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 */
68typedef enum {
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
119extern DECLSPEC SDL_Thread *SDLCALL
120SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
121 pfnSDL_CurrentBeginThread pfnBeginThread,
122 pfnSDL_CurrentEndThread pfnEndThread);
123
124extern DECLSPEC SDL_Thread *SDLCALL
126 const char *name, const size_t stacksize, void *data,
127 pfnSDL_CurrentBeginThread pfnBeginThread,
128 pfnSDL_CurrentEndThread pfnEndThread);
129
130
131#if defined(SDL_CreateThread) && SDL_DYNAMIC_API
132#undef SDL_CreateThread
133#define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
134#undef SDL_CreateThreadWithStackSize
135#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize_REAL(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
136#else
137#define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
138#define SDL_CreateThreadWithStackSize(fn, name, stacksize, data) SDL_CreateThreadWithStackSize(fn, name, stacksize, data, (pfnSDL_CurrentBeginThread)SDL_beginthread, (pfnSDL_CurrentEndThread)SDL_endthread)
139#endif
140
141#else
142
143/**
144 * Create a new thread with a default stack size.
145 *
146 * This is equivalent to calling:
147 *
148 * ```c
149 * SDL_CreateThreadWithStackSize(fn, name, 0, data);
150 * ```
151 *
152 * \param fn the SDL_ThreadFunction function to call in the new thread
153 * \param name the name of the thread
154 * \param data a pointer that is passed to `fn`
155 * \returns an opaque pointer to the new thread object on success, NULL if the
156 * new thread could not be created; call SDL_GetError() for more
157 * information.
158 *
159 * \since This function is available since SDL 3.0.0.
160 *
161 * \sa SDL_CreateThreadWithStackSize
162 * \sa SDL_WaitThread
163 */
164extern DECLSPEC SDL_Thread *SDLCALL
166
167/**
168 * Create a new thread with a specific stack size.
169 *
170 * SDL makes an attempt to report `name` to the system, so that debuggers can
171 * display it. Not all platforms support this.
172 *
173 * Thread naming is a little complicated: Most systems have very small limits
174 * for the string length (Haiku has 32 bytes, Linux currently has 16, Visual
175 * C++ 6.0 has _nine_!), and possibly other arbitrary rules. You'll have to
176 * see what happens with your system's debugger. The name should be UTF-8 (but
177 * using the naming limits of C identifiers is a better bet). There are no
178 * requirements for thread naming conventions, so long as the string is
179 * null-terminated UTF-8, but these guidelines are helpful in choosing a name:
180 *
181 * https://stackoverflow.com/questions/149932/naming-conventions-for-threads
182 *
183 * If a system imposes requirements, SDL will try to munge the string for it
184 * (truncate, etc), but the original string contents will be available from
185 * SDL_GetThreadName().
186 *
187 * The size (in bytes) of the new stack can be specified. Zero means "use the
188 * system default" which might be wildly different between platforms. x86
189 * Linux generally defaults to eight megabytes, an embedded device might be a
190 * few kilobytes instead. You generally need to specify a stack that is a
191 * multiple of the system's page size (in many cases, this is 4 kilobytes, but
192 * check your system documentation).
193 *
194 * In SDL 2.1, stack size will be folded into the original SDL_CreateThread
195 * function, but for backwards compatibility, this is currently a separate
196 * function.
197 *
198 * \param fn the SDL_ThreadFunction function to call in the new thread
199 * \param name the name of the thread
200 * \param stacksize the size, in bytes, to allocate for the new thread stack.
201 * \param data a pointer that is passed to `fn`
202 * \returns an opaque pointer to the new thread object on success, NULL if the
203 * new thread could not be created; call SDL_GetError() for more
204 * information.
205 *
206 * \since This function is available since SDL 3.0.0.
207 *
208 * \sa SDL_WaitThread
209 */
210extern DECLSPEC SDL_Thread *SDLCALL
211SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data);
212
213#endif
214
215/**
216 * Get the thread name as it was specified in SDL_CreateThread().
217 *
218 * This is internal memory, not to be freed by the caller, and remains valid
219 * until the specified thread is cleaned up by SDL_WaitThread().
