Subversion Repositories yacc

//Reed Solomon Program
//This program is based on Phil Karn
//Rewritten for YACC CPU (has no C library) by Tak.Sugawara Apr.3.2005
//Consideration for embedded CPU
// 1) Has no C library. Ex. Not have printf/random...
// 2) Not have plenty of stack 

#define POLY 0x80000057




#define print_port 0x3ff0
#define print_char_port 0x3ff1
#define print_int_port 0x3ff2
#define print_long_port 0x3ff4





#define uart_port               0x03ffc //for 16KRAM
#define uart_wport uart_port
#define uart_rport uart_port
#define int_set_address 0x03ff8 //for 16KRAM

//#define PC

void print_uart(unsigned char* ptr)// 
{
        unsigned int uport;
        #define WRITE_BUSY 0x0100


        while (*ptr) {
        
                do {
                  uport=*(volatile unsigned*)   uart_port;
                } while (uport & WRITE_BUSY);
                *(volatile unsigned char*)uart_wport=*(ptr++);
        }
        //*(volatile unsigned char*)uart_wport=0x00;//Write Done
}       


void putc_uart(unsigned char c)// 
{
        unsigned int uport;
        

        do {
                  uport=*(volatile unsigned*)   uart_port;
        } while (uport & WRITE_BUSY);
        *(volatile unsigned char*)uart_wport=c;
        
}       

unsigned char read_uart()//Verilog Test Bench Use 
{
                unsigned uport;
                uport= *(volatile unsigned *)uart_rport;
                return uport;
}       

void print(unsigned char* ptr)//Verilog Test Bench Use 
{

        while (*ptr) {
                #ifdef PC
                        putchar(*(ptr++));
                #else   
                *(volatile unsigned char*)print_port=*(ptr++);
                #endif
        }
        #ifndef PC
                *(volatile unsigned char*)print_port=0x00;//Write Done
        #endif
}
void print_char(unsigned char val)//Little Endian write out 16bit number 
{
        #ifdef PC
                putchar(val);
        #else   
                *(volatile unsigned char*)print_port=(unsigned char)val ;
        #endif
}
void print_uchar(unsigned char val)//Little Endian write out 16bit number 
{
        #ifdef PC
        
                printf("%x",val);
        #else
        *(volatile unsigned char*)print_char_port=(unsigned char)val ;
        #endif  
}







static unsigned lfsr_state=1;

unsigned random (void)
{
  if (lfsr_state & 0x1)
    {
      lfsr_state = (lfsr_state >> 1) ^ POLY;
    }
  else
    {
      lfsr_state = (lfsr_state >> 1);
    }
  return lfsr_state;
}
/*
void print_uart(unsigned char* ptr)
{
        while(*(ptr)) putchar(*(ptr++));        
        
}
*/      
void print_num(unsigned long num)
{
   unsigned long digit,offset;
   for(offset=1000;offset;offset/=10) {
      digit=num/offset;
      
      putc_uart(digit+'0');//putchar(digit+'0');
      num-=digit*offset;
   }
}

void memcpy(unsigned char* dest,unsigned char* source,unsigned size)
{
        unsigned i;
        for (i=0;i< size;i++){  
                *(dest++)=*(source++);
        }
}       

unsigned memcmp(unsigned char* dest,unsigned char* source,unsigned size)
{
        unsigned i;
        for (i=0;i< size;i++){  
                if (*(dest++)!=*(source++) ) return 1;
        }
        return 0;
}       
/*
 * Reed-Solomon coding and decoding
 * Phil Karn (karn@ka9q.ampr.org) September 1996
 * 
 * This file is derived from the program "new_rs_erasures.c" by Robert
 * Morelos-Zaragoza (robert@spectra.eng.hawaii.edu) and Hari Thirumoorthy
 * (harit@spectra.eng.hawaii.edu), Aug 1995
 *
 * I've made changes to improve performance, clean up the code and make it
 * easier to follow. Data is now passed to the encoding and decoding functions
 * through arguments rather than in global arrays. The decode function returns
 * the number of corrected symbols, or -1 if the word is uncorrectable.
 *
 * This code supports a symbol size from 2 bits up to 16 bits,
 * implying a block size of 3 2-bit symbols (6 bits) up to 65535
 * 16-bit symbols (1,048,560 bits). The code parameters are set in rs.h.
 *
 * Note that if symbols larger than 8 bits are used, the type of each
 * data array element switches from unsigned char to unsigned int. The
 * caller must ensure that elements larger than the symbol range are
 * not passed to the encoder or decoder.
 *
 */
//#include <stdio.h>
#include "rs.h"

