Function producer_id_block_allocation 

pub fn producer_id_block_allocation(
    broker_id_valid: bool,
    broker_registered: bool,
    requested_broker_epoch: i64,
    registered_broker_epoch: i64,
    first: i64,
    block_len: i32,
) -> ProducerIdBlockAllocationDecision

Fence one broker generation and construct its exact positive contiguous producer-ID block without signed overflow.