rs_encode.cpp

RS码（255

#include "stdio.h"
#include "stdlib.h"


#define TT 32
#define N 255
#define K 223
int T[8][8]={
1,0,0,0,1,1,0,1,
1,1,1,0,1,1,1,1,
1,1,1,0,1,1,0,0,
1,0,0,0,0,1,1,0,
1,1,1,1,1,0,1,0,
1,0,0,1,1,0,0,1,
1,0,1,0,1,1,1,1,
0,1,1,1,1,0,1,1
};
int TI[8][8]={
1,1,0,0,0,1,0,1,
0,1,0,0,0,0,1,0,
0,0,1,0,1,1,1,0,
1,1,1,1,1,1,0,1,
1,1,1,1,0,0,0,0,
0,1,1,1,1,0,0,1,
1,0,1,0,1,1,0,0,
1,1,0,0,1,1,0,0
};
int u[8],z[8];
unsigned char x,B[TT],G[TT+1],H[N],F[N+1],VV;
FILE *finp, *fout;
int symbol_no, word_no;
void exit();

FILE *fwtest;


void main()
{
		int i,j;
		int bit;
		int k,t;
		finp=fopen("encinp","rb");
		fout=fopen("encout","w");
		fwtest=fopen("11.txt","w");
		/*** H[ ] and F[ ] compute the power and log in GF(256) ********/
		H[0]=1;
		for(i=0;i<8;i++) H[i+1]=2*H[i];
		for(i=8;i<N;i++) H[i]=H[i-1]^H[i-6]^H[i-7]^H[i-8];
		for(j=1;j<N+1;j++)
			for(i=0;i<N;i++) if(H[i]==j) F[j]=i;
		/*
		for(i=0;i<N;i++) printf("\n%4d %4d",i,H[i]);
		for(i=0;i<=N;i++) printf("\n%4d %4d",i,F[i]);
		*/
		/////
		
	//	for(i=0;i<N;i++) fprintf(fwtest,"\n%4d %4d",i,H[i]);
		for(i=0;i<=N;i++) fprintf(fwtest,"\n%4d %4d",i,F[i]);

		////
		symbol_no=0;
		word_no=0;
		VV=0;
		F[0]=0;
		/*** g[ ] are the coefficients of the generating polynomial ****/
		G[0]=H[0];
		G[1]=H[249];
		G[2]=H[59];
		G[3]=H[66];
		G[4]=H[4];
		G[5]=H[43];
		G[6]=H[126];
		G[7]=H[251];
		G[8]=H[97];
		G[9]=H[30];
		G[10]=H[3];
		G[11]=H[213];
		G[12]=H[50];
		G[13]=H[66];
		G[14]=H[170];
		G[15]=H[5];
		G[16]=H[24];
		for(i=0;i<TT/2;i++) G[TT-i]=G[i];
		while(1>0)
		{
			if(symbol_no==0)
			{
				for(i=0;i<TT;i++) 
					B[i]=0; 
				word_no++; 
				if(word_no==2) 
					exit(1);
			}
			/******************************************************************************************/
			printf("\n%4d ",symbol_no+1);
			if(symbol_no<K) /* information bits */
			{
				 x=getc(finp); /* encoder gets one symbol from input data */
	//		     printf(" %2x ",x); 
	//			 for(bit=0;bit<8;bit++) 
	//				 printf("%1d",(x>>(7-bit))&1);
				/***** transformation T^-1 from dual basis (Berlekamp) to standard basis (conventional) */
				/* Input symbols x are in dual basis, x=z_0*l_0,...,z_7*l_7 */
				for(k=0;k<8;k++)
					z[7-k]=(x>>k)&1;
				for(t=0;t<8;t++) 
				{
					u[7-t]=0; 
					for(k=0;k<8;k++)
						u[7-t] ^= z[k]*TI[k][t];
				}
				x=0;
				for(t=0;t<8;t++)
					x ^= u[t]<<t;
				/* Output symbols x are in standard basis,x=u_7*alpha^7,...,u_0*alpha^0 */
				/**** end of transformation ***************************************************************/
				printf(" %2x ",x);
				for(bit=0;bit<8;bit++)
					printf("%1d",(x>>(7-bit))&1);
				/* beginning of conventional (not Berlekamp) RS encoder.
				Input symbols x are in standard basis, x=u_7*alpha^7,...,u_0*alpha^0 */
				VV=x^B[TT-1];
			}
			else /** parity bits **/
			{
				VV=0;
				x=B[TT-1];
			}
			for(i=TT-1;i>0;i--)
			    B[i]=B[i-1]^(VV!=0)*(H[(F[G[i]]+F[VV])%N]);
			B[0]=(VV!=0)*(H[(F[G[0]]+F[VV])%N]);
			/* end of conventional (not Berlekamp) RS encoder.
			Output symbols x are in standard basis, x=u_7*alpha^7,...,u_0*alpha^0 */
			if(symbol_no>=K)
				printf(" ");
			printf(" %2x ",x);
			for(bit=0;bit<8;bit++)
				printf("%1d",(x>>(7-bit))&1);
			/***** transformation T from standard basis (conventional) to dual basis (Berlekamp) ****/
			/* Input symbols x are in standard basis, x=u_7*alpha^7,...,u_0*alpha^0 */
			for(t=0;t<8;t++)
				u[t]=(x>>t)&1;
			for(k=0;k<8;k++)
			{
				z[k]=0;
				for(t=0;t<8;t++) 
					z[k] ^= u[7-t]*T[t][k];
			}
			x=0; 
			for(k=0;k<8;k++) 
				x ^= z[7-k]<<k;
			/* Output symbols x are in dual basis, x=z_0*l_0,...,z_7*l_7 */
			/**** end of transformation *************************************************************/
			printf(" %2x ",x);
			for(bit=0;bit<8;bit++) 
				printf("%1d",(x>>(7-bit))&1);
			putc(x,fout);
			symbol_no=(symbol_no+1)%N;
		}
}