#if (KK >= NN)
#error "KK must be less than 2**MM - 1"
#endif

/* This defines the type used to store an element of the Galois Field
 * used by the code. Make sure this is something larger than a char if
 * if anything larger than GF(256) is used.
 *
 * Note: unsigned char will work up to GF(256) but int seems to run
 * faster on the Pentium.
 */
typedef int gf;

/* Primitive polynomials - see Lin & Costello, Appendix A,
 * and  Lee & Messerschmitt, p. 453.
 */
#if(MM == 2)/* Admittedly silly */
int Pp[MM+1] = { 1, 1, 1 };

#elif(MM == 3)
/* 1 + x + x^3 */
int Pp[MM+1] = { 1, 1, 0, 1 };

#elif(MM == 4)
/* 1 + x + x^4 */
int Pp[MM+1] = { 1, 1, 0, 0, 1 };

#elif(MM == 5)
/* 1 + x^2 + x^5 */
int Pp[MM+1] = { 1, 0, 1, 0, 0, 1 };

#elif(MM == 6)
/* 1 + x + x^6 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 1 };

#elif(MM == 7)
/* 1 + x^3 + x^7 */
int Pp[MM+1] = { 1, 0, 0, 1, 0, 0, 0, 1 };

#elif(MM == 8)
/* 1+x^2+x^3+x^4+x^8 */
int Pp[MM+1] = { 1, 0, 1, 1, 1, 0, 0, 0, 1 };

#elif(MM == 9)
/* 1+x^4+x^9 */
int Pp[MM+1] = { 1, 0, 0, 0, 1, 0, 0, 0, 0, 1 };

#elif(MM == 10)
/* 1+x^3+x^10 */
int Pp[MM+1] = { 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1 };

#elif(MM == 11)
/* 1+x^2+x^11 */
int Pp[MM+1] = { 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 };

#elif(MM == 12)
/* 1+x+x^4+x^6+x^12 */
int Pp[MM+1] = { 1, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1 };

#elif(MM == 13)
/* 1+x+x^3+x^4+x^13 */
int Pp[MM+1] = { 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 };

#elif(MM == 14)
/* 1+x+x^6+x^10+x^14 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1 };

#elif(MM == 15)
/* 1+x+x^15 */
int Pp[MM+1] = { 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 };

#elif(MM == 16)
/* 1+x+x^3+x^12+x^16 */
int Pp[MM+1] = { 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1 };

#else
#error "MM must be in range 2-16"
#endif

/* Alpha exponent for the first root of the generator polynomial */
#define B0      1

/* index->polynomial form conversion table */
gf Alpha_to[NN + 1];

/* Polynomial->index form conversion table */
gf Index_of[NN + 1];

/* No legal value in index form represents zero, so
 * we need a special value for this purpose
 */
#define A0      (NN)

/* Generator polynomial g(x)
 * Degree of g(x) = 2*TT
 * has roots @**B0, @**(B0+1), ... ,@^(B0+2*TT-1)
 */
gf Gg[NN - KK + 1];

/* Compute x % NN, where NN is 2**MM - 1,
 * without a slow divide
 */
static inline gf
modnn(int x)
{
//      print_uart("modnn input="); print_num(x);
        while (x >= NN) {
                x -= NN;
                x = (x >> MM) + (x & NN);
        }
//      print_uart("modnn output=");print_num(x);
//      print_uart("\n");
        return x;
}

#define min(a,b)        ((a) < (b) ? (a) : (b))

#define CLEAR(a,n) {    int ci; for(ci=(n)-1;ci >=0;ci--)               (a)[ci] = 0;    }

