ekasami.c

在linux系统下开发研究移动通信的工具型代码

/*
 * $Log: ekasami.c,v $
 * Revision 1.1  2000/05/03 14:30:04  bjc97r
 * Initial revision
 *
 */
char *_ekasami_id = "$Id: ekasami.c,v 1.1 2000/05/03 14:30:04 bjc97r Exp $";

#include <stdio.h>
#include <stdlib.h>

#include "ekasami.h"
#include "u2long.h"
#include "gf.h"
#include "lmseq.h"
#include "mseq.h"

/*
 * It create a eKasami code generator with a pair of preferred m-sequences
 * and a decimated sequence with the given seeds. The Kasami code generator
 * id is returned.
 */
EKasami *ekasami_create( unsigned deg, char *p1, char *p2,
			 u2long s1, u2long s2, unsigned long ssub )
{
  EKasami *kasami;
  unsigned long    subpoly;
  unsigned subdeg;

  if ( deg & 1 ) {
    fprintf(stderr, "ekasami_create: the degree of the main m-seq polynomial"
	    " should be even.\n");
    return NULL;  /* odd main degree */
  }

  if ( deg > 62 ) {
    fprintf(stderr, "ekasami_create: ..cannot handle deg > 62\n");
    return NULL;  /* too high degree */
  }
  
  subdeg  = deg >> 1;
  subpoly = find_longsubpoly( deg, p2 );
  kasami = (EKasami*) malloc( sizeof(EKasami) );
  kasami->mseq0 = lmseq_create( deg, p1, s1.h, s1.l );
  kasami->mseq1 = lmseq_create( deg, p2, s2.h, s2.l );
  kasami->mseq2 =  mseq_create( subdeg, subpoly, ssub & ((1<<subdeg)-1) );

  return kasami;
}

void ekasami_free( EKasami *kasami )
{
  lmseq_free( kasami->mseq0 );
  lmseq_free( kasami->mseq1 );
  mseq_free ( kasami->mseq2 );

  free( kasami );
}

/*
 * ekasami() gives the next long Extended Kasami sequence in unipolar form,
 * ie 1 or 0.
 */
char ekasami( EKasami *kasami )
{
  return lmseq(kasami->mseq0) ^ lmseq(kasami->mseq1) ^ mseq(kasami->mseq2);
}