Binary mode: Fix progressive import consumed bytes calculation

The previous implementation returned the position behind the ID if only
the ID could be successfully decoded, but not the value (because some
bytes are missing). Same issue if the ID was not found and the value
could not be successfully skipped because of incomplete data.

src/thingset_bin.c

@@ -818,38 +818,53 @@ int thingset_bin_import_data_progressively(struct thingset_context *ts, uint8_t
      */
     zcbor_new_decode_state(ts->decoder, ZCBOR_ARRAY_SIZE(ts->decoder), ts->decoder->payload_mut,
                            size - (ts->decoder->payload - ts->msg), ts->decoder->elem_count);
+
     uint32_t id;
+    size_t successfully_parsed_bytes = 0;
     while (zcbor_uint32_decode(ts->decoder, &id)) {
         if (id <= UINT16_MAX) {
             const struct thingset_data_object *object = thingset_get_object_by_id(ts, id);
             if (object != NULL && (object->access & THINGSET_WRITE_MASK & auth_flags) != 0) {
-                if (ts->api->deserialize_value(ts, object, false)) {
+                if (ts->api->deserialize_value(ts, object, false) == 0) {
+                    successfully_parsed_bytes = ts->decoder->payload - ts->msg;
+                }
+                else {
                     if (id == *last_id) {
                         /* we got stuck here last time, so no point going back and asking
                             for more data; just skip it and move on */
-                        zcbor_any_skip(ts->decoder, NULL);
+                        if (zcbor_any_skip(ts->decoder, NULL)) {
+                            successfully_parsed_bytes = ts->decoder->payload - ts->msg;
+                        }
+                        else {
+                            /* if we can't even skip the element, the data must be corrupted */
+                            *consumed = successfully_parsed_bytes;
+                            return -THINGSET_ERR_REQUEST_INCOMPLETE;
+                        }
                     }
                     else {
                         /* reset decoder position to the beginning of the buffer */
                         ts->decoder->payload = ts->msg;
-                        /* reincrement element count; empirical testing so far suggests
-                           this should be 2, even though surely we have only successfully
-                           parsed 1 (the ID; the element parsing failed?) */
-                        ts->decoder->elem_count += 2;
+                        /* reincrement element count because ID will be parsed again */
+                        ts->decoder->elem_count++;
+                        *consumed = successfully_parsed_bytes;
                         return 1; /* ask for more data */
                     }
                 }
             }
             else {
-                zcbor_any_skip(ts->decoder, NULL);
+                if (zcbor_any_skip(ts->decoder, NULL)) {
+                    successfully_parsed_bytes = ts->decoder->payload - ts->msg;
+                }
+                else {
+                    /* reincrement element count because ID will be parsed again */
+                    ts->decoder->elem_count++;
+                }
             }
             *last_id = id;
         }
-
-        *consumed = ts->decoder->payload - ts->msg;
     }
 
-    *consumed = ts->decoder->payload - ts->msg;
+    *consumed = successfully_parsed_bytes;
     if (*consumed == 0 && size > 0) {
         /* if we didn't manage to consume anything at this point, the data must be completely
          * invalid, because it means we didn't even parse an ID, so just bail out