clock.h (2778B)
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 74 inline void absl::SleepFor(absl::Duration duration) { 75 ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(duration); 76 } 77 78 #endif // ABSL_TIME_CLOCK_H_