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 #ifndef SDL_thread_h_ 23 #define SDL_thread_h_ 24 25 /** 26 * # CategoryThread 27 * 28 * Header for the SDL thread management routines. 29 */ 30 31 #include "SDL_stdinc.h" 32 #include "SDL_error.h" 33 34 /* Thread synchronization primitives */ 35 #include "SDL_atomic.h" 36 #include "SDL_mutex.h" 37 38 #if (defined(__WIN32__) || defined(__GDK__)) && !defined(__WINRT__) 39 #include <process.h> /* _beginthreadex() and _endthreadex() */ 40 #endif 41 #if defined(__OS2__) /* for _beginthread() and _endthread() */ 42 #ifndef __EMX__ 43 #include <process.h> 44 #else 45 #include <stdlib.h> 46 #endif 47 #endif 48 49 #include "begin_code.h" 50 /* Set up for C function definitions, even when using C++ */ 51 #ifdef __cplusplus 52 extern "C" { 53 #endif 54 55 /* The SDL thread structure, defined in SDL_thread.c */ 56 struct SDL_Thread; 57 typedef struct SDL_Thread SDL_Thread; 58 59 /* The SDL thread ID */ 60 typedef unsigned long SDL_threadID; 61 62 /* Thread local storage ID, 0 is the invalid ID */ 63 typedef unsigned int SDL_TLSID; 64 65 /** 66 * The SDL thread priority. 67 * 68 * SDL will make system changes as necessary in order to apply the thread 69 * priority. Code which attempts to control thread state related to priority 70 * should be aware that calling SDL_SetThreadPriority may alter such state. 71 * SDL_HINT_THREAD_PRIORITY_POLICY can be used to control aspects of this 72 * behavior. 73 * 74 * On many systems you require special privileges to set high or time critical 75 * priority. 76 */ 77 typedef enum SDL_ThreadPriority { 78 SDL_THREAD_PRIORITY_LOW, 79 SDL_THREAD_PRIORITY_NORMAL, 80 SDL_THREAD_PRIORITY_HIGH, 81 SDL_THREAD_PRIORITY_TIME_CRITICAL 82 } SDL_ThreadPriority; 83 84 /** 85 * The function passed to SDL_CreateThread(). 86 * 87 * \param data what was passed as `data` to SDL_CreateThread(). 88 * \returns a value that can be reported through SDL_WaitThread(). 89 */ 90 typedef int (SDLCALL * SDL_ThreadFunction) (void *data); 91 92 93 #if (defined(__WIN32__) || defined(__GDK__)) && !defined(__WINRT__) 94 /** 95 * \file SDL_thread.h 96 * 97 * We compile SDL into a DLL. This means, that it's the DLL which 98 * creates a new thread for the calling process with the SDL_CreateThread() 99 * API. There is a problem with this, that only the RTL of the SDL2.DLL will 100 * be initialized for those threads, and not the RTL of the calling 101 * application! 102 * 103 * To solve this, we make a little hack here. 104 * 105 * We'll always use the caller's _beginthread() and _endthread() APIs to 106 * start a new thread. This way, if it's the SDL2.DLL which uses this API, 107 * then the RTL of SDL2.DLL will be used to create the new thread, and if it's 108 * the application, then the RTL of the application will be used. 109 * 110 * So, in short: 111 * Always use the _beginthread() and _endthread() of the calling runtime 112 * library! 113 */ 114 #define SDL_PASSED_BEGINTHREAD_ENDTHREAD 115 116 typedef uintptr_t (__cdecl * pfnSDL_CurrentBeginThread) 117 (void *, unsigned, unsigned (__stdcall *func)(void *), 118 void * /*arg*/, unsigned, unsigned * /* threadID */); 119 typedef void (__cdecl * pfnSDL_CurrentEndThread) (unsigned code); 120 121 #ifndef SDL_beginthread 122 #define SDL_beginthread _beginthreadex 123 #endif 124 #ifndef SDL_endthread 125 #define SDL_endthread _endthreadex 126 #endif 127 128 extern DECLSPEC SDL_Thread *SDLCALL 129 SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data, 130 pfnSDL_CurrentBeginThread pfnBeginThread, 131 pfnSDL_CurrentEndThread pfnEndThread); 132 133 extern DECLSPEC SDL_Thread *SDLCALL 134 SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, 135 const char *name, const size_t stacksize, void *data, 136 pfnSDL_CurrentBeginThread pfnBeginThread, 137 pfnSDL_CurrentEndThread pfnEndThread); 138 139 140 #if defined(SDL_CreateThread) && SDL_DYNAMIC_API 141 #undef SDL_CreateThread 142 #define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 143 #undef SDL_CreateThreadWithStackSize 144 #define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 145 #else 146 #define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 147 #define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 148 #endif 149 150 #elif defined(__OS2__) 151 /* 152 * just like the windows case above: We compile SDL2 153 * into a dll with Watcom's runtime statically linked. 