []; | ||
169 | #else | ||
170 | #define SDL_CompilerBarrier() \ | ||
171 | { SDL_SpinLock _tmp = 0; SDL_LockSpinlock(&_tmp); SDL_UnlockSpinlock(&_tmp); } | ||
172 | #endif | ||
173 | |||
174 | /** | ||
175 | * Insert a memory release barrier (function version). | ||
176 | * | ||
177 | * Please refer to SDL_MemoryBarrierRelease for details. This is a function | ||
178 | * version, which might be useful if you need to use this functionality from a | ||
179 | * scripting language, etc. Also, some of the macro versions call this | ||
180 | * function behind the scenes, where more heavy lifting can happen inside of | ||
181 | * SDL. Generally, though, an app written in C/C++/etc should use the macro | ||
182 | * version, as it will be more efficient. | ||
183 | * | ||
184 | * \threadsafety Obviously this function is safe to use from any thread at any | ||
185 | * time, but if you find yourself needing this, you are probably | ||
186 | * dealing with some very sensitive code; be careful! | ||
187 | * | ||
188 | * \since This function is available since SDL 3.2.0. | ||
189 | * | ||
190 | * \sa SDL_MemoryBarrierRelease | ||
191 | */ | ||
192 | extern SDL_DECLSPEC void SDLCALL SDL_MemoryBarrierReleaseFunction(void); | ||
193 | |||
194 | /** | ||
195 | * Insert a memory acquire barrier (function version). | ||
196 | * | ||
197 | * Please refer to SDL_MemoryBarrierRelease for details. This is a function | ||
198 | * version, which might be useful if you need to use this functionality from a | ||
199 | * scripting language, etc. Also, some of the macro versions call this | ||
200 | * function behind the scenes, where more heavy lifting can happen inside of | ||
201 | * SDL. Generally, though, an app written in C/C++/etc should use the macro | ||
202 | * version, as it will be more efficient. | ||
203 | * | ||
204 | * \threadsafety Obviously this function is safe to use from any thread at any | ||
205 | * time, but if you find yourself needing this, you are probably | ||
206 | * dealing with some very sensitive code; be careful! | ||
207 | * | ||
208 | * \since This function is available since SDL 3.2.0. | ||
209 | * | ||
210 | * \sa SDL_MemoryBarrierAcquire | ||
211 | */ | ||
212 | extern SDL_DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void); | ||
213 | |||
214 | |||
215 | #ifdef SDL_WIKI_DOCUMENTATION_SECTION | ||
216 | |||
217 | /** | ||
218 | * Insert a memory release barrier (macro version). | ||
219 | * | ||
220 | * Memory barriers are designed to prevent reads and writes from being | ||
221 | * reordered by the compiler and being seen out of order on multi-core CPUs. | ||
222 | * | ||
223 | * A typical pattern would be for thread A to write some data and a flag, and | ||
224 | * for thread B to read the flag and get the data. In this case you would | ||
225 | * insert a release barrier between writing the data and the flag, | ||
226 | * guaranteeing that the data write completes no later than the flag is | ||
227 | * written, and you would insert an acquire barrier between reading the flag | ||
228 | * and reading the data, to ensure that all the reads associated with the flag | ||
229 | * have completed. | ||
230 | * | ||
231 | * In this pattern you should always see a release barrier paired with an | ||
232 | * acquire barrier and you should gate the data reads/writes with a single | ||
233 | * flag variable. | ||
234 | * | ||
235 | * For more information on these semantics, take a look at the blog post: | ||
236 | * http://preshing.com/20120913/acquire-and-release-semantics | ||
237 | * | ||
238 | * This is the macro version of this functionality; if possible, SDL will use | ||
239 | * compiler intrinsics or inline assembly, but some platforms might need to | ||
240 | * call the function version of this, SDL_MemoryBarrierReleaseFunction to do | ||
