Function message_reader_kernel 

pub fn message_reader_kernel(
    clock_reset: ClockReset,
    input: ReaderInput,
    q: MessageReaderQ,
) -> (ReaderOutput, MessageReaderD)

The reader’s logic.

Runs once per clock and has four parts, in the order of a message’s journey: issue read addresses (AR), store returned beats in the FIFO (R → FIFO), free slice buffers that were taken, and unpack the head beat into the next slice’s buffer (unpack + deal).

• Inputs: clock_reset, the ReaderInput (host settings, memory signals, per-slice taken), and q, the current FIFO output, control and data registers.
• Outputs: the ReaderOutput and MessageReaderD, the next register values plus this clock’s FIFO read and write ports.
• Timing: a message dealt in cycle t appears as valid to its slice in cycle t + 1 (the outputs come from registers); a slice’s taken in cycle t lets a new message be dealt into its buffer in cycle t + 1.