// It does not allocate. Unlike [Addr.Prefix], [PrefixFrom] does not mask
// off the host bits of ip.
//
// If bits is less than zero or greater than ip.BitLen, [Prefix.Bits]
// will return an invalid value -1.
func PrefixFrom(ip Addr, bits int) Prefix {
	var bitsPlusOne uint8
	if !ip.isZero() && bits >= 0 && bits <= ip.BitLen() {
		bitsPlusOne = uint8(bits) + 1
	}
	return Prefix{
		ip:          ip.withoutZone(),

// call. Bits are numbered in big endian order so the
// leftmost bit (the MSB) is at index 0.
type queryResult struct {
	bits [2]uint64
}

// Has reports whether the given functions are present.
func (q *queryResult) Has(fns ...function) bool {
	if len(fns) == 0 {
		panic("no function codes provided")
	}
	for _, f := range fns {
		if !bitIsSet(q.bits[:], uint(f)) {
			return false
		}
	}

const m1 = 0x3333333333333333 // 00110011 ...
const m2 = 0x0f0f0f0f0f0f0f0f // 00001111 ...

// OnesCount64 returns the number of one bits ("population count") in x.
func OnesCount64(x uint64) int {
	// Implementation: Parallel summing of adjacent bits.
	// See "Hacker's Delight", Chap. 5: Counting Bits.
	// The following pattern shows the general approach:
	//
	//   x = x>>1&(m0&m) + x&(m0&m)
	//   x = x>>2&(m1&m) + x&(m1&m)

// Bits are numbered in big endian order so the
// leftmost bit (the MSB) is at index 0.
type facilityList struct {
	bits [4]uint64
}

// Has reports whether the given facilities are present.
func (s *facilityList) Has(fs ...facility) bool {
	if len(fs) == 0 {
		panic("no facility bits provided")
	}
	for _, f := range fs {
		if !bitIsSet(s.bits[:], uint(f)) {
			return false
		}
	}

	return p
}

// CIDRMask returns an [IPMask] consisting of 'ones' 1 bits
// followed by 0s up to a total length of 'bits' bits.
// For a mask of this form, CIDRMask is the inverse of [IPMask.Size].
func CIDRMask(ones, bits int) IPMask {
	if bits != 8*IPv4len && bits != 8*IPv6len {
		return nil
	}
	if ones < 0 || ones > bits {
		return nil
	}
	l := bits / 8
	m := make(IPMask, l)
	n := uint(ones)
	for i := 0; i < l; i++ {

	//
	// We want to compute
	// 	hi, lo := bits.Mul64(r.Uint64(), n)
	// In terms of 32-bit halves, this is:
	// 	x1:x0 := r.Uint64()
	// 	0:hi, lo1:lo0 := bits.Mul64(x1:x0, 0:n)
	// Writing out the multiplication in terms of bits.Mul32 allows
	// using direct hardware instructions and avoiding
	// the computations involving these zeros.
	x := r.Uint64()
	lo1a, lo0 := bits.Mul32(uint32(x), n)

	fixedOnce.Do(func() {
		// These come from the RFC section 3.2.6.
		var bits [288]int
		for i := 0; i < 144; i++ {
			bits[i] = 8
		}
		for i := 144; i < 256; i++ {
			bits[i] = 9
		}
		for i := 256; i < 280; i++ {
			bits[i] = 7
		}
		for i := 280; i < 288; i++ {
			bits[i] = 8
		}
		fixedHuffmanDecoder.init(bits[:])
	})
}

func (f *decompressor) Reset(r io.Reader, dict []byte) error {

			if err != nil {
				t.Fatal(err)
			}
			if prefix.Addr() != test.ip {
				t.Errorf("IP=%s, want %s", prefix.Addr(), test.ip)
			}
			if prefix.Bits() != test.bits {
				t.Errorf("bits=%d, want %d", prefix.Bits(), test.bits)
			}
			for _, ip := range test.contains {
				if !prefix.Contains(ip) {
					t.Errorf("does not contain %s", ip)
				}
			}

 * the operation and the desired access bits are compared to the SID
 * and access mask of each ACE. If the SID matches, the allow/deny flags
 * and access mask are considered. If the ACE is a "deny"
 * ACE and <i>any</i> of the desired access bits match bits in the access
 * mask of the ACE, the whole access check fails. If the ACE is an "allow"
 * ACE and <i>all</i> of the bits in the desired access bits match bits in

public abstract class HashCode {
  HashCode() {}

  /** Returns the number of bits in this hash code; a positive multiple of 8. */
  public abstract int bits();

  /**
   * Returns the first four bytes of {@linkplain #asBytes() this hashcode's bytes}, converted to an
   * {@code int} value in little-endian order.
   *
   * @throws IllegalStateException if {@code bits() < 32}
   */
  public abstract int asInt();

  /**