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     unsigned size;
  52     /* Stack that contains pointers stored into free list */
  53     pa_atomic_ptr_t stored;
  54     /* Stack that contains empty list elements */
  55     pa_atomic_ptr_t empty;
  56     pa_flist_elem table[0];
  57 };
  58
  59 /* Lock free pop from linked list stack */
  60 static pa_flist_elem *stack_pop(pa_atomic_ptr_t *list) {
  61     pa_flist_elem *poped;
  62     pa_assert(list);
  63
  64     do {
  65         poped = (pa_flist_elem *) pa_atomic_ptr_load(list);
  66     } while (poped != NULL && !pa_atomic_ptr_cmpxchg(list, poped, pa_atomic_ptr_load(&poped->next)));
  67
  68     return poped;
  69 }
  70
  71 /* Lock free push to linked list stack */
  72 static void stack_push(pa_atomic_ptr_t *list, pa_flist_elem *new_elem) {
  73     pa_flist_elem *next;
  74     pa_assert(list);
  75
  76     do {
  77         next = pa_atomic_ptr_load(list);
  78         pa_atomic_ptr_store(&new_elem->next, next);
  79     } while (!pa_atomic_ptr_cmpxchg(list, next, new_elem));
  80 }
  81
  82 pa_flist *pa_flist_new(unsigned size) {
  83     pa_flist *l;
  84     unsigned i;
  85
  86     if (!size)
  87         size = FLIST_SIZE;
  88
  89     l = pa_xmalloc0(sizeof(pa_flist) + sizeof(pa_flist_elem) * size);
  90
  91     l->size = size;
  92     pa_atomic_ptr_store(&l->stored, NULL);
  93     pa_atomic_ptr_store(&l->empty, NULL);
  94     for (i=0; i < size; i++) {
  95         stack_push(&l->empty, &l->table[i]);
  96     }
  97     return l;
  98 }
  99
 100 void pa_flist_free(pa_flist *l, pa_free_cb_t free_cb) {
 101     pa_assert(l);
 102
 103     if (free_cb) {
 104         pa_flist_elem *elem;
 105         while((elem = stack_pop(&l->stored)))
 106             free_cb(pa_atomic_ptr_load(&elem->ptr));
 107     }
 108
 109     pa_xfree(l);
 110 }
 111
 112 int pa_flist_push(pa_flist *l, void *p) {
 113     pa_flist_elem *elem;
 114     pa_assert(l);
 115     pa_assert(p);
 116
 117     elem = stack_pop(&l->empty);
 118     if (elem == NULL) {
 119         pa_log_warn("flist is full");
 120         return -1;
 121     }
 122     pa_atomic_ptr_store(&elem->ptr, p);
 123     stack_push(&l->stored, elem);
 124
 125     return 0;
 126 }
 127
 128 void* pa_flist_pop(pa_flist *l) {
 129     pa_flist_elem *elem;
 130     void *ptr;
 131     pa_assert(l);
 132
 133     elem = stack_pop(&l->stored);
 134     if (elem == NULL)
 135         return NULL;
 136
 137     ptr = pa_atomic_ptr_load(&elem->ptr);
 138
 139     stack_push(&l->empty, elem);
 140
 141     return ptr;
 142 }