shapiro.c

在linux系统下开发研究移动通信的工具型代码

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

#include <stdlib.h>
#include <string.h>

void shapiro( char *s, char *c, int n )
     /*
      * s should point to a valid char array of 2^n 
      * c should point to a valid char array of 2^n 
      * The generated pair of Shapiro-Rudin sequences will be
      * stored in s and c.
      * n is the order of the sequence. The actual length
      * will be 2^n.
      */
{
  s[0] = 1; s[1] = 1;
  c[0] = 1; c[1] = -1;
  if ( n < 2 ) return;

  {
    int i, j, N0, N;
    
    N0 = 1;
    N = 2;
    for ( i=1; i < n; i++ ) {
      N0 <<= 1; N <<= 1;
      memcpy( s+N0, c, N0 );
      memcpy( c, s, N0);
      for ( j=N0; j < N; j++ ) c[j] = -s[j];
    }
  }
}

static void invcpy( char *d, char *s, int size )
{
  int i;

  for( i=0; i < size; i++ ) {
    d[i] = -s[i];
  }
}

void sivaswamy4( char **S, int n )
     /*
      * S[0], S[1], S[2], S[3] point to a valid char array of 2^n
      * n is the order of the sequence. The actual length
      * will be 2^n
      */
{
  char *s, *c;
  int  N;

  N = 1 << (n-1);
  s = (char*) malloc( N * sizeof(char) );
  c = (char*) malloc( N * sizeof(char) );
  shapiro( s, c, n-1 );

  memcpy( S[0], s, N ); memcpy( S[0]+N, s, N );
  memcpy( S[1], s, N ); invcpy( S[1]+N, s, N );
  memcpy( S[2], c, N ); memcpy( S[2]+N, c, N );
  memcpy( S[3], c, N ); invcpy( S[3]+N, c, N );

  free(s); free(c);
}