FIXUP: attempt to simplify the code

We can specify how lua_mysql_push_value() works with data == NULL and
use this fact to simplify the code.

Author: Totktonada

mysql/driver.c

@@ -183,7 +183,12 @@ lua_mysql_field_type_to_string(enum enum_field_types type)
 	return mysql_field_type_strs[hash];
 }
 
-/* Push value retrieved from mysql field to lua stack */
+/**
+ * Push value retrieved from mysql field to lua stack.
+ *
+ * When `data` is NULL, `field` and len` parameters are
+ * ignored and Lua nil or LuaJIT FFI NULL is pushed.
+ */
 static void
 lua_mysql_push_value(struct lua_State *L, MYSQL_FIELD *field, void *data,
 		     unsigned long len, int keep_null)
@@ -263,11 +268,8 @@ lua_mysql_fetch_result(struct lua_State *L)
 		unsigned long *len = mysql_fetch_lengths(result);
 		unsigned col_no;
 		for (col_no = 0; col_no < num_fields; ++col_no) {
-			void *data = conn->keep_null == 1 && !row[col_no] ? NULL
-				: row[col_no];
-			lua_mysql_push_value(L, fields + col_no, data,
-					     data == NULL ? 0 : len[col_no],
-					     conn->keep_null);
+			lua_mysql_push_value(L, fields + col_no, row[col_no],
+					     len[col_no], conn->keep_null);
 			if (conn->use_numeric_result) {
 				/* Assign to a column number. */
 				lua_rawseti(L, -2, col_no + 1);
@@ -380,14 +382,11 @@ lua_mysql_stmt_push_row(struct lua_State *L)
 	lua_newtable(L);
 	unsigned col_no;
 	for (col_no = 0; col_no < col_count; ++col_no) {
-		void *data = NULL;
-		if (*results[col_no].is_null && keep_null == 0)
-			continue;
-		else if (!(*results[col_no].is_null))
-			data = results[col_no].buffer;
+		void *data = *results[col_no].is_null ? NULL :
+			results[col_no].buffer;
 		lua_pushstring(L, fields[col_no].name);
-		lua_mysql_push_value(L, fields + col_no, data, data == NULL ? 0
-				     : *results[col_no].length, keep_null);
+		lua_mysql_push_value(L, fields + col_no, data,
+				     *results[col_no].length, keep_null);
 		lua_settable(L, -3);
 	}
 	return 1;