Golang Int.Sub方法代码示例

// ProbablyPrimeBigInt returns true if n is prime or n is a pseudoprime to base
// a. It implements the Miller-Rabin primality test for one specific value of
// 'a' and k == 1.  See also ProbablyPrimeUint32.
func ProbablyPrimeBigInt(n, a *big.Int) bool {
	var d big.Int
	d.Set(n)
	d.Sub(&d, _1) // d <- n-1
	s := 0
	for ; d.Bit(s) == 0; s++ {
	}
	nMinus1 := big.NewInt(0).Set(&d)
	d.Rsh(&d, uint(s))

	x := ModPowBigInt(a, &d, n)
	if x.Cmp(_1) == 0 || x.Cmp(nMinus1) == 0 {
		return true
	}

	for ; s > 1; s-- {
		if x = x.Mod(x.Mul(x, x), n); x.Cmp(_1) == 0 {
			return false
		}

		if x.Cmp(nMinus1) == 0 {
			return true
		}
	}
	return false
}

func q2() {
	n := new(big.Int)
	a := new(big.Int)
	asquared := new(big.Int)
	one := new(big.Int)
	x := new(big.Int)
	xsquared := new(big.Int)
	p := new(big.Int)
	q := new(big.Int)
	candidate := new(big.Int)

	n.SetString("648455842808071669662824265346772278726343720706976263060439070378797308618081116462714015276061417569195587321840254520655424906719892428844841839353281972988531310511738648965962582821502504990264452100885281673303711142296421027840289307657458645233683357077834689715838646088239640236866252211790085787877", 10)
	one.SetString("1", 10)

	a = mathutil.SqrtBig(n)
	for {
		a.Add(a, one)
		asquared.Mul(a, a)
		xsquared.Sub(asquared, n)
		x = mathutil.SqrtBig(xsquared)
		p.Sub(a, x)
		q.Add(a, x)
		if candidate.Mul(p, q).Cmp(n) == 0 {
			fmt.Println(p.String())
			break
		}
	}
}

// CalcGasLimit computes the gas limit of the next block after parent.
// The result may be modified by the caller.
// This is miner strategy, not consensus protocol.
func CalcGasLimit(parent *types.Block) *big.Int {
	// contrib = (parentGasUsed * 3 / 2) / 1024
	contrib := new(big.Int).Mul(parent.GasUsed(), big.NewInt(3))
	contrib = contrib.Div(contrib, big.NewInt(2))
	contrib = contrib.Div(contrib, params.GasLimitBoundDivisor)

	// decay = parentGasLimit / 1024 -1
	decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
	decay.Sub(decay, big.NewInt(1))

	/*
		strategy: gasLimit of block-to-mine is set based on parent's
		gasUsed value.  if parentGasUsed > parentGasLimit * (2/3) then we
		increase it, otherwise lower it (or leave it unchanged if it's right
		at that usage) the amount increased/decreased depends on how far away
		from parentGasLimit * (2/3) parentGasUsed is.
	*/
	gl := new(big.Int).Sub(parent.GasLimit(), decay)
	gl = gl.Add(gl, contrib)
	gl.Set(common.BigMax(gl, params.MinGasLimit))

	// however, if we're now below the target (TargetGasLimit) we increase the
	// limit as much as we can (parentGasLimit / 1024 -1)
	if gl.Cmp(params.TargetGasLimit) < 0 {
		gl.Add(parent.GasLimit(), decay)
		gl.Set(common.BigMin(gl, params.TargetGasLimit))
	}
	return gl
}

