From 91533d3c3332d0adb76d0f70f82983ceb3f0497b Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Thu, 9 Dec 2021 06:55:31 -0800
Subject: [PATCH] Minor tweaks to chrono subsecond formatting

---
 include/fmt/chrono.h | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index b71195d0..5285d420 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -1459,11 +1459,13 @@ inline std::chrono::duration<Rep, std::milli> get_milliseconds(
 #endif
 }
 
-// Returns the number of digits according to the c++ 20 spec
-// In the range [0, 18], if more than 18 fractional digits are required,
-// then we return 6 for microseconds precision.
-constexpr int num_digits(long long num, long long den, int n = 0) {
-  return num % den == 0 ? n : (n > 18 ? 6 : num_digits(num * 10, den, n + 1));
+// Returns the number of fractional digits in the range [0, 18] according to the
+// C++20 spec. If more than 18 fractional digits are required then returns 6 for
+// microseconds precision.
+constexpr int count_fractional_digits(long long num, long long den, int n = 0) {
+  return num % den == 0
+             ? n
+             : (n > 18 ? 6 : count_fractional_digits(num * 10, den, n + 1));
 }
 
 constexpr long long pow10(std::uint32_t n) {
@@ -1479,13 +1481,13 @@ constexpr std::chrono::duration<Rep, Period> abs(
   // when -Wzero-as-null-pointer-constant is enabled.
   // In clang-12 the bug has been fixed. See
   // https://bugs.llvm.org/show_bug.cgi?id=46235 and the reproducible example:
-  // https://www.godbolt.org/z/Knbb5joYx
+  // https://www.godbolt.org/z/Knbb5joYx.
   return d.count() >= d.zero().count() ? d : -d;
 }
 
 template <class Rep, class Period,
           FMT_ENABLE_IF(!std::numeric_limits<Rep>::is_signed)>
-static constexpr std::chrono::duration<Rep, Period> abs(
+constexpr std::chrono::duration<Rep, Period> abs(
     std::chrono::duration<Rep, Period> d) {
   return d;
 }
@@ -1651,14 +1653,13 @@ struct chrono_formatter {
   }
 
   template <class Duration> void write_fractional_seconds(Duration d) {
-    constexpr auto fractional_width =
-        detail::num_digits(Duration::period::num, Duration::period::den);
+    constexpr auto num_fractional_digits =
+        count_fractional_digits(Duration::period::num, Duration::period::den);
 
     using subsecond_precision = std::chrono::duration<
         typename std::common_type<typename Duration::rep,
                                   std::chrono::seconds::rep>::type,
-        std::ratio<1, detail::pow10(fractional_width)>>;
-    // We could use c++ 17 if constexpr here.
+        std::ratio<1, detail::pow10(num_fractional_digits)>>;
     if (std::ratio_less<typename subsecond_precision::period,
                         std::chrono::seconds::period>::value) {
       *out++ = '.';
@@ -1675,9 +1676,8 @@ struct chrono_formatter {
       uint32_or_64_or_128_t<long long> n =
           to_unsigned(to_nonnegative_int(subseconds, max_value<long long>()));
       int num_digits = detail::count_digits(n);
-      if (fractional_width > num_digits) {
-        out = std::fill_n(out, fractional_width - num_digits, '0');
-      }
+      if (num_fractional_digits > num_digits)
+        out = std::fill_n(out, num_fractional_digits - num_digits, '0');
       out = format_decimal<char_type>(out, n, num_digits).end;
     }
   }