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51 lines
2.1 KiB
C
51 lines
2.1 KiB
C
// clang-format off
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/* Copyright 2016 Google Inc.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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#ifndef NSYNC_PUBLIC_NSYNC_ONCE_H_
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#define NSYNC_PUBLIC_NSYNC_ONCE_H_
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#include "libc/fmt/conv.h"
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#include "libc/inttypes.h"
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#include "libc/thread/nsync_cpp.h"
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#include "libc/thread/nsync_atomic.h"
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NSYNC_CPP_START_
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/* An nsync_once allows a function to be called exactly once, when first referenced. */
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typedef nsync_atomic_uint32_ nsync_once;
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/* An initializer for nsync_once; it is guaranteed to be all zeroes. */
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#define NSYNC_ONCE_INIT NSYNC_ATOMIC_UINT32_INIT_
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/* The first time nsync_run_once() or nsync_run_once_arg() is applied to *once,
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the supplied function is run (with argument, in the case of nsync_run_once_arg()).
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Other callers will wait until the run of the function is complete, and then
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return without running the function again. */
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void nsync_run_once (nsync_once *once, void (*f) (void));
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void nsync_run_once_arg (nsync_once *once, void (*farg) (void *arg), void *arg);
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/* Same as nsync_run_once()/nsync_run_once_arg() but uses a spinloop.
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Can be used on the same nsync_once as nsync_run_once/nsync_run_once_arg().
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These *_spin variants should be used only in contexts where normal blocking
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is disallowed, such as within user-space schedulers, when the runtime is
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not fully initialized, etc. They provide no significant performance benefit,
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and they should be avoided in normal code. */
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void nsync_run_once_spin (nsync_once *once, void (*f) (void));
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void nsync_run_once_arg_spin (nsync_once *once, void (*farg) (void *arg), void *arg);
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NSYNC_CPP_END_
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#endif /*NSYNC_PUBLIC_NSYNC_ONCE_H_*/
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