// polyPowMod computes ``f**n`` in ``GF(p)[x]/(g)`` using repeated squaring.
// Given polynomials ``f`` and ``g`` in ``GF(p)[x]`` and a non-negative
// integer ``n``, efficiently computes ``f**n (mod g)`` i.e. the remainder
// of ``f**n`` from division by ``g``, using the repeated squaring algorithm.
// This function was ported from sympy.polys.galoistools.
func polyPowMod(f *Poly, n *big.Int, g *Poly) (h *Poly, err error) {
	zero := big.NewInt(int64(0))
	one := big.NewInt(int64(1))
	n = big.NewInt(int64(0)).Set(n)
	if n.BitLen() < 3 {
		// Small values of n not useful for recon
		err = powModSmallN
		return
	}
	h = NewPoly(Zi(f.p, 1))
	for {
		if n.Bit(0) > 0 {
			h = NewPoly().Mul(h, f)
			h, err = PolyMod(h, g)
			if err != nil {
				return
			}
			n.Sub(n, one)
		}
		n.Rsh(n, 1)
		if n.Cmp(zero) == 0 {
			break
		}
		f = NewPoly().Mul(f, f)
		f, err = PolyMod(f, g)
		if err != nil {
			return
		}
	}
	return
}

func main() {
	var s string
	var n, two, tmp big.Int
	two.SetInt64(2)

	in, _ := os.Open("10519.in")
	defer in.Close()
	out, _ := os.Create("10519.out")
	defer out.Close()

	for {
		if _, err := fmt.Fscanf(in, "%s", &s); err != nil {
			break
		}
		if s == "0" {
			fmt.Fprintln(out, 1)
			continue
		}
		n.SetString(s, 10)
		tmp.Mul(&n, &n)
		tmp.Sub(&tmp, &n)
		tmp.Add(&tmp, &two)
		fmt.Fprintln(out, &tmp)
	}
}

func (block *Block) PayFee(addr []byte, fee *big.Int) bool {
	contract := block.state.GetContract(addr)
	// If we can't pay the fee return
	if contract == nil || contract.Amount.Cmp(fee) < 0 /* amount < fee */ {
		fmt.Println("Contract has insufficient funds", contract.Amount, fee)

		return false
	}

	base := new(big.Int)
	contract.Amount = base.Sub(contract.Amount, fee)
	block.state.trie.Update(string(addr), string(contract.RlpEncode()))

	data := block.state.trie.Get(string(block.Coinbase))

	// Get the ether (Coinbase) and add the fee (gief fee to miner)
	ether := NewAccountFromData([]byte(data))

	base = new(big.Int)
	ether.Amount = base.Add(ether.Amount, fee)

	block.state.trie.Update(string(block.Coinbase), string(ether.RlpEncode()))

	return true
}

// signRFC6979 generates a deterministic ECDSA signature according to RFC 6979
// and BIP 62.
func signRFC6979(privateKey *PrivateKey, hash []byte) (*Signature, error) {

	privkey := privateKey.ToECDSA()
	N := order
	k := NonceRFC6979(privkey.D, hash, nil, nil)
	inv := new(big.Int).ModInverse(k, N)
	r, _ := privkey.Curve.ScalarBaseMult(k.Bytes())
	if r.Cmp(N) == 1 {
		r.Sub(r, N)
	}

	if r.Sign() == 0 {
		return nil, errors.New("calculated R is zero")
	}

	e := hashToInt(hash, privkey.Curve)
	s := new(big.Int).Mul(privkey.D, r)
	s.Add(s, e)
	s.Mul(s, inv)
	s.Mod(s, N)

	if s.Cmp(halforder) == 1 {
		s.Sub(N, s)
	}
	if s.Sign() == 0 {
		return nil, errors.New("calculated S is zero")
	}
	return &Signature{R: r, S: s}, nil
}

func (d *DHTNode) lookup(hash string) *DHTNode {

	if between([]byte(d.id), []byte(d.successor.id), []byte(hash)) {
		return d
	}

	dist := distance(d.id, hash, len(d.finger))
	index := dist.BitLen() - 1
	if index < 0 {
		return d
	}
	fmt.Println("INDEX", index)

	// scroll down until your finger is not pointing at himself
	for ; index > 0 && d.finger[index].node == d; index-- {

