Subversion Repositories reedsolomon

//----------------------------------------------------------------------//

// The MIT License

//

// Copyright (c) 2010 Abhinav Agarwal, Alfred Man Cheuk Ng

// Contact: abhiag@gmail.com

//

// Permission is hereby granted, free of charge, to any person

// obtaining a copy of this software and associated documentation

// files (the "Software"), to deal in the Software without

// restriction, including without limitation the rights to use,

// copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the

// Software is furnished to do so, subject to the following conditions:

//

// The above copyright notice and this permission notice shall be

// included in all copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

// OTHER DEALINGS IN THE SOFTWARE.

//----------------------------------------------------------------------//

import FIFO::*;

import GFArith::*;

import GFTypes::*;

import Vector::*;

// ---------------------------------------------------------

// Reed-Solomon Error Magnitude computer interface

// ---------------------------------------------------------

interface IErrorMagnitude;

   method Action              k_in(Byte k_new);

   method Action              no_error_flag_in(Bool no_error_new);

   method Action              loc_in(Maybe#(Byte) loc_new);

   method Action              alpha_inv_in(Maybe#(Byte) alpha_inv_new);

   method Action              lambda_in(Syndrome#(T) lambda_new);

   method Action              omega_in(Syndrome#(T) omega_new);

   method ActionValue#(Byte)  error_out();

endinterface

// ---------------------------------------------------------

// Reed-Solomon Error Magnitude computer module

// ---------------------------------------------------------

(* synthesize *)

module mkErrorMagnitude (IErrorMagnitude);

   // input queues

   FIFO#(Byte)             k_q             <- mkSizedFIFO(1);

   FIFO#(Bool)             no_error_flag_q <- mkSizedFIFO(1);

   FIFO#(Syndrome#(T))     lambda_q        <- mkSizedFIFO(1);

   FIFO#(Syndrome#(T))     omega_q         <- mkSizedFIFO(1);

   FIFO#(Maybe#(Byte))     loc_q           <- mkSizedFIFO(valueOf(TwoT));

   FIFO#(Maybe#(Byte))     alpha_inv_q     <- mkSizedFIFO(valueOf(T));

   // output queues

   FIFO#(Byte)             err_q           <- mkSizedFIFO(2);

   // internal quques

   FIFO#(Byte)             int_err_q       <- mkSizedFIFO(valueOf(T));

   // booking state

   Reg#(Byte)              omega_val       <- mkReg(0);

   Reg#(Byte)              lambda_d_val    <- mkReg(0);

   Reg#(Byte)              i               <- mkReg(0);

   Reg#(Byte)              count           <- mkReg(0);

   Reg#(Byte)              block_number    <- mkReg(1);

   // variables

   Byte t = fromInteger(valueOf(T));

   let k = k_q.first();

   let no_error_flag = no_error_flag_q.first();

   let loc = fromMaybe(255,loc_q.first()); // next location has no error?

   let alpha_inv = fromMaybe(?,alpha_inv_q.first());

   let lambda = lambda_q.first();

   let omega  = omega_q.first();

   // -----------------------------------------------

   rule eval_lambda_omega (count < t && isValid(alpha_inv_q.first()));

      // Derivative of Lambda is done by dropping even terms and shifting odd terms by one

      // So count is incremented by 2

      // valid_t - 2 is the index used as the final term since valid_t - 1 term gets dropped

      Byte idx = (t - 1) - count;

      Byte lambda_add_val = ((count & 8'd1) == 8'd1) ? lambda[idx] : 0;

      lambda_d_val <= gf_add(gf_mult(lambda_d_val, alpha_inv),lambda_add_val);

      omega_val <= gf_mult(omega_val, alpha_inv) ^ omega[idx];

      count <= count + 1;

      $display ("  [errMag %d]  Evaluating Lambda_der count : %d, lambda_d_val[prev] : %d, lambda_add_val : %d, idx : %d",

                block_number, count, lambda_d_val, lambda_add_val, idx);

      $display ("  [errMag %d]  Evaluating Omega count : %d, omega_val[prev] : %d",

                block_number, count, omega_val);

   endrule

   // ------------------------------------------------

   rule enq_error (count == t);

      $display ("  [errMag %d]  Finish Evaluating Lambda Omega", block_number);

      let err_val = gf_mult(omega_val, gf_inv(lambda_d_val));

      int_err_q.enq(err_val);

      count <= 0;

      lambda_d_val <= 0;

      omega_val <= 0;

      alpha_inv_q.deq();

   endrule

   rule deq_invalid_alpha_inv (alpha_inv_q.first() matches Invalid);

      $display ("  [errMag %d]  Deq Invalid Alpha Inv", block_number);

      alpha_inv_q.deq();

      lambda_q.deq();

      omega_q.deq();

   endrule

   // ------------------------------------------------

   rule process_error_no_error (i < k && !no_error_flag);

      Byte err_val;

      if (i == loc)

         begin

            $display ("  [errMag %d]  Processing location %d which is in error ", block_number, i);

            err_val = int_err_q.first();

            int_err_q.deq();

            loc_q.deq();

         end

      else

         begin

            $display ("  [errMag %d]  process location %d which has no error ", block_number, i);

            err_val = 0;

         end

      err_q.enq(err_val);

      i <= i + 1;

   endrule

   // ------------------------------------------------

   rule bypass(i < k && no_error_flag);

      $display ("  [errMag %d]  process location %d bypass which has no error ", block_number, i);

      i <= k;

   endrule

   // ------------------------------------------------

   rule start_next_errMag (i == k);

      $display ("Start Next ErrMag");

      k_q.deq();

      no_error_flag_q.deq();

      i <= 0;

      block_number <= block_number + 1;

      if (!no_error_flag)

         begin

            loc_q.deq(); // this one should be the Invalid denomiator

         end

   endrule

   // ------------------------------------------------

   method Action k_in(Byte k_new);

      $display ("  [errMag %d]  k_in : %d", block_number, k_new);

      k_q.enq(k_new);

   endmethod

   // ------------------------------------------------

   method Action no_error_flag_in(Bool no_error_new);

      $display ("  [errMag %d]  no_error_flag_in : %d", block_number, no_error_new);

      no_error_flag_q.enq(no_error_new);

   endmethod

   // ------------------------------------------------

   method Action loc_in(Maybe#(Byte) loc_new);

      $display ("  [errMag %d]  loc_in : %d", block_number, loc_new);

      loc_q.enq(loc_new);

   endmethod

   // ------------------------------------------------

   method Action alpha_inv_in(Maybe#(Byte) alpha_inv_new);

      $display ("  [errMag %d]  alpha_inv_in : %d", block_number, alpha_inv_new);

      alpha_inv_q.enq(alpha_inv_new);

   endmethod

   // ------------------------------------------------

   method Action lambda_in(Syndrome#(T) lambda_new);

      $display ("  [errMag %d]  lambda_in : %d", block_number, lambda_new);

      lambda_q.enq(lambda_new);

   endmethod

   // ------------------------------------------------

   method Action omega_in(Syndrome#(T) omega_new);

      $display ("  [errMag %d]  w_in : %d", block_number, omega_new);

      omega_q.enq(omega_new);

   endmethod

   // ------------------------------------------------

   method ActionValue#(Byte) error_out();

      $display ("  [errMag %d]  err_out: %d", block_number, err_q.first());

      err_q.deq();

      return err_q.first();

   endmethod

endmodule