subversion/include/private/svn_atomic.h

   1 /**
   2  * @copyright
   3  * ====================================================================
   4  * Copyright (c) 2006 CollabNet.  All rights reserved.
   5  *
   6  * This software is licensed as described in the file COPYING, which
   7  * you should have received as part of this distribution.  The terms
   8  * are also available at http://subversion.tigris.org/license-1.html.
   9  * If newer versions of this license are posted there, you may use a
  10  * newer version instead, at your option.
  11  *
  12  * This software consists of voluntary contributions made by many
  13  * individuals.  For exact contribution history, see the revision
  14  * history and logs, available at http://subversion.tigris.org/.
  15  * ====================================================================
  16  * @endcopyright
  17  *
  18  * @file svn_atomic.h
  19  * @brief Macros and functions for atomic operations
  20  */
  21
  22 #ifndef SVN_ATOMIC_H
  23 #define SVN_ATOMIC_H
  24
  25 #include <apr_version.h>
  26 #include <apr_atomic.h>
  27
  28 #include "svn_error.h"
  29 #include "private/svn_dep_compat.h"
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif /* __cplusplus */
  34
  35 /**
  36  * @name Macro definitions for atomic types and operations
  37  *
  38  * @note These are necessary because the apr_atomic API changed somewhat
  39  *       between apr-0.x and apr-1.x.
  40  * @{
  41  */
  42
  43 /** The type used by all the other atomic operations. */
  44 #if APR_VERSION_AT_LEAST(1, 0, 0)
  45 #define svn_atomic_t apr_uint32_t
  46 #else
  47 #define svn_atomic_t apr_atomic_t
  48 #endif
  49
  50 /** Atomically read an #svn_atomic_t from memory. */
  51 #if APR_VERSION_AT_LEAST(1, 0, 0)
  52 #define svn_atomic_read(mem) apr_atomic_read32((mem))
  53 #else
  54 #define svn_atomic_read(mem) apr_atomic_read((mem))
  55 #endif
  56
  57 /** Atomically set an #svn_atomic_t in memory. */
  58 #if APR_VERSION_AT_LEAST(1, 0, 0)
  59 #define svn_atomic_set(mem, val) apr_atomic_set32((mem), (val))
  60 #else
  61 #define svn_atomic_set(mem, val) apr_atomic_set((mem), (val))
  62 #endif
  63
  64 /** Atomically increment an #svn_atomic_t. */
  65 #if APR_VERSION_AT_LEAST(1, 0, 0)
  66 #define svn_atomic_inc(mem) apr_atomic_inc32(mem)
  67 #else
  68 #define svn_atomic_inc(mem) apr_atomic_inc(mem)
  69 #endif
  70
  71 /** Atomically decrement an #svn_atomic_t. */
  72 #if APR_VERSION_AT_LEAST(1, 0, 0)
  73 #define svn_atomic_dec(mem) apr_atomic_dec32(mem)
  74 #else
  75 #define svn_atomic_dec(mem) apr_atomic_dec(mem)
  76 #endif
  77
  78 /**
  79  * Atomic compare-and-swap.
  80  *
  81  * Compare the value that @a mem points to with @a cmp. If they are
  82  * the same swap the value with @a with.
  83  *
  84  * @note svn_atomic_cas should not be combined with the other
  85  *       svn_atomic operations.  A comment in apr_atomic.h explains
  86  *       that on some platforms, the CAS function is implemented in a
  87  *       way that is incompatible with the other atomic operations.
  88  */
  89 #if APR_VERSION_AT_LEAST(1, 0, 0)
  90 #define svn_atomic_cas(mem, with, cmp) \
  91     apr_atomic_cas32((mem), (with), (cmp))
  92 #else
  93 #define svn_atomic_cas(mem, with, cmp) \
  94     apr_atomic_cas((mem), (with), (cmp))
  95 #endif
  96 /** @} */
  97
  98 /**
  99  * Call an initialization function in a thread-safe manner.
 100  *
 101  * @a global_status must be a pointer to a global, zero-initialized
 102  * #svn_atomic_t. @a init_func is a pointer to the function that performs
 103  * the actual initialization, and @a pool is passed on to the init_func
 104  * for its use.
 105  *
 106  * @since New in 1.5.
 107  */
 108 svn_error_t *
 109 svn_atomic__init_once(volatile svn_atomic_t *global_status,
 110                       svn_error_t *(*init_func)(apr_pool_t*), apr_pool_t* pool);
 111
 112 #ifdef __cplusplus
 113 }
 114 #endif /* __cplusplus */
 115
 116 #endif /* SVN_ATOMIC_H */