	}
	// Viewing so we do not end up too far
	diff := big.Int{}
	diff.Sub(dist, distance(d.id, d.finger[index].node.id, len(d.finger)))
	for index > 0 && diff.Sign() < 0 {
		index--
		diff.Sub(dist, distance(d.id, d.finger[index].node.id, len(d.finger)))
	}
	//check so we do not point at ourselves
	if d.finger[index].node == d || diff.Sign() < 0 {
		fmt.Println("ERROR ERROR alles gebort auf the baut")
		return d.successor.lookup(hash)

	}

	return d.finger[index].node.lookup(hash)

	//	return d.successor.lookup(hash)
}

func (d *DatasourceDerive) CalculatePdpPrep(newValue string, interval float64) (float64, error) {
	if float64(d.Heartbeat) < interval {
		d.LastValue = Undefined
	}

	rate := math.NaN()
	newPdp := math.NaN()
	if newValue != Undefined && float64(d.Heartbeat) >= interval {
		newInt := new(big.Int)
		_, err := fmt.Sscan(newValue, newInt)
		if err != nil {
			return math.NaN(), errors.Errorf("not a simple signed integer: %s", newValue)
		}
		if d.LastValue != "U" {
			prevInt := new(big.Int)
			_, err := fmt.Sscan(d.LastValue, prevInt)
			if err != nil {
				return math.NaN(), errors.Wrap(err, 0)
			}
			diff := new(big.Int)
			diff.Sub(newInt, prevInt)

			newPdp = float64(diff.Uint64())
			rate = newPdp / interval
		}
	}

	if !d.checkRateBounds(rate) {
		newPdp = math.NaN()
	}

	d.LastValue = newValue

	return newPdp, nil
}

// ComputeKey computes the session key given the salt and the value of B.
func (cs *ClientSession) ComputeKey(salt, B []byte) ([]byte, error) {
	cs.salt = salt

	err := cs.setB(B)
	if err != nil {
		return nil, err
	}

	// x = H(s, p)                 (user enters password)
	x := new(big.Int).SetBytes(cs.SRP.KeyDerivationFunc(cs.salt, cs.password))

	// S = (B - kg^x) ^ (a + ux)   (computes session key)
	// t1 = g^x
	t1 := new(big.Int).Exp(cs.SRP.Group.Generator, x, cs.SRP.Group.Prime)
	// unblind verifier
	t1.Sub(cs.SRP.Group.Prime, t1)
	t1.Mul(cs.SRP._k, t1)
	t1.Add(t1, cs._B)
	t1.Mod(t1, cs.SRP.Group.Prime)

	// t2 = ux
	t2 := new(big.Int).Mul(cs._u, x)
	// t2 = a + ux
	t2.Add(cs._a, t2)

	// t1 = (B - kg^x) ^ (a + ux)
	t3 := new(big.Int).Exp(t1, t2, cs.SRP.Group.Prime)
	// K = H(S)
	cs.key = quickHash(cs.SRP.HashFunc, t3.Bytes())

	return cs.key, nil
}

// decBigInt2C sets the value of n to the big-endian two's complement
// value stored in the given data. If data[0]&80 != 0, the number
// is negative. If data is empty, the result will be 0.
func decBigInt2C(data []byte) *big.Int {
	n := new(big.Int).SetBytes(data)
	if len(data) > 0 && data[0]&0x80 > 0 {
		n.Sub(n, new(big.Int).Lsh(bigOne, uint(len(data))*8))
	}
	return n
}

// Try to generate a point on this curve from a chosen x-coordinate,
// with a random sign.
func (p *curvePoint) genPoint(x *big.Int, rand cipher.Stream) bool {

	// Compute the corresponding Y coordinate, if any
	y2 := new(big.Int).Mul(x, x)
	y2.Mul(y2, x)
	threeX := new(big.Int).Lsh(x, 1)
	threeX.Add(threeX, x)
	y2.Sub(y2, threeX)
	y2.Add(y2, p.c.p.B)
	y2.Mod(y2, p.c.p.P)
	y := p.c.sqrt(y2)

	// Pick a random sign for the y coordinate
	b := make([]byte, 1)
	rand.XORKeyStream(b, b)
	if (b[0] & 0x80) != 0 {
		y.Sub(p.c.p.P, y)
	}