#define COPY(a,b,n) {   int ci; for(ci=(n)-1;ci >=0;ci--)       (a)[ci] = (b)[ci];      }
#define COPYDOWN(a,b,n) {       int ci; for(ci=(n)-1;ci >=0;ci--) (a)[ci] = (b)[ci];    }

void init_rs(void)
{
        generate_gf();
        gen_poly();
}

/* generate GF(2**m) from the irreducible polynomial p(X) in p[0]..p[m]
   lookup tables:  index->polynomial form   alpha_to[] contains j=alpha**i;
                   polynomial form -> index form  index_of[j=alpha**i] = i
   alpha=2 is the primitive element of GF(2**m)
   HARI's COMMENT: (4/13/94) alpha_to[] can be used as follows:
        Let @ represent the primitive element commonly called "alpha" that
   is the root of the primitive polynomial p(x). Then in GF(2^m), for any
   0 <= i <= 2^m-2,
        @^i = a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
   where the binary vector (a(0),a(1),a(2),...,a(m-1)) is the representation
   of the integer "alpha_to[i]" with a(0) being the LSB and a(m-1) the MSB. Thus for
   example the polynomial representation of @^5 would be given by the binary
   representation of the integer "alpha_to[5]".
                   Similarily, index_of[] can be used as follows:
        As above, let @ represent the primitive element of GF(2^m) that is
   the root of the primitive polynomial p(x). In order to find the power
   of @ (alpha) that has the polynomial representation
        a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
   we consider the integer "i" whose binary representation with a(0) being LSB
   and a(m-1) MSB is (a(0),a(1),...,a(m-1)) and locate the entry
   "index_of[i]". Now, @^index_of[i] is that element whose polynomial 
    representation is (a(0),a(1),a(2),...,a(m-1)).
   NOTE:
        The element alpha_to[2^m-1] = 0 always signifying that the
   representation of "@^infinity" = 0 is (0,0,0,...,0).
        Similarily, the element index_of[0] = A0 always signifying
   that the power of alpha which has the polynomial representation
   (0,0,...,0) is "infinity".
 
*/

void
generate_gf(void)
{
        register int i, mask;

        mask = 1;
        Alpha_to[MM] = 0;
        for (i = 0; i < MM; i++) {
                Alpha_to[i] = mask;
                Index_of[Alpha_to[i]] = i;
                /* If Pp[i] == 1 then, term @^i occurs in poly-repr of @^MM */
                if (Pp[i] != 0)
                        Alpha_to[MM] ^= mask;   /* Bit-wise EXOR operation */
                mask <<= 1;     /* single left-shift */
        }
        Index_of[Alpha_to[MM]] = MM;
        /*
         * Have obtained poly-repr of @^MM. Poly-repr of @^(i+1) is given by
         * poly-repr of @^i shifted left one-bit and accounting for any @^MM
         * term that may occur when poly-repr of @^i is shifted.
         */
        mask >>= 1;
        for (i = MM + 1; i < NN; i++) {
                if (Alpha_to[i - 1] >= mask)
                        Alpha_to[i] = Alpha_to[MM] ^ ((Alpha_to[i - 1] ^ mask) << 1);
                else
                        Alpha_to[i] = Alpha_to[i - 1] << 1;
                Index_of[Alpha_to[i]] = i;
        }
        Index_of[0] = A0;
        Alpha_to[NN] = 0;
        //print_uart("index dump\n");
    //for (i=0;i<NN;i++){
        //      print_uchar(Index_of[i]);
        //      print_uart(" ");        
        //}
        //print_uart("\n");
        //print_uart("Alpha_to dump\n");
    //for (i=0;i<NN;i++){
        //      print_uchar(Alpha_to[i]);
        //      print_uart(" ");        
        //}
        //print_uart("\n");
                
}


/*
 * Obtain the generator polynomial of the TT-error correcting, length
 * NN=(2**MM -1) Reed Solomon code from the product of (X+@**(B0+i)), i = 0,
 * ... ,(2*TT-1)
 *
 * Examples:
 *
 * If B0 = 1, TT = 1. deg(g(x)) = 2*TT = 2.
 * g(x) = (x+@) (x+@**2)
 *
 * If B0 = 0, TT = 2. deg(g(x)) = 2*TT = 4.
 * g(x) = (x+1) (x+@) (x+@**2) (x+@**3)
 */
void
gen_poly(void)
{
        register int i, j;

