py: Change vstr so that it doesn't null terminate buffer by default.

This cleans up vstr so that it's a pure "variable buffer", and the user
can decide whether they need to add a terminating null byte.  In most
places where vstr is used, the vstr did not need to be null terminated
and so this patch saves code size, a tiny bit of RAM, and makes vstr
usage more efficient.  When null termination is needed it must be
done explicitly using vstr_null_terminate.

1 files changed, 1 insertions, 3 deletions

diff --git a/extmod/modujson.c b/extmod/modujson.c
index 5023d8151..a7b889676 100644
--- a/extmod/modujson.c
+++ b/extmod/modujson.c
@@ -39,9 +39,7 @@ STATIC mp_obj_t mod_ujson_dumps(mp_obj_t obj) {
     vstr_t vstr;
     vstr_init(&vstr, 8);
     mp_obj_print_helper((void (*)(void *env, const char *fmt, ...))vstr_printf, &vstr, obj, PRINT_JSON);
-    mp_obj_t ret = mp_obj_new_str(vstr.buf, vstr.len, false);
-    vstr_clear(&vstr);
-    return ret;
+    return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_dumps_obj, mod_ujson_dumps);