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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   9  * without limitation the rights to use, copy, modify, merge, publish,
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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
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
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  25  *
  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 static INLINE bool
  55 pipe_is_referenced(struct pipe_reference *reference)
  56 {
  57    return p_atomic_read(&reference->count) != 0;
  58 }
  59
  60
  61 /**
  62  * Set 'ptr' to point to 'reference' and update reference counting.
  63  * The old thing pointed to, if any, will be unreferenced first.
  64  * 'reference' may be NULL.
  65  */
  66 static INLINE bool
  67 pipe_reference(struct pipe_reference **ptr, struct pipe_reference *reference)
  68 {
  69    bool destroy = FALSE;
  70
  71    if(*ptr != reference) {
  72       /* bump the reference.count first */
  73       if (reference) {
  74          assert(pipe_is_referenced(reference));
  75          p_atomic_inc(&reference->count);
  76       }
  77
  78       if (*ptr) {
  79          assert(pipe_is_referenced(*ptr));
  80          if (p_atomic_dec_zero(&(*ptr)->count)) {
  81             destroy = TRUE;
  82          }
  83       }
  84
  85       *ptr = reference;
  86    }
  87
  88    return destroy;
  89 }
  90
  91
  92 #ifdef __cplusplus
  93 }
  94 #endif
  95
  96 #endif /* P_REFCNT_H */