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bitstring.h

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Paul Vixie.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *    @(#)bitstring.h   5.2 (Berkeley) 4/4/90
 */

typedef     unsigned char bitstr_t;

/* internal macros */
                        /* byte of the bitstring bit is in */
#define     _bit_byte(bit) \
      ((bit) >> 3)

                        /* mask for the bit within its byte */
#define     _bit_mask(bit) \
      (1 << ((bit)&0x7))

/* external macros */
                        /* bytes in a bitstring of nbits bits */
#define     bitstr_size(nbits) \
      ((((nbits) - 1) >> 3) + 1)

                        /* allocate a bitstring */
#define     bit_alloc(nbits) \
      (bitstr_t *)malloc(1, \
          (unsigned int)bitstr_size(nbits) * sizeof(bitstr_t))

                        /* allocate a bitstring on the stack */
#define     bit_decl(name, nbits) \
      (name)[bitstr_size(nbits)]

                        /* is bit N of bitstring name set? */
#define     bit_test(name, bit) \
      ((name)[_bit_byte(bit)] & _bit_mask(bit))

                        /* set bit N of bitstring name */
#define     bit_set(name, bit) \
      (name)[_bit_byte(bit)] |= _bit_mask(bit)

                        /* clear bit N of bitstring name */
#define     bit_clear(name, bit) \
      (name)[_bit_byte(bit)] &= ~_bit_mask(bit)

                        /* clear bits start ... stop in bitstring */
#define     bit_nclear(name, start, stop) { \
      register bitstr_t *_name = name; \
      register int _start = start, _stop = stop; \
      register int _startbyte = _bit_byte(_start); \
      register int _stopbyte = _bit_byte(_stop); \
      if (_startbyte == _stopbyte) { \
            _name[_startbyte] &= ((0xff >> (8 - (_start&0x7))) | \
                              (0xff << ((_stop&0x7) + 1))); \
      } else { \
            _name[_startbyte] &= 0xff >> (8 - (_start&0x7)); \
            while (++_startbyte < _stopbyte) \
                  _name[_startbyte] = 0; \
            _name[_stopbyte] &= 0xff << ((_stop&0x7) + 1); \
      } \
}

                        /* set bits start ... stop in bitstring */
#define     bit_nset(name, start, stop) { \
      register bitstr_t *_name = name; \
      register int _start = start, _stop = stop; \
      register int _startbyte = _bit_byte(_start); \
      register int _stopbyte = _bit_byte(_stop); \
      if (_startbyte == _stopbyte) { \
            _name[_startbyte] |= ((0xff << (_start&0x7)) & \
                            (0xff >> (7 - (_stop&0x7)))); \
      } else { \
            _name[_startbyte] |= 0xff << ((_start)&0x7); \
            while (++_startbyte < _stopbyte) \
                  _name[_startbyte] = 0xff; \
            _name[_stopbyte] |= 0xff >> (7 - (_stop&0x7)); \
      } \
}

                        /* find first bit clear in name */
#define     bit_ffc(name, nbits, value) { \
      register bitstr_t *_name = name; \
      register int _byte, _nbits = nbits; \
      register int _stopbyte = _bit_byte(_nbits), _value = -1; \
      for (_byte = 0; _byte <= _stopbyte; ++_byte) \
            if (_name[_byte] != 0xff) { \
                  _value = _byte << 3; \
                  for (_stopbyte = _name[_byte]; (_stopbyte&0x1); \
                      ++_value, _stopbyte >>= 1); \
                  break; \
            } \
      *(value) = _value; \
}

                        /* find first bit set in name */
#define     bit_ffs(name, nbits, value) { \
      register bitstr_t *_name = name; \
      register int _byte, _nbits = nbits; \
      register int _stopbyte = _bit_byte(_nbits), _value = -1; \
      for (_byte = 0; _byte <= _stopbyte; ++_byte) \
            if (_name[_byte]) { \
                  _value = _byte << 3; \
                  for (_stopbyte = _name[_byte]; !(_stopbyte&0x1); \
                      ++_value, _stopbyte >>= 1); \
                  break; \
            } \
      *(value) = _value; \
}

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