1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2022 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 "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__)
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
52extern "C" {
53#endif
54
55/* The SDL thread structure, defined in SDL_thread.c */
56struct SDL_Thread;
57typedef struct SDL_Thread SDL_Thread;
58
59/* The SDL thread ID */
60typedef unsigned long SDL_threadID;
61
62/* Thread local storage ID, 0 is the invalid ID */
63typedef 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 priority.
69 * Code which attempts to control thread state related to priority should be aware
70 * that calling SDL_SetThreadPriority may alter such state.
71 * SDL_HINT_THREAD_PRIORITY_POLICY can be used to control aspects of this behavior.
72 *
73 * \note On many systems you require special privileges to set high or time critical priority.
74 */
75typedef enum {
76 SDL_THREAD_PRIORITY_LOW,
77 SDL_THREAD_PRIORITY_NORMAL,
78 SDL_THREAD_PRIORITY_HIGH,
79 SDL_THREAD_PRIORITY_TIME_CRITICAL
80} SDL_ThreadPriority;
81
82/**
83 * The function passed to SDL_CreateThread().
84 *
85 * \param data what was passed as `data` to SDL_CreateThread()
86 * \returns a value that can be reported through SDL_WaitThread().
87 */
88typedef int (SDLCALL * SDL_ThreadFunction) (void *data);
89
90
91#if defined(__WIN32__)
92/**
93 * \file SDL_thread.h
94 *
95 * We compile SDL into a DLL. This means, that it's the DLL which
96 * creates a new thread for the calling process with the SDL_CreateThread()
97 * API. There is a problem with this, that only the RTL of the SDL2.DLL will
98 * be initialized for those threads, and not the RTL of the calling
99 * application!
100 *
101 * To solve this, we make a little hack here.
102 *
103 * We'll always use the caller's _beginthread() and _endthread() APIs to
104 * start a new thread. This way, if it's the SDL2.DLL which uses this API,
105 * then the RTL of SDL2.DLL will be used to create the new thread, and if it's
106 * the application, then the RTL of the application will be used.
107 *
108 * So, in short:
109 * Always use the _beginthread() and _endthread() of the calling runtime
110 * library!
111 */
112#define SDL_PASSED_BEGINTHREAD_ENDTHREAD
113
114typedef uintptr_t (__cdecl * pfnSDL_CurrentBeginThread)
115 (void *, unsigned, unsigned (__stdcall *func)(void *),
116 void * /*arg*/, unsigned, unsigned * /* threadID */);
117typedef void (__cdecl * pfnSDL_CurrentEndThread) (unsigned code);
118
119#ifndef SDL_beginthread
120#define SDL_beginthread _beginthreadex
121#endif
122#ifndef SDL_endthread
123#define SDL_endthread _endthreadex
124#endif
125
126extern DECLSPEC SDL_Thread *SDLCALL
127SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
128 pfnSDL_CurrentBeginThread pfnBeginThread,
129 pfnSDL_CurrentEndThread pfnEndThread);
130
131extern DECLSPEC SDL_Thread *SDLCALL
132SDL_CreateThreadWithStackSize(int (SDLCALL * fn) (void *),
133 const char *name, const size_t stacksize, void *data,
134 pfnSDL_CurrentBeginThread pfnBeginThread,
135 pfnSDL_CurrentEndThread pfnEndThread);
136
137
138#if defined(SDL_CreateThread) && SDL_DYNAMIC_API
139#undef SDL_CreateThread
140#define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
141#undef SDL_CreateThreadWithStackSize
142#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
143#else
144#define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
145#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, data, (pfnSDL_CurrentBeginThread)_beginthreadex, (pfnSDL_CurrentEndThread)SDL_endthread)
146#endif
147
148#elif defined(__OS2__)
149/*
150 * just like the windows case above: We compile SDL2
151 * into a dll with Watcom's runtime statically linked.
