absl/time/clock.h

0001 // Copyright 2017 The Abseil Authors.
0002 //
0003 // Licensed under the Apache License, Version 2.0 (the "License");
0004 // you may not use this file except in compliance with the License.
0005 // You may obtain a copy of the License at
0006 //
0007 //      https://www.apache.org/licenses/LICENSE-2.0
0008 //
0009 // Unless required by applicable law or agreed to in writing, software
0010 // distributed under the License is distributed on an "AS IS" BASIS,
0011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0012 // See the License for the specific language governing permissions and
0013 // limitations under the License.
0014 //
0015 // -----------------------------------------------------------------------------
0016 // File: clock.h
0017 // -----------------------------------------------------------------------------
0018 //
0019 // This header file contains utility functions for working with the system-wide
0020 // realtime clock. For descriptions of the main time abstractions used within
0021 // this header file, consult the time.h header file.
0022 #ifndef ABSL_TIME_CLOCK_H_
0023 #define ABSL_TIME_CLOCK_H_
0024
0025 #include <cstdint>
0026
0027 #include "absl/base/config.h"
0028 #include "absl/base/macros.h"
0029 #include "absl/time/time.h"
0030
0031 namespace absl {
0032 ABSL_NAMESPACE_BEGIN
0033
0034 // Now()
0035 //
0036 // Returns the current time, expressed as an `absl::Time` absolute time value.
0037 absl::Time Now();
0038
0039 // GetCurrentTimeNanos()
0040 //
0041 // Returns the current time, expressed as a count of nanoseconds since the Unix
0042 // Epoch (https://en.wikipedia.org/wiki/Unix_time). Prefer `absl::Now()` instead
0043 // for all but the most performance-sensitive cases (i.e. when you are calling
0044 // this function hundreds of thousands of times per second).
0045 int64_t GetCurrentTimeNanos();
0046
0047 // SleepFor()
0048 //
0049 // Sleeps for the specified duration, expressed as an `absl::Duration`.
0050 //
0051 // Notes:
0052 // * Signal interruptions will not reduce the sleep duration.
0053 // * Returns immediately when passed a nonpositive duration.
0054 void SleepFor(absl::Duration duration);
0055
0056 ABSL_NAMESPACE_END
0057 }  // namespace absl
0058
0059 // -----------------------------------------------------------------------------
0060 // Implementation Details
0061 // -----------------------------------------------------------------------------
0062
0063 // In some build configurations we pass --detect-odr-violations to the
0064 // gold linker.  This causes it to flag weak symbol overrides as ODR
0065 // violations.  Because ODR only applies to C++ and not C,
0066 // --detect-odr-violations ignores symbols not mangled with C++ names.
0067 // By changing our extension points to be extern "C", we dodge this
0068 // check.
0069 extern "C" {
0070 ABSL_DLL void ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(
0071     absl::Duration duration);
0072 }  // extern "C"
0073
0074 inline void absl::SleepFor(absl::Duration duration) {
0075   ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(duration);
0076 }
0077
0078 #endif  // ABSL_TIME_CLOCK_H_