1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 // -----------------------------------------------------------------------------
16 // File: clock.h
17 // -----------------------------------------------------------------------------
18 //
19 // This header file contains utility functions for working with the system-wide
20 // realtime clock. For descriptions of the main time abstractions used within
21 // this header file, consult the time.h header file.
22 #ifndef ABSL_TIME_CLOCK_H_
23 #define ABSL_TIME_CLOCK_H_
24
25 #include "absl/base/macros.h"
26 #include "absl/time/time.h"
27
28 namespace absl {
29 ABSL_NAMESPACE_BEGIN
30
31 // Now()
32 //
33 // Returns the current time, expressed as an `absl::Time` absolute time value.
34 absl::Time Now();
35
36 // GetCurrentTimeNanos()
37 //
38 // Returns the current time, expressed as a count of nanoseconds since the Unix
39 // Epoch (https://en.wikipedia.org/wiki/Unix_time). Prefer `absl::Now()` instead
40 // for all but the most performance-sensitive cases (i.e. when you are calling
41 // this function hundreds of thousands of times per second).
42 int64_t GetCurrentTimeNanos();
43
44 // SleepFor()
45 //
46 // Sleeps for the specified duration, expressed as an `absl::Duration`.
47 //
48 // Notes:
49 // * Signal interruptions will not reduce the sleep duration.
50 // * Returns immediately when passed a nonpositive duration.
51 void SleepFor(absl::Duration duration);
52
53 ABSL_NAMESPACE_END
54 } // namespace absl
55
56 // -----------------------------------------------------------------------------
57 // Implementation Details
58 // -----------------------------------------------------------------------------
59
60 // In some build configurations we pass --detect-odr-violations to the
61 // gold linker. This causes it to flag weak symbol overrides as ODR
62 // violations. Because ODR only applies to C++ and not C,
63 // --detect-odr-violations ignores symbols not mangled with C++ names.
64 // By changing our extension points to be extern "C", we dodge this
65 // check.
66 extern "C" {
67 void ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(absl::Duration duration);
68 } // extern "C"
69
SleepFor(absl::Duration duration)70 inline void absl::SleepFor(absl::Duration duration) {
71 ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(duration);
72 }
73
74 #endif // ABSL_TIME_CLOCK_H_
75