        Gg[0] = Alpha_to[B0];
        Gg[1] = 1;              /* g(x) = (X+@**B0) initially */
        for (i = 2; i <= NN - KK; i++) {
                Gg[i] = 1;
                /*
                 * Below multiply (Gg[0]+Gg[1]*x + ... +Gg[i]x^i) by
                 * (@**(B0+i-1) + x)
                 */
                for (j = i - 1; j > 0; j--){
                        if (Gg[j] != 0)
                                Gg[j] = Gg[j - 1] ^ Alpha_to[modnn((Index_of[Gg[j]]) + B0 + i - 1)];
                        else
                                Gg[j] = Gg[j - 1];
                        
                //      print_uart("Gg[");print_num(j);print_uart("]=");print_num(Gg[j]);print_uart("\n");
                //      print_uart("Gg[");print_num(j-1);print_uart("]=");print_num(Gg[j-1]);print_uart("\n");
                }               
                /* Gg[0] can never be zero */
                Gg[0] = Alpha_to[modnn((Index_of[Gg[0]]) + B0 + i - 1)];
        }
        /* convert Gg[] to index form for quicker encoding */
        for (i = 0; i <= NN - KK; i++)
                Gg[i] = Index_of[Gg[i]];
                
        //print_uart("Gg dump\n");
        //for (i=0;i<=NN-KK;i++){
        //      print_uchar(Gg[i]);
        //      print_uart(" ");        
        //}
        //print_uart("\n");             
}


/*
 * take the string of symbols in data[i], i=0..(k-1) and encode
 * systematically to produce NN-KK parity symbols in bb[0]..bb[NN-KK-1] data[]
 * is input and bb[] is output in polynomial form. Encoding is done by using
 * a feedback shift register with appropriate connections specified by the
 * elements of Gg[], which was generated above. Codeword is   c(X) =
 * data(X)*X**(NN-KK)+ b(X)
 */
int
encode_rs(dtype data[KK], dtype bb[NN-KK])
{
        register int i, j;
        gf feedback;

        CLEAR(bb,NN-KK);
        for (i = KK - 1; i >= 0; i--) {
#if (MM != 8)
                if(data[i] > NN)
                        return -1;      /* Illegal symbol */
#endif
                feedback = Index_of[data[i] ^ bb[NN - KK - 1]];
                if (feedback != A0) {   /* feedback term is non-zero */
                        for (j = NN - KK - 1; j > 0; j--)
                                if (Gg[j] != A0)
                                        bb[j] = bb[j - 1] ^ Alpha_to[modnn(Gg[j] + feedback)];
                                else
                                        bb[j] = bb[j - 1];
                        bb[0] = Alpha_to[modnn(Gg[0] + feedback)];
                } else {        /* feedback term is zero. encoder becomes a
                                 * single-byte shifter */
                        for (j = NN - KK - 1; j > 0; j--)
                                bb[j] = bb[j - 1];
                        bb[0] = 0;
                }
        }
        return 0;
}

/*
 * Performs ERRORS+ERASURES decoding of RS codes. If decoding is successful,
 * writes the codeword into data[] itself. Otherwise data[] is unaltered.
 *
 * Return number of symbols corrected, or -1 if codeword is illegal
 * or uncorrectable.
 * 
 * First "no_eras" erasures are declared by the calling program. Then, the
 * maximum # of errors correctable is t_after_eras = floor((NN-KK-no_eras)/2).
 * If the number of channel errors is not greater than "t_after_eras" the
 * transmitted codeword will be recovered. Details of algorithm can be found
 * in R. Blahut's "Theory ... of Error-Correcting Codes".
 */
int
eras_dec_rs(dtype data[NN], int eras_pos[NN-KK], int no_eras)
{
        int deg_lambda, el, deg_omega;
        int i, j, r;
        gf u,q,tmp,num1,num2,den,discr_r;
        gf recd[NN];
        gf lambda[NN-KK + 1], s[NN-KK + 1];     /* Err+Eras Locator poly
                                                 * and syndrome poly */
        gf b[NN-KK + 1], t[NN-KK + 1], omega[NN-KK + 1];
        gf root[NN-KK], reg[NN-KK + 1], loc[NN-KK];
        int syn_error, count;

