From fbf53a25702ab40e59cb231974037dc0c31793be Mon Sep 17 00:00:00 2001
From: Kefu Chai <kchai@redhat.com>
Date: Thu, 7 Jan 2021 11:56:25 +0800
Subject: [PATCH] common/ceph_time: add operator<< for signedspan

* templatize operator<<(ostream&, duration<>), so it works for more
  duration<> classes with minimal efforts -- we just need to explicitly
  instantiate these template operators
* explicitly instantiate operator<< for timespan, signedspan, seconds
  and milliseconds. they are most likely to be used in Ceph. we can add
  more of them when necessary.

Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit a64b96dba14df1e61ee6eb449535a6ff4a9d64b3)
---
 src/common/ceph_time.cc | 29 +++++++++++++++++++++++++----
 src/common/ceph_time.h  |  3 ++-
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/common/ceph_time.cc b/src/common/ceph_time.cc
index 9b85fc88224d3..603165efb43c5 100644
--- a/src/common/ceph_time.cc
+++ b/src/common/ceph_time.cc
@@ -322,10 +322,31 @@ std::chrono::seconds parse_timespan(const std::string& s)
 }
 
 namespace std {
-ostream& operator<<(ostream& m, const ::ceph::timespan& t) {
-  static_assert(is_unsigned_v<::ceph::timespan::rep>);
-  using seconds_t = chrono::duration<float>;
-  ::fmt::print(m, "{:.9}", chrono::duration_cast<seconds_t>(t));
+template<typename Rep, typename Period>
+ostream& operator<<(ostream& m, const chrono::duration<Rep, Period>& t) {
+  if constexpr (chrono::treat_as_floating_point_v<Rep>) {
+    using seconds_t = chrono::duration<float>;
+    ::fmt::print(m, "{:.9}", chrono::duration_cast<seconds_t>(t));
+  } else {
+    ::fmt::print(m, "{}", t);
+  }
   return m;
 }
+
+template ostream&
+operator<< <::ceph::timespan::rep,
+            ::ceph::timespan::period> (ostream&, const ::ceph::timespan&);
+
+template ostream&
+operator<< <::ceph::signedspan::rep,
+            ::ceph::signedspan::period> (ostream&, const ::ceph::signedspan&);
+
+template ostream&
+operator<< <chrono::seconds::rep,
+            chrono::seconds::period> (ostream&, const chrono::seconds&);
+
+template ostream&
+operator<< <chrono::milliseconds::rep,
+            chrono::milliseconds::period> (ostream&, const chrono::milliseconds&);
+
 } // namespace std
diff --git a/src/common/ceph_time.h b/src/common/ceph_time.h
index 663d05f8feb2b..2f99188e439b4 100644
--- a/src/common/ceph_time.h
+++ b/src/common/ceph_time.h
@@ -519,7 +519,8 @@ static Rep to_microseconds(T t) {
 } // namespace ceph
 
 namespace std {
-ostream& operator<<(ostream& m, const ::ceph::timespan& t);
+template<typename Rep, typename Period>
+ostream& operator<<(ostream& m, const chrono::duration<Rep, Period>& t);
 }
 
 #endif // COMMON_CEPH_TIME_H
-- 
2.39.5