e14743d1 |
1 | /* |
2 | SDL - Simple DirectMedia Layer |
3 | Copyright (C) 1997-2009 Sam Lantinga |
4 | |
5 | This library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | This library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with this library; if not, write to the Free Software |
17 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
18 | |
19 | Sam Lantinga |
20 | slouken@libsdl.org |
21 | */ |
22 | #include "SDL_config.h" |
23 | |
24 | #include "SDL_thread.h" |
25 | #include "SDL_timer.h" |
26 | |
27 | |
28 | #include <stdio.h> |
29 | #include <stdlib.h> |
30 | #include <sys/types.h> |
31 | #include <sys/ipc.h> |
32 | #include <sys/sem.h> |
33 | #include <errno.h> |
34 | |
35 | #include "SDL_error.h" |
36 | #include "SDL_thread.h" |
37 | |
38 | |
39 | struct SDL_semaphore { |
40 | int id; |
41 | }; |
42 | |
43 | /* Not defined by many operating systems, use configure to detect */ |
44 | /* |
45 | #if !defined(HAVE_SEMUN) |
46 | union semun { |
47 | int val; |
48 | struct semid_ds *buf; |
49 | ushort *array; |
50 | }; |
51 | #endif |
52 | */ |
53 | |
54 | static struct sembuf op_trywait[2] = { |
55 | { 0, -1, (IPC_NOWAIT|SEM_UNDO) } /* Decrement semaphore, no block */ |
56 | }; |
57 | static struct sembuf op_wait[2] = { |
58 | { 0, -1, SEM_UNDO } /* Decrement semaphore */ |
59 | }; |
60 | static struct sembuf op_post[1] = { |
61 | { 0, 1, (IPC_NOWAIT|SEM_UNDO) } /* Increment semaphore */ |
62 | }; |
63 | |
64 | /* Create a blockable semaphore */ |
65 | SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) |
66 | { |
67 | extern int _creating_thread_lock; /* SDL_threads.c */ |
68 | SDL_sem *sem; |
69 | union semun init; |
70 | |
71 | sem = (SDL_sem *)SDL_malloc(sizeof(*sem)); |
72 | if ( sem == NULL ) { |
73 | SDL_OutOfMemory(); |
74 | return(NULL); |
75 | } |
76 | sem->id = semget(IPC_PRIVATE, 1, (0600|IPC_CREAT)); |
77 | if ( sem->id < 0 ) { |
78 | SDL_SetError("Couldn't create semaphore"); |
79 | SDL_free(sem); |
80 | return(NULL); |
81 | } |
82 | init.val = initial_value; /* Initialize semaphore */ |
83 | semctl(sem->id, 0, SETVAL, init); |
84 | return(sem); |
85 | } |
86 | |
87 | void SDL_DestroySemaphore(SDL_sem *sem) |
88 | { |
89 | if ( sem ) { |
90 | #ifdef __IRIX__ |
91 | semctl(sem->id, 0, IPC_RMID); |
92 | #else |
93 | union semun dummy; |
94 | dummy.val = 0; |
95 | semctl(sem->id, 0, IPC_RMID, dummy); |
96 | #endif |
97 | SDL_free(sem); |
98 | } |
99 | } |
100 | |
101 | int SDL_SemTryWait(SDL_sem *sem) |
102 | { |
103 | int retval; |
104 | |
105 | if ( ! sem ) { |
106 | SDL_SetError("Passed a NULL semaphore"); |
107 | return -1; |
108 | } |
109 | |
110 | retval = 0; |
111 | tryagain: |
112 | if ( semop(sem->id, op_trywait, 1) < 0 ) { |
113 | if ( errno == EINTR ) { |
114 | goto tryagain; |
115 | } |
116 | retval = SDL_MUTEX_TIMEDOUT; |
117 | } |
118 | return retval; |
119 | } |
120 | |
121 | int SDL_SemWait(SDL_sem *sem) |
122 | { |
123 | int retval; |
124 | |
125 | if ( ! sem ) { |
126 | SDL_SetError("Passed a NULL semaphore"); |
127 | return -1; |
128 | } |
129 | |
130 | retval = 0; |
131 | tryagain: |
132 | if ( semop(sem->id, op_wait, 1) < 0 ) { |
133 | if ( errno == EINTR ) { |
134 | goto tryagain; |
135 | } |
136 | SDL_SetError("Semaphore operation error"); |
137 | retval = -1; |
138 | } |
139 | return retval; |
140 | } |
141 | |
142 | int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) |
143 | { |
144 | int retval; |
145 | |
146 | if ( ! sem ) { |
147 | SDL_SetError("Passed a NULL semaphore"); |
148 | return -1; |
149 | } |
150 | |
151 | /* Try the easy cases first */ |
152 | if ( timeout == 0 ) { |
153 | return SDL_SemTryWait(sem); |
154 | } |
155 | if ( timeout == SDL_MUTEX_MAXWAIT ) { |
156 | return SDL_SemWait(sem); |
157 | } |
158 | |
159 | /* Ack! We have to busy wait... */ |
160 | timeout += SDL_GetTicks(); |
161 | do { |
162 | retval = SDL_SemTryWait(sem); |
163 | if ( retval == 0 ) { |
164 | break; |
165 | } |
166 | SDL_Delay(1); |
167 | } while ( SDL_GetTicks() < timeout ); |
168 | |
169 | return retval; |
170 | } |
171 | |
172 | Uint32 SDL_SemValue(SDL_sem *sem) |
173 | { |
174 | int semval; |
175 | Uint32 value; |
176 | |
177 | value = 0; |
178 | if ( sem ) { |
179 | tryagain: |
180 | #ifdef __IRIX__ |
181 | semval = semctl(sem->id, 0, GETVAL); |
182 | #else |
183 | { |
184 | union semun arg; |
185 | arg.val = 0; |
186 | semval = semctl(sem->id, 0, GETVAL, arg); |
187 | } |
188 | #endif |
189 | if ( semval < 0 ) { |
190 | if ( errno == EINTR ) { |
191 | goto tryagain; |
192 | } |
193 | } else { |
194 | value = (Uint32)semval; |
195 | } |
196 | } |
197 | return value; |
198 | } |
199 | |
200 | int SDL_SemPost(SDL_sem *sem) |
201 | { |
202 | int retval; |
203 | |
204 | if ( ! sem ) { |
205 | SDL_SetError("Passed a NULL semaphore"); |
206 | return -1; |
207 | } |
208 | |
209 | retval = 0; |
210 | tryagain: |
211 | if ( semop(sem->id, op_post, 1) < 0 ) { |
212 | if ( errno == EINTR ) { |
213 | goto tryagain; |
214 | } |
215 | SDL_SetError("Semaphore operation error"); |
216 | retval = -1; |
217 | } |
218 | return retval; |
219 | } |