        /* data[] is in polynomial form, copy and convert to index form */
        for (i = NN-1; i >= 0; i--){
#if (MM != 8)
                if(data[i] > NN)
                        return -1;      /* Illegal symbol */
#endif
                recd[i] = Index_of[data[i]];
        }
        /* first form the syndromes; i.e., evaluate recd(x) at roots of g(x)
         * namely @**(B0+i), i = 0, ... ,(NN-KK-1)
         */
        syn_error = 0;
        for (i = 1; i <= NN-KK; i++) {
                tmp = 0;
                for (j = 0; j < NN; j++)
                        if (recd[j] != A0)      /* recd[j] in index form */
                                tmp ^= Alpha_to[modnn(recd[j] + (B0+i-1)*j)];
                syn_error |= tmp;       /* set flag if non-zero syndrome =>
                                         * error */
                /* store syndrome in index form  */
                s[i] = Index_of[tmp];
        }
        if (!syn_error) {
                /*
                 * if syndrome is zero, data[] is a codeword and there are no
                 * errors to correct. So return data[] unmodified
                 */
                return 0;
        }
        CLEAR(&lambda[1],NN-KK);
        lambda[0] = 1;
        if (no_eras > 0) {
                /* Init lambda to be the erasure locator polynomial */
                lambda[1] = Alpha_to[eras_pos[0]];
                for (i = 1; i < no_eras; i++) {
                        u = eras_pos[i];
                        for (j = i+1; j > 0; j--) {
                                tmp = Index_of[lambda[j - 1]];
                                if(tmp != A0)
                                        lambda[j] ^= Alpha_to[modnn(u + tmp)];
                        }
                }
#ifdef ERASURE_DEBUG
                /* find roots of the erasure location polynomial */
                for(i=1;i<=no_eras;i++)
                        reg[i] = Index_of[lambda[i]];
                count = 0;
                for (i = 1; i <= NN; i++) {
                        q = 1;
                        for (j = 1; j <= no_eras; j++)
                                if (reg[j] != A0) {
                                        reg[j] = modnn(reg[j] + j);
                                        q ^= Alpha_to[reg[j]];
                                }
                        if (!q) {
                                /* store root and error location
                                 * number indices
                                 */
                                root[count] = i;
                                loc[count] = NN - i;
                                count++;
                        }
                }
                if (count != no_eras) {
                        print_uart("\n lambda(x) is WRONG\n");
                        return -1;
                }
#ifndef NO_PRINT
                print_uart("\n Erasure positions as determined by roots of Eras Loc Poly:\n");
                for (i = 0; i < count; i++)
                        print_num(loc[i]);
                print_uart("\n");
#endif
#endif
        }
        for(i=0;i<NN-KK+1;i++)
                b[i] = Index_of[lambda[i]];

        /*
         * Begin Berlekamp-Massey algorithm to determine error+erasure
         * locator polynomial
         */
        r = no_eras;
        el = no_eras;
        while (++r <= NN-KK) {  /* r is the step number */
                /* Compute discrepancy at the r-th step in poly-form */
                discr_r = 0;
                for (i = 0; i < r; i++){
                        if ((lambda[i] != 0) && (s[r - i] != A0)) {
                                discr_r ^= Alpha_to[modnn(Index_of[lambda[i]] + s[r - i])];
                        }
                }
                discr_r = Index_of[discr_r];    /* Index form */
                if (discr_r == A0) {
                        /* 2 lines below: B(x) <-- x*B(x) */
                        COPYDOWN(&b[1],b,NN-KK);
                        b[0] = A0;
                } else {
                        /* 7 lines below: T(x) <-- lambda(x) - discr_r*x*b(x) */
                        t[0] = lambda[0];
                        for (i = 0 ; i < NN-KK; i++) {
                                if(b[i] != A0)
                                        t[i+1] = lambda[i+1] ^ Alpha_to[modnn(discr_r + b[i])];
                                else
                                        t[i+1] = lambda[i+1];
                        }
                        if (2 * el <= r + no_eras - 1) {
                                el = r + no_eras - el;
                                /*
                                 * 2 lines below: B(x) <-- inv(discr_r) *
                                 * lambda(x)
                                 */
                                for (i = 0; i <= NN-KK; i++)
                                        b[i] = (lambda[i] == 0) ? A0 : modnn(Index_of[lambda[i]] - discr_r + NN);
                        } else {
                                /* 2 lines below: B(x) <-- x*B(x) */
                                COPYDOWN(&b[1],b,NN-KK);
                                b[0] = A0;
                        }
                        COPY(lambda,t,NN-KK+1);
                }
        }