154 */ 155 #define SDL_PASSED_BEGINTHREAD_ENDTHREAD 156 157 typedef int (*pfnSDL_CurrentBeginThread)(void (*func)(void *), void *, unsigned, void * /*arg*/); 158 typedef void (*pfnSDL_CurrentEndThread)(void); 159 160 #ifndef SDL_beginthread 161 #define SDL_beginthread _beginthread 162 #endif 163 #ifndef SDL_endthread 164 #define SDL_endthread _endthread 165 #endif 166 167 extern DECLSPEC SDL_Thread *SDLCALL 168 SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data, 169 pfnSDL_CurrentBeginThread pfnBeginThread, 170 pfnSDL_CurrentEndThread pfnEndThread); 171 extern DECLSPEC SDL_Thread *SDLCALL 172 SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data, 173 pfnSDL_CurrentBeginThread pfnBeginThread, 174 pfnSDL_CurrentEndThread pfnEndThread); 175 176 #if defined(SDL_CreateThread) && SDL_DYNAMIC_API 177 #undef SDL_CreateThread 178 #define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 179 #undef SDL_CreateThreadWithStackSize 180 #define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 181 #else 182 #define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 183 #define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread) 184 #endif 185 186 #else 187 188 /** 189 * Create a new thread with a default stack size. 190 * 191 * This is equivalent to calling: 192 * 193 * ```c 194 * SDL_CreateThreadWithStackSize(fn, name, 0, data); 195 * ``` 196 * 197 * \param fn the SDL_ThreadFunction function to call in the new thread. 198 * \param name the name of the thread. 199 * \param data a pointer that is passed to `fn`. 200 * \returns an opaque pointer to the new thread object on success, NULL if the 201 * new thread could not be created; call SDL_GetError() for more 202 * information. 203 * 204 * \since This function is available since SDL 2.0.0. 205 * 206 * \sa SDL_CreateThreadWithStackSize 207 * \sa SDL_WaitThread 208 */ 209 extern DECLSPEC SDL_Thread *SDLCALL 210 SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data); 211 212 /** 213 * Create a new thread with a specific stack size. 214 * 215 * SDL makes an attempt to report `name` to the system, so that debuggers can 216 * display it. Not all platforms support this. 217 * 218 * Thread naming is a little complicated: Most systems have very small limits 219 * for the string length (Haiku has 32 bytes, Linux currently has 16, Visual 220 * C++ 6.0 has _nine_!), and possibly other arbitrary rules. You'll have to 221 * see what happens with your system's debugger. The name should be UTF-8 (but 222 * using the naming limits of C identifiers is a better bet). There are no 223 * requirements for thread naming conventions, so long as the string is 224 * null-terminated UTF-8, but these guidelines are helpful in choosing a name: 225 * 226 * https://stackoverflow.com/questions/149932/naming-conventions-for-threads 227 * 228 * If a system imposes requirements, SDL will try to munge the string for it 229 * (truncate, etc), but the original string contents will be available from 230 * SDL_GetThreadName(). 231 * 232 * The size (in bytes) of the new stack can be specified. Zero means "use the 233 * system default" which might be wildly different between platforms. x86 234 * Linux generally defaults to eight megabytes, an embedded device might be a 235 * few kilobytes instead. You generally need to specify a stack that is a 236 * multiple of the system's page size (in many cases, this is 4 kilobytes, but 237 * check your system documentation). 238 * 239 * In SDL 2.1, stack size will be folded into the original SDL_CreateThread 240 * function, but for backwards compatibility, this is currently a separate 241 * function. 242 * 243 * \param fn the SDL_ThreadFunction function to call in the new thread. 244 * \param name the name of the thread. 245 * \param stacksize the size, in bytes, to allocate for the new thread stack. 