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code.delx.au - pulseaudio/blob - src/pulsecore/shmasyncq.c
2 This file is part of PulseAudio.
4 Copyright 2006 Lennart Poettering
6 PulseAudio is free software; you can redistribute it and/or modify
7 it under the terms of the GNU Lesser General Public License as
8 published by the Free Software Foundation; either version 2.1 of the
9 License, or (at your option) any later version.
11 PulseAudio is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with PulseAudio; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
29 #include <pulsecore/atomic.h>
30 #include <pulsecore/log.h>
31 #include <pulsecore/thread.h>
32 #include <pulsecore/macro.h>
33 #include <pulsecore/core-util.h>
34 #include <pulse/xmalloc.h>
38 /* For debugging purposes we can define _Y to put and extra thread
39 * yield between each operation. */
44 #define _Y pa_thread_yield()
46 #define _Y do { } while(0)
50 pa_fdsem
*read_fdsem
, *write_fdsem
;
51 pa_shmasyncq_data
*data
;
54 static int is_power_of_two(unsigned size
) {
55 return !(size
& (size
- 1));
58 static int reduce(pa_shmasyncq
*l
, int value
) {
59 return value
& (unsigned) (l
->n_elements
- 1);
62 static pa_atomic_t
* get_cell(pa_shmasyncq
*l
, unsigned i
) {
63 pa_assert(i
< l
->data
->n_elements
);
65 return (pa_atomic_t
*) ((uint8
*t
) l
->data
+ PA_ALIGN(sizeof(pa_shmasyncq_data
)) + i
* (PA_ALIGN(sizeof(pa_atomic_t
)) + PA_ALIGN(element_size
)))
68 static void *get_cell_data(pa_atomic_t
*a
) {
69 return (uint8_t*) a
+ PA_ALIGN(sizeof(atomic_t
));
72 pa_shmasyncq
*pa_shmasyncq_new(unsigned n_elements
, size_t element_size
, void *data
, int fd
[2]) {
75 pa_assert(n_elements
> 0);
76 pa_assert(is_power_of_two(n_elements
));
77 pa_assert(element_size
> 0);
81 l
= pa_xnew(pa_shmasyncq
, 1);
84 memset(data
, 0, PA_SHMASYNCQ_SIZE(n_elements
, element_size
));
86 l
->data
->n_elements
= n_elements
;
87 l
->data
->element_size
= element_size
;
89 if (!(l
->read_fdsem
= pa_fdsem_new_shm(&d
->read_fdsem_data
, &fd
[0]))) {
94 if (!(l
->write_fdsem
= pa_fdsem_new(&d
->write_fdsem_data
, &fd
[1]))) {
95 pa_fdsem_free(l
->read_fdsem
);
103 void pa_shmasyncq_free(pa_shmasyncq
*l
, pa_free_cb_t free_cb
) {
109 while ((p
= pa_shmasyncq_pop(l
, 0)))
113 pa_fdsem_free(l
->read_fdsem
);
114 pa_fdsem_free(l
->write_fdsem
);
118 int pa_shmasyncq_push(pa_shmasyncq
*l
, void *p
, int wait
) {
120 pa_atomic_ptr_t
*cells
;
125 cells
= PA_SHMASYNCQ_CELLS(l
);
128 idx
= reduce(l
, l
->write_idx
);
130 if (!pa_atomic_ptr_cmpxchg(&cells
[idx
], NULL
, p
)) {
135 /* pa_log("sleeping on push"); */
138 pa_fdsem_wait(l
->read_fdsem
);
139 } while (!pa_atomic_ptr_cmpxchg(&cells
[idx
], NULL
, p
));
145 pa_fdsem_post(l
->write_fdsem
);
150 void* pa_shmasyncq_pop(pa_shmasyncq
*l
, int wait
) {
153 pa_atomic_ptr_t
*cells
;
157 cells
= PA_SHMASYNCQ_CELLS(l
);
160 idx
= reduce(l
, l
->read_idx
);
162 if (!(ret
= pa_atomic_ptr_load(&cells
[idx
]))) {
167 /* pa_log("sleeping on pop"); */
170 pa_fdsem_wait(l
->write_fdsem
);
171 } while (!(ret
= pa_atomic_ptr_load(&cells
[idx
])));
176 /* Guaranteed to succeed if we only have a single reader */
177 pa_assert_se(pa_atomic_ptr_cmpxchg(&cells
[idx
], ret
, NULL
));
182 pa_fdsem_post(l
->read_fdsem
);
187 int pa_shmasyncq_get_fd(pa_shmasyncq
*q
) {
190 return pa_fdsem_get(q
->write_fdsem
);
193 int pa_shmasyncq_before_poll(pa_shmasyncq
*l
) {
195 pa_atomic_ptr_t
*cells
;
199 cells
= PA_SHMASYNCQ_CELLS(l
);
202 idx
= reduce(l
, l
->read_idx
);
205 if (pa_atomic_ptr_load(&cells
[idx
]))
208 if (pa_fdsem_before_poll(l
->write_fdsem
) >= 0)
215 void pa_shmasyncq_after_poll(pa_shmasyncq
*l
) {
218 pa_fdsem_after_poll(l
->write_fdsem
);