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

#define MAXSYM 128	// size of the alphabet. E.g.: 128 for ASCII code.
#define WORD   32	// word size in bits (32 in our case).
#define B      1	// B: number of bits per individual state

/* Search pat[1..m] in text[1..n] */

int SOsearch(char *text, int n, char *pat, int m ) 
{

   register char *end;

   register unsigned int state, lim;

   unsigned int T[MAXSYM], i, j;

   char *start;

   if( m > WORD )
   {
      printf( "Use pat size <= word size\n" );
      return(-1);
   }

   for( i=0; i<MAXSYM; i++ ) 
      T[i] = ~0;        /* Preprocessing */

   for( lim=0, j=1, i=1; i<=m; lim |= j, j <<= B, i++ )
      T[pat[i]] &= ~j;

   lim = ~(lim >>B);

   text++; 
   end = text+n+1;                     /* Search */

   state = ~0;                         /* Initial state */

   for( start=text; text < end; text++ )
   {
      state = (state <<B) | T[*text];  /* Next state */

      if( state < lim ) 
         return( text-start-m+2 );
   }

   return -1;

}


int main( int argc, char ** argv)
{
   char *T = " xababayababa";
   char *P = " yab";
   int  r;

   r = SOsearch( T, strlen(T)-1, P, strlen(P)-1 );

   printf("r = %d\n", r);

}