241 | * the heavy lifting. Apps that can use the macro should favor it over the | ||
242 | * function. | ||
243 | * | ||
244 | * \threadsafety Obviously this macro is safe to use from any thread at any | ||
245 | * time, but if you find yourself needing this, you are probably | ||
246 | * dealing with some very sensitive code; be careful! | ||
247 | * | ||
248 | * \since This macro is available since SDL 3.2.0. | ||
249 | * | ||
250 | * \sa SDL_MemoryBarrierAcquire | ||
251 | * \sa SDL_MemoryBarrierReleaseFunction | ||
252 | */ | ||
253 | #define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction() | ||
254 | |||
255 | /** | ||
256 | * Insert a memory acquire barrier (macro version). | ||
257 | * | ||
258 | * Please see SDL_MemoryBarrierRelease for the details on what memory barriers | ||
259 | * are and when to use them. | ||
260 | * | ||
261 | * This is the macro version of this functionality; if possible, SDL will use | ||
262 | * compiler intrinsics or inline assembly, but some platforms might need to | ||
263 | * call the function version of this, SDL_MemoryBarrierAcquireFunction, to do | ||
264 | * the heavy lifting. Apps that can use the macro should favor it over the | ||
265 | * function. | ||
266 | * | ||
267 | * \threadsafety Obviously this macro is safe to use from any thread at any | ||
268 | * time, but if you find yourself needing this, you are probably | ||
269 | * dealing with some very sensitive code; be careful! | ||
270 | * | ||
271 | * \since This macro is available since SDL 3.2.0. | ||
272 | * | ||
273 | * \sa SDL_MemoryBarrierRelease | ||
274 | * \sa SDL_MemoryBarrierAcquireFunction | ||
275 | */ | ||
276 | #define SDL_MemoryBarrierAcquire() SDL_MemoryBarrierAcquireFunction() | ||
277 | |||
278 | #elif defined(__GNUC__) && (defined(__powerpc__) || defined(__ppc__)) | ||
279 | #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("lwsync" : : : "memory") | ||
280 | #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("lwsync" : : : "memory") | ||
281 | #elif defined(__GNUC__) && defined(__aarch64__) | ||
282 | #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") | ||
283 | #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") | ||
284 | #elif defined(__GNUC__) && defined(__arm__) | ||
285 | #if 0 /* defined(SDL_PLATFORM_LINUX) || defined(SDL_PLATFORM_ANDROID) */ | ||
286 | /* Information from: | ||
287 | https://chromium.googlesource.com/chromium/chromium/+/trunk/base/atomicops_internals_arm_gcc.h#19 | ||
288 | |||
289 | The Linux kernel provides a helper function which provides the right code for a memory barrier, | ||
290 | hard-coded at address 0xffff0fa0 | ||
291 | */ | ||
292 | typedef void (*SDL_KernelMemoryBarrierFunc)(); | ||
293 | #define SDL_MemoryBarrierRelease() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)() | ||
294 | #define SDL_MemoryBarrierAcquire() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)() | ||
295 | #else | ||
296 | #if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7S__) || defined(__ARM_ARCH_8A__) | ||
297 | #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") | ||
298 | #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") | ||
299 | #elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) | ||
300 | #ifdef __thumb__ | ||
301 | /* The mcr instruction isn't available in thumb mode, use real functions */ | ||
302 | #define SDL_MEMORY_BARRIER_USES_FUNCTION | ||
303 | #define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction() | ||
304 | #define SDL_MemoryBarrierAcquire() SDL_MemoryBarrierAcquireFunction() | ||
305 | #else | ||
306 | #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory") | ||
307 | #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory") | ||
308 | #endif /* __thumb__ */ | ||
309 | #else | ||
