py: Remove mp_obj_str_builder and use vstr instead.

With this patch str/bytes construction is streamlined.  Always use a
vstr to build a str/bytes object.  If the size is known beforehand then
use vstr_init_len to allocate only required memory.  Otherwise use
vstr_init and the vstr will grow as needed.  Then use
mp_obj_new_str_from_vstr to create a str/bytes object using the vstr
memory.

Saves code ROM: 68 bytes on stmhal, 108 bytes on bare-arm, and 336 bytes
on unix x64.

1 files changed, 4 insertions, 4 deletions

diff --git a/stmhal/can.c b/stmhal/can.c
index 28f00c994..b10ecd13d 100644
--- a/stmhal/can.c
+++ b/stmhal/can.c
@@ -395,12 +395,12 @@ STATIC mp_obj_t pyb_can_recv(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_
     }
     tuple->items[1] = MP_OBJ_NEW_SMALL_INT(rx_msg.RTR);
     tuple->items[2] = MP_OBJ_NEW_SMALL_INT(rx_msg.FMI);
-    byte *data;
-    tuple->items[3] = mp_obj_str_builder_start(&mp_type_bytes, rx_msg.DLC, &data);
+    vstr_t vstr;
+    vstr_init_len(&vstr, rx_msg.DLC);
     for (mp_uint_t i = 0; i < rx_msg.DLC; i++) {
-        data[i] = rx_msg.Data[i]; // Data is uint32_t but holds only 1 byte
+        vstr.buf[i] = rx_msg.Data[i]; // Data is uint32_t but holds only 1 byte
     }
-    tuple->items[3] = mp_obj_str_builder_end(tuple->items[3]);
+    tuple->items[3] = mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
     return tuple;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_can_recv_obj, 1, pyb_can_recv);