SDL 3.0
SDL_thread.h
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1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2023 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 * \file SDL_thread.h
27 *
28 * Header for the SDL thread management routines.
29 */
30
31#include <SDL3/SDL_stdinc.h>
32#include <SDL3/SDL_error.h>
33
34/* Thread synchronization primitives */
35#include <SDL3/SDL_atomic.h>
36#include <SDL3/SDL_mutex.h>
37
38#if (defined(__WIN32__) || defined(__GDK__)) && !defined(__WINRT__)
39#include <process.h> /* _beginthreadex() and _endthreadex() */
40#endif
41
42#include <SDL3/SDL_begin_code.h>
43/* Set up for C function definitions, even when using C++ */
44#ifdef __cplusplus
45extern "C" {
46#endif
47
48/* The SDL thread structure, defined in SDL_thread.c */
49struct SDL_Thread;
50typedef struct SDL_Thread SDL_Thread;
51
52/* The SDL thread ID */
53typedef unsigned long SDL_threadID;
54
55/* Thread local storage ID, 0 is the invalid ID */
56typedef unsigned int SDL_TLSID;
57
58/**
59 * The SDL thread priority.
60 *
61 * SDL will make system changes as necessary in order to apply the thread priority.
62 * Code which attempts to control thread state related to priority should be aware
63 * that calling SDL_SetThreadPriority may alter such state.
64 * SDL_HINT_THREAD_PRIORITY_POLICY can be used to control aspects of this behavior.
65 *
66 * \note On many systems you require special privileges to set high or time critical priority.
67 */
74
75/**
76 * The function passed to SDL_CreateThread().
77 *
78 * \param data what was passed as `data` to SDL_CreateThread()
79 * \returns a value that can be reported through SDL_WaitThread().
80 */
81typedef int (SDLCALL * SDL_ThreadFunction) (void *data);
82
83
84#if (defined(__WIN32__) || defined(__GDK__)) && !defined(__WINRT__)
85/**
86 * \file SDL_thread.h
87 *
88 * We compile SDL into a DLL. This means, that it's the DLL which
89 * creates a new thread for the calling process with the SDL_CreateThread()
90 * API. There is a problem with this, that only the RTL of the SDL3.DLL will
91 * be initialized for those threads, and not the RTL of the calling
92 * application!
93 *
94 * To solve this, we make a little hack here.
95 *
96 * We'll always use the caller's _beginthread() and _endthread() APIs to
97 * start a new thread. This way, if it's the SDL3.DLL which uses this API,
98 * then the RTL of SDL3.DLL will be used to create the new thread, and if it's
99 * the application, then the RTL of the application will be used.
100 *
101 * So, in short:
102 * Always use the _beginthread() and _endthread() of the calling runtime
103 * library!
104 */
105#define SDL_PASSED_BEGINTHREAD_ENDTHREAD
106
107typedef uintptr_t (__cdecl * pfnSDL_CurrentBeginThread)
108 (void *, unsigned, unsigned (__stdcall *func)(void *),
109 void * /*arg*/, unsigned, unsigned * /* threadID */);
110typedef void (__cdecl * pfnSDL_CurrentEndThread) (unsigned code);
111
112#ifndef SDL_beginthread
113#define SDL_beginthread _beginthreadex
114#endif
115#ifndef SDL_endthread
116#define SDL_endthread _endthreadex
117#endif
118
119
120/*
121 * Create a SDL Thread
122 *
123 * \param fn Thread function
124 * \param name name
125 * \param data some data
126 * \param pfnBeginThread begin function
127 * \param pfnEndThread end function
128 *
129 * \returns SDL_Thread pointer
130 *
131 * \since This function is available since SDL 3.0.0.
132 */
133extern DECLSPEC SDL_Thread *SDLCALL
134SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
135 pfnSDL_CurrentBeginThread pfnBeginThread,
136 pfnSDL_CurrentEndThread pfnEndThread);
137
138/*
139 * Create a SDL Thread, with explicit stack size
140 *
141 * \param fn Thread function
142 * \param name name
143 * \param stacksize stack size
144 * \param data some data
145 * \param pfnBeginThread begin function
146 * \param pfnEndThread end function
147 *
148 * \returns SDL_Thread pointer
149 *
150 * \since This function is available since SDL 3.0.0.
