Repository navigation
Expand file tree
/
Copy pathSDL_syscond.c
More file actions
218 lines (186 loc) · 6.07 KB
/
Copy pathSDL_syscond.c
File metadata and controls
218 lines (186 loc) · 6.07 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
/*
Simple DirectMedia Layer
Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"
#if SDL_THREAD_VITA
/* An implementation of condition variables using semaphores and mutexes */
/*
This implementation borrows heavily from the BeOS condition variable
implementation, written by Christopher Tate and Owen Smith. Thanks!
*/
#include "SDL_thread.h"
struct SDL_cond
{
SDL_mutex *lock;
int waiting;
int signals;
SDL_sem *wait_sem;
SDL_sem *wait_done;
};
/* Create a condition variable */
SDL_cond *SDL_CreateCond(void)
{
SDL_cond *cond;
cond = (SDL_cond *)SDL_malloc(sizeof(SDL_cond));
if (cond != NULL) {
cond->lock = SDL_CreateMutex();
cond->wait_sem = SDL_CreateSemaphore(0);
cond->wait_done = SDL_CreateSemaphore(0);
cond->waiting = cond->signals = 0;
if (!cond->lock || !cond->wait_sem || !cond->wait_done) {
SDL_DestroyCond(cond);
cond = NULL;
}
} else {
SDL_OutOfMemory();
}
return cond;
}
/* Destroy a condition variable */
void SDL_DestroyCond(SDL_cond *cond)
{
if (cond != NULL) {
if (cond->wait_sem) {
SDL_DestroySemaphore(cond->wait_sem);
}
if (cond->wait_done) {
SDL_DestroySemaphore(cond->wait_done);
}
if (cond->lock) {
SDL_DestroyMutex(cond->lock);
}
SDL_free(cond);
}
}
/* Restart one of the threads that are waiting on the condition variable */
int SDL_CondSignal(SDL_cond *cond)
{
if (cond == NULL) {
return SDL_InvalidParamError("cond");
}
/* If there are waiting threads not already signalled, then
signal the condition and wait for the thread to respond.
*/
SDL_LockMutex(cond->lock);
if (cond->waiting > cond->signals) {
++cond->signals;
SDL_SemPost(cond->wait_sem);
SDL_UnlockMutex(cond->lock);
SDL_SemWait(cond->wait_done);
} else {
SDL_UnlockMutex(cond->lock);
}
return 0;
}
/* Restart all threads that are waiting on the condition variable */
int SDL_CondBroadcast(SDL_cond *cond)
{
if (cond == NULL) {
return SDL_InvalidParamError("cond");
}
/* If there are waiting threads not already signalled, then
signal the condition and wait for the thread to respond.
*/
SDL_LockMutex(cond->lock);
if (cond->waiting > cond->signals) {
int i, num_waiting;
num_waiting = (cond->waiting - cond->signals);
cond->signals = cond->waiting;
for (i = 0; i < num_waiting; ++i) {
SDL_SemPost(cond->wait_sem);
}
/* Now all released threads are blocked here, waiting for us.
Collect them all (and win fabulous prizes!) :-)
*/
SDL_UnlockMutex(cond->lock);
for (i = 0; i < num_waiting; ++i) {
SDL_SemWait(cond->wait_done);
}
} else {
SDL_UnlockMutex(cond->lock);
}
return 0;
}
/* Wait on the condition variable for at most 'ms' milliseconds.
The mutex must be locked before entering this function!
The mutex is unlocked during the wait, and locked again after the wait.
Typical use:
Thread A:
SDL_LockMutex(lock);
while ( ! condition ) {
SDL_CondWait(cond, lock);
}
SDL_UnlockMutex(lock);
Thread B:
SDL_LockMutex(lock);
...
condition = true;
...
SDL_CondSignal(cond);
SDL_UnlockMutex(lock);
*/
int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms)
{
int retval;
if (cond == NULL) {
return SDL_InvalidParamError("cond");
}
/* Obtain the protection mutex, and increment the number of waiters.
This allows the signal mechanism to only perform a signal if there
are waiting threads.
*/
SDL_LockMutex(cond->lock);
++cond->waiting;
SDL_UnlockMutex(cond->lock);
/* Unlock the mutex, as is required by condition variable semantics */
SDL_UnlockMutex(mutex);
/* Wait for a signal */
if (ms == SDL_MUTEX_MAXWAIT) {
retval = SDL_SemWait(cond->wait_sem);
} else {
retval = SDL_SemWaitTimeout(cond->wait_sem, ms);
}
/* Let the signaler know we have completed the wait, otherwise
the signaler can race ahead and get the condition semaphore
if we are stopped between the mutex unlock and semaphore wait,
giving a deadlock. See the following URL for details:
http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html
*/
SDL_LockMutex(cond->lock);
if (cond->signals > 0) {
/* If we timed out, we need to eat a condition signal */
if (retval > 0) {
SDL_SemWait(cond->wait_sem);
}
/* We always notify the signal thread that we are done */
SDL_SemPost(cond->wait_done);
/* Signal handshake complete */
--cond->signals;
}
--cond->waiting;
SDL_UnlockMutex(cond->lock);
/* Lock the mutex, as is required by condition variable semantics */
SDL_LockMutex(mutex);
return retval;
}
/* Wait on the condition variable forever */
int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex)
{
return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
}
#endif /* SDL_THREAD_VITA */
/* vi: set ts=4 sw=4 expandtab: */