libc/src/__support/time/linux/abs_timeout.h

   1 //===--- Linux absolute timeout ---------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H
  10 #define LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H
  11
  12 #include "hdr/time_macros.h"
  13 #include "hdr/types/struct_timespec.h"
  14 #include "src/__support/CPP/expected.h"
  15 #include "src/__support/macros/config.h"
  16 #include "src/__support/time/units.h"
  17
  18 namespace LIBC_NAMESPACE_DECL {
  19 namespace internal {
  20 // We use AbsTimeout to remind ourselves that the timeout is an absolute time.
  21 // This is a simple wrapper around the timespec struct that also keeps track of
  22 // whether the time is in realtime or monotonic time.
  23 class AbsTimeout {
  24   timespec timeout;
  25   bool realtime_flag;
  26   LIBC_INLINE constexpr explicit AbsTimeout(timespec ts, bool realtime)
  27       : timeout(ts), realtime_flag(realtime) {}
  28
  29 public:
  30   enum class Error { Invalid, BeforeEpoch };
  31   LIBC_INLINE const timespec &get_timespec() const { return timeout; }
  32   LIBC_INLINE bool is_realtime() const { return realtime_flag; }
  33   LIBC_INLINE static constexpr cpp::expected<AbsTimeout, Error>
  34   from_timespec(timespec ts, bool realtime) {
  35     using namespace time_units;
  36     if (ts.tv_nsec < 0 || ts.tv_nsec >= 1_s_ns)
  37       return cpp::unexpected(Error::Invalid);
  38
  39     // POSIX allows tv_sec to be negative. We interpret this as an expired
  40     // timeout.
  41     if (ts.tv_sec < 0)
  42       return cpp::unexpected(Error::BeforeEpoch);
  43
  44     return AbsTimeout{ts, realtime};
  45   }
  46 };
  47 } // namespace internal
  48 } // namespace LIBC_NAMESPACE_DECL
  49
  50 #endif // LLVM_LIBC_SRC___SUPPORT_TIME_LINUX_ABS_TIMEOUT_H