310 | #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("" : : : "memory") | ||
311 | #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("" : : : "memory") | ||
312 | #endif /* SDL_PLATFORM_LINUX || SDL_PLATFORM_ANDROID */ | ||
313 | #endif /* __GNUC__ && __arm__ */ | ||
314 | #else | ||
315 | #if (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120)) | ||
316 | /* This is correct for all CPUs on Solaris when using Solaris Studio 12.1+. */ | ||
317 | #include <mbarrier.h> | ||
318 | #define SDL_MemoryBarrierRelease() __machine_rel_barrier() | ||
319 | #define SDL_MemoryBarrierAcquire() __machine_acq_barrier() | ||
320 | #else | ||
321 | /* This is correct for the x86 and x64 CPUs, and we'll expand this over time. */ | ||
322 | #define SDL_MemoryBarrierRelease() SDL_CompilerBarrier() | ||
323 | #define SDL_MemoryBarrierAcquire() SDL_CompilerBarrier() | ||
324 | #endif | ||
325 | #endif | ||
326 | |||
327 | /* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */ | ||
328 | #ifdef SDL_WIKI_DOCUMENTATION_SECTION | ||
329 | |||
330 | /** | ||
331 | * A macro to insert a CPU-specific "pause" instruction into the program. | ||
332 | * | ||
333 | * This can be useful in busy-wait loops, as it serves as a hint to the CPU as | ||
334 | * to the program's intent; some CPUs can use this to do more efficient | ||
335 | * processing. On some platforms, this doesn't do anything, so using this | ||
336 | * macro might just be a harmless no-op. | ||
337 | * | ||
338 | * Note that if you are busy-waiting, there are often more-efficient | ||
339 | * approaches with other synchronization primitives: mutexes, semaphores, | ||
340 | * condition variables, etc. | ||
341 | * | ||
342 | * \threadsafety This macro is safe to use from any thread. | ||
343 | * | ||
344 | * \since This macro is available since SDL 3.2.0. | ||
345 | */ | ||
346 | #define SDL_CPUPauseInstruction() DoACPUPauseInACompilerAndArchitectureSpecificWay | ||
347 | |||
348 | #elif (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__)) | ||
349 | #define SDL_CPUPauseInstruction() __asm__ __volatile__("pause\n") /* Some assemblers can't do REP NOP, so go with PAUSE. */ | ||
350 | #elif (defined(__arm__) && defined(__ARM_ARCH) && __ARM_ARCH >= 7) || defined(__aarch64__) | ||
351 | #define SDL_CPUPauseInstruction() __asm__ __volatile__("yield" ::: "memory") | ||
352 | #elif (defined(__powerpc__) || defined(__powerpc64__)) | ||
353 | #define SDL_CPUPauseInstruction() __asm__ __volatile__("or 27,27,27"); | ||
354 | #elif (defined(__riscv) && __riscv_xlen == 64) | ||
355 | #define SDL_CPUPauseInstruction() __asm__ __volatile__(".insn i 0x0F, 0, x0, x0, 0x010"); | ||
356 | #elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) | ||
357 | #define SDL_CPUPauseInstruction() _mm_pause() /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */ | ||
358 | #elif defined(_MSC_VER) && (defined(_M_ARM) || defined(_M_ARM64)) | ||
359 | #define SDL_CPUPauseInstruction() __yield() | ||
360 | #elif defined(__WATCOMC__) && defined(__386__) | ||
361 | extern __inline void SDL_CPUPauseInstruction(void); | ||
362 | #pragma aux SDL_CPUPauseInstruction = ".686p" ".xmm2" "pause" | ||
363 | #else | ||
364 | #define SDL_CPUPauseInstruction() | ||
365 | #endif | ||
366 | |||
367 | |||
368 | /** | ||
369 | * A type representing an atomic integer value. | ||
370 | * | ||
371 | * This can be used to manage a value that is synchronized across multiple | ||
372 | * CPUs without a race condition; when an app sets a value with | ||
373 | * SDL_SetAtomicInt all other threads, regardless of the CPU it is running on, | ||
374 | * will see that value when retrieved with SDL_GetAtomicInt, regardless of CPU | ||
375 | * caches, etc. | ||
376 | * | ||
377 | * This is also useful for atomic compare-and-swap operations: a thread can | ||
