Charconv is used for serialization

Author: grisumbras

include/boost/json/detail/impl/format.ipp

@@ -11,7 +11,8 @@
 #ifndef BOOST_JSON_DETAIL_IMPL_FORMAT_IPP
 #define BOOST_JSON_DETAIL_IMPL_FORMAT_IPP
 
-#include <boost/json/detail/ryu/ryu.hpp>
+#include <boost/charconv/to_chars.hpp>
+#include <boost/json/detail/ryu/detail/common.hpp>
 #include <cstring>
 
 namespace boost {
@@ -114,8 +115,36 @@ unsigned
 format_double(
     char* dest, double d, bool allow_infinity_and_nan) noexcept
 {
-    return static_cast<int>(
-        ryu::d2s_buffered_n(d, dest, allow_infinity_and_nan));
+    namespace ryud = ryu::detail;
+    // Copyright 2018 Ulf Adams
+    //
+    // Decode bits into sign, mantissa, and exponent.
+    std::uint64_t const bits = ryud::double_to_bits(d);
+    const bool ieeeSign = ((bits >> (ryud::DOUBLE_MANTISSA_BITS + ryud::DOUBLE_EXPONENT_BITS)) & 1) != 0;
+    const std::uint64_t ieeeMantissa = bits & ((1ull << ryud::DOUBLE_MANTISSA_BITS) - 1);
+    const std::uint32_t ieeeExponent = (std::uint32_t)((bits >> ryud::DOUBLE_MANTISSA_BITS) & ((1u << ryud::DOUBLE_EXPONENT_BITS) - 1));
+    // Case distinction; exit early for the easy cases.
+    if(BOOST_JSON_UNLIKELY(
+        ieeeExponent == ((1u << ryud::DOUBLE_EXPONENT_BITS) - 1u) ||
+        (ieeeExponent == 0
+          && ieeeMantissa == 0) ))
+    {
+        // We changed how special numbers are output by default
+        if (allow_infinity_and_nan)
+            return ryud::copy_special_str(
+                dest, ieeeSign, ieeeExponent != 0, ieeeMantissa != 0);
+        else
+            return ryud::copy_special_str_conforming(
+                dest, ieeeSign, ieeeExponent != 0, ieeeMantissa != 0);
+
+    }
+
+    auto const result = charconv::to_chars(
+        dest,
+        dest + detail::max_number_chars,
+        d,
+        charconv::chars_format::scientific);
+    return result.ptr - dest;
 }
 
 } // detail