246 * \param data a pointer that is passed to `fn`. 247 * \returns an opaque pointer to the new thread object on success, NULL if the 248 * new thread could not be created; call SDL_GetError() for more 249 * information. 250 * 251 * \since This function is available since SDL 2.0.9. 252 * 253 * \sa SDL_WaitThread 254 */ 255 extern DECLSPEC SDL_Thread *SDLCALL 256 SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data); 257 258 #endif 259 260 /** 261 * Get the thread name as it was specified in SDL_CreateThread(). 262 * 263 * This is internal memory, not to be freed by the caller, and remains valid 264 * until the specified thread is cleaned up by SDL_WaitThread(). 265 * 266 * \param thread the thread to query. 267 * \returns a pointer to a UTF-8 string that names the specified thread, or 268 * NULL if it doesn't have a name. 269 * 270 * \since This function is available since SDL 2.0.0. 271 * 272 * \sa SDL_CreateThread 273 */ 274 extern DECLSPEC const char *SDLCALL SDL_GetThreadName(SDL_Thread *thread); 275 276 /** 277 * Get the thread identifier for the current thread. 278 * 279 * This thread identifier is as reported by the underlying operating system. 280 * If SDL is running on a platform that does not support threads the return 281 * value will always be zero. 282 * 283 * This function also returns a valid thread ID when called from the main 284 * thread. 285 * 286 * \returns the ID of the current thread. 287 * 288 * \since This function is available since SDL 2.0.0. 289 * 290 * \sa SDL_GetThreadID 291 */ 292 extern DECLSPEC SDL_threadID SDLCALL SDL_ThreadID(void); 293 294 /** 295 * Get the thread identifier for the specified thread. 296 * 297 * This thread identifier is as reported by the underlying operating system. 298 * If SDL is running on a platform that does not support threads the return 299 * value will always be zero. 300 * 301 * \param thread the thread to query. 302 * \returns the ID of the specified thread, or the ID of the current thread if 303 * `thread` is NULL. 304 * 305 * \since This function is available since SDL 2.0.0. 306 * 307 * \sa SDL_ThreadID 308 */ 309 extern DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID(SDL_Thread * thread); 310 311 /** 312 * Set the priority for the current thread. 313 * 314 * Note that some platforms will not let you alter the priority (or at least, 315 * promote the thread to a higher priority) at all, and some require you to be 316 * an administrator account. Be prepared for this to fail. 317 * 318 * \param priority the SDL_ThreadPriority to set. 319 * \returns 0 on success or a negative error code on failure; call 320 * SDL_GetError() for more information. 321 * 322 * \since This function is available since SDL 2.0.0. 323 */ 324 extern DECLSPEC int SDLCALL SDL_SetThreadPriority(SDL_ThreadPriority priority); 325 326 /** 327 * Wait for a thread to finish. 328 * 329 * Threads that haven't been detached will remain (as a "zombie") until this 330 * function cleans them up. Not doing so is a resource leak. 331 * 332 * Once a thread has been cleaned up through this function, the SDL_Thread 333 * that references it becomes invalid and should not be referenced again. As 334 * such, only one thread may call SDL_WaitThread() on another. 335 * 336 * The return code for the thread function is placed in the area pointed to by 337 * `status`, if `status` is not NULL. 338 * 339 * You may not wait on a thread that has been used in a call to 340 * SDL_DetachThread(). Use either that function or this one, but not both, or 341 * behavior is undefined. 342 * 343 * It is safe to pass a NULL thread to this function; it is a no-op. 344 * 345 * Note that the thread pointer is freed by this function and is not valid 346 * afterward. 347 * 348 * \param thread the SDL_Thread pointer that was returned from the 349 * SDL_CreateThread() call that started this thread. 350 * \param status pointer to an integer that will receive the value returned 351 * from the thread function by its 'return', or NULL to not 352 * receive such value back. 353 * 354 * \since This function is available since SDL 2.0.0. 