unsigned int bitmap_find_zero_bit(const unsigned long *bitmap,
unsigned int nbits, unsigned int start) {
const unsigned long *p, *pend;
unsigned long tmp;
if (start >= nbits)
return nbits;
p = bitmap + BITMAP_OFFSET(start);
pend = bitmap + BITMAP_OFFSET(nbits);
tmp = *p | ((1 << BITMAP_SHIFT(start)) - 1);
while (p < pend) {
if (~tmp)
goto found;
tmp = *(++p);
}
tmp |= ~(1 << BITMAP_SHIFT(nbits)) + 1;
if (!~tmp)
return nbits;
found:
return LONG_BIT * (p - bitmap) + bit_ctz(~tmp);
}
/* if end is 0, clear to end of disk */
int writelog_clear(struct tdlog_state* s, uint64_t start, uint64_t end)
{
if (!end)
end = s->size;
/* clear to word boundaries */
while (BITMAP_SHIFT(start))
clear_bit(start++, s->writelog);
while (BITMAP_SHIFT(end))
clear_bit(end--, s->writelog);
memset(s->writelog + start / BITS_PER_LONG, 0, (end - start) >> 3);
return 0;
}
unsigned int bitmap_find_bit(const unsigned long *bitmap,
unsigned int nbits, unsigned int start) {
const unsigned long *p = bitmap + BITMAP_OFFSET(start); /* start word */
unsigned int shift = BITMAP_SHIFT(start); /* within the start word */
unsigned int result = start - shift; /* LONG_BIT-aligned down start */
unsigned long tmp;
if (start >= nbits)
return nbits;
nbits -= result;
tmp = *(p++) & (~0x0ul << shift); /* mask out the beginning */
while (nbits > LONG_BIT) {
if (tmp)
goto found;
result += LONG_BIT;
nbits -= LONG_BIT;
tmp = *(p++);
}
tmp &= (~0x0ul >> (LONG_BIT - nbits)); /* ...and the ending */
if (!tmp)
return result + nbits;
found:
return result + bit_ctz(tmp);
}