128 lines
3.6 KiB
C
128 lines
3.6 KiB
C
/*
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* Copyright (c) 2008-2010 Apple Inc. All rights reserved.
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*
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* @APPLE_APACHE_LICENSE_HEADER_START@
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* @APPLE_APACHE_LICENSE_HEADER_END@
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*/
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#ifndef __DISPATCH_ONCE__
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#define __DISPATCH_ONCE__
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#ifndef __DISPATCH_INDIRECT__
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#error "Please #include <dispatch/dispatch.h> instead of this file directly."
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#include <dispatch/base.h> // for HeaderDoc
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#endif
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DISPATCH_ASSUME_NONNULL_BEGIN
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DISPATCH_ASSUME_ABI_SINGLE_BEGIN
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__BEGIN_DECLS
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/*!
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* @typedef dispatch_once_t
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*
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* @abstract
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* A predicate for use with dispatch_once(). It must be initialized to zero.
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* Note: static and global variables default to zero.
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*/
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DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
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typedef intptr_t dispatch_once_t;
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#if defined(__x86_64__) || defined(__i386__) || defined(__s390x__)
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#define DISPATCH_ONCE_INLINE_FASTPATH 1
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#elif defined(__APPLE__)
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#define DISPATCH_ONCE_INLINE_FASTPATH 1
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#else
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#define DISPATCH_ONCE_INLINE_FASTPATH 0
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#endif
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/*!
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* @function dispatch_once
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*
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* @abstract
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* Execute a block once and only once.
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*
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* @param predicate
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* A pointer to a dispatch_once_t that is used to test whether the block has
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* completed or not.
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*
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* @param block
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* The block to execute once.
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*
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* @discussion
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* Always call dispatch_once() before using or testing any variables that are
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* initialized by the block.
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*/
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#ifdef __BLOCKS__
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API_AVAILABLE(macos(10.6), ios(4.0))
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DISPATCH_EXPORT DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
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DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
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void
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dispatch_once(dispatch_once_t *predicate,
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DISPATCH_NOESCAPE dispatch_block_t block);
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#if DISPATCH_ONCE_INLINE_FASTPATH
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DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
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DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
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void
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_dispatch_once(dispatch_once_t *predicate,
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DISPATCH_NOESCAPE dispatch_block_t block)
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{
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if (DISPATCH_EXPECT(*predicate, ~0l) != ~0l) {
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dispatch_once(predicate, block);
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} else {
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dispatch_compiler_barrier();
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}
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DISPATCH_COMPILER_CAN_ASSUME(*predicate == ~0l);
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}
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#undef dispatch_once
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#define dispatch_once _dispatch_once
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#endif
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#endif // DISPATCH_ONCE_INLINE_FASTPATH
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API_AVAILABLE(macos(10.6), ios(4.0))
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DISPATCH_EXPORT DISPATCH_NONNULL1 DISPATCH_NONNULL3 DISPATCH_NOTHROW
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DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
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void
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dispatch_once_f(dispatch_once_t *predicate, void *_Nullable context,
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dispatch_function_t function);
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#if DISPATCH_ONCE_INLINE_FASTPATH
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DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL1 DISPATCH_NONNULL3
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DISPATCH_NOTHROW
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DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
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void
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_dispatch_once_f(dispatch_once_t *predicate, void *_Nullable context,
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dispatch_function_t function)
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{
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if (DISPATCH_EXPECT(*predicate, ~0l) != ~0l) {
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dispatch_once_f(predicate, context, function);
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} else {
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dispatch_compiler_barrier();
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}
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DISPATCH_COMPILER_CAN_ASSUME(*predicate == ~0l);
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}
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#undef dispatch_once_f
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#define dispatch_once_f _dispatch_once_f
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#endif // DISPATCH_ONCE_INLINE_FASTPATH
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__END_DECLS
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DISPATCH_ASSUME_ABI_SINGLE_END
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DISPATCH_ASSUME_NONNULL_END
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#endif
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