1 files changed, 155 insertions, 0 deletions
diff --git a/src/log/LogClock.h b/src/log/LogClock.h
new file mode 100644
index 00000000..5cd4e77d
--- /dev/null
+++ b/src/log/LogClock.h
@@ -0,0 +1,155 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_LOG_CLOCK_H
+#define CEPH_LOG_CLOCK_H
+
+#include <cstdio>
+#include <chrono>
+#include <ctime>
+#include <sys/time.h>
+
+#include "include/ceph_assert.h"
+#include "common/ceph_time.h"
+
+namespace ceph {
+namespace logging {
+namespace _logclock {
+// Because the underlying representations of a duration can be any
+// arithmetic type we wish, slipping a coarseness tag there is the
+// least hacky way to tag them. I'd also considered doing bit-stealing
+// and just setting the low bit of the representation unconditionally
+// to mark it as fine, BUT that would cut our nanosecond precision in
+// half which sort of obviates the point of 'fine'…admittedly real
+// computers probably don't care. More to the point it wouldn't be
+// durable under arithmetic unless we wrote a whole class to support
+// it /anyway/, and if I'm going to do that I may as well add a bool.
+
+// (Yes I know we don't do arithmetic on log timestamps, but I don't
+// want everything to suddenly break because someone did something
+// that the std::chrono::timepoint contract actually supports.)
+struct taggedrep {
+  uint64_t count;
+  bool coarse;
+
+  explicit taggedrep(uint64_t count) : count(count), coarse(true) {}
+  taggedrep(uint64_t count, bool coarse) : count(count), coarse(coarse) {}
+
+  explicit operator uint64_t() {
+    return count;
+  }
+};
+
+// Proper significant figure support would be a bit excessive. Also
+// we'd have to know the precision of the clocks on Linux and FreeBSD
+// and whatever else we want to support.
+inline taggedrep operator +(const taggedrep& l, const taggedrep& r) {
+  return { l.count + r.count, l.coarse || r.coarse };
+}
+inline taggedrep operator -(const taggedrep& l, const taggedrep& r) {
+  return { l.count - r.count, l.coarse || r.coarse };
+}
+inline taggedrep operator *(const taggedrep& l, const taggedrep& r) {
+  return { l.count * r.count, l.coarse || r.coarse };
+}
+inline taggedrep operator /(const taggedrep& l, const taggedrep& r) {
+  return { l.count / r.count, l.coarse || r.coarse };
+}
+inline taggedrep operator %(const taggedrep& l, const taggedrep& r) {
+  return { l.count % r.count, l.coarse || r.coarse };
+}
+
+// You can compare coarse and fine time. You shouldn't do so in any
+// case where ordering actually MATTERS but in practice people won't
+// actually ping-pong their logs back and forth between them.
+inline bool operator ==(const taggedrep& l, const taggedrep& r) {
+  return l.count == r.count;
+}
+inline bool operator !=(const taggedrep& l, const taggedrep& r) {
+  return l.count != r.count;
+}
+inline bool operator <(const taggedrep& l, const taggedrep& r) {
+  return l.count < r.count;
+}
+inline bool operator <=(const taggedrep& l, const taggedrep& r) {
+  return l.count <= r.count;
+}
+inline bool operator >=(const taggedrep& l, const taggedrep& r) {
+  return l.count >= r.count;
+}
+inline bool operator >(const taggedrep& l, const taggedrep& r) {
+  return l.count > r.count;
+}
+}
+class log_clock {
+public:
+  using rep = _logclock::taggedrep;
+  using period = std::nano;
+  using duration = std::chrono::duration<rep, period>;
+  // The second template parameter defaults to the clock's duration
+  // type.
+  using time_point = std::chrono::time_point<log_clock>;
+  static constexpr const bool is_steady = false;
+
+  time_point now() noexcept {
+    return appropriate_now();
+  }
+
+  void coarsen() {
+    appropriate_now = coarse_now;
+  }
+
+  void refine() {
+    appropriate_now = fine_now;
+  }
+
+  // Since our formatting is done in microseconds and we're using it
+  // anyway, we may as well keep this one
+  static timeval to_timeval(time_point t) {
+    auto rep = t.time_since_epoch().count();
+    timespan ts(rep.count);
+    return { static_cast<time_t>(std::chrono::duration_cast<std::chrono::seconds>(ts).count()),
+             static_cast<suseconds_t>(std::chrono::duration_cast<std::chrono::microseconds>(
+               ts % std::chrono::seconds(1)).count()) };
+  }
+private:
+  static time_point coarse_now() {
+    return time_point(
+      duration(_logclock::taggedrep(coarse_real_clock::now()
+				    .time_since_epoch().count(), true)));
+  }
+  static time_point fine_now() {
+    return time_point(
+      duration(_logclock::taggedrep(real_clock::now()
+				    .time_since_epoch().count(), false)));
+  }
+  time_point(*appropriate_now)() = coarse_now;
+};
+using log_time = log_clock::time_point;
+inline int append_time(const log_time& t, char *out, int outlen) {
+  bool coarse = t.time_since_epoch().count().coarse;
+  auto tv = log_clock::to_timeval(t);
+  std::tm bdt;
+  localtime_r(&tv.tv_sec, &bdt);
+
+  int r;
+  if (coarse) {
+    r = std::snprintf(out, outlen, "%04d-%02d-%02d %02d:%02d:%02d.%03ld",
+		      bdt.tm_year + 1900, bdt.tm_mon + 1, bdt.tm_mday,
+		      bdt.tm_hour, bdt.tm_min, bdt.tm_sec,
+		      static_cast<long>(tv.tv_usec / 1000));
+  } else {
+    r = std::snprintf(out, outlen, "%04d-%02d-%02d %02d:%02d:%02d.%06ld",
+		      bdt.tm_year + 1900, bdt.tm_mon + 1, bdt.tm_mday,
+		      bdt.tm_hour, bdt.tm_min, bdt.tm_sec,
+		      static_cast<long>(tv.tv_usec));
+  }
+  // Since our caller just adds the return value to something without
+  // checking it…
+  ceph_assert(r >= 0);
+  return r;
+}
+}
+}
+
+#endif