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comparison src/thread/nds/SDL_sysmutex.c @ 2735:204be4fc2726

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Final merge of Google Summer of Code 2008 work... Port SDL 1.3 to the Nintendo DS by Darren Alton, mentored by Sam Lantinga
author Sam Lantinga <slouken@libsdl.org>
date Wed, 27 Aug 2008 15:10:03 +0000
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children 99210400e8b9
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2734:dd25eabe441c 2735:204be4fc2726
1 /*
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga
4
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public
7 License as published by the Free Software Foundation; either
8 version 2 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 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with this library; if not, write to the Free
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18
19 Sam Lantinga
20 slouken@devolution.com
21 */
22
23 #ifdef SAVE_RCSID
24 static char rcsid =
25 "@(#) $Id: SDL_sysmutex.c,v 1.2 2001/04/26 16:50:18 hercules Exp $";
26 #endif
27
28 /* An implementation of mutexes using semaphores */
29
30 #include <stdio.h>
31 #include <stdlib.h>
32
33 #include "SDL_error.h"
34 #include "SDL_thread.h"
35 #include "SDL_systhread_c.h"
36
37
38 struct SDL_mutex
39 {
40 int recursive;
41 Uint32 owner;
42 SDL_sem *sem;
43 };
44
45 /* Create a mutex */
46 SDL_mutex *
47 SDL_CreateMutex(void)
48 {
49 SDL_mutex *mutex;
50
51 /* Allocate mutex memory */
52 mutex = (SDL_mutex *) malloc(sizeof(*mutex));
53 if (mutex) {
54 /* Create the mutex semaphore, with initial value 1 */
55 mutex->sem = SDL_CreateSemaphore(1);
56 mutex->recursive = 0;
57 mutex->owner = 0;
58 if (!mutex->sem) {
59 free(mutex);
60 mutex = NULL;
61 }
62 } else {
63 SDL_OutOfMemory();
64 }
65 return mutex;
66 }
67
68 /* Free the mutex */
69 void
70 SDL_DestroyMutex(SDL_mutex * mutex)
71 {
72 if (mutex) {
73 if (mutex->sem) {
74 SDL_DestroySemaphore(mutex->sem);
75 }
76 free(mutex);
77 }
78 }
79
80 /* Lock the semaphore */
81 int
82 SDL_mutexP(SDL_mutex * mutex)
83 {
84 #ifdef DISABLE_THREADS
85 return 0;
86 #else
87 Uint32 this_thread;
88
89 if (mutex == NULL) {
90 SDL_SetError("Passed a NULL mutex");
91 return -1;
92 }
93
94 this_thread = SDL_ThreadID();
95 if (mutex->owner == this_thread) {
96 ++mutex->recursive;
97 } else {
98 /* The order of operations is important.
99 We set the locking thread id after we obtain the lock
100 so unlocks from other threads will fail.
101 */
102 SDL_SemWait(mutex->sem);
103 mutex->owner = this_thread;
104 mutex->recursive = 0;
105 }
106
107 return 0;
108 #endif /* DISABLE_THREADS */
109 }
110
111 /* Unlock the mutex */
112 int
113 SDL_mutexV(SDL_mutex * mutex)
114 {
115 #ifdef DISABLE_THREADS
116 return 0;
117 #else
118 if (mutex == NULL) {
119 SDL_SetError("Passed a NULL mutex");
120 return -1;
121 }
122
123 /* If we don't own the mutex, we can't unlock it */
124 if (SDL_ThreadID() != mutex->owner) {
125 SDL_SetError("mutex not owned by this thread");
126 return -1;
127 }
128
129 if (mutex->recursive) {
130 --mutex->recursive;
131 } else {
132 /* The order of operations is important.
133 First reset the owner so another thread doesn't lock
134 the mutex and set the ownership before we reset it,
135 then release the lock semaphore.
136 */
137 mutex->owner = 0;
138 SDL_SemPost(mutex->sem);
139 }
140 return 0;
141 #endif /* DISABLE_THREADS */
142 }