Write a MessagePack float that is not in an array of numbers into reserved space

A float that was not part of a run in an array (an object member, a float in a
mixed array) went through write_compact_float(), with a sink call for its
marker and one through a std::array for its bytes.

It is now encoded by the function that encodes the floats of a run, into space
reserved from the sink.

CBOR keeps the previous code for these floats: giving them the same treatment
made GCC 13 stop inlining the encoder into the loop for the floats of an array,
which cost 4 percent more instructions for canada and citm_catalog.

Instructions per call (Linux, GCC 13, thousands), to_msgpack: 20000 small objects 14601 -> 13641.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/output/binary_writer.hpp

@@ -429,7 +429,7 @@ class binary_writer
 
             case value_t::number_float:
             {
-                write_compact_float(j.m_data.m_value.number_float, to_char_type(0xCA), to_char_type(0xCB));
+                write_msgpack_float(j.m_data.m_value.number_float);
                 break;
             }
 
@@ -2899,6 +2899,13 @@ class binary_writer
         }
     }
 
+    /// write a float as MessagePack, into space reserved from the sink
+    JSON_HEDLEY_NEVER_INLINE
+    void write_msgpack_float(const number_float_t n)
+    {
+        oa.commit(encode_compact_float(oa.reserve(integer_encoding_space), n, to_char_type(0xCA), to_char_type(0xCB)));
+    }
+
     /*!
     @brief write an object value (head and members) as MessagePack
 
@@ -2931,6 +2938,10 @@ class binary_writer
                     write_msgpack_integer(value, std::integral_constant<bool, integers_fit_64_bits()>());
                     break;
 
+                case value_t::number_float:
+                    write_msgpack_float(value.m_data.m_value.number_float);
+                    break;
+
                 case value_t::string:
                     write_msgpack_string(*value.m_data.m_value.string, value);
                     break;
@@ -2938,7 +2949,6 @@ class binary_writer
                 case value_t::object:
                 case value_t::array:
                 case value_t::binary:
-                case value_t::number_float:
                 case value_t::discarded:
                 default:
                     write_msgpack(value, depth + 1);

single_include/nlohmann/json.hpp

@@ -25260,7 +25260,7 @@ class binary_writer
 
             case value_t::number_float:
             {
-                write_compact_float(j.m_data.m_value.number_float, to_char_type(0xCA), to_char_type(0xCB));
+                write_msgpack_float(j.m_data.m_value.number_float);
                 break;
             }
 
@@ -27730,6 +27730,13 @@ class binary_writer
         }
     }
 
+    /// write a float as MessagePack, into space reserved from the sink
+    JSON_HEDLEY_NEVER_INLINE
+    void write_msgpack_float(const number_float_t n)
+    {
+        oa.commit(encode_compact_float(oa.reserve(integer_encoding_space), n, to_char_type(0xCA), to_char_type(0xCB)));
+    }
+
     /*!
     @brief write an object value (head and members) as MessagePack
 
@@ -27762,6 +27769,10 @@ class binary_writer
                     write_msgpack_integer(value, std::integral_constant<bool, integers_fit_64_bits()>());
                     break;
 
+                case value_t::number_float:
+                    write_msgpack_float(value.m_data.m_value.number_float);
+                    break;
+
                 case value_t::string:
                     write_msgpack_string(*value.m_data.m_value.string, value);
                     break;
@@ -27769,7 +27780,6 @@ class binary_writer
                 case value_t::object:
                 case value_t::array:
                 case value_t::binary:
-                case value_t::number_float:
                 case value_t::discarded:
                 default:
                     write_msgpack(value, depth + 1);