+int nxm_field_bytes(uint32_t header);
+int nxm_field_bits(uint32_t header);
+
+const char *nxm_parse_field_bits(const char *s,
+ uint32_t *headerp, int *ofsp, int *n_bitsp);
+void nxm_format_field_bits(struct ds *, uint32_t header, int ofs, int n_bits);
+