/*  book.c  --  the text keeper module  */

#define HALF_SIZE 50000

static char  BOOK [HALF_SIZE];

int       fromBOOK ( long int n );
void      toBOOK ( long int n, int i );
long int  searchBOOK ( long int start, long int end, int desired );

int fromBOOK ( long int n )
{   long int m; int x;
 m = n;  if ( n >= HALF_SIZE ) m = n - HALF_SIZE;
 x = (unsigned char) BOOK [m];
 if ( n < HALF_SIZE )
     return ( (unsigned char) (x & 0xF ) );
 return ( x >> 4 );
}

void toBOOK ( long int n, int i )
{   long int m;  int x;
 m = n;  if ( n >= HALF_SIZE ) m = n - HALF_SIZE;
 x = BOOK [m];
 if ( n < HALF_SIZE ) {
   x = x & 0xF0;
   x = x | i;
 }
 else {
   x = x & 0x0F;
   x = x | ( i << 4 );
 }
 BOOK [m] = (char) x;
}

long int  searchBOOK ( long int start, long int end, int desired )
{   long int  from, to, n;
 from = start;   to = end;
 if ( from < HALF_SIZE ) {
   if ( to > HALF_SIZE )  to = HALF_SIZE;
   for ( n=from; n<to; n++ )
     if ( desired == ( (int) BOOK [n] & 0xF ) )
       return (n);
   if ( to == end )  return (-1);
   from = HALF_SIZE;
   to = end;
 }
 from -= HALF_SIZE;   to -= HALF_SIZE;
 desired <<= 4;
 for ( n=from; n<to; n++ )
   if ( desired == ( (int) BOOK [n] & 0xF0 ) )
     return ( n + HALF_SIZE );
 return (-1);
}

/*  end of  book.c  */