378 | * change the value as long as its current value matches expectations. When | ||
379 | * done in a loop, one can guarantee data consistency across threads without a | ||
380 | * lock (but the usual warnings apply: if you don't know what you're doing, or | ||
381 | * you don't do it carefully, you can confidently cause any number of | ||
382 | * disasters with this, so in most cases, you _should_ use a mutex instead of | ||
383 | * this!). | ||
384 | * | ||
385 | * This is a struct so people don't accidentally use numeric operations on it | ||
386 | * directly. You have to use SDL atomic functions. | ||
387 | * | ||
388 | * \since This struct is available since SDL 3.2.0. | ||
389 | * | ||
390 | * \sa SDL_CompareAndSwapAtomicInt | ||
391 | * \sa SDL_GetAtomicInt | ||
392 | * \sa SDL_SetAtomicInt | ||
393 | * \sa SDL_AddAtomicInt | ||
394 | */ | ||
395 | typedef struct SDL_AtomicInt { int value; } SDL_AtomicInt; | ||
396 | |||
397 | /** | ||
398 | * Set an atomic variable to a new value if it is currently an old value. | ||
399 | * | ||
400 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
401 | * it!*** | ||
402 | * | ||
403 | * \param a a pointer to an SDL_AtomicInt variable to be modified. | ||
404 | * \param oldval the old value. | ||
405 | * \param newval the new value. | ||
406 | * \returns true if the atomic variable was set, false otherwise. | ||
407 | * | ||
408 | * \threadsafety It is safe to call this function from any thread. | ||
409 | * | ||
410 | * \since This function is available since SDL 3.2.0. | ||
411 | * | ||
412 | * \sa SDL_GetAtomicInt | ||
413 | * \sa SDL_SetAtomicInt | ||
414 | */ | ||
415 | extern SDL_DECLSPEC bool SDLCALL SDL_CompareAndSwapAtomicInt(SDL_AtomicInt *a, int oldval, int newval); | ||
416 | |||
417 | /** | ||
418 | * Set an atomic variable to a value. | ||
419 | * | ||
420 | * This function also acts as a full memory barrier. | ||
421 | * | ||
422 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
423 | * it!*** | ||
424 | * | ||
425 | * \param a a pointer to an SDL_AtomicInt variable to be modified. | ||
426 | * \param v the desired value. | ||
427 | * \returns the previous value of the atomic variable. | ||
428 | * | ||
429 | * \threadsafety It is safe to call this function from any thread. | ||
430 | * | ||
431 | * \since This function is available since SDL 3.2.0. | ||
432 | * | ||
433 | * \sa SDL_GetAtomicInt | ||
434 | */ | ||
435 | extern SDL_DECLSPEC int SDLCALL SDL_SetAtomicInt(SDL_AtomicInt *a, int v); | ||
436 | |||
437 | /** | ||
438 | * Get the value of an atomic variable. | ||
439 | * | ||
440 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
441 | * it!*** | ||
442 | * | ||
443 | * \param a a pointer to an SDL_AtomicInt variable. | ||
444 | * \returns the current value of an atomic variable. | ||
445 | * | ||
446 | * \threadsafety It is safe to call this function from any thread. | ||
447 | * | ||
448 | * \since This function is available since SDL 3.2.0. | ||
449 | * | ||
450 | * \sa SDL_SetAtomicInt | ||
451 | */ | ||
452 | extern SDL_DECLSPEC int SDLCALL SDL_GetAtomicInt(SDL_AtomicInt *a); | ||
453 | |||
454 | /** | ||
455 | * Add to an atomic variable. | ||
456 | * | ||
457 | * This function also acts as a full memory barrier. | ||
458 | * | ||
459 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
460 | * it!*** | ||
461 | * | ||
462 | * \param a a pointer to an SDL_AtomicInt variable to be modified. | ||
463 | * \param v the desired value to add. | ||
464 | * \returns the previous value of the atomic variable. | ||
465 | * | ||
466 | * \threadsafety It is safe to call this function from any thread. | ||
467 | * | ||
468 | * \since This function is available since SDL 3.2.0. | ||
469 | * | ||
470 | * \sa SDL_AtomicDecRef | ||
471 | * \sa SDL_AtomicIncRef | ||
472 | */ | ||
