Compute the number of object properties to serialize.

src/cbor/serializable.cr

@@ -136,6 +136,7 @@ module CBOR
       end
 
       private def self.new_from_cbor_decoder(decoder : ::CBOR::Decoder)
+        # puts "self.new_from_cbor_decoder"
         instance = allocate
         instance.initialize(__decoder_for_cbor_serializable: decoder)
         GC.add_finalizer(instance) if instance.responds_to?(:finalize)
@@ -268,7 +269,25 @@ module CBOR
           {% end %}
         {% end %}
 
-        cbor.object do
+        # Compute the size of the final list of properties to serialize.
+        # This allows a more compact encoding, and a faster decoding.
+        nb_properties_to_serialize = 0
+        {% for name, value in properties %}
+            _{{name}} = @{{name}}
+          {% unless value[:emit_null] %}
+            unless _{{name}}.nil?
+              nb_properties_to_serialize += 1
+            end
+          {% else %}
+            nb_properties_to_serialize += 1
+          {% end %} # macro unless value[:emit_null]
+        {% end %} # macro for properties
+
+
+
+        {% if properties.size > 0 %}
+          cbor.write_object_start nb_properties_to_serialize
+
           {% for name, value in properties %}
               _{{name}} = @{{name}}
 
@@ -285,17 +304,17 @@ module CBOR
               else
                 cbor.write(nil, use_undefined: value[:nil_as_undefined])
               end
-              {% else %}
+            {% else %} # macro if value[:converter]
               _{{name}}.to_cbor(cbor)
-              {% end %}
+            {% end %} # macro if value[:converter]
 
             {% unless value[:emit_null] %}
-              end
-            {% end %}
-          {% end %}
+              end # unless _{{name}}.nil?
+            {% end %} # macro unless value[:emit_null]
+          {% end %} # macro for properties
           on_to_cbor(cbor)
-        end
-      {% end %}
+        {% end %} # macro if properties.size > 0
+      {% end %} # begin
     end
 
     module Unmapped