units::volume and units::mass readers for mandatory and optional

src/generic_factory.h

@@ -833,6 +833,38 @@ class auto_flags_reader : public generic_typed_reader<auto_flags_reader<FlagType
 
 using string_reader = auto_flags_reader<>;
 
+class volume_reader : public generic_typed_reader<units::volume>
+{
+    public:
+        bool operator()( const JsonObject &jo, const std::string &member_name,
+                         units::volume &member, bool /* was_loaded */ ) const {
+            if( !jo.has_member( member_name ) ) {
+                return false;
+            }
+            member = read_from_json_string<units::volume>( *jo.get_raw( member_name ), units::volume_units );
+            return true;
+        }
+        units::volume get_next( JsonIn &jin ) const {
+            return read_from_json_string<units::volume>( jin, units::volume_units );
+        }
+};
+
+class mass_reader : public generic_typed_reader<units::mass>
+{
+    public:
+        bool operator()( const JsonObject &jo, const std::string &member_name,
+                         units::mass &member, bool /* was_loaded */ ) const {
+            if( !jo.has_member( member_name ) ) {
+                return false;
+            }
+            member = read_from_json_string<units::mass>( *jo.get_raw( member_name ), units::mass_units );
+            return true;
+        }
+        units::mass get_next( JsonIn &jin ) const {
+            return read_from_json_string<units::mass>( jin, units::mass_units );
+        }
+};
+
 /**
  * Uses a map (unordered or standard) to convert strings from JSON to some other type
  * (the mapped type of the map: `C::mapped_type`). It works for all mapped types, not just enums.

src/mapdata.cpp

@@ -1255,7 +1255,7 @@ void furn_t::load( const JsonObject &jo, const std::string &src )
     optional( jo, was_loaded, "bonus_fire_warmth_feet", bonus_fire_warmth_feet, 300 );
     optional( jo, was_loaded, "keg_capacity", keg_capacity, legacy_volume_reader, 0_ml );
     mandatory( jo, was_loaded, "required_str", move_str_req );
-    assign( jo, "max_volume", max_volume, src == "dda" );
+    optional( jo, was_loaded, "max_volume", max_volume, volume_reader(), 0_ml );
     optional( jo, was_loaded, "crafting_pseudo_item", crafting_pseudo_item, "" );
     optional( jo, was_loaded, "deployed_item", deployed_item );
     load_symbol( jo );

src/units.cpp

@@ -0,0 +1,27 @@
+#include "json.h"
+#include "units.h"
+
+namespace units
+{
+template<>
+void volume::serialize( JsonOut &jsout ) const
+{
+    if( value_ % 1000 == 0 ) {
+        jsout.write( string_format( "%d L", value_ ) );
+    } else {
+        jsout.write( string_format( "%d ml", value_ ) );
+    }
+}
+
+template<>
+void mass::serialize( JsonOut &jsout ) const
+{
+    if( value_ % 1000000 == 0 ) {
+        jsout.write( string_format( "%d kg", value_ ) );
+    } else if( value_ % 1000 == 0 ) {
+        jsout.write( string_format( "%d g", value_ ) );
+    } else {
+        jsout.write( string_format( "%d mg", value_ ) );
+    }
+}
+} // namespace units

src/units.h

@@ -656,6 +656,11 @@ static const std::vector<std::pair<std::string, money>> money_units = { {
         { "kUSD", 1_kUSD },
     }
 };
+static const std::vector<std::pair<std::string, volume>> volume_units = { {
+        { "ml", 1_ml },
+        { "L", 1_liter }
+    }
+};
 } // namespace units
 
 template<typename T>