220 *
221 * \param thread the thread to query
222 * \returns a pointer to a UTF-8 string that names the specified thread, or
223 * NULL if it doesn't have a name.
224 *
225 * \since This function is available since SDL 3.0.0.
226 *
227 * \sa SDL_CreateThread
228 */
229extern DECLSPEC const char *SDLCALL SDL_GetThreadName(SDL_Thread *thread);
230
231/**
232 * Get the thread identifier for the current thread.
233 *
234 * This thread identifier is as reported by the underlying operating system.
235 * If SDL is running on a platform that does not support threads the return
236 * value will always be zero.
237 *
238 * This function also returns a valid thread ID when called from the main
239 * thread.
240 *
241 * \returns the ID of the current thread.
242 *
243 * \since This function is available since SDL 3.0.0.
244 *
245 * \sa SDL_GetThreadID
246 */
247extern DECLSPEC SDL_threadID SDLCALL SDL_ThreadID(void);
248
249/**
250 * Get the thread identifier for the specified thread.
251 *
252 * This thread identifier is as reported by the underlying operating system.
253 * If SDL is running on a platform that does not support threads the return
254 * value will always be zero.
255 *
256 * \param thread the thread to query
257 * \returns the ID of the specified thread, or the ID of the current thread if
258 * `thread` is NULL.
259 *
260 * \since This function is available since SDL 3.0.0.
261 *
262 * \sa SDL_ThreadID
263 */
264extern DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID(SDL_Thread * thread);
265
266/**
267 * Set the priority for the current thread.
268 *
269 * Note that some platforms will not let you alter the priority (or at least,
270 * promote the thread to a higher priority) at all, and some require you to be
271 * an administrator account. Be prepared for this to fail.
272 *
273 * \param priority the SDL_ThreadPriority to set
274 * \returns 0 on success or a negative error code on failure; call
275 * SDL_GetError() for more information.
276 *
277 * \since This function is available since SDL 3.0.0.
278 */
279extern DECLSPEC int SDLCALL SDL_SetThreadPriority(SDL_ThreadPriority priority);
280
281/**
282 * Wait for a thread to finish.
283 *
284 * Threads that haven't been detached will remain (as a "zombie") until this
285 * function cleans them up. Not doing so is a resource leak.
286 *
287 * Once a thread has been cleaned up through this function, the SDL_Thread
288 * that references it becomes invalid and should not be referenced again. As
289 * such, only one thread may call SDL_WaitThread() on another.
290 *
291 * The return code for the thread function is placed in the area pointed to by
292 * `status`, if `status` is not NULL.
293 *
294 * You may not wait on a thread that has been used in a call to
295 * SDL_DetachThread(). Use either that function or this one, but not both, or
296 * behavior is undefined.
297 *
298 * It is safe to pass a NULL thread to this function; it is a no-op.
299 *
300 * Note that the thread pointer is freed by this function and is not valid
301 * afterward.
302 *
303 * \param thread the SDL_Thread pointer that was returned from the
304 * SDL_CreateThread() call that started this thread
305 * \param status pointer to an integer that will receive the value returned
306 * from the thread function by its 'return', or NULL to not
307 * receive such value back.
308 *
309 * \since This function is available since SDL 3.0.0.
310 *
311 * \sa SDL_CreateThread
312 * \sa SDL_DetachThread
313 */
314extern DECLSPEC void SDLCALL SDL_WaitThread(SDL_Thread * thread, int *status);
315
316/**
317 * Let a thread clean up on exit without intervention.
318 *
319 * A thread may be "detached" to signify that it should not remain until
320 * another thread has called SDL_WaitThread() on it. Detaching a thread is
321 * useful for long-running threads that nothing needs to synchronize with or
322 * further manage. When a detached thread is done, it simply goes away.
323 *
324 * There is no way to recover the return code of a detached thread. If you
325 * need this, don't detach the thread and instead use SDL_WaitThread().
326 *
327 * Once a thread is detached, you should usually assume the SDL_Thread isn't
328 * safe to reference again, as it will become invalid immediately upon the
329 * detached thread's exit, instead of remaining until someone has called
330 * SDL_WaitThread() to finally clean it up. As such, don't detach the same
331 * thread more than once.