        /* Convert lambda to index form and compute deg(lambda(x)) */
        deg_lambda = 0;
        for(i=0;i<NN-KK+1;i++){
                lambda[i] = Index_of[lambda[i]];
                if(lambda[i] != A0)
                        deg_lambda = i;
        }
        /*
         * Find roots of the error+erasure locator polynomial. By Chien
         * Search
         */
        COPY(&reg[1],&lambda[1],NN-KK);
        count = 0;              /* Number of roots of lambda(x) */
        for (i = 1; i <= NN; i++) {
                q = 1;
                for (j = deg_lambda; j > 0; j--)
                        if (reg[j] != A0) {
                                reg[j] = modnn(reg[j] + j);
                                q ^= Alpha_to[reg[j]];
                        }
                if (!q) {
                        /* store root (index-form) and error location number */
                        root[count] = i;
                        loc[count] = NN - i;
                        count++;
                }
        }

#ifdef DEBUG
        print_uart("\n Final error positions:\t");
        for (i = 0; i < count; i++)
                print_num(loc[i]);
        print_uart("\n");
#endif
        if (deg_lambda != count) {
                /*
                 * deg(lambda) unequal to number of roots => uncorrectable
                 * error detected
                 */
                return -1;
        }
        /*
         * Compute err+eras evaluator poly omega(x) = s(x)*lambda(x) (modulo
         * x**(NN-KK)). in index form. Also find deg(omega).
         */
        deg_omega = 0;
        for (i = 0; i < NN-KK;i++){
                tmp = 0;
                j = (deg_lambda < i) ? deg_lambda : i;
                for(;j >= 0; j--){
                        if ((s[i + 1 - j] != A0) && (lambda[j] != A0))
                                tmp ^= Alpha_to[modnn(s[i + 1 - j] + lambda[j])];
                }
                if(tmp != 0)
                        deg_omega = i;
                omega[i] = Index_of[tmp];
        }
        omega[NN-KK] = A0;

        /*
         * Compute error values in poly-form. num1 = omega(inv(X(l))), num2 =
         * inv(X(l))**(B0-1) and den = lambda_pr(inv(X(l))) all in poly-form
         */
        for (j = count-1; j >=0; j--) {
                num1 = 0;
                for (i = deg_omega; i >= 0; i--) {
                        if (omega[i] != A0)
                                num1  ^= Alpha_to[modnn(omega[i] + i * root[j])];
                }
                num2 = Alpha_to[modnn(root[j] * (B0 - 1) + NN)];
                den = 0;

                /* lambda[i+1] for i even is the formal derivative lambda_pr of lambda[i] */
                for (i = min(deg_lambda,NN-KK-1) & ~1; i >= 0; i -=2) {
                        if(lambda[i+1] != A0)
                                den ^= Alpha_to[modnn(lambda[i+1] + i * root[j])];
                }
                if (den == 0) {
#ifdef DEBUG
                        print_uart("\n ERROR: denominator = 0\n");
#endif
                        return -1;
                }
                /* Apply error to data */
                if (num1 != 0) {
                        data[loc[j]] ^= Alpha_to[modnn(Index_of[num1] + Index_of[num2] + NN - Index_of[den])];
                }
        }
        return count;
}

void
fill_eras(int eras_pos[],int n)
{
        int i,j,t,work[NN];

        for(i=0;i<NN;i++)
                work[i] = i;
        for(j=NN-1;j>0;j--){
                i = random() % j;       /* not really uniform, I know */
                t = work[i];
                work[i] = work[j];
                work[j] = t;
        }
#ifdef notdef
        for(i=0;i<NN;i++)
          print_num(work[i]);
        print_uart("\n");
#endif
        for(i=0;i<n;i++)
                eras_pos[i] = work[i];
}

