static long getSignificand(double d) {
    checkArgument(isFinite(d), "not a normal value");
    int exponent = getExponent(d);
    long bits = doubleToRawLongBits(d);
    bits &= SIGNIFICAND_MASK;
    return (exponent == MIN_EXPONENT - 1) ? bits << 1 : bits | IMPLICIT_BIT;
  }

  static boolean isFinite(double d) {
    return getExponent(d) <= MAX_EXPONENT;
  }

  static boolean isNormal(double d) {

		const halfMinusULP = (1 << (shift - 1)) - 1
		e -= bias
		bits += (halfMinusULP + (bits>>(shift-e))&1) >> e
		bits &^= fracMask >> e
	} else if e == bias-1 && bits&fracMask != 0 {
		// Round 0.5 < abs(x) < 1.
		bits = bits&signMask | uvone // +-1
	} else {
		// Round abs(x) <= 0.5 including denormals.
		bits &= signMask // +-0
	}
	return Float64frombits(bits)

	code := uint16(0)
	for n, bits := range bitCount {
		code <<= 1
		if n == 0 || bits == 0 {
			continue
		}
		// The literals list[len(list)-bits] .. list[len(list)-bits]
		// are encoded using "bits" bits, and get the values
		// code, code + 1, ....  The code values are
		// assigned in literal order (not frequency order).
		chunk := list[len(list)-int(bits):]

		h.lns.sort(chunk)

// So RotRight(x, k) == ⎣x/(2^k)⎦ <= ⎣a/(2^k)⎦
//
// If x does not end in k zero bits, then RotRight(x, k)
// has some non-zero bits in the k highest bits.
// ⎣x/(2^k)⎦ has all zeroes in the k highest bits,
// so RotRight(x, k) > ⎣x/(2^k)⎦
//
// Finally, if x > a and has k trailing zero bits, then RotRight(x, k) == ⎣x/(2^k)⎦

package zstd

import (
	"io"
	"math/bits"
)

// maxHuffmanBits is the largest possible Huffman table bits.
const maxHuffmanBits = 11

// readHuff reads Huffman table from data starting at off into table.
// Each entry in a Huffman table is a pair of bytes.
// The high byte is the encoded value. The low byte is the number
// of bits used to encode that value. We index into the table

		b.set(i)
		return
	}
	// Set bits [i, j].
	j := i + n - 1
	if i/64 == j/64 {
		b[i/64] |= ((uint64(1) << n) - 1) << (i % 64)
		return
	}
	_ = b[j/64]
	// Set leading bits.
	b[i/64] |= ^uint64(0) << (i % 64)
	for k := i/64 + 1; k < j/64; k++ {
		b[k] = ^uint64(0)
	}
	// Set trailing bits.
	b[j/64] |= (uint64(1) << (j%64 + 1)) - 1
}

// setAll sets all the bits of b.
func (b *pageBits) setAll() {

// Set adds fd to the set fds.
func (fds *FdSet) Set(fd int) {
	fds.Bits[fd/NFDBITS] |= (1 << (uintptr(fd) % NFDBITS))
}

// Clear removes fd from the set fds.
func (fds *FdSet) Clear(fd int) {
	fds.Bits[fd/NFDBITS] &^= (1 << (uintptr(fd) % NFDBITS))
}

// IsSet returns whether fd is in the set fds.
func (fds *FdSet) IsSet(fd int) bool {
	return fds.Bits[fd/NFDBITS]&(1<<(uintptr(fd)%NFDBITS)) != 0
}

	// Multiply mantissa by the digits and extract the upper two digits (hi, lo).
	z2hi, _ := bits.Mul64(z2, ix)
	z1hi, z1lo := bits.Mul64(z1, ix)
	z0lo := z0 * ix
	lo, c := bits.Add64(z1lo, z2hi, 0)
	hi, _ := bits.Add64(z0lo, z1hi, c)
	// The top 3 bits are j.
	j = hi >> 61
	// Extract the fraction and find its magnitude.
	hi = hi<<3 | lo>>61
	lz := uint(bits.LeadingZeros64(hi))
	e := uint64(bias - (lz + 1))

	"hash"
)

// New224 creates a new SHA3-224 hash.
// Its generic security strength is 224 bits against preimage attacks,
// and 112 bits against collision attacks.
func New224() hash.Hash {
	return new224()
}

// New256 creates a new SHA3-256 hash.
// Its generic security strength is 256 bits against preimage attacks,
// and 128 bits against collision attacks.
func New256() hash.Hash {
	return new256()
}

	if mask == 0 {
		return nil
	}

	// normalize the mask so that the set bits are left aligned
	o := bits.LeadingZeros64(^mask)
	mask = bits.RotateLeft64(mask, o)
	z := bits.LeadingZeros64(mask)
	mask = bits.RotateLeft64(mask, z)

	// check that the normalized mask is contiguous
	l := bits.LeadingZeros64(^mask)
	if l+bits.TrailingZeros64(mask) != 64 {
		return nil
	}