1 /*
2 * IPC SHM area manager
3 * Copyright (c) 2003 by Jaroslav Kysela <perex@perex.cz>
4 *
5 * This library is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU Lesser General Public License as
7 * published by the Free Software Foundation; either version 2.1 of
8 * the License, or (at your option) any later version.
9 *
10 * This program 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
13 * GNU 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 Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 */
20
21 #include "config.h"
22
23 /* These funcs are only used by pcm_mmap when sys/shm.h is available. */
24 #ifdef HAVE_SYS_SHM_H
25
26 #include <stdio.h>
27 #include <malloc.h>
28 #include <string.h>
29 #include <errno.h>
30 #include <poll.h>
31 #include <sys/mman.h>
32 #include <sys/shm.h>
33 #include "list.h"
34
35 #ifndef DOC_HIDDEN
36 struct snd_shm_area {
37 struct list_head list;
38 int shmid;
39 void *ptr;
40 int share;
41 };
42 #endif
43
44 static LIST_HEAD(shm_areas);
45
46 /**
47 * \brief Create a shm area record
48 * \param shmid IPC SHM ID
49 * \param ptr the shared area pointer
50 * \return The allocated shm area record, NULL if fail
51 *
52 * Allocates a shared area record with the given SHM ID and pointer.
53 * The record has a reference counter, which is initialized to 1 by this function.
54 */
snd_shm_area_create(int shmid,void * ptr)55 struct snd_shm_area *snd_shm_area_create(int shmid, void *ptr)
56 {
57 struct snd_shm_area *area = malloc(sizeof(*area));
58 if (area) {
59 area->shmid = shmid;
60 area->ptr = ptr;
61 area->share = 1;
62 list_add_tail(&area->list, &shm_areas);
63 }
64 return area;
65 }
66
67 /**
68 * \brief Increase the reference counter of shm area record
69 * \param area shm area record
70 * \return the shm area record (identical with the argument)
71 *
72 * Increases the reference counter of the given shared area record.
73 */
snd_shm_area_share(struct snd_shm_area * area)74 struct snd_shm_area *snd_shm_area_share(struct snd_shm_area *area)
75 {
76 if (area == NULL)
77 return NULL;
78 area->share++;
79 return area;
80 }
81
82 /**
83 * \brief Release the shared area record
84 * \param area the shared are record
85 * \return 0 if successful, or a negative error code
86 *
87 * Decreases the reference counter of the given shared area record, and
88 * releases the resources automaticall if it reaches to 0.
89 */
snd_shm_area_destroy(struct snd_shm_area * area)90 int snd_shm_area_destroy(struct snd_shm_area *area)
91 {
92 if (area == NULL)
93 return -ENOENT;
94 if (--area->share)
95 return 0;
96 list_del(&area->list);
97 shmdt(area->ptr);
98 free(area);
99 return 0;
100 }
101
102 void snd_shm_area_destructor(void) __attribute__ ((destructor));
103
snd_shm_area_destructor(void)104 void snd_shm_area_destructor(void)
105 {
106 struct list_head *pos;
107 struct snd_shm_area *area;
108
109 list_for_each(pos, &shm_areas) {
110 area = list_entry(pos, struct snd_shm_area, list);
111 shmdt(area->ptr);
112 }
113 }
114
115 #endif
116