SDL  2.0
SDL_timer.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 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 #include "../SDL_internal.h"
22 
23 #include "SDL_timer.h"
24 #include "SDL_timer_c.h"
25 #include "SDL_atomic.h"
26 #include "SDL_cpuinfo.h"
27 #include "../thread/SDL_systhread.h"
28 
29 /* #define DEBUG_TIMERS */
30 
31 typedef struct _SDL_Timer
32 {
33  int timerID;
35  void *param;
39  struct _SDL_Timer *next;
40 } SDL_Timer;
41 
42 typedef struct _SDL_TimerMap
43 {
44  int timerID;
46  struct _SDL_TimerMap *next;
47 } SDL_TimerMap;
48 
49 /* The timers are kept in a sorted list */
50 typedef struct {
51  /* Data used by the main thread */
56 
57  /* Padding to separate cache lines between threads */
58  char cache_pad[SDL_CACHELINE_SIZE];
59 
60  /* Data used to communicate with the timer thread */
62  SDL_sem *sem;
66 
67  /* List of timers - this is only touched by the timer thread */
70 
72 
73 /* The idea here is that any thread might add a timer, but a single
74  * thread manages the active timer queue, sorted by scheduling time.
75  *
76  * Timers are removed by simply setting a canceled flag
77  */
78 
79 static void
81 {
82  SDL_Timer *prev, *curr;
83 
84  prev = NULL;
85  for (curr = data->timers; curr; prev = curr, curr = curr->next) {
86  if ((Sint32)(timer->scheduled-curr->scheduled) < 0) {
87  break;
88  }
89  }
90 
91  /* Insert the timer here! */
92  if (prev) {
93  prev->next = timer;
94  } else {
95  data->timers = timer;
96  }
97  timer->next = curr;
98 }
99 
100 static int SDLCALL
101 SDL_TimerThread(void *_data)
102 {
103  SDL_TimerData *data = (SDL_TimerData *)_data;
104  SDL_Timer *pending;
105  SDL_Timer *current;
106  SDL_Timer *freelist_head = NULL;
107  SDL_Timer *freelist_tail = NULL;
108  Uint32 tick, now, interval, delay;
109 
110  /* Threaded timer loop:
111  * 1. Queue timers added by other threads
112  * 2. Handle any timers that should dispatch this cycle
113  * 3. Wait until next dispatch time or new timer arrives
114  */
115  for ( ; ; ) {
116  /* Pending and freelist maintenance */
117  SDL_AtomicLock(&data->lock);
118  {
119  /* Get any timers ready to be queued */
120  pending = data->pending;
121  data->pending = NULL;
122 
123  /* Make any unused timer structures available */
124  if (freelist_head) {
125  freelist_tail->next = data->freelist;
126  data->freelist = freelist_head;
127  }
128  }
129  SDL_AtomicUnlock(&data->lock);
130 
131  /* Sort the pending timers into our list */
132  while (pending) {
133  current = pending;
134  pending = pending->next;
135  SDL_AddTimerInternal(data, current);
136  }
137  freelist_head = NULL;
138  freelist_tail = NULL;
139 
140  /* Check to see if we're still running, after maintenance */
141  if (!SDL_AtomicGet(&data->active)) {
142  break;
143  }
144 
145  /* Initial delay if there are no timers */
146  delay = SDL_MUTEX_MAXWAIT;
147 
148  tick = SDL_GetTicks();
149 
150  /* Process all the pending timers for this tick */
151  while (data->timers) {
152  current = data->timers;
153 
154  if ((Sint32)(tick-current->scheduled) < 0) {
155  /* Scheduled for the future, wait a bit */
156  delay = (current->scheduled - tick);
157  break;
158  }
159 
160  /* We're going to do something with this timer */
161  data->timers = current->next;
162 
163  if (SDL_AtomicGet(&current->canceled)) {
164  interval = 0;
165  } else {
166  interval = current->callback(current->interval, current->param);
167  }
168 
169  if (interval > 0) {
170  /* Reschedule this timer */
171  current->interval = interval;
172  current->scheduled = tick + interval;
173  SDL_AddTimerInternal(data, current);
174  } else {
175  if (!freelist_head) {
176  freelist_head = current;
177  }
178  if (freelist_tail) {
179  freelist_tail->next = current;
180  }
181  freelist_tail = current;
182 
183  SDL_AtomicSet(&current->canceled, 1);
184  }
185  }
186 
187  /* Adjust the delay based on processing time */
188  now = SDL_GetTicks();
189  interval = (now - tick);
190  if (interval > delay) {
191  delay = 0;
192  } else {
193  delay -= interval;
194  }
195 
196  /* Note that each time a timer is added, this will return
197  immediately, but we process the timers added all at once.
