/***
This file is part of PulseAudio.
Copyright 2006 Lennart Poettering
PulseAudio is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
PulseAudio is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with PulseAudio; if not, see .
***/
#ifdef HAVE_CONFIG_H
#include
#endif
#include
#include
#include
#include
#include
#include
#include
#include
#include "fdsem.h"
/* For debugging purposes we can define _Y to put and extra thread
* yield between each operation. */
/* #define PROFILE */
#ifdef PROFILE
#define _Y pa_thread_yield()
#else
#define _Y do { } while(0)
#endif
struct pa_shmasyncq {
pa_fdsem *read_fdsem, *write_fdsem;
pa_shmasyncq_data *data;
};
static int is_power_of_two(unsigned size) {
return !(size & (size - 1));
}
static int reduce(pa_shmasyncq *l, int value) {
return value & (unsigned) (l->n_elements - 1);
}
static pa_atomic_t* get_cell(pa_shmasyncq *l, unsigned i) {
pa_assert(i < l->data->n_elements);
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)))
}
static void *get_cell_data(pa_atomic_t *a) {
return (uint8_t*) a + PA_ALIGN(sizeof(atomic_t));
}
pa_shmasyncq *pa_shmasyncq_new(unsigned n_elements, size_t element_size, void *data, int fd[2]) {
pa_shmasyncq *l;
pa_assert(n_elements > 0);
pa_assert(is_power_of_two(n_elements));
pa_assert(element_size > 0);
pa_assert(data);
pa_assert(fd);
l = pa_xnew(pa_shmasyncq, 1);
l->data = data;
memset(data, 0, PA_SHMASYNCQ_SIZE(n_elements, element_size));
l->data->n_elements = n_elements;
l->data->element_size = element_size;
if (!(l->read_fdsem = pa_fdsem_new_shm(&d->read_fdsem_data))) {
pa_xfree(l);
return NULL;
}
fd[0] = pa_fdsem_get(l->read_fdsem);
if (!(l->write_fdsem = pa_fdsem_new(&d->write_fdsem_data, &fd[1]))) {
pa_fdsem_free(l->read_fdsem);
pa_xfree(l);
return NULL;
}
return l;
}
void pa_shmasyncq_free(pa_shmasyncq *l, pa_free_cb_t free_cb) {
pa_assert(l);
if (free_cb) {
void *p;
while ((p = pa_shmasyncq_pop(l, 0)))
free_cb(p);
}
pa_fdsem_free(l->read_fdsem);
pa_fdsem_free(l->write_fdsem);
pa_xfree(l);
}
int pa_shmasyncq_push(pa_shmasyncq*l, void *p, int wait) {
int idx;
pa_atomic_ptr_t *cells;
pa_assert(l);
pa_assert(p);
cells = PA_SHMASYNCQ_CELLS(l);
_Y;
idx = reduce(l, l->write_idx);
if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
if (!wait)
return -1;
/* pa_log("sleeping on push"); */
do {
pa_fdsem_wait(l->read_fdsem);
} while (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p));
}
_Y;
l->write_idx++;
pa_fdsem_post(l->write_fdsem);
return 0;
}
void* pa_shmasyncq_pop(pa_shmasyncq*l, int wait) {
int idx;
void *ret;
pa_atomic_ptr_t *cells;
pa_assert(l);
cells = PA_SHMASYNCQ_CELLS(l);
_Y;
idx = reduce(l, l->read_idx);
if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
if (!wait)
return NULL;
/* pa_log("sleeping on pop"); */
do {
pa_fdsem_wait(l->write_fdsem);
} while (!(ret = pa_atomic_ptr_load(&cells[idx])));
}
pa_assert(ret);
/* Guaranteed to succeed if we only have a single reader */
pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL));
_Y;
l->read_idx++;
pa_fdsem_post(l->read_fdsem);
return ret;
}
int pa_shmasyncq_get_fd(pa_shmasyncq *q) {
pa_assert(q);
return pa_fdsem_get(q->write_fdsem);
}
int pa_shmasyncq_before_poll(pa_shmasyncq *l) {
int idx;
pa_atomic_ptr_t *cells;
pa_assert(l);
cells = PA_SHMASYNCQ_CELLS(l);
_Y;
idx = reduce(l, l->read_idx);
for (;;) {
if (pa_atomic_ptr_load(&cells[idx]))
return -1;
if (pa_fdsem_before_poll(l->write_fdsem) >= 0)
return 0;
}
return 0;
}
void pa_shmasyncq_after_poll(pa_shmasyncq *l) {
pa_assert(l);
pa_fdsem_after_poll(l->write_fdsem);
}