include/os/once_private.h

   1 /*
   2  * Copyright (c) 2008-2013 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_APACHE_LICENSE_HEADER_START@
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  *
  18  * @APPLE_APACHE_LICENSE_HEADER_END@
  19  */
  20
  21 #ifndef __OS_ONCE_PRIVATE__
  22 #define __OS_ONCE_PRIVATE__
  23
  24 #include <Availability.h>
  25 #include <os/base_private.h>
  26
  27 OS_ASSUME_NONNULL_BEGIN
  28
  29 __BEGIN_DECLS
  30
  31 #define OS_ONCE_SPI_VERSION 20130313
  32
  33 OS_SWIFT_UNAVAILABLE("Swift has lazy init")
  34 typedef long os_once_t;
  35
  36 __OSX_AVAILABLE_STARTING(__MAC_10_9,__IPHONE_7_0)
  37 OS_EXPORT OS_NONNULL1 OS_NONNULL3 OS_NOTHROW
  38 OS_SWIFT_UNAVAILABLE("Swift has lazy init")
  39 void
  40 _os_once(os_once_t *predicate, void *_Nullable context, os_function_t function);
  41
  42 OS_NONNULL1 OS_NONNULL3 OS_NOTHROW
  43 __header_always_inline void
  44 os_once(os_once_t *predicate, void *_Nullable context, os_function_t function)
  45 {
  46         if (OS_EXPECT(*predicate, ~0l) != ~0l) {
  47                 _os_once(predicate, context, function);
  48                 OS_COMPILER_CAN_ASSUME(*predicate == ~0l);
  49         } else {
  50                 os_compiler_barrier();
  51         }
  52 }
  53
  54 /* This SPI is *strictly* for the use of pthread_once only. This is not
  55  * safe in general use of os_once.
  56  */
  57 __OSX_AVAILABLE_STARTING(__MAC_10_9, __IPHONE_7_0)
  58 OS_EXPORT OS_NONNULL1 OS_NOTHROW
  59 OS_SWIFT_UNAVAILABLE("Swift has lazy init")
  60 void
  61 __os_once_reset(os_once_t *val);
  62
  63 __END_DECLS
  64
  65 OS_ASSUME_NONNULL_END
  66
  67 #endif // __OS_ONCE_PRIVATE__