merge glitch-free branch back into trunk

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@2445 fefdeb5f-60dc-0310-8127-8f9354f1896f

src/pulsecore/shmasyncq.c

@@ -0,0 +1,222 @@
+/* $Id$ */
+
+/***
+  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, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <unistd.h>
+#include <errno.h>
+
+#include <pulsecore/atomic.h>
+#include <pulsecore/log.h>
+#include <pulsecore/thread.h>
+#include <pulsecore/macro.h>
+#include <pulsecore/core-util.h>
+#include <pulse/xmalloc.h>
+
+#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, &fd[0]))) {
+        pa_xfree(l);
+        return NULL;
+    }
+
+    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);
+}