152 */
153#define SDL_PASSED_BEGINTHREAD_ENDTHREAD
154
155typedef int (*pfnSDL_CurrentBeginThread)(void (*func)(void *), void *, unsigned, void * /*arg*/);
156typedef void (*pfnSDL_CurrentEndThread)(void);
157
158#ifndef SDL_beginthread
159#define SDL_beginthread _beginthread
160#endif
161#ifndef SDL_endthread
162#define SDL_endthread _endthread
163#endif
164
165extern DECLSPEC SDL_Thread *SDLCALL
166SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
167 pfnSDL_CurrentBeginThread pfnBeginThread,
168 pfnSDL_CurrentEndThread pfnEndThread);
169extern DECLSPEC SDL_Thread *SDLCALL
170SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data,
171 pfnSDL_CurrentBeginThread pfnBeginThread,
172 pfnSDL_CurrentEndThread pfnEndThread);
173
174#if defined(SDL_CreateThread) && SDL_DYNAMIC_API
175#undef SDL_CreateThread
176#define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
177#undef SDL_CreateThreadWithStackSize
178#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
179#else
180#define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
181#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
182#endif
183
184#else
185
186/**
187 * Create a new thread with a default stack size.
188 *
189 * This is equivalent to calling:
190 *
191 * ```c
192 * SDL_CreateThreadWithStackSize(fn, name, 0, data);
193 * ```
194 *
195 * \param fn the SDL_ThreadFunction function to call in the new thread
196 * \param name the name of the thread
197 * \param data a pointer that is passed to `fn`
198 * \returns an opaque pointer to the new thread object on success, NULL if the
199 * new thread could not be created; call SDL_GetError() for more
200 * information.
201 *
202 * \since This function is available since SDL 2.0.0.
203 *
204 * \sa SDL_CreateThreadWithStackSize
205 * \sa SDL_WaitThread
206 */
207extern DECLSPEC SDL_Thread *SDLCALL
208SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data);
209
210/**
211 * Create a new thread with a specific stack size.
212 *
213 * SDL makes an attempt to report `name` to the system, so that debuggers can
214 * display it. Not all platforms support this.
215 *
216 * Thread naming is a little complicated: Most systems have very small limits
217 * for the string length (Haiku has 32 bytes, Linux currently has 16, Visual
218 * C++ 6.0 has _nine_!), and possibly other arbitrary rules. You'll have to
219 * see what happens with your system's debugger. The name should be UTF-8 (but
220 * using the naming limits of C identifiers is a better bet). There are no
221 * requirements for thread naming conventions, so long as the string is
222 * null-terminated UTF-8, but these guidelines are helpful in choosing a name:
223 *
224 * https://stackoverflow.com/questions/149932/naming-conventions-for-threads
225 *
226 * If a system imposes requirements, SDL will try to munge the string for it
227 * (truncate, etc), but the original string contents will be available from
228 * SDL_GetThreadName().
229 *
230 * The size (in bytes) of the new stack can be specified. Zero means "use the
231 * system default" which might be wildly different between platforms. x86
232 * Linux generally defaults to eight megabytes, an embedded device might be a
233 * few kilobytes instead. You generally need to specify a stack that is a
234 * multiple of the system's page size (in many cases, this is 4 kilobytes, but
235 * check your system documentation).
236 *
237 * In SDL 2.1, stack size will be folded into the original SDL_CreateThread
238 * function, but for backwards compatibility, this is currently a separate
239 * function.
240 *
241 * \param fn the SDL_ThreadFunction function to call in the new thread
242 * \param name the name of the thread
243 * \param stacksize the size, in bytes, to allocate for the new thread stack.
244 * \param data a pointer that is passed to `fn`
245 * \returns an opaque pointer to the new thread object on success, NULL if the
246 * new thread could not be created; call SDL_GetError() for more
247 * information.
248 *
249 * \since This function is available since SDL 2.0.9.
