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38 lines
1.5 KiB
C
38 lines
1.5 KiB
C
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#ifndef NSYNC_ONCE_H_
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#define NSYNC_ONCE_H_
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#include "third_party/nsync/atomic.h"
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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COSMOPOLITAN_C_START_
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/* An nsync_once allows a function to be called exactly once, when first
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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
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*once, the supplied function is run (with argument, in the case of
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nsync_run_once_arg()). Other callers will wait until the run of the
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function is complete, and then return without running the function
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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
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nsync_run_once/nsync_run_once_arg().
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These *_spin variants should be used only in contexts where normal
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blocking is disallowed, such as within user-space schedulers, when
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the runtime is not fully initialized, etc. They provide no
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significant performance benefit, and they should be avoided in normal
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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),
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void *arg);
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COSMOPOLITAN_C_END_
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* NSYNC_ONCE_H_ */
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