151 */
152extern DECLSPEC SDL_Thread *SDLCALL
154 const char *name, const size_t stacksize, void *data,
155 pfnSDL_CurrentBeginThread pfnBeginThread,
156 pfnSDL_CurrentEndThread pfnEndThread);
157
158#if !defined(__BUILDING_SDL2_COMPAT__) /* do not conflict with sdl2-compat::sdl3_include_wrapper.h */
159#if defined(SDL_CreateThread) && SDL_DYNAMIC_API
160#undef SDL_CreateThread
161#define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
162#undef SDL_CreateThreadWithStackSize
163#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
164#else
165#define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
166#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
167#endif
168#endif /* !__BUILDING_SDL2_COMPAT__ */
169
170#else
171
172/**
173 * Create a new thread with a default stack size.
174 *
175 * This is equivalent to calling:
176 *
177 * ```c
178 * SDL_CreateThreadWithStackSize(fn, name, 0, data);
179 * ```
180 *
181 * \param fn the SDL_ThreadFunction function to call in the new thread
182 * \param name the name of the thread
183 * \param data a pointer that is passed to `fn`
184 * \returns an opaque pointer to the new thread object on success, NULL if the
185 * new thread could not be created; call SDL_GetError() for more
186 * information.
187 *
188 * \since This function is available since SDL 3.0.0.
189 *
190 * \sa SDL_CreateThreadWithStackSize
191 * \sa SDL_WaitThread
192 */
193extern DECLSPEC SDL_Thread *SDLCALL
194SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data);
195
196/**
197 * Create a new thread with a specific stack size.
198 *
199 * SDL makes an attempt to report `name` to the system, so that debuggers can
200 * display it. Not all platforms support this.
201 *
202 * Thread naming is a little complicated: Most systems have very small limits
203 * for the string length (Haiku has 32 bytes, Linux currently has 16, Visual
204 * C++ 6.0 has _nine_!), and possibly other arbitrary rules. You'll have to
205 * see what happens with your system's debugger. The name should be UTF-8 (but
206 * using the naming limits of C identifiers is a better bet). There are no
207 * requirements for thread naming conventions, so long as the string is
208 * null-terminated UTF-8, but these guidelines are helpful in choosing a name:
209 *
210 * https://stackoverflow.com/questions/149932/naming-conventions-for-threads
211 *
212 * If a system imposes requirements, SDL will try to munge the string for it
213 * (truncate, etc), but the original string contents will be available from
214 * SDL_GetThreadName().
215 *
216 * The size (in bytes) of the new stack can be specified. Zero means "use the
217 * system default" which might be wildly different between platforms. x86
218 * Linux generally defaults to eight megabytes, an embedded device might be a
219 * few kilobytes instead. You generally need to specify a stack that is a
220 * multiple of the system's page size (in many cases, this is 4 kilobytes, but
221 * check your system documentation).
222 *
223 * In SDL 2.1, stack size will be folded into the original SDL_CreateThread
224 * function, but for backwards compatibility, this is currently a separate
225 * function.
226 *
227 * \param fn the SDL_ThreadFunction function to call in the new thread
228 * \param name the name of the thread
229 * \param stacksize the size, in bytes, to allocate for the new thread stack.
230 * \param data a pointer that is passed to `fn`
231 * \returns an opaque pointer to the new thread object on success, NULL if the
232 * new thread could not be created; call SDL_GetError() for more
233 * information.
234 *
235 * \since This function is available since SDL 3.0.0.
236 *
237 * \sa SDL_WaitThread
238 */
239extern DECLSPEC SDL_Thread *SDLCALL
240SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data);
241
242#endif
243
244/**
245 * Get the thread name as it was specified in SDL_CreateThread().
246 *
247 * This is internal memory, not to be freed by the caller, and remains valid
248 * until the specified thread is cleaned up by SDL_WaitThread().
249 *
250 * \param thread the thread to query
251 * \returns a pointer to a UTF-8 string that names the specified thread, or
252 * NULL if it doesn't have a name.
253 *
254 * \since This function is available since SDL 3.0.0.
255 *
256 * \sa SDL_CreateThread
257 */
258extern DECLSPEC const char *SDLCALL SDL_GetThreadName(SDL_Thread *thread);
259
260/**
261 * Get the thread identifier for the current thread.
