/***************************
 ********** sets.h *********
 ***************************/

#ifndef SETS_H
#define SETS_H


/*
 * The following typedef establishes a 'handle'
 * for struct set_t* allowing for modules that
 * link against this module to be able to
 * handle pointers to struct set_t, but they
 * cannot access it's data members directly.
 */

typedef struct set_t* set_h;


void
set_insert(int, struct set_t*);

void
set_remove(int, struct set_t*);


#endif /* SETS_H */

/***************************
 ********** sets.c *********
 ***************************/

#include "sets.h"
#include <assert.h>
#define WORD_SIZE 15
#define NBITS 32


/*********************************
 *** Encapsulated Implentation ***
 *********************************/


struct set_t {

  unsigned short bits[NBITS];

};

static unsigned short
bit_or(unsigned short v1, unsigned short v2)
{
  return (v1 | v2);
}

static unsigned short
bit_and(unsigned short v1, unsigned short v2)
{
  return (v1 & v2);
}


static void
set_mutate( int val
      , unsigned short mask
      , struct set_t *pset
      , unsigned short (*bit_op)(unsigned short, unsigned short))
{
  assert((val >= 0) && (val < 512));

  int target_ix = val / WORD_SIZE;
  int ix;

  for (ix = 0; ix <= target_ix; ++ix) {
    if (ix == target_ix) {
      pset->bits[ix] = bit_op(pset->bits[ix], mask);
    }
  }
}

/*****************************
 **** Interface Functions ****
 *****************************/


void
set_remove(int val, struct set_t *pset)
{
  unsigned short mask = ~(1 << val / WORD_SIZE);

  set_mutate(val, mask, pset, bit_and);

}