// Add appends the bits given its size to the vector.
func (v *BitVector) Add(bits uint64, size int) {
if size <= 0 || size > 64 {
panic("ranksel: bit size must be in range [1,64]")
}
// Add bits
v.bits.Add(bits, size)
vlength := v.bits.Len()
// Increment popcount
popcnt := bit.PopCount(bits)
v.popcount += popcnt
// Update rank sampling
lenranks := len(v.ranks)
overflow := vlength - (lenranks * v.opts.Sr)
if overflow > 0 {
v.ranks = append(v.ranks, 0)
rank := bit.Rank(bits, size-overflow-1)
v.ranks[lenranks] = v.popcount - popcnt + rank
}
// Update select sampling
lenidx := len(v.indices)
overflow = v.popcount - (lenidx * v.opts.Ss)
if overflow > 0 {
v.indices = append(v.indices, 0)
sel := bit.Select(bits, popcnt-overflow+1)
v.indices[lenidx] = (vlength - size + sel) & ^0x3F
}
}
// Rank1 counts the number of 1s from
// the beginning up to the ith index.
func (v *BitVector) Rank1(i int) int {
if i >= v.bits.Len() {
panic("ranksel: index out of range")
}
j := i / v.opts.Sr
ip := (j * v.opts.Sr) >> 6
rank := v.ranks[j]
aidx := i & 63
bidx := i >> 6
vbits := v.bits.Bits()
for _, b := range vbits[ip:bidx] {
rank += bit.PopCount(b)
}
return rank + bit.Rank(vbits[bidx], aidx)
}