262 *
263 * This thread identifier is as reported by the underlying operating system.
264 * If SDL is running on a platform that does not support threads the return
265 * value will always be zero.
266 *
267 * This function also returns a valid thread ID when called from the main
268 * thread.
269 *
270 * \returns the ID of the current thread.
271 *
272 * \since This function is available since SDL 3.0.0.
273 *
274 * \sa SDL_GetThreadID
275 */
276extern DECLSPEC SDL_threadID SDLCALL SDL_ThreadID(void);
277
278/**
279 * Get the thread identifier for the specified thread.
280 *
281 * This thread identifier is as reported by the underlying operating system.
282 * If SDL is running on a platform that does not support threads the return
283 * value will always be zero.
284 *
285 * \param thread the thread to query
286 * \returns the ID of the specified thread, or the ID of the current thread if
287 * `thread` is NULL.
288 *
289 * \since This function is available since SDL 3.0.0.
290 *
291 * \sa SDL_ThreadID
292 */
293extern DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID(SDL_Thread * thread);
294
295/**
296 * Set the priority for the current thread.
297 *
298 * Note that some platforms will not let you alter the priority (or at least,
299 * promote the thread to a higher priority) at all, and some require you to be
300 * an administrator account. Be prepared for this to fail.
301 *
302 * \param priority the SDL_ThreadPriority to set
303 * \returns 0 on success or a negative error code on failure; call
304 * SDL_GetError() for more information.
305 *
306 * \since This function is available since SDL 3.0.0.
307 */
308extern DECLSPEC int SDLCALL SDL_SetThreadPriority(SDL_ThreadPriority priority);
309
310/**
311 * Wait for a thread to finish.
312 *
313 * Threads that haven't been detached will remain (as a "zombie") until this
314 * function cleans them up. Not doing so is a resource leak.
315 *
316 * Once a thread has been cleaned up through this function, the SDL_Thread
317 * that references it becomes invalid and should not be referenced again. As
318 * such, only one thread may call SDL_WaitThread() on another.
319 *
320 * The return code for the thread function is placed in the area pointed to by
321 * `status`, if `status` is not NULL.
322 *
323 * You may not wait on a thread that has been used in a call to
324 * SDL_DetachThread(). Use either that function or this one, but not both, or
325 * behavior is undefined.
326 *
327 * It is safe to pass a NULL thread to this function; it is a no-op.
328 *
329 * Note that the thread pointer is freed by this function and is not valid
330 * afterward.
331 *
332 * \param thread the SDL_Thread pointer that was returned from the
333 * SDL_CreateThread() call that started this thread
334 * \param status pointer to an integer that will receive the value returned
335 * from the thread function by its 'return', or NULL to not
336 * receive such value back.
337 *
338 * \since This function is available since SDL 3.0.0.
339 *
340 * \sa SDL_CreateThread
341 * \sa SDL_DetachThread
342 */
343extern DECLSPEC void SDLCALL SDL_WaitThread(SDL_Thread * thread, int *status);
344
345/**
346 * Let a thread clean up on exit without intervention.
347 *
348 * A thread may be "detached" to signify that it should not remain until
349 * another thread has called SDL_WaitThread() on it. Detaching a thread is
350 * useful for long-running threads that nothing needs to synchronize with or
351 * further manage. When a detached thread is done, it simply goes away.
352 *
353 * There is no way to recover the return code of a detached thread. If you
354 * need this, don't detach the thread and instead use SDL_WaitThread().
355 *
356 * Once a thread is detached, you should usually assume the SDL_Thread isn't
357 * safe to reference again, as it will become invalid immediately upon the
358 * detached thread's exit, instead of remaining until someone has called
359 * SDL_WaitThread() to finally clean it up. As such, don't detach the same
360 * thread more than once.
361 *
362 * If a thread has already exited when passed to SDL_DetachThread(), it will
363 * stop waiting for a call to SDL_WaitThread() and clean up immediately. It is
364 * not safe to detach a thread that might be used with SDL_WaitThread().
365 *
366 * You may not call SDL_WaitThread() on a thread that has been detached. Use
367 * either that function or this one, but not both, or behavior is undefined.
