Simplify and optimize schematic replacements

doc/lua_api.txt

@@ -1719,7 +1719,7 @@ minetest.place_schematic(pos, schematic, rotation, replacements, force_placement
 ^ Place the schematic specified by schematic (see: Schematic specifier) at pos.
 ^ Rotation can be "0", "90", "180", "270", or "random".
 ^ If the rotation parameter is omitted, the schematic is not rotated.
-^ replacements = {{"oldname", "convert_to"}, ...}
+^ replacements = {["old_name"] = "convert_to", ...}
 ^ force_placement is a boolean indicating whether nodes other than air and
 ^ ignore are replaced by the schematic
 
@@ -2634,7 +2634,7 @@ Decoration definition (register_decoration)
         },
     },
     ^ See 'Schematic specifier' for details.
-    replacements = {{"oldname", "convert_to"}, ...},
+    replacements = {["oldname"] = "convert_to", ...},
     flags = "place_center_x, place_center_z",
     ^ Flags for schematic decorations.  See 'Schematic attributes'.
     rotation = "90" -- rotate schematic 90 degrees on placement

src/script/lua_api/l_mapgen.cpp

@@ -78,6 +78,31 @@ struct EnumString ModApiMapgen::es_Rotation[] =
 };
 
 
+static void read_schematic_replacements(lua_State *L, DecoSchematic *dschem, int index)
+{
+	lua_pushnil(L);
+	while (lua_next(L, index)) {
+		// key at index -2 and value at index -1
+		std::string replace_from;
+		std::string replace_to;
+		if (lua_istable(L, -1)) {  // Old {{"x", "y"}, ...} format
+			lua_rawgeti(L, -1, 1);
+			replace_from = lua_tostring(L, -1);
+			lua_pop(L, 1);
+			lua_rawgeti(L, -1, 2);
+			replace_to = lua_tostring(L, -1);
+			lua_pop(L, 1);
+		} else {  // New {x = "y", ...} format
+			replace_from = lua_tostring(L, -2);
+			replace_to = lua_tostring(L, -1);
+		}
+		dschem->replacements[replace_from] = replace_to;
+		// removes value, keeps key for next iteration
+		lua_pop(L, 1);
+	}
+}
+
+
 // get_mapgen_object(objectname)
 // returns the requested object used during map generation
 int ModApiMapgen::l_get_mapgen_object(lua_State *L)
@@ -414,20 +439,7 @@ int ModApiMapgen::l_register_decoration(lua_State *L)
 
 			lua_getfield(L, index, "replacements");
 			if (lua_istable(L, -1)) {
-				int i = lua_gettop(L);
+				read_schematic_replacements(L, dschem, lua_gettop(L));
-				lua_pushnil(L);
-				while (lua_next(L, i) != 0) {
-					// key at index -2 and value at index -1
-					lua_rawgeti(L, -1, 1);
-					std::string replace_from = lua_tostring(L, -1);
-					lua_pop(L, 1);
-					lua_rawgeti(L, -1, 2);
-					std::string replace_to = lua_tostring(L, -1);
-					lua_pop(L, 1);
-					dschem->replacements[replace_from] = replace_to;
-					// removes value, keeps key for next iteration
-					lua_pop(L, 1);
-				}
 			}
 			lua_pop(L, 1);
 
@@ -602,19 +614,7 @@ int ModApiMapgen::l_place_schematic(lua_State *L)
 	dschem.rotation = (Rotation)rot;
 
 	if (lua_istable(L, 4)) {
-		lua_pushnil(L);
+		read_schematic_replacements(L, &dschem, 4);
-		while (lua_next(L, 4) != 0) {
-			// key at index -2 and value at index -1
-			lua_rawgeti(L, -1, 1);
-			std::string replace_from = lua_tostring(L, -1);
-			lua_pop(L, 1);
-			lua_rawgeti(L, -1, 2);
-			std::string replace_to = lua_tostring(L, -1);
-			lua_pop(L, 1);
-			dschem.replacements[replace_from] = replace_to;
-			// removes value, keeps key for next iteration
-			lua_pop(L, 1);
-		}
 	}
 
 	bool force_placement = true;