code.delx.au - pulseaudio/blob - src/pulsecore/flist.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2006-2008 Lennart Poettering
   5   Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
   6
   7   Contact: Jyri Sarha <Jyri.Sarha@nokia.com>
   8
   9   PulseAudio is free software; you can redistribute it and/or modify
  10   it under the terms of the GNU Lesser General Public License as
  11   published by the Free Software Foundation; either version 2.1 of the
  12   License, or (at your option) any later version.
  13
  14   PulseAudio is distributed in the hope that it will be useful, but
  15   WITHOUT ANY WARRANTY; without even the implied warranty of
  16   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17   Lesser General Public License for more details.
  18
  19   You should have received a copy of the GNU Lesser General Public
  20   License along with PulseAudio; if not, write to the Free Software
  21   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  22   USA.
  23 ***/
  24
  25 #ifdef HAVE_CONFIG_H
  26 #include <config.h>
  27 #endif
  28
  29 #include <pulse/xmalloc.h>
  30
  31 #include <pulsecore/atomic.h>
  32 #include <pulsecore/log.h>
  33 #include <pulsecore/thread.h>
  34 #include <pulsecore/macro.h>
  35 #include <pulsecore/core-util.h>
  36 #include <pulsecore/macro.h>
  37
  38 #include "flist.h"
  39
  40 #define FLIST_SIZE 128
  41
  42 /* Lock free single linked list element. */
  43 struct pa_flist_elem {
  44     pa_atomic_ptr_t next;
  45     pa_atomic_ptr_t ptr;
  46 };
  47
  48 typedef struct pa_flist_elem pa_flist_elem;
  49
  50 struct pa_flist {
  51     const char *name;
  52     unsigned size;
  53     /* Stack that contains pointers stored into free list */
  54     pa_atomic_ptr_t stored;
  55     /* Stack that contains empty list elements */
  56     pa_atomic_ptr_t empty;
  57     pa_flist_elem table[0];
  58 };
  59
  60 /* Lock free pop from linked list stack */
  61 static pa_flist_elem *stack_pop(pa_atomic_ptr_t *list) {
  62     pa_flist_elem *poped;
  63     pa_assert(list);
  64
  65     do {
  66         poped = (pa_flist_elem *) pa_atomic_ptr_load(list);
  67     } while (poped != NULL && !pa_atomic_ptr_cmpxchg(list, poped, pa_atomic_ptr_load(&poped->next)));
  68
  69     return poped;
  70 }
  71
  72 /* Lock free push to linked list stack */
  73 static void stack_push(pa_atomic_ptr_t *list, pa_flist_elem *new_elem) {
  74     pa_flist_elem *next;
  75     pa_assert(list);
  76
  77     do {
  78         next = pa_atomic_ptr_load(list);
  79         pa_atomic_ptr_store(&new_elem->next, next);
  80     } while (!pa_atomic_ptr_cmpxchg(list, next, new_elem));
  81 }
  82
  83 pa_flist *pa_flist_new_with_name(unsigned size, const char *name) {
  84     pa_flist *l;
  85     unsigned i;
  86     pa_assert(name);
  87
  88     if (!size)
  89         size = FLIST_SIZE;
  90
  91     l = pa_xmalloc0(sizeof(pa_flist) + sizeof(pa_flist_elem) * size);
  92
  93     l->name = pa_xstrdup(name);
  94     l->size = size;
  95     pa_atomic_ptr_store(&l->stored, NULL);
  96     pa_atomic_ptr_store(&l->empty, NULL);
  97     for (i=0; i < size; i++) {
  98         stack_push(&l->empty, &l->table[i]);
  99     }
 100     return l;
 101 }
 102
 103 pa_flist *pa_flist_new(unsigned size) {
 104     return pa_flist_new_with_name(size, "unknown");
 105 }
 106
 107 void pa_flist_free(pa_flist *l, pa_free_cb_t free_cb) {
 108     pa_assert(l);
 109     pa_assert(l->name);
 110
 111     if (free_cb) {
 112         pa_flist_elem *elem;
 113         while((elem = stack_pop(&l->stored)))
 114             free_cb(pa_atomic_ptr_load(&elem->ptr));
 115     }
 116
 117     pa_xfree(l);
 118 }
 119
 120 int pa_flist_push(pa_flist *l, void *p) {
 121     pa_flist_elem *elem;
 122     pa_assert(l);
 123     pa_assert(p);
 124
 125     elem = stack_pop(&l->empty);
 126     if (elem == NULL) {
 127         if (pa_log_ratelimit(PA_LOG_DEBUG))
 128             pa_log_debug("%s flist is full (don't worry)", l->name);
 129         return -1;
 130     }
 131     pa_atomic_ptr_store(&elem->ptr, p);
 132     stack_push(&l->stored, elem);
 133
 134     return 0;
 135 }
 136
 137 void* pa_flist_pop(pa_flist *l) {
 138     pa_flist_elem *elem;
 139     void *ptr;
 140     pa_assert(l);
 141
 142     elem = stack_pop(&l->stored);
 143     if (elem == NULL)
 144         return NULL;
 145
 146     ptr = pa_atomic_ptr_load(&elem->ptr);
 147
 148     stack_push(&l->empty, elem);
 149
 150     return ptr;
 151 }