src/gallium/include/pipe/p_refcnt.h

   1 /**************************************************************************
   2  *
   3  * Copyright 2009 VMware, Inc.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
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  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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  26  **************************************************************************/
  27
  28 #ifndef P_REFCNT_H
  29 #define P_REFCNT_H
  30
  31
  32 #include "p_defines.h"
  33 #include "p_atomic.h"
  34
  35
  36 #ifdef __cplusplus
  37 extern "C" {
  38 #endif
  39
  40
  41 struct pipe_reference
  42 {
  43    struct pipe_atomic count;
  44 };
  45
  46
  47 static INLINE void
  48 pipe_reference_init(struct pipe_reference *reference, unsigned count)
  49 {
  50    p_atomic_set(&reference->count, count);
  51 }
  52
  53
  54 /**
  55  * Set 'ptr' to point to 'reference' and update reference counting.
  56  * The old thing pointed to, if any, will be unreferenced first.
  57  * 'reference' may be NULL.
  58  *
  59  * XXX: thread safety issues!
  60  */
  61 static INLINE bool
  62 pipe_reference(struct pipe_reference **ptr, struct pipe_reference *reference)
  63 {
  64    bool destroy = FALSE;
  65
  66    /* bump the reference.count first */
  67    if (reference) {
  68       assert(p_atomic_read(&reference->count) != 0);
  69       p_atomic_inc(&reference->count);
  70    }
  71
  72    if (*ptr) {
  73       assert(p_atomic_read(&(*ptr)->count) != 0);
  74       if (p_atomic_dec_zero(&(*ptr)->count)) {
  75          destroy = TRUE;
  76       }
  77    }
  78
  79    *ptr = reference;
  80
  81    return destroy;
  82 }
  83
  84 #ifdef __cplusplus
  85 }
  86 #endif
  87
  88 #endif /* P_REFCNT_H */