355 * 356 * \sa SDL_CreateThread 357 * \sa SDL_DetachThread 358 */ 359 extern DECLSPEC void SDLCALL SDL_WaitThread(SDL_Thread * thread, int *status); 360 361 /** 362 * Let a thread clean up on exit without intervention. 363 * 364 * A thread may be "detached" to signify that it should not remain until 365 * another thread has called SDL_WaitThread() on it. Detaching a thread is 366 * useful for long-running threads that nothing needs to synchronize with or 367 * further manage. When a detached thread is done, it simply goes away. 368 * 369 * There is no way to recover the return code of a detached thread. If you 370 * need this, don't detach the thread and instead use SDL_WaitThread(). 371 * 372 * Once a thread is detached, you should usually assume the SDL_Thread isn't 373 * safe to reference again, as it will become invalid immediately upon the 374 * detached thread's exit, instead of remaining until someone has called 375 * SDL_WaitThread() to finally clean it up. As such, don't detach the same 376 * thread more than once. 377 * 378 * If a thread has already exited when passed to SDL_DetachThread(), it will 379 * stop waiting for a call to SDL_WaitThread() and clean up immediately. It is 380 * not safe to detach a thread that might be used with SDL_WaitThread(). 381 * 382 * You may not call SDL_WaitThread() on a thread that has been detached. Use 383 * either that function or this one, but not both, or behavior is undefined. 384 * 385 * It is safe to pass NULL to this function; it is a no-op. 386 * 387 * \param thread the SDL_Thread pointer that was returned from the 388 * SDL_CreateThread() call that started this thread. 389 * 390 * \since This function is available since SDL 2.0.2. 391 * 392 * \sa SDL_CreateThread 393 * \sa SDL_WaitThread 394 */ 395 extern DECLSPEC void SDLCALL SDL_DetachThread(SDL_Thread * thread); 396 397 /** 398 * Create a piece of thread-local storage. 399 * 400 * This creates an identifier that is globally visible to all threads but 401 * refers to data that is thread-specific. 402 * 403 * \returns the newly created thread local storage identifier or 0 on error. 404 * 405 * \since This function is available since SDL 2.0.0. 406 * 407 * \sa SDL_TLSGet 408 * \sa SDL_TLSSet 409 */ 410 extern DECLSPEC SDL_TLSID SDLCALL SDL_TLSCreate(void); 411 412 /** 413 * Get the current thread's value associated with a thread local storage ID. 414 * 415 * \param id the thread local storage ID. 416 * \returns the value associated with the ID for the current thread or NULL if 417 * no value has been set; call SDL_GetError() for more information. 418 * 419 * \since This function is available since SDL 2.0.0. 420 * 421 * \sa SDL_TLSCreate 422 * \sa SDL_TLSSet 423 */ 424 extern DECLSPEC void * SDLCALL SDL_TLSGet(SDL_TLSID id); 425 426 typedef void (SDLCALL *SDL_TLSDestructorCallback)(void*); 427 428 /** 429 * Set the current thread's value associated with a thread local storage ID. 430 * 431 * The function prototype for `destructor` is: 432 * 433 * ```c 434 * void destructor(void *value) 435 * ``` 436 * 437 * where its parameter `value` is what was passed as `value` to SDL_TLSSet(). 438 * 439 * \param id the thread local storage ID. 440 * \param value the value to associate with the ID for the current thread. 441 * \param destructor a function called when the thread exits, to free the 442 * value. 443 * \returns 0 on success or a negative error code on failure; call 444 * SDL_GetError() for more information. 445 * 446 * \since This function is available since SDL 2.0.0. 447 * 448 * \sa SDL_TLSCreate 449 * \sa SDL_TLSGet 450 */ 451 extern DECLSPEC int SDLCALL SDL_TLSSet(SDL_TLSID id, const void *value, SDL_TLSDestructorCallback destructor); 452 453 /** 454 * Cleanup all TLS data for this thread. 455 * 456 * \since This function is available since SDL 2.0.16. 457 */ 458 extern DECLSPEC void SDLCALL SDL_TLSCleanup(void); 459 460 /* Ends C function definitions when using C++ */ 461 #ifdef __cplusplus 462 } 463 #endif 464 #include "close_code.h" 465 466 #endif /* SDL_thread_h_ */ 467 468 /* vi: set ts=4 sw=4 expandtab: */