1 /*
2 * Copyright (c) 2008-2010 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 __DISPATCH_ONCE__
22 #define __DISPATCH_ONCE__
23
24 #ifndef __DISPATCH_INDIRECT__
25 #error "Please #include <dispatch/dispatch.h> instead of this file directly."
26 #include <dispatch/base.h> // for HeaderDoc
27 #endif
28
29 __BEGIN_DECLS
30
31 /*!
32 * @typedef dispatch_once_t
33 *
34 * @abstract
35 * A predicate for use with dispatch_once(). It must be initialized to zero.
36 * Note: static and global variables default to zero.
37 */
38 typedef long dispatch_once_t;
39
40 /*!
41 * @function dispatch_once
42 *
43 * @abstract
44 * Execute a block once and only once.
45 *
46 * @param predicate
47 * A pointer to a dispatch_once_t that is used to test whether the block has
48 * completed or not.
49 *
50 * @param block
51 * The block to execute once.
52 *
53 * @discussion
54 * Always call dispatch_once() before using or testing any variables that are
55 * initialized by the block.
56 */
57 #ifdef __BLOCKS__
58 __OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0)
59 DISPATCH_EXPORT DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
60 void
61 dispatch_once(dispatch_once_t *predicate, dispatch_block_t block);
62
63 DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
64 void
_dispatch_once(dispatch_once_t * predicate,dispatch_block_t block)65 _dispatch_once(dispatch_once_t *predicate, dispatch_block_t block)
66 {
67 if (DISPATCH_EXPECT(*predicate, ~0l) != ~0l) {
68 dispatch_once(predicate, block);
69 }
70 }
71 #undef dispatch_once
72 #define dispatch_once _dispatch_once
73 #endif
74
75 __OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0)
76 DISPATCH_EXPORT DISPATCH_NONNULL1 DISPATCH_NONNULL3 DISPATCH_NOTHROW
77 void
78 dispatch_once_f(dispatch_once_t *predicate, void *context,
79 dispatch_function_t function);
80
81 DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL1 DISPATCH_NONNULL3
82 DISPATCH_NOTHROW
83 void
_dispatch_once_f(dispatch_once_t * predicate,void * context,dispatch_function_t function)84 _dispatch_once_f(dispatch_once_t *predicate, void *context,
85 dispatch_function_t function)
86 {
87 if (DISPATCH_EXPECT(*predicate, ~0l) != ~0l) {
88 dispatch_once_f(predicate, context, function);
89 }
90 }
91 #undef dispatch_once_f
92 #define dispatch_once_f _dispatch_once_f
93
94 __END_DECLS
95
96 #endif
97