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 <cstdint>
26
27 #include "absl/base/config.h"
28 #include "absl/base/macros.h"
29 #include "absl/time/time.h"
30
31 namespace absl {
32 ABSL_NAMESPACE_BEGIN
33
34 // Now()
35 //
36 // Returns the current time, expressed as an `absl::Time` absolute time value.
37 absl::Time Now();
38
39 // GetCurrentTimeNanos()
40 //
41 // Returns the current time, expressed as a count of nanoseconds since the Unix
42 // Epoch (https://en.wikipedia.org/wiki/Unix_time). Prefer `absl::Now()` instead
43 // for all but the most performance-sensitive cases (i.e. when you are calling
44 // this function hundreds of thousands of times per second).
45 int64_t GetCurrentTimeNanos();
46
47 // SleepFor()
48 //
49 // Sleeps for the specified duration, expressed as an `absl::Duration`.
50 //
51 // Notes:
52 // * Signal interruptions will not reduce the sleep duration.
53 // * Returns immediately when passed a nonpositive duration.
54 void SleepFor(absl::Duration duration);
55
56 ABSL_NAMESPACE_END
57 } // namespace absl
58
59 // -----------------------------------------------------------------------------
60 // Implementation Details
61 // -----------------------------------------------------------------------------
62
63 // In some build configurations we pass --detect-odr-violations to the
64 // gold linker. This causes it to flag weak symbol overrides as ODR
65 // violations. Because ODR only applies to C++ and not C,
66 // --detect-odr-violations ignores symbols not mangled with C++ names.
67 // By changing our extension points to be extern "C", we dodge this
68 // check.
69 extern "C" {
70 ABSL_DLL void ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(
71 absl::Duration duration);
72 } // extern "C"
73
SleepFor(absl::Duration duration)74 inline void absl::SleepFor(absl::Duration duration) {
75 ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(duration);
76 }
77
78 #endif // ABSL_TIME_CLOCK_H_
79