473 | extern SDL_DECLSPEC int SDLCALL SDL_AddAtomicInt(SDL_AtomicInt *a, int v); | ||
474 | |||
475 | #ifndef SDL_AtomicIncRef | ||
476 | |||
477 | /** | ||
478 | * Increment an atomic variable used as a reference count. | ||
479 | * | ||
480 | * ***Note: If you don't know what this macro is for, you shouldn't use it!*** | ||
481 | * | ||
482 | * \param a a pointer to an SDL_AtomicInt to increment. | ||
483 | * \returns the previous value of the atomic variable. | ||
484 | * | ||
485 | * \threadsafety It is safe to call this macro from any thread. | ||
486 | * | ||
487 | * \since This macro is available since SDL 3.2.0. | ||
488 | * | ||
489 | * \sa SDL_AtomicDecRef | ||
490 | */ | ||
491 | #define SDL_AtomicIncRef(a) SDL_AddAtomicInt(a, 1) | ||
492 | #endif | ||
493 | |||
494 | #ifndef SDL_AtomicDecRef | ||
495 | |||
496 | /** | ||
497 | * Decrement an atomic variable used as a reference count. | ||
498 | * | ||
499 | * ***Note: If you don't know what this macro is for, you shouldn't use it!*** | ||
500 | * | ||
501 | * \param a a pointer to an SDL_AtomicInt to decrement. | ||
502 | * \returns true if the variable reached zero after decrementing, false | ||
503 | * otherwise. | ||
504 | * | ||
505 | * \threadsafety It is safe to call this macro from any thread. | ||
506 | * | ||
507 | * \since This macro is available since SDL 3.2.0. | ||
508 | * | ||
509 | * \sa SDL_AtomicIncRef | ||
510 | */ | ||
511 | #define SDL_AtomicDecRef(a) (SDL_AddAtomicInt(a, -1) == 1) | ||
512 | #endif | ||
513 | |||
514 | /** | ||
515 | * A type representing an atomic unsigned 32-bit value. | ||
516 | * | ||
517 | * This can be used to manage a value that is synchronized across multiple | ||
518 | * CPUs without a race condition; when an app sets a value with | ||
519 | * SDL_SetAtomicU32 all other threads, regardless of the CPU it is running on, | ||
520 | * will see that value when retrieved with SDL_GetAtomicU32, regardless of CPU | ||
521 | * caches, etc. | ||
522 | * | ||
523 | * This is also useful for atomic compare-and-swap operations: a thread can | ||
524 | * change the value as long as its current value matches expectations. When | ||
525 | * done in a loop, one can guarantee data consistency across threads without a | ||
526 | * lock (but the usual warnings apply: if you don't know what you're doing, or | ||
527 | * you don't do it carefully, you can confidently cause any number of | ||
528 | * disasters with this, so in most cases, you _should_ use a mutex instead of | ||
529 | * this!). | ||
530 | * | ||
531 | * This is a struct so people don't accidentally use numeric operations on it | ||
532 | * directly. You have to use SDL atomic functions. | ||
533 | * | ||
534 | * \since This struct is available since SDL 3.2.0. | ||
535 | * | ||
536 | * \sa SDL_CompareAndSwapAtomicU32 | ||
537 | * \sa SDL_GetAtomicU32 | ||
538 | * \sa SDL_SetAtomicU32 | ||
539 | */ | ||
540 | typedef struct SDL_AtomicU32 { Uint32 value; } SDL_AtomicU32; | ||
541 | |||
542 | /** | ||
543 | * Set an atomic variable to a new value if it is currently an old value. | ||
544 | * | ||
545 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
546 | * it!*** | ||
547 | * | ||
548 | * \param a a pointer to an SDL_AtomicU32 variable to be modified. | ||
549 | * \param oldval the old value. | ||
550 | * \param newval the new value. | ||
551 | * \returns true if the atomic variable was set, false otherwise. | ||
552 | * | ||
553 | * \threadsafety It is safe to call this function from any thread. | ||
554 | * | ||
555 | * \since This function is available since SDL 3.2.0. | ||
556 | * | ||
557 | * \sa SDL_GetAtomicU32 | ||
558 | * \sa SDL_SetAtomicU32 | ||
559 | */ | ||
560 | extern SDL_DECLSPEC bool SDLCALL SDL_CompareAndSwapAtomicU32(SDL_AtomicU32 *a, Uint32 oldval, Uint32 newval); | ||
