| 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 | } |