1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
11 #define _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
12 
13 #include <__config>
14 
15 #ifndef _LIBCPP_HAS_NO_THREADS
16 
17 #  include <__chrono/duration.h>
18 #  include <__threading_support>
19 
20 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 #    pragma GCC system_header
22 #  endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 struct __libcpp_timed_backoff_policy {
operator__libcpp_timed_backoff_policy27   _LIBCPP_HIDE_FROM_ABI bool operator()(chrono::nanoseconds __elapsed) const {
28     if (__elapsed > chrono::milliseconds(128))
29       __libcpp_thread_sleep_for(chrono::milliseconds(8));
30     else if (__elapsed > chrono::microseconds(64))
31       __libcpp_thread_sleep_for(__elapsed / 2);
32     else if (__elapsed > chrono::microseconds(4))
33       __libcpp_thread_yield();
34     else {
35     } // poll
36     return false;
37   }
38 };
39 
40 _LIBCPP_END_NAMESPACE_STD
41 
42 #endif // _LIBCPP_HAS_NO_THREADS
43 
44 #endif // _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
45