BCMP_CHUNK_SIZE
uint8_t *chunk = mdb_alloc(BCMP_CHUNK_SIZE, UM_SLEEP | UM_GC);
uint8_t *other_chunk = mdb_alloc(BCMP_CHUNK_SIZE, UM_SLEEP | UM_GC);
size_t readsize = (length - offset > BCMP_CHUNK_SIZE) ?
BCMP_CHUNK_SIZE : length - offset;