	// Check that it's a valid point
	y2t := new(big.Int).Mul(y, y)
	y2t.Mod(y2t, p.c.p.P)
	if y2t.Cmp(y2) != 0 {
		return false // Doesn't yield a valid point!
	}

	p.x = x
	p.y = y
	return true
}

func (self *Decoder) unsigned_to_signed(x *big.Int, bits uint) *big.Int {
	// return x - ((x >> (bits - 1)) << bits)
	temp := new(big.Int)
	temp.Rsh(x, bits-1)
	temp.Lsh(temp, bits)
	return temp.Sub(x, temp)
}

func makeBigInt(n *big.Int) (encoder, error) {
	if n == nil {
		return nil, StructuralError{"empty integer"}
	}

	if n.Sign() < 0 {
		// A negative number has to be converted to two's-complement
		// form. So we'll invert and subtract 1. If the
		// most-significant-bit isn't set then we'll need to pad the
		// beginning with 0xff in order to keep the number negative.
		nMinus1 := new(big.Int).Neg(n)
		nMinus1.Sub(nMinus1, bigOne)
		bytes := nMinus1.Bytes()
		for i := range bytes {
			bytes[i] ^= 0xff
		}
		if len(bytes) == 0 || bytes[0]&0x80 == 0 {
			return multiEncoder([]encoder{byteFFEncoder, bytesEncoder(bytes)}), nil
		}
		return bytesEncoder(bytes), nil
	} else if n.Sign() == 0 {
		// Zero is written as a single 0 zero rather than no bytes.
		return byte00Encoder, nil
	} else {
		bytes := n.Bytes()
		if len(bytes) > 0 && bytes[0]&0x80 != 0 {
			// We'll have to pad this with 0x00 in order to stop it
			// looking like a negative number.
			return multiEncoder([]encoder{byte00Encoder, bytesEncoder(bytes)}), nil
		}
		return bytesEncoder(bytes), nil
	}
}

// privateEncrypt implements OpenSSL's RSA_private_encrypt function
func privateEncrypt(key *rsa.PrivateKey, data []byte) (enc []byte, err error) {
	k := (key.N.BitLen() + 7) / 8
	tLen := len(data)

	// rfc2313, section 8:
	// The length of the data D shall not be more than k-11 octets
	if tLen > k-11 {
		err = errors.New("Data too long")
		return
	}
	em := make([]byte, k)
	em[1] = 1
	for i := 2; i < k-tLen-1; i++ {
		em[i] = 0xff
	}
	copy(em[k-tLen:k], data)
	c := new(big.Int).SetBytes(em)
	if c.Cmp(key.N) > 0 {
		err = nil
		return
	}
	var m *big.Int
	var ir *big.Int
	if key.Precomputed.Dp == nil {
		m = new(big.Int).Exp(c, key.D, key.N)
	} else {
		// We have the precalculated values needed for the CRT.
		m = new(big.Int).Exp(c, key.Precomputed.Dp, key.Primes[0])
		m2 := new(big.Int).Exp(c, key.Precomputed.Dq, key.Primes[1])
		m.Sub(m, m2)
		if m.Sign() < 0 {
			m.Add(m, key.Primes[0])
		}
		m.Mul(m, key.Precomputed.Qinv)
		m.Mod(m, key.Primes[0])
		m.Mul(m, key.Primes[1])
		m.Add(m, m2)

		for i, values := range key.Precomputed.CRTValues {
			prime := key.Primes[2+i]
			m2.Exp(c, values.Exp, prime)
			m2.Sub(m2, m)
			m2.Mul(m2, values.Coeff)
			m2.Mod(m2, prime)
			if m2.Sign() < 0 {
				m2.Add(m2, prime)
			}
			m2.Mul(m2, values.R)
			m.Add(m, m2)
		}
	}

	if ir != nil {
		// Unblind.
		m.Mul(m, ir)
		m.Mod(m, key.N)
	}
	enc = m.Bytes()
	return
}