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/macro.h>
  34 #include <pulsecore/core-util.h>
  35 #include <pulsecore/macro.h>
  36
  37 #include "flist.h"
  38
  39 #define FLIST_SIZE 128
  40
  41 /* Lock free single linked list element. */
  42 struct pa_flist_elem {
  43     pa_atomic_ptr_t next;
  44     pa_atomic_ptr_t ptr;
  45 };
  46
  47 typedef struct pa_flist_elem pa_flist_elem;
  48
  49 struct pa_flist {
  50     const char *name;
  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_with_name(unsigned size, const char *name) {
  83     pa_flist *l;
  84     unsigned i;
  85     pa_assert(name);
  86
  87     if (!size)
  88         size = FLIST_SIZE;
  89
  90     l = pa_xmalloc0(sizeof(pa_flist) + sizeof(pa_flist_elem) * size);
  91
  92     l->name = pa_xstrdup(name);
  93     l->size = size;
  94     pa_atomic_ptr_store(&l->stored, NULL);
  95     pa_atomic_ptr_store(&l->empty, NULL);
  96     for (i=0; i < size; i++) {
  97         stack_push(&l->empty, &l->table[i]);
  98     }
  99     return l;
 100 }
 101
 102 pa_flist *pa_flist_new(unsigned size) {
 103     return pa_flist_new_with_name(size, "unknown");
 104 }
 105
 106 void pa_flist_free(pa_flist *l, pa_free_cb_t free_cb) {
 107     pa_assert(l);
 108     pa_assert(l->name);
 109
 110     if (free_cb) {
 111         pa_flist_elem *elem;
 112         while((elem = stack_pop(&l->stored)))
 113             free_cb(pa_atomic_ptr_load(&elem->ptr));
 114     }
 115
 116     pa_xfree(l);
 117 }
 118
 119 int pa_flist_push(pa_flist *l, void *p) {
 120     pa_flist_elem *elem;
 121     pa_assert(l);
 122     pa_assert(p);
 123
 124     elem = stack_pop(&l->empty);
 125     if (elem == NULL) {
 126         if (pa_log_ratelimit(PA_LOG_DEBUG))
 127             pa_log_debug("%s flist is full (don't worry)", l->name);
 128         return -1;
 129     }
 130     pa_atomic_ptr_store(&elem->ptr, p);
 131     stack_push(&l->stored, elem);
 132
 133     return 0;
 134 }
 135
 136 void* pa_flist_pop(pa_flist *l) {
 137     pa_flist_elem *elem;
 138     void *ptr;
 139     pa_assert(l);
 140
 141     elem = stack_pop(&l->stored);
 142     if (elem == NULL)
 143         return NULL;
 144
 145     ptr = pa_atomic_ptr_load(&elem->ptr);
 146
 147     stack_push(&l->empty, elem);
 148
 149     return ptr;
 150 }