Timeout.h

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//===-- Timeout.h -----------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef LLDB_UTILITY_TIMEOUT_H
#define LLDB_UTILITY_TIMEOUT_H
 
#include "llvm/Support/Chrono.h"
#include "llvm/Support/FormatProviders.h"
#include <optional>
 
namespace lldb_private {
 
// A general purpose class for representing timeouts for various APIs. It's
// basically an std::optional<std::chrono::duration<int64_t, Ratio>>, but we
// customize it a bit to enable the standard chrono implicit conversions (e.g.
// from Timeout<std::milli> to Timeout<std::micro>.
//
// The intended meaning of the values is:
// - std::nullopt - no timeout, the call should wait forever - 0 - poll, only
// complete the call if it will not block - >0 - wait for a given number of
// units for the result
template <typename Ratio>
class Timeout : public std::optional<std::chrono::duration<int64_t, Ratio>> {
private:
  template <typename Ratio2> using Dur = std::chrono::duration<int64_t, Ratio2>;
  template <typename Rep2, typename Ratio2>
  using EnableIf = std::enable_if<
      std::is_convertible<std::chrono::duration<Rep2, Ratio2>,
                          std::chrono::duration<int64_t, Ratio>>::value>;
 
  using Base = std::optional<Dur<Ratio>>;
 
public:
  Timeout(std::nullopt_t none) : Base(none) {}
 
  template <typename Ratio2,
            typename = typename EnableIf<int64_t, Ratio2>::type>
  Timeout(const Timeout<Ratio2> &other)
      : Base(other ? Base(Dur<Ratio>(*other)) : std::nullopt) {}
 
  template <typename Rep2, typename Ratio2,
            typename = typename EnableIf<Rep2, Ratio2>::type>
  Timeout(const std::chrono::duration<Rep2, Ratio2> &other)
      : Base(Dur<Ratio>(other)) {}
};
 
} // namespace lldb_private
 
namespace llvm {
template<typename Ratio>
struct format_provider<lldb_private::Timeout<Ratio>, void> {
  static void format(const lldb_private::Timeout<Ratio> &timeout,
                     raw_ostream &OS, StringRef Options) {
    typedef typename lldb_private::Timeout<Ratio>::value_type Dur;
 
    if (!timeout)
      OS << "<infinite>";
    else
      format_provider<Dur>::format(*timeout, OS, Options);
  }
};
}
 
#endif // LLDB_UTILITY_TIMEOUT_H