Refactor quantum preservation to be a chars_format option

Author: mborland

include/boost/decimal/charconv.hpp

@@ -26,7 +26,6 @@
 #include <boost/decimal/detail/countl.hpp>
 #include <boost/decimal/detail/remove_trailing_zeros.hpp>
 #include <boost/decimal/detail/promotion.hpp>
-#include <boost/decimal/detail/quantum_preservation_format.hpp>
 
 #ifndef BOOST_DECIMAL_BUILD_MODULE
 #include <cstdint>
@@ -1212,6 +1211,20 @@ constexpr auto to_chars_impl(char* first, char* last, const TargetDecimalType& v
                 return to_chars_scientific_impl(first, last, value, fmt);
             case chars_format::hex:
                 return to_chars_hex_impl(first, last, value);
+            case chars_format::cohort_preserving_scientific:
+                BOOST_DECIMAL_IF_CONSTEXPR (detail::is_fast_type_v<TargetDecimalType>)
+                {
+                    // Fast types have no concept of cohorts
+                    return {last, std::errc::invalid_argument};
+                }
+
+                if (local_precision != -1)
+                {
+                    // Precision and cohort preservation are mutually exclusive options
+                    return {last, std::errc::invalid_argument};
+                }
+
+                return to_chars_cohort_preserving_scientific(first, last, value);
             // LCOV_EXCL_START
             default:
                 BOOST_DECIMAL_UNREACHABLE;
@@ -1243,38 +1256,6 @@ constexpr auto to_chars_impl(char* first, char* last, const TargetDecimalType& v
     return to_chars_scientific_impl(first, last, value, fmt, local_precision); // LCOV_EXCL_LINE
 }
 
-// TODO(mborland): Remove once other modes are inplace
-#ifdef _MSC_VER
-#  pragma warning(push)
-#  pragma warning(disable: 4065)
-#endif
-
-template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE TargetDecimalType>
-constexpr auto to_chars_impl(char* first, char* last, const TargetDecimalType& value, const chars_format fmt, const quantum_preservation method) noexcept -> to_chars_result
-{
-    // No quantum preservation is the same thing as regular to_chars
-    if (method == quantum_preservation::off)
-    {
-        return to_chars_impl(first, last, value, fmt);
-    }
-
-    // Sanity check our bounds
-    if (BOOST_DECIMAL_UNLIKELY(first >= last))
-    {
-        return {last, std::errc::invalid_argument};
-    }
-
-    switch (fmt)
-    {
-        default:
-            return to_chars_cohort_preserving_scientific(first, last, value);
-    }
-}
-
-#ifdef _MSC_VER
-# pragma warning(pop)
-#endif
-
 } //namespace detail
 
 BOOST_DECIMAL_EXPORT template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE TargetDecimalType>
@@ -1300,13 +1281,6 @@ constexpr auto to_chars(char* first, char* last, const TargetDecimalType& value,
     return detail::to_chars_impl(first, last, value, fmt, precision);
 }
 
-BOOST_DECIMAL_EXPORT template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE TargetDecimalType>
-constexpr auto to_chars(char* first, char* last, const TargetDecimalType& value, const chars_format fmt, const quantum_preservation method) noexcept -> to_chars_result
-{
-    static_assert(detail::is_ieee_type_v<TargetDecimalType>, "Fast types are automatically normalized, so they have no concept of quantum preservation");
-    return detail::to_chars_impl(first, last, value, fmt, method);
-}
-
 #ifdef BOOST_DECIMAL_HAS_STD_CHARCONV
 
 BOOST_DECIMAL_EXPORT template <typename DecimalType>

include/boost/decimal/detail/chars_format.hpp

@@ -17,6 +17,7 @@ BOOST_DECIMAL_EXPORT enum class chars_format : unsigned
     scientific = 1 << 0,
     fixed = 1 << 1,
     hex = 1 << 2,
+    cohort_preserving_scientific = 1 << 3,
     general = fixed | scientific
 };
 

include/boost/decimal/detail/quantum_preservation_format.hpp

@@ -22,28 +22,12 @@ void test_to_chars_scientific(const ResultsType& decimals, const StringsType& st
     for (std::size_t i {}; i < decimals.size(); ++i)
     {
         char buffer[64] {};
-        const auto r {to_chars(buffer, buffer + sizeof(buffer), decimals[i], chars_format::scientific, quantum_preservation::on)};
+        const auto r {to_chars(buffer, buffer + sizeof(buffer), decimals[i], chars_format::cohort_preserving_scientific)};
         BOOST_TEST(r);
         *r.ptr = '\0';
 
         BOOST_TEST_CSTR_EQ(buffer, strings[i]);
     }
-
-    for (std::size_t i {}; i < decimals.size(); ++i)
-    {
-        char quantum_buffer[64] {};
-        const auto r_quantum {to_chars(quantum_buffer, quantum_buffer + sizeof(quantum_buffer), decimals[i], chars_format::scientific, quantum_preservation::off)};
-        BOOST_TEST(r_quantum);
-        *r_quantum.ptr = '\0';
-
-        char buffer[64] {};
-        const auto r {to_chars(buffer, buffer + sizeof(buffer), decimals[i], chars_format::scientific)};
-        BOOST_TEST(r);
-        *r.ptr = '\0';
-
-        BOOST_TEST_CSTR_EQ(quantum_buffer, buffer);
-        BOOST_TEST_CSTR_EQ(quantum_buffer, strings[0]);
-    }
 }
 
 template <typename T>