-int data_bits(struct sr_output *o, const char *data_in, uint64_t length_in,
- char **data_out, uint64_t *length_out)
+SR_PRIV int data_bits(struct sr_output *o, const uint8_t *data_in,
+ uint64_t length_in, uint8_t **data_out,
+ uint64_t *length_out)