250 *
251 * \sa SDL_WaitThread
252 */
253extern DECLSPEC SDL_Thread *SDLCALL
254SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data);
255
256#endif
257
258/**
259 * Get the thread name as it was specified in SDL_CreateThread().
260 *
261 * This is internal memory, not to be freed by the caller, and remains valid
262 * until the specified thread is cleaned up by SDL_WaitThread().
263 *
264 * \param thread the thread to query
265 * \returns a pointer to a UTF-8 string that names the specified thread, or
266 * NULL if it doesn't have a name.
267 *
268 * \since This function is available since SDL 2.0.0.
269 *
270 * \sa SDL_CreateThread
271 */
272extern DECLSPEC const char *SDLCALL SDL_GetThreadName(SDL_Thread *thread);
273
274/**
275 * Get the thread identifier for the current thread.
276 *
277 * This thread identifier is as reported by the underlying operating system.
278 * If SDL is running on a platform that does not support threads the return
279 * value will always be zero.
280 *
281 * This function also returns a valid thread ID when called from the main
282 * thread.
283 *
284 * \returns the ID of the current thread.
285 *
286 * \since This function is available since SDL 2.0.0.
287 *
288 * \sa SDL_GetThreadID
289 */
290extern DECLSPEC SDL_threadID SDLCALL SDL_ThreadID(void);
291
292/**
293 * Get the thread identifier for the specified thread.
294 *
295 * This thread identifier is as reported by the underlying operating system.
296 * If SDL is running on a platform that does not support threads the return
297 * value will always be zero.
298 *
299 * \param thread the thread to query
300 * \returns the ID of the specified thread, or the ID of the current thread if
301 * `thread` is NULL.
302 *
303 * \since This function is available since SDL 2.0.0.
304 *
305 * \sa SDL_ThreadID
306 */
307extern DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID(SDL_Thread * thread);
308
309/**
310 * Set the priority for the current thread.
311 *
312 * Note that some platforms will not let you alter the priority (or at least,
313 * promote the thread to a higher priority) at all, and some require you to be
314 * an administrator account. Be prepared for this to fail.
315 *
316 * \param priority the SDL_ThreadPriority to set
317 * \returns 0 on success or a negative error code on failure; call
318 * SDL_GetError() for more information.
319 *
320 * \since This function is available since SDL 2.0.0.
321 */
322extern DECLSPEC int SDLCALL SDL_SetThreadPriority(SDL_ThreadPriority priority);
323
324/**
325 * Wait for a thread to finish.
326 *
327 * Threads that haven't been detached will remain (as a "zombie") until this
328 * function cleans them up. Not doing so is a resource leak.
329 *
330 * Once a thread has been cleaned up through this function, the SDL_Thread
331 * that references it becomes invalid and should not be referenced again. As
332 * such, only one thread may call SDL_WaitThread() on another.
333 *
334 * The return code for the thread function is placed in the area pointed to by
335 * `status`, if `status` is not NULL.
336 *
337 * You may not wait on a thread that has been used in a call to
338 * SDL_DetachThread(). Use either that function or this one, but not both, or
339 * behavior is undefined.
340 *
341 * It is safe to pass a NULL thread to this function; it is a no-op.
342 *
343 * Note that the thread pointer is freed by this function and is not valid
344 * afterward.
345 *
346 * \param thread the SDL_Thread pointer that was returned from the
347 * SDL_CreateThread() call that started this thread
348 * \param status pointer to an integer that will receive the value returned
349 * from the thread function by its 'return', or NULL to not
350 * receive such value back.
351 *
352 * \since This function is available since SDL 2.0.0.
353 *
354 * \sa SDL_CreateThread
355 * \sa SDL_DetachThread
356 */
357extern DECLSPEC void SDLCALL SDL_WaitThread(SDL_Thread * thread, int *status);
358
359/**
360 * Let a thread clean up on exit without intervention.
