// 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(),

	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 {

	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)

			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)
				}
			}

}

// readLSB returns the next code for "Least Significant Bits first" data.
func (r *Reader) readLSB() (uint16, error) {
	for r.nBits < r.width {
		x, err := r.r.ReadByte()
		if err != nil {
			return 0, err
		}
		r.bits |= uint32(x) << r.nBits
		r.nBits += 8
	}
	code := uint16(r.bits & (1<<r.width - 1))
	r.bits >>= r.width
	r.nBits -= r.width
	return code, nil
}

	// R_ARM64_LDST8 sets a LD/ST immediate value to bits [11:0] of a local address.
	R_ARM64_LDST8

	// R_ARM64_LDST16 sets a LD/ST immediate value to bits [11:1] of a local address.
	R_ARM64_LDST16

	// R_ARM64_LDST32 sets a LD/ST immediate value to bits [11:2] of a local address.
	R_ARM64_LDST32

	// R_ARM64_LDST64 sets a LD/ST immediate value to bits [11:3] of a local address.
	R_ARM64_LDST64

// trailing CCC shifted left 2 bits. The two least-significant bits of tccc
// are the number of trailing non-starters.

const (
	qcInfoMask      = 0x3F // to clear all but the relevant bits in a qcInfo
	headerLenMask   = 0x3F // extract the length value from the header byte
	headerFlagsMask = 0xC0 // extract the qcInfo bits from the header byte
)

 *
 * ```
 *  0..63 : Length of the UTF-16 sequence that this range maps to. The offset is b2b3.
 * 64..79 : Offset by a fixed negative offset. The bottom 4 bits of b1 are the top 4 bits of the offset.
 * 80..95 : Offset by a fixed positive offset. The bottom 4 bits of b1 are the top 4 bits of the offset.
 *    119 : Ignored.
 *    120 : Valid.
 *    121 : Disallowed
 *    122 : Mapped inline to the sequence: [b2].

		return nil, errors.New("edwards25519: invalid field element input size")
	}

	// Bits 0:51 (bytes 0:8, bits 0:64, shift 0, mask 51).
	v.l0 = byteorder.LeUint64(x[0:8])
	v.l0 &= maskLow51Bits
	// Bits 51:102 (bytes 6:14, bits 48:112, shift 3, mask 51).
	v.l1 = byteorder.LeUint64(x[6:14]) >> 3
	v.l1 &= maskLow51Bits
	// Bits 102:153 (bytes 12:20, bits 96:160, shift 6, mask 51).
	v.l2 = byteorder.LeUint64(x[12:20]) >> 6