198  That's okay, it just means we run through the loop a few
199  extra times.
200  */
201  SDL_SemWaitTimeout(data->sem, delay);
202  }
203  return 0;
204 }
205 
206 int
208 {
210 
211  if (!SDL_AtomicGet(&data->active)) {
212  const char *name = "SDLTimer";
213  data->timermap_lock = SDL_CreateMutex();
214  if (!data->timermap_lock) {
215  return -1;
216  }
217 
218  data->sem = SDL_CreateSemaphore(0);
219  if (!data->sem) {
221  return -1;
222  }
223 
224  SDL_AtomicSet(&data->active, 1);
225 
226  /* Timer threads use a callback into the app, so we can't set a limited stack size here. */
227  data->thread = SDL_CreateThreadInternal(SDL_TimerThread, name, 0, data);
228  if (!data->thread) {
229  SDL_TimerQuit();
230  return -1;
231  }
232 
233  SDL_AtomicSet(&data->nextID, 1);
234  }
235  return 0;
236 }
237 
238 void
240 {
242  SDL_Timer *timer;
243  SDL_TimerMap *entry;
244 
245  if (SDL_AtomicCAS(&data->active, 1, 0)) { /* active? Move to inactive. */
246  /* Shutdown the timer thread */
247  if (data->thread) {
248  SDL_SemPost(data->sem);
249  SDL_WaitThread(data->thread, NULL);
250  data->thread = NULL;
251  }
252 
253  SDL_DestroySemaphore(data->sem);
254  data->sem = NULL;
255 
256  /* Clean up the timer entries */
257  while (data->timers) {
258  timer = data->timers;
259  data->timers = timer->next;
260  SDL_free(timer);
261  }
262  while (data->freelist) {
263  timer = data->freelist;
264  data->freelist = timer->next;
265  SDL_free(timer);
266  }
267  while (data->timermap) {
268  entry = data->timermap;
269  data->timermap = entry->next;
270  SDL_free(entry);
271  }
272 
274  data->timermap_lock = NULL;
275  }
276 }
277 
280 {
282  SDL_Timer *timer;
283  SDL_TimerMap *entry;
284 
285  SDL_AtomicLock(&data->lock);
286  if (!SDL_AtomicGet(&data->active)) {
287  if (SDL_TimerInit() < 0) {
288  SDL_AtomicUnlock(&data->lock);
289  return 0;
290  }
291  }
292 
293  timer = data->freelist;
294  if (timer) {
295  data->freelist = timer->next;
296  }
297  SDL_AtomicUnlock(&data->lock);
298 
299  if (timer) {
300  SDL_RemoveTimer(timer->timerID);
301  } else {
302  timer = (SDL_Timer *)SDL_malloc(sizeof(*timer));
303  if (!timer) {
304  SDL_OutOfMemory();
305  return 0;
306  }
307  }
308  timer->timerID = SDL_AtomicIncRef(&data->nextID);
309  timer->callback = callback;
310  timer->param = param;
311  timer->interval = interval;
312  timer->scheduled = SDL_GetTicks() + interval;
313  SDL_AtomicSet(&timer->canceled, 0);
314 
315  entry = (SDL_TimerMap *)SDL_malloc(sizeof(*entry));
316  if (!entry) {
317  SDL_free(timer);
318  SDL_OutOfMemory();
319  return 0;
320  }
321  entry->timer = timer;
322  entry->timerID = timer->timerID;
323 
325  entry->next = data->timermap;
326  data->timermap = entry;
328 
329  /* Add the timer to the pending list for the timer thread */
330  SDL_AtomicLock(&data->lock);
331  timer->next = data->pending;
332  data->pending = timer;
333  SDL_AtomicUnlock(&data->lock);
334 
335  /* Wake up the timer thread if necessary */
336  SDL_SemPost(data->sem);
337 
338  return entry->timerID;
339 }
340 
341 SDL_bool
343 {
345  SDL_TimerMap *prev, *entry;
346  SDL_bool canceled = SDL_FALSE;
347 
348  /* Find the timer */
350  prev = NULL;
351  for (entry = data->timermap; entry; prev = entry, entry = entry->next) {
352  if (entry->timerID == id) {
353  if (prev) {
354  prev->next = entry->next;
355  } else {
356  data->timermap = entry->next;
357  }
358  break;
359  }
360  }
362 
363  if (entry) {
364  if (!SDL_AtomicGet(&entry->timer->canceled)) {
365  SDL_AtomicSet(&entry->timer->canceled, 1);
366  canceled = SDL_TRUE;
367  }
368  SDL_free(entry);
369  }
370  return canceled;
371 }
372 
373 /* vi: set ts=4 sw=4 expandtab: */
static int SDL_TimerThread(void *_data)
Definition: SDL_timer.c:101
#define SDL_LockMutex
void SDL_TimerQuit(void)
Definition: SDL_timer.c:239
SDL_Timer * timer
Definition: SDL_timer.c:45
SDL_TimerMap * timermap
Definition: SDL_timer.c:54
#define SDL_AtomicLock
Uint32(* SDL_TimerCallback)(Uint32 interval, void *param)
Definition: SDL_timer.h:81
A type representing an atomic integer value. It is a struct so people don&#39;t accidentally use numeric ...