361 *
362 * A thread may be "detached" to signify that it should not remain until
363 * another thread has called SDL_WaitThread() on it. Detaching a thread is
364 * useful for long-running threads that nothing needs to synchronize with or
365 * further manage. When a detached thread is done, it simply goes away.
366 *
367 * There is no way to recover the return code of a detached thread. If you
368 * need this, don't detach the thread and instead use SDL_WaitThread().
369 *
370 * Once a thread is detached, you should usually assume the SDL_Thread isn't
371 * safe to reference again, as it will become invalid immediately upon the
372 * detached thread's exit, instead of remaining until someone has called
373 * SDL_WaitThread() to finally clean it up. As such, don't detach the same
374 * thread more than once.
375 *
376 * If a thread has already exited when passed to SDL_DetachThread(), it will
377 * stop waiting for a call to SDL_WaitThread() and clean up immediately. It is
378 * not safe to detach a thread that might be used with SDL_WaitThread().
379 *
380 * You may not call SDL_WaitThread() on a thread that has been detached. Use
381 * either that function or this one, but not both, or behavior is undefined.
382 *
383 * It is safe to pass NULL to this function; it is a no-op.
384 *
385 * \param thread the SDL_Thread pointer that was returned from the
386 * SDL_CreateThread() call that started this thread
387 *
388 * \since This function is available since SDL 2.0.2.
389 *
390 * \sa SDL_CreateThread
391 * \sa SDL_WaitThread
392 */
393extern DECLSPEC void SDLCALL SDL_DetachThread(SDL_Thread * thread);
394
395/**
396 * Create a piece of thread-local storage.
397 *
398 * This creates an identifier that is globally visible to all threads but
399 * refers to data that is thread-specific.
400 *
401 * \returns the newly created thread local storage identifier or 0 on error.
402 *
403 * \since This function is available since SDL 2.0.0.
404 *
405 * \sa SDL_TLSGet
406 * \sa SDL_TLSSet
407 */
408extern DECLSPEC SDL_TLSID SDLCALL SDL_TLSCreate(void);
409
410/**
411 * Get the current thread's value associated with a thread local storage ID.
412 *
413 * \param id the thread local storage ID
414 * \returns the value associated with the ID for the current thread or NULL if
415 * no value has been set; call SDL_GetError() for more information.
416 *
417 * \since This function is available since SDL 2.0.0.
418 *
419 * \sa SDL_TLSCreate
420 * \sa SDL_TLSSet
421 */
422extern DECLSPEC void * SDLCALL SDL_TLSGet(SDL_TLSID id);
423
424/**
425 * Set the current thread's value associated with a thread local storage ID.
426 *
427 * The function prototype for `destructor` is:
428 *
429 * ```c
430 * void destructor(void *value)
431 * ```
432 *
433 * where its parameter `value` is what was passed as `value` to SDL_TLSSet().
434 *
435 * \param id the thread local storage ID
436 * \param value the value to associate with the ID for the current thread
437 * \param destructor a function called when the thread exits, to free the
438 * value
439 * \returns 0 on success or a negative error code on failure; call
440 * SDL_GetError() for more information.
441 *
442 * \since This function is available since SDL 2.0.0.
443 *
444 * \sa SDL_TLSCreate
445 * \sa SDL_TLSGet
446 */
447extern DECLSPEC int SDLCALL SDL_TLSSet(SDL_TLSID id, const void *value, void (SDLCALL *destructor)(void*));
448
449/**
450 * Cleanup all TLS data for this thread.
451 *
452 * \since This function is available since SDL 2.0.16.
453 */
454extern DECLSPEC void SDLCALL SDL_TLSCleanup(void);
455
456/* Ends C function definitions when using C++ */
457#ifdef __cplusplus
458}
459#endif
460#include "close_code.h"
461
462#endif /* SDL_thread_h_ */
463
464/* vi: set ts=4 sw=4 expandtab: */
465

source code of include/SDL2/SDL_thread.h