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// file : butl/timestamp -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUTL_TIMESTAMP
#define BUTL_TIMESTAMP
#include <chrono>
#include <iosfwd>
#include <butl/path>
namespace butl
{
// On all three main platforms that we target (GNU/Linux, Windows (both
// VC++ and GCC/MinGW64), and MacOS X) with recent C++ runtimes,
// system_clock has nanoseconds resolution and counts from the UNIX
// epoch. The latter is important since struct stat also returns times
// based on UNIX epoch.
//
// The underlying type for nanoseconds duration is signed integer type
// of at least 64 bits (currently int64_t). Because it is signed, we
// will overflow in year 2262 but by then the underlying type will
// most likely have changed to something larger than 64-bit.
//
// So to support other platforms that could possibly use a different
// system_clock resolutions (e.g., microseconds), we actually not going
// to assume anywhere (except perhaps timestamp.cxx) that we are dealing
// with nanoseconds or the 64-bit underlying type.
//
using std::chrono::system_clock;
using timestamp = system_clock::time_point;
using duration = system_clock::duration;
// Generally-useful special values.
//
const timestamp timestamp_unknown {duration {-1}};
const timestamp timestamp_nonexistent {duration {0}};
// Human-readable representation. Note that these operators
// may throw std::system_error.
//
std::ostream&
operator<< (std::ostream&, const timestamp&);
std::ostream&
operator<< (std::ostream&, const duration&);
};
#endif // BUTL_TIMESTAMP
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