ship: Rotator

== Ports ===========================================================
in:   in
in:   inAmount

out:  out

  
== TeX ==============================================================

The Rotator performs bitwise rotations of words.  When a value is
present at both {\tt in} and {\tt inAmount}, both values are consumed,
the value {\tt in} is rotated {\it towards the most significant bit}
by {\tt inAmount} bits and emitted at {\tt out}.

The output is undefined if {\tt inAmount} is greater than or equal to
the number of bits in a word.


== Fleeterpreter ====================================================

public void service() {
  if (box_inAmount.dataReadyForShip() && box_in.dataReadyForShip() && box_out.readyForDataFromShip()) {
    long amount = box_inAmount.removeDataForShip();
    long data   = box_in.removeDataForShip();
    long mask = ~((-1L) << getInterpreter().getWordWidth());
    data = data & mask;
    box_out.addDataFromShip(((data << amount) | (data >> (getInterpreter().getWordWidth()-amount))) & mask);
  }
}


== FPGA ==============================================================

  wire [`DATAWIDTH*2-1:0] double;
  assign double = { in_d[`DATAWIDTH-1:0], in_d[`DATAWIDTH-1:0] };

  always @(posedge clk) begin
    if (!rst) begin
      `reset
    end else begin
      if (!in_r        && in_a)       in_a    <= 0;
      if (!inAmount_r  && inAmount_a) inAmount_a  <= 0;
      if (out_r        && out_a)      out_r   <= 0;
      if (in_r && !in_a && inAmount_r && !inAmount_a && !out_r && !out_a) begin
        in_a <= 1;
        inAmount_a <= 1;
        out_r <= 1;
        out_d <= double >> (`DATAWIDTH - inAmount_d);
      end
    end
  end

== Test ==============================================================


// expected output
#expect 2
#expect 44627559471


// ships required in order to run this code
#ship debug        : Debug
#ship rotator      : Rotator

rotator.in:         literal 1; deliver; literal 21615257152;  deliver;
rotator.inAmount:   literal 1; deliver; literal 20;           deliver;
rotator.out:        [*] take, sendto debug.in;
debug.in:           [*] take, deliver;


== Contributors =========================================================
Amir Kamil <kamil@cs.berkeley.edu>
Adam Megacz <megacz@cs.berkeley.edu>