561 | |||
562 | /** | ||
563 | * Set an atomic variable to a value. | ||
564 | * | ||
565 | * This function also acts as a full memory barrier. | ||
566 | * | ||
567 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
568 | * it!*** | ||
569 | * | ||
570 | * \param a a pointer to an SDL_AtomicU32 variable to be modified. | ||
571 | * \param v the desired value. | ||
572 | * \returns the previous value of the atomic variable. | ||
573 | * | ||
574 | * \threadsafety It is safe to call this function from any thread. | ||
575 | * | ||
576 | * \since This function is available since SDL 3.2.0. | ||
577 | * | ||
578 | * \sa SDL_GetAtomicU32 | ||
579 | */ | ||
580 | extern SDL_DECLSPEC Uint32 SDLCALL SDL_SetAtomicU32(SDL_AtomicU32 *a, Uint32 v); | ||
581 | |||
582 | /** | ||
583 | * Get the value of an atomic variable. | ||
584 | * | ||
585 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
586 | * it!*** | ||
587 | * | ||
588 | * \param a a pointer to an SDL_AtomicU32 variable. | ||
589 | * \returns the current value of an atomic variable. | ||
590 | * | ||
591 | * \threadsafety It is safe to call this function from any thread. | ||
592 | * | ||
593 | * \since This function is available since SDL 3.2.0. | ||
594 | * | ||
595 | * \sa SDL_SetAtomicU32 | ||
596 | */ | ||
597 | extern SDL_DECLSPEC Uint32 SDLCALL SDL_GetAtomicU32(SDL_AtomicU32 *a); | ||
598 | |||
599 | /** | ||
600 | * Set a pointer to a new value if it is currently an old value. | ||
601 | * | ||
602 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
603 | * it!*** | ||
604 | * | ||
605 | * \param a a pointer to a pointer. | ||
606 | * \param oldval the old pointer value. | ||
607 | * \param newval the new pointer value. | ||
608 | * \returns true if the pointer was set, false otherwise. | ||
609 | * | ||
610 | * \threadsafety It is safe to call this function from any thread. | ||
611 | * | ||
612 | * \since This function is available since SDL 3.2.0. | ||
613 | * | ||
614 | * \sa SDL_CompareAndSwapAtomicInt | ||
615 | * \sa SDL_GetAtomicPointer | ||
616 | * \sa SDL_SetAtomicPointer | ||
617 | */ | ||
618 | extern SDL_DECLSPEC bool SDLCALL SDL_CompareAndSwapAtomicPointer(void **a, void *oldval, void *newval); | ||
619 | |||
620 | /** | ||
621 | * Set a pointer to a value atomically. | ||
622 | * | ||
623 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
624 | * it!*** | ||
625 | * | ||
626 | * \param a a pointer to a pointer. | ||
627 | * \param v the desired pointer value. | ||
628 | * \returns the previous value of the pointer. | ||
629 | * | ||
630 | * \threadsafety It is safe to call this function from any thread. | ||
631 | * | ||
632 | * \since This function is available since SDL 3.2.0. | ||
633 | * | ||
634 | * \sa SDL_CompareAndSwapAtomicPointer | ||
635 | * \sa SDL_GetAtomicPointer | ||
636 | */ | ||
637 | extern SDL_DECLSPEC void * SDLCALL SDL_SetAtomicPointer(void **a, void *v); | ||
638 | |||
639 | /** | ||
640 | * Get the value of a pointer atomically. | ||
641 | * | ||
642 | * ***Note: If you don't know what this function is for, you shouldn't use | ||
643 | * it!*** | ||
644 | * | ||
645 | * \param a a pointer to a pointer. | ||
646 | * \returns the current value of a pointer. | ||
647 | * | ||
648 | * \threadsafety It is safe to call this function from any thread. | ||
649 | * | ||
650 | * \since This function is available since SDL 3.2.0. | ||
651 | * | ||
652 | * \sa SDL_CompareAndSwapAtomicPointer | ||
653 | * \sa SDL_SetAtomicPointer | ||
654 | */ | ||
655 | extern SDL_DECLSPEC void * SDLCALL SDL_GetAtomicPointer(void **a); | ||
656 | |||
657 | /* Ends C function definitions when using C++ */ | ||
658 | #ifdef __cplusplus | ||
659 | } | ||
660 | #endif | ||
661 | |||
662 | #include <SDL3/SDL_close_code.h> | ||
663 | |||
664 | #endif /* SDL_atomic_h_ */ | ||