/* Return non-zero random number in range 0 - NN (NN power of 2 minus 1) */
int
randomnz(void)
{
        int i;

        while((i = random() & NN) == 0)
                ;
        return i;
}

dtype data[NN];
dtype tdata[NN];
dtype ddata[NN];
int eras_pos[NN];
int
main(int argc,char *argv[])
{


        int i,trials,k;
        long t;
        int nerrors,nerase,ntrials,verbose,timetest;
        int detfails,fails;
        extern char *optarg;

        nerrors = nerase = 0;
        timetest = verbose = 0;
        ntrials = 120;
        verbose = 1;
        nerrors=11;
        nerase=10;
//      while((i = getopt(argc,argv,"e:E:n:vt")) != EOF){
//              switch(i){
///             case 'e':       /* Number of errors per block */
//                      nerrors = atoi(optarg);
//                      break;
//              case 'E':       /* Number of erasures per block */
//                      nerase = atoi(optarg);
//                      break;
//              case 'n':       /* Number of trials */
//                      ntrials = atoi(optarg);
//                      break;
//              case 'v':       /* Be verbose */
//                      verbose = 1;
//                      break;
//              case 't':       /* Repeatedly decode the same block */
//                      timetest = 1;
//                      break;
//              default:
//                      printf("usage: %s [-v] [-t] [-e errors] [-E erasures] [-n ntrials]\n",argv[0]);
//                      exit(1);
//              }
//      }
        print_uart("It takes very long time for RTL Simulation.");
        print_uart("Reed-Solomon code is ");
//      for (i=3;i>0;i--){ 
                print_num(NN), print_uart(" "); print_num(KK); print_uart("over GF(");
                print_num(NN+1);print_uart(")\n");
                print_uart("i=");print_num(i);print_uart("\n");
//      }
        print_uart("test erasures: ");print_num(nerase);print_uart("errors ");print_num(nerrors);print_uart("\n");
        if(2*nerrors + nerase > NN-KK){
                print_uart("Warning: ");
                print_num(nerrors); print_uart("errors and ");
                print_num(nerase); print_uart("erasures exceeds the correction ability of the code\n");
        }       

        init_rs();
        print_uart("Init_RS Done");

        fails = detfails = 0;
        for(trials=0;trials < ntrials;trials++){
                if(verbose){
                        print_uart("\n Trial ");
                        print_num(trials);
                }
                print_uart("\n");       
                for(i=0;i<KK;i++)
                        data[i] = random() & NN;
                encode_rs(data,&data[KK]);
                fill_eras(eras_pos,nerase+nerrors);
                if(verbose && nerase){
                        print_uart(" erasing:");
                        for(i=0;i<nerase;i++){
                                print_uart(" ");print_num(eras_pos[i]);
                        }
                        print_uart("\n");
                }
                if(verbose && nerrors){
                        print_uart(" erroring:");
                        for(i=nerase;i<nerase+nerrors;i++){
                                print_uart(" ");print_num(eras_pos[i]);
                        }
                        print_uart("\n");       
                }
                if(verbose){
                        //for(i=0;i<NN;i++){
                        //      print_uchar(data[i]);
                        //    print_uart(" ");
                        //}
                        //print_uart("\n");    
                }       
                memcpy(ddata,data,sizeof(data));
                for(i=0;i<nerase+nerrors;i++)
                        ddata[eras_pos[i]] ^= randomnz();

                i = eras_dec_rs(ddata,eras_pos,nerase);
                if(verbose){
                        print_uart("errs + erasures corrected: ");print_num(i);
                        print_uart("\n");
                }
                if(i == -1){
                        detfails++;
                        print_uart("RS decoder detected failure\n");
                } else if(memcmp(ddata,data,NN) != 0){
                        fails++;
                        print_uart(" Undetected decoding failure!\n");
                }else {
                        print_uart("Compare Done. Passed.\n");  
                        
                }       
        }
        print_uart("\n\n\n Trials: ");
        print_num(ntrials);
        print_uart(" decoding failures: ");
        print_num(detfails); print_uart(" not detected by decoder: ");
        print_num(fails); print_uart("\n");
        print_uart("$finish");
        return 0;
}