Charconv is used to serialize doubles

Author: grisumbras

include/boost/json/detail/format.hpp

@@ -33,7 +33,7 @@ format_int64(
     char* dest, int64_t i) noexcept;
 
 BOOST_JSON_DECL
-unsigned
+std::size_t
 format_double(
     char* dest, double d, bool allow_infinity_and_nan = false) noexcept;
 

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

@@ -11,8 +11,10 @@
 #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 <cmath>
 #include <cstring>
+#include <limits>
 
 namespace boost {
 namespace json {
@@ -110,12 +112,57 @@ format_int64(
     return 1 + format_uint64(dest, ui);
 }
 
-unsigned
+std::size_t
 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));
+    unsigned variant = allow_infinity_and_nan ? 8 : 0;
+    variant |= std::isnan(d) ? 1 : 0;
+    if( std::isinf(d) )
+    {
+        variant |= 2;
+        variant |= std::signbit(d) ? 4 : 0;
+    }
+
+    char const* end;
+    switch( variant )
+    {
+    default:
+    {
+        end = charconv::to_chars(
+            dest,
+            dest + detail::max_number_chars,
+            d,
+            charconv::chars_format::scientific).ptr;
+        break;
+    }
+    case (8 + 1):
+        std::memcpy(dest, "NaN", 3);
+        end = dest + 3;
+        break;
+    case (0 + 1):
+        std::memcpy(dest, "null", 4);
+        end = dest + 4;
+        break;
+    case (8 + 0 + 2):
+        std::memcpy(dest, "Infinity", 8);
+        end = dest + 8;
+        break;
+    case (8 + 4 + 2):
+        std::memcpy(dest, "-Infinity", 9);
+        end = dest + 9;
+        break;
+    case (0 + 0 + 2):
+        std::memcpy(dest, "1e99999", 7);
+        end = dest + 7;
+        break;
+    case (0 + 4 + 2):
+        std::memcpy(dest, "-1e99999", 8);
+        end = dest + 8;
+        break;
+    }
+
+    return end - dest;
 }
 
 } // detail