368 *
369 * It is safe to pass NULL to this function; it is a no-op.
370 *
371 * \param thread the SDL_Thread pointer that was returned from the
372 * SDL_CreateThread() call that started this thread
373 *
374 * \since This function is available since SDL 3.0.0.
375 *
376 * \sa SDL_CreateThread
377 * \sa SDL_WaitThread
378 */
379extern DECLSPEC void SDLCALL SDL_DetachThread(SDL_Thread * thread);
380
381/**
382 * Create a piece of thread-local storage.
383 *
384 * This creates an identifier that is globally visible to all threads but
385 * refers to data that is thread-specific.
386 *
387 * \returns the newly created thread local storage identifier or 0 on error.
388 *
389 * \since This function is available since SDL 3.0.0.
390 *
391 * \sa SDL_GetTLS
392 * \sa SDL_SetTLS
393 */
394extern DECLSPEC SDL_TLSID SDLCALL SDL_CreateTLS(void);
395
396/**
397 * Get the current thread's value associated with a thread local storage ID.
398 *
399 * \param id the thread local storage ID
400 * \returns the value associated with the ID for the current thread or NULL if
401 * no value has been set; call SDL_GetError() for more information.
402 *
403 * \since This function is available since SDL 3.0.0.
404 *
405 * \sa SDL_CreateTLS
406 * \sa SDL_SetTLS
407 */
408extern DECLSPEC void * SDLCALL SDL_GetTLS(SDL_TLSID id);
409
410/**
411 * Set the current thread's value associated with a thread local storage ID.
412 *
413 * The function prototype for `destructor` is:
414 *
415 * ```c
416 * void destructor(void *value)
417 * ```
418 *
419 * where its parameter `value` is what was passed as `value` to SDL_SetTLS().
420 *
421 * \param id the thread local storage ID
422 * \param value the value to associate with the ID for the current thread
423 * \param destructor a function called when the thread exits, to free the
424 * value
425 * \returns 0 on success or a negative error code on failure; call
426 * SDL_GetError() for more information.
427 *
428 * \since This function is available since SDL 3.0.0.
429 *
430 * \sa SDL_CreateTLS
431 * \sa SDL_GetTLS
432 */
433extern DECLSPEC int SDLCALL SDL_SetTLS(SDL_TLSID id, const void *value, void (SDLCALL *destructor)(void*));
434
435/**
436 * Cleanup all TLS data for this thread.
437 *
438 * \since This function is available since SDL 3.0.0.
439 */
440extern DECLSPEC void SDLCALL SDL_CleanupTLS(void);
441
442/* Ends C function definitions when using C++ */
443#ifdef __cplusplus
444}
445#endif
446#include <SDL3/SDL_close_code.h>
447
448#endif /* SDL_thread_h_ */
unsigned int SDL_TLSID
Definition SDL_thread.h:56
void SDL_DetachThread(SDL_Thread *thread)
SDL_TLSID SDL_CreateTLS(void)
void SDL_CleanupTLS(void)
SDL_threadID SDL_GetThreadID(SDL_Thread *thread)
const char * SDL_GetThreadName(SDL_Thread *thread)
SDL_Thread * SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data)
struct SDL_Thread SDL_Thread
Definition SDL_thread.h:50
int SDL_SetThreadPriority(SDL_ThreadPriority priority)
void SDL_WaitThread(SDL_Thread *thread, int *status)
unsigned long SDL_threadID
Definition SDL_thread.h:53
SDL_ThreadPriority
Definition SDL_thread.h:68
@ SDL_THREAD_PRIORITY_TIME_CRITICAL
Definition SDL_thread.h:72
@ SDL_THREAD_PRIORITY_LOW
Definition SDL_thread.h:69
@ SDL_THREAD_PRIORITY_HIGH
Definition SDL_thread.h:71
@ SDL_THREAD_PRIORITY_NORMAL
Definition SDL_thread.h:70
int SDL_SetTLS(SDL_TLSID id, const void *value, void(*destructor)(void *))
int(* SDL_ThreadFunction)(void *data)
Definition SDL_thread.h:81
void * SDL_GetTLS(SDL_TLSID id)
SDL_threadID SDL_ThreadID(void)
SDL_Thread * SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data)