bitset.c

/* bitset - a set of bits
 * Copyright (c) 2003 Michael B. Allen <mba2000 ioplex.com>
 *
 * The MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <limits.h>
#include <errno.h>

#include "mba/msgno.h"
#include "mba/bitset.h"

#define bitset_elem(ptr,bit) ((unsigned char *)(ptr))[(bit)/CHAR_BIT]
#define bitset_mask(bit) (1U << ((bit) % CHAR_BIT))

int
bitset_isset(void *ptr, int bit)
{
  return (bitset_elem(ptr,bit) & bitset_mask(bit)) != 0;
}
int
bitset_set(void *ptr, int bit)
{
  unsigned char *b = (unsigned char *)ptr + (bit / CHAR_BIT);
  unsigned char m = bitset_mask(bit);

  if ((*b & m)) return 0;
  *b |= m;

  return 1;
}
int
bitset_unset(void *ptr, int bit)
{
  unsigned char *b = (unsigned char *)ptr + (bit / CHAR_BIT);
  unsigned char m = bitset_mask(bit);

  if ((*b & m) == 0) return 0;
  *b &= ~m;

  return 1;
}
void
bitset_toggle(void *ptr, int bit)
{
  bitset_elem(ptr,bit) ^= bitset_mask(bit);
}
int
bitset_find_first(void *ptr, void *plim, int val)
{
  unsigned char *start = ptr;
  unsigned char *bs;
  int cond = val ? 0x00 : 0xFF;

  for (bs = start; bs < (unsigned char *)plim; bs++) {
    if ((*bs & 0xFF) != cond) {
      int b = *bs & 0xFF;

        /* Index of the first bit that is 0 if
         * val is 0 or 1 if val is 1.
         */
      if (!val) {
        b = ~b;
      }
      b = b & -b;
      switch (b) {
        case 1: b = 0; break;
        case 2: b = 1; break;
        case 4: b = 2; break;
        case 8: b = 3; break;
        case 16: b = 4; break;
        case 32: b = 5; break;
        case 64: b = 6; break;
        case 128: b = 7; break;
      }

      return b + (bs - start) * 8;
    }
  }

  PMNO(errno = ENOENT);
  return -1;
}
void
bitset_iterate(iter_t *iter)
{
  iter->i1 = 0;
}
int
bitset_next(void *ptr, void *plim, iter_t *iter)
{
  unsigned char *b = (unsigned char *)ptr + iter->i1 / 8;
  int ret = -1;

  if (b < (unsigned char *)plim) {
    unsigned long mask = 1 << (iter->i1 % 8);
    iter->i1++;
    ret = (*b & mask) != 0;
  }

  return ret;
}