Simplify format_decimal

include/fmt/chrono.h

@@ -1147,7 +1147,7 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
                         std::chrono::seconds::period>::value) {
       *out++ = '.';
       out = detail::fill_n(out, leading_zeroes, '0');
-      out = format_decimal<Char>(out, n, num_digits).end;
+      out = format_decimal<Char>(out, n, num_digits);
     }
   } else if (precision > 0) {
     *out++ = '.';
@@ -1158,12 +1158,12 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
       int num_truncated_digits = num_digits - remaining;
       n /= to_unsigned(detail::pow10(to_unsigned(num_truncated_digits)));
       if (n) {
-        out = format_decimal<Char>(out, n, remaining).end;
+        out = format_decimal<Char>(out, n, remaining);
       }
       return;
     }
     if (n) {
-      out = format_decimal<Char>(out, n, num_digits).end;
+      out = format_decimal<Char>(out, n, num_digits);
       remaining -= num_digits;
     }
     out = detail::fill_n(out, remaining, '0');
@@ -1319,7 +1319,7 @@ class tm_writer {
     const int num_digits = count_digits(n);
     if (width > num_digits)
       out_ = detail::fill_n(out_, width - num_digits, '0');
-    out_ = format_decimal<Char>(out_, n, num_digits).end;
+    out_ = format_decimal<Char>(out_, n, num_digits);
   }
   void write_year(long long year) {
     if (year >= 0 && year < 10000) {
@@ -1881,7 +1881,7 @@ struct chrono_formatter {
     if (width > num_digits) {
       out = detail::write_padding(out, pad, width - num_digits);
     }
-    out = format_decimal<char_type>(out, n, num_digits).end;
+    out = format_decimal<char_type>(out, n, num_digits);
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }

include/fmt/format.h

@@ -1283,45 +1283,45 @@ FMT_CONSTEXPR20 FMT_INLINE void copy2(Char* dst, const char* src) {
   *dst = static_cast<Char>(*src);
 }
 
-template <typename Iterator> struct format_decimal_result {
+// Formats a decimal unsigned integer value writing to out pointing to a buffer
-  Iterator begin;
+// of specified size. The caller must ensure that the buffer is large enough.
-  Iterator end;
-};
-
-// Formats a decimal unsigned integer value writing into out pointing to a
-// buffer of specified size. The caller must ensure that the buffer is large
-// enough.
 template <typename Char, typename UInt>
-FMT_CONSTEXPR20 auto format_decimal(Char* out, UInt value, int size)
+FMT_CONSTEXPR20 auto do_format_decimal(Char* out, UInt value, int size)
-    -> format_decimal_result<Char*> {
+    -> Char* {
   FMT_ASSERT(size >= count_digits(value), "invalid digit count");
-  auto begin = out, end = out + size;
   unsigned n = to_unsigned(size);
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
     // "Three Optimization Tips for C++". See speed-test for a comparison.
     n -= 2;
-    copy2(begin + n, digits2(static_cast<unsigned>(value % 100)));
+    copy2(out + n, digits2(static_cast<unsigned>(value % 100)));
     value /= 100;
   }
   if (value >= 10) {
     n -= 2;
-    copy2(begin + n, digits2(static_cast<unsigned>(value)));
+    copy2(out + n, digits2(static_cast<unsigned>(value)));
   } else {
-    begin[--n] = static_cast<Char>('0' + value);
+    out[--n] = static_cast<Char>('0' + value);
   }
-  return {begin + n, end};
+  return out + n;
+}
+
+template <typename Char, typename UInt>
+FMT_CONSTEXPR FMT_INLINE auto format_decimal(Char* out, UInt value, int size)
+    -> Char* {
+  do_format_decimal(out, value, size);
+  return out + size;
 }
 
 template <typename Char, typename UInt, typename OutputIt,
           FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value)>
 FMT_CONSTEXPR inline auto format_decimal(OutputIt out, UInt value, int size)
-    -> format_decimal_result<OutputIt> {
+    -> OutputIt {
   // Buffer is large enough to hold all digits (digits10 + 1).
-  Char buffer[digits10<UInt>() + 1] = {};
+  char buffer[digits10<UInt>() + 1] = {};
-  auto end = format_decimal(buffer, value, size).end;
+  do_format_decimal(buffer, value, size);
-  return {out, detail::copy_noinline<Char>(buffer, end, out)};
+  return detail::copy_noinline<Char>(buffer, buffer + size, out);
 }
 
 template <unsigned BASE_BITS, typename Char, typename UInt>
@@ -2167,7 +2167,7 @@ FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, write_int_arg<T> arg,
     int num_digits = count_digits(abs_value);
     return write_int<Char>(
         out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
-          return format_decimal<Char>(it, abs_value, num_digits).end;
+          return format_decimal<Char>(it, abs_value, num_digits);
         });
   }
   case presentation_type::hex: {
@@ -2295,7 +2295,7 @@ FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
     return out;
   }
   if (negative) *out++ = static_cast<Char>('-');
-  return format_decimal<Char>(out, abs_value, num_digits).end;
+  return format_decimal<Char>(out, abs_value, num_digits);
 }
 
 // DEPRECATED!
@@ -2426,7 +2426,7 @@ constexpr auto write_significand(OutputIt out, const char* significand,
 template <typename Char, typename OutputIt, typename UInt>
 inline auto write_significand(OutputIt out, UInt significand,
                               int significand_size) -> OutputIt {
-  return format_decimal<Char>(out, significand, significand_size).end;
+  return format_decimal<Char>(out, significand, significand_size);
 }
 template <typename Char, typename OutputIt, typename T, typename Grouping>
 FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
@@ -2446,8 +2446,7 @@ template <typename Char, typename UInt,
           FMT_ENABLE_IF(std::is_integral<UInt>::value)>
 inline auto write_significand(Char* out, UInt significand, int significand_size,
                               int integral_size, Char decimal_point) -> Char* {
-  if (!decimal_point)
+  if (!decimal_point) return format_decimal(out, significand, significand_size);
-    return format_decimal(out, significand, significand_size).end;
   out += significand_size + 1;
   Char* end = out;
   int floating_size = significand_size - integral_size;
@@ -3889,7 +3888,7 @@ class format_int {
   template <typename UInt>
   FMT_CONSTEXPR20 auto format_unsigned(UInt value) -> char* {
     auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
-    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
+    return detail::do_format_decimal(buffer_, n, buffer_size - 1);
   }
 
   template <typename Int>