Definition: SDL_atomic.h:198
#define SDL_AtomicCAS
Uint32 interval
Definition: SDL_timer.c:36
#define SDL_CreateSemaphore
#define SDL_CreateMutex
int SDL_TimerInit(void)
Definition: SDL_timer.c:207
SDL_Thread * thread
Definition: SDL_timer.c:52
GLint GLenum GLsizei GLsizei GLsizei GLint GLsizei const GLvoid * data
Definition: SDL_opengl.h:1974
SDL_TimerID SDL_AddTimer(Uint32 interval, SDL_TimerCallback callback, void *param)
Add a new timer to the pool of timers already running.
Definition: SDL_timer.c:279
uint32_t Uint32
Definition: SDL_stdinc.h:181
SDL_atomic_t nextID
Definition: SDL_timer.c:53
GLuint const GLchar * name
#define SDL_SemPost
#define SDL_AtomicUnlock
SDL_bool SDL_RemoveTimer(SDL_TimerID id)
Remove a timer knowing its ID.
Definition: SDL_timer.c:342
SDL_Thread * SDL_CreateThreadInternal(int(*fn)(void *), const char *name, const size_t stacksize, void *data)
Definition: SDL_thread.c:427
#define SDL_SemWaitTimeout
struct _SDL_Timer * next
Definition: SDL_timer.c:39
#define SDL_MUTEX_MAXWAIT
Definition: SDL_mutex.h:49
SDL_atomic_t active
Definition: SDL_timer.c:65
Uint32 SDL_GetTicks(void)
Get the number of milliseconds since the SDL library initialization.
#define SDL_free
Uint32 scheduled
Definition: SDL_timer.c:37
SDL_TimerCallback callback
Definition: SDL_timer.c:34
int timerID
Definition: SDL_timer.c:33
#define SDL_CACHELINE_SIZE
Definition: SDL_cpuinfo.h:92
static Uint32 callback(Uint32 interval, void *param)
Definition: testtimer.c:34
int32_t Sint32
Definition: SDL_stdinc.h:175
SDL_sem * sem
Definition: SDL_timer.c:62
#define SDL_AtomicIncRef(a)
Increment an atomic variable used as a reference count.
Definition: SDL_atomic.h:234
struct _SDL_TimerMap * next
Definition: SDL_timer.c:46
#define NULL
Definition: begin_code.h:164
void * param
Definition: SDL_timer.c:35
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
SDL_bool
Definition: SDL_stdinc.h:139
static void SDL_AddTimerInternal(SDL_TimerData *data, SDL_Timer *timer)
Definition: SDL_timer.c:80
SDL_Timer * freelist
Definition: SDL_timer.c:64
SDL_mutex * timermap_lock
Definition: SDL_timer.c:55
SDL_Timer * pending
Definition: SDL_timer.c:63
#define SDL_DestroyMutex
#define SDL_DestroySemaphore
static SDL_TimerData SDL_timer_data
Definition: SDL_timer.c:71
#define SDL_AtomicSet
SDL_atomic_t canceled
Definition: SDL_timer.c:38
#define SDL_AtomicGet
#define SDL_UnlockMutex
#define SDL_malloc
SDL_SpinLock lock
Definition: SDL_timer.c:61
int SDL_SpinLock
Definition: SDL_atomic.h:89
GLfloat param
SDL_Timer * timers
Definition: SDL_timer.c:68
#define SDLCALL
Definition: SDL_internal.h:45
int SDL_TimerID
Definition: SDL_timer.h:86
#define SDL_WaitThread