Function bit_ffc_at

freebsd/sys/bitstring.h:231–262

Find the first bit clear in bit string at or after bit start. */

/* Find the first bit clear in bit string at or after bit start. */
static inline void
bit_ffc_at(bitstr_t *_bitstr, int _start, int _nbits, int *_result)
{
	bitstr_t *_curbitstr;
	bitstr_t *_stopbitstr;
	bitstr_t _test;
	int _value, _offset;

	if (_start >= _nbits) {
		*_result = -1;
		return;
	}

	if (_nbits > 0) {
		_curbitstr = _bitstr + _bit_idx(_start);
		_stopbitstr = _bitstr + _bit_idx(_nbits - 1);

		_test = *_curbitstr;
		if (_bit_offset(_start) != 0)
			_test |= _bit_make_mask(0, _start - 1);
		while (_test == _BITSTR_MASK && _curbitstr < _stopbitstr)
			_test = *(++_curbitstr);

		_offset = ffsl(~_test);
		_value = ((_curbitstr - _bitstr) * _BITSTR_BITS) + _offset - 1;
		if (_offset == 0 || _value >= _nbits)
			_value = -1;
	} else {
		_value = -1;
	}
	*_result = _value;
}

/* Find the first bit set in bit string. */
static inline void