332 *
333 * If a thread has already exited when passed to SDL_DetachThread(), it will
334 * stop waiting for a call to SDL_WaitThread() and clean up immediately. It is
335 * not safe to detach a thread that might be used with SDL_WaitThread().
336 *
337 * You may not call SDL_WaitThread() on a thread that has been detached. Use
338 * either that function or this one, but not both, or behavior is undefined.
339 *
340 * It is safe to pass NULL to this function; it is a no-op.
341 *
342 * \param thread the SDL_Thread pointer that was returned from the
343 * SDL_CreateThread() call that started this thread
344 *
345 * \since This function is available since SDL 3.0.0.
346 *
347 * \sa SDL_CreateThread
348 * \sa SDL_WaitThread
349 */
350extern DECLSPEC void SDLCALL SDL_DetachThread(SDL_Thread * thread);
351
352/**
353 * Create a piece of thread-local storage.
354 *
355 * This creates an identifier that is globally visible to all threads but
356 * refers to data that is thread-specific.
357 *
358 * \returns the newly created thread local storage identifier or 0 on error.
359 *
360 * \since This function is available since SDL 3.0.0.
361 *
362 * \sa SDL_TLSGet
363 * \sa SDL_TLSSet
364 */
365extern DECLSPEC SDL_TLSID SDLCALL SDL_TLSCreate(void);
366
367/**
368 * Get the current thread's value associated with a thread local storage ID.
369 *
370 * \param id the thread local storage ID
371 * \returns the value associated with the ID for the current thread or NULL if
372 * no value has been set; call SDL_GetError() for more information.
373 *
374 * \since This function is available since SDL 3.0.0.
375 *
376 * \sa SDL_TLSCreate
377 * \sa SDL_TLSSet
378 */
379extern DECLSPEC void * SDLCALL SDL_TLSGet(SDL_TLSID id);
380
381/**
382 * Set the current thread's value associated with a thread local storage ID.
383 *
384 * The function prototype for `destructor` is:
385 *
386 * ```c
387 * void destructor(void *value)
388 * ```
389 *
390 * where its parameter `value` is what was passed as `value` to SDL_TLSSet().
391 *
392 * \param id the thread local storage ID
393 * \param value the value to associate with the ID for the current thread
394 * \param destructor a function called when the thread exits, to free the
395 * value
396 * \returns 0 on success or a negative error code on failure; call
397 * SDL_GetError() for more information.
398 *
399 * \since This function is available since SDL 3.0.0.
400 *
401 * \sa SDL_TLSCreate
402 * \sa SDL_TLSGet
403 */
404extern DECLSPEC int SDLCALL SDL_TLSSet(SDL_TLSID id, const void *value, void (SDLCALL *destructor)(void*));
405
406/**
407 * Cleanup all TLS data for this thread.
408 *
409 * \since This function is available since SDL 3.0.0.
410 */
411extern DECLSPEC void SDLCALL SDL_TLSCleanup(void);
412
413/* Ends C function definitions when using C++ */
414#ifdef __cplusplus
415}
416#endif
417#include <SDL3/SDL_close_code.h>
418
419#endif /* SDL_thread_h_ */
unsigned long uintptr_t
typedef void(APIENTRYP PFNGLDRAWRANGEELEMENTSPROC)(GLenum mode
GLint GLenum GLsizei GLsizei GLsizei GLint GLsizei const GLvoid * data
Definition: SDL_opengl.h:1967
GLenum func
GLuint const GLchar * name
GLsizei const GLfloat * value
void * SDL_TLSGet(SDL_TLSID id)
unsigned int SDL_TLSID
Definition: SDL_thread.h:56
void SDL_DetachThread(SDL_Thread *thread)
SDL_threadID SDL_GetThreadID(SDL_Thread *thread)
const char * SDL_GetThreadName(SDL_Thread *thread)
SDL_TLSID SDL_TLSCreate(void)
SDL_Thread * SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data)
void SDL_TLSCleanup(void)
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
int SDL_TLSSet(SDL_TLSID id, const void *value, void(*destructor)(void *))
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_ThreadFunction)(void *data)
Definition: SDL_thread.h:81
SDL_threadID SDL_ThreadID(void)
SDL_Thread * SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data)