var p Bits
	for _, x := range x {
		for _, y := range y {
			p = append(p, x+y)
		}
	}
	return p
}

func TestMulBits(t *testing.T) {
	for _, test := range []struct {
		x, y, want Bits
	}{
		{nil, nil, nil},
		{Bits{}, Bits{}, nil},
		{Bits{0}, Bits{0}, Bits{0}},
		{Bits{0}, Bits{1}, Bits{1}},
		{Bits{1}, Bits{1, 2, 3}, Bits{2, 3, 4}},
		{Bits{-1}, Bits{1}, Bits{0}},

		d = a + bits.RotateLeft32((a^b^c)+d+x4+0x4bdecfa9, 11)
		c = d + bits.RotateLeft32((d^a^b)+c+x7+0xf6bb4b60, 16)
		b = c + bits.RotateLeft32((c^d^a)+b+xa+0xbebfbc70, 23)
		a = b + bits.RotateLeft32((b^c^d)+a+xd+0x289b7ec6, 4)
		d = a + bits.RotateLeft32((a^b^c)+d+x0+0xeaa127fa, 11)
		c = d + bits.RotateLeft32((d^a^b)+c+x3+0xd4ef3085, 16)
		b = c + bits.RotateLeft32((c^d^a)+b+x6+0x04881d05, 23)

}

// uint128 holds a 128-bit number as two 64-bit limbs, for use with the
// bits.Mul64 and bits.Add64 intrinsics.
type uint128 struct {
	lo, hi uint64
}

func mul64(a, b uint64) uint128 {
	hi, lo := bits.Mul64(a, b)
	return uint128{lo, hi}
}

func add128(a, b uint128) uint128 {
	lo, c := bits.Add64(a.lo, b.lo, 0)
	hi, c := bits.Add64(a.hi, b.hi, c)
	if c != 0 {
		panic("poly1305: unexpected overflow")
	}

  private final int bits;
  private final String toString;

  ChecksumHashFunction(
      ImmutableSupplier<? extends Checksum> checksumSupplier, int bits, String toString) {
    this.checksumSupplier = checkNotNull(checksumSupplier);
    checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits);
    this.bits = bits;
    this.toString = checkNotNull(toString);
  }

// 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)⎦

		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() {

	"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()
}

	a[2] = a[1] & bits.RotateLeft64(a[0], 13)
	// arm64: "ORR\tR[0-9]+@>51, R[0-9]+, R[0-9]+"
	a[5] = a[4] | bits.RotateLeft64(a[3], 13)
	// arm64: "EOR\tR[0-9]+@>51, R[0-9]+, R[0-9]+"
	a[8] = a[7] ^ bits.RotateLeft64(a[6], 13)
	// arm64: "MVN\tR[0-9]+@>51, R[0-9]+"
	a[10] = ^bits.RotateLeft64(a[9], 13)
	// arm64: "BIC\tR[0-9]+@>51, R[0-9]+, R[0-9]+"
	a[13] = a[12] &^ bits.RotateLeft64(a[11], 13)

    /**
     * Sets {@code numHashFunctions} bits of the given bit array, by hashing a user element.
     *
     * <p>Returns whether any bits changed as a result of this operation.
     */
    <T extends @Nullable Object> boolean put(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits);

    /**

	// n must always be a multiple of 8, since gcBits is
	// always rounded up 8 bytes.
	for _, n := range []int{8, 16, 32, 64, 128} {
		b.Run(fmt.Sprintf("bits=%d", n*8), func(b *testing.B) {
			// Initialize a new byte slice with pseduo-random data.
			bits := make([]byte, n)
			rand.Read(bits)

			b.ResetTimer()
			for i := 0; i < b.N; i++ {
				runtime.MSpanCountAlloc(s, bits)
			}
		})
	}
}