#include <assert.h>#include "shuffle.h" voidshuffle_init(Shuffle *s, int (*rndrange)(int max_excluding), int total, int first){	assert(first < total && total > 0);	s->m = s->n = total;	s->i = 0;	s->xi = s->x0 = first; 	if(total < 4){		s->a = 1;		s->c = 3;		s->m = 7;		return;	} 	s->m += 1;	s->m |= s->m >> 1;	s->m |= s->m >> 2;	s->m |= s->m >> 4;	s->m |= s->m >> 8;	s->m |= s->m >> 16; 	s->a = 1 + rndrange(s->m/4)*4;     /* 1 ≤ a < m   && a mod 4 = 1 */	s->c = 3 + rndrange((s->m-2)/2)*2; /* 3 ≤ c < m-1 && c mod 2 = 1 */} voidshuffle_resize(Shuffle *s, int total){	assert(total > 0);	s->n = total;} static intnext(Shuffle *s){	int res; 	res = s->xi;	if(s->n < 2){		/* if it's less than two items, just use the first one (if any) */		s->x0 = s->xi = s->i = 0;		return 0;	}else if(s->x0 >= s->n){		/* if items were removed up to this one -- update for a period */		s->x0 = 0;	} 	for(;;){		s->xi = (s->a*s->xi + s->c) & s->m;		if(s->xi < s->n){			s->i++;			if(s->xi == s->x0)				s->i = 0;			break;		}	} 	return res;} intshuffle_one(Shuffle *s, int index){	assert(index >= 0); 	if(s->n < 1 || index < 0)		return 0;	index %= s->n;	while(s->i < s->n && s->i != index)		next(s); 	return next(s);}