Esempio n. 1
0
func B64ToBigInt(in string, b *big.Int) (err os.Error) {
	bsize := base64.StdEncoding.DecodedLen(len(in))
	buff := make([]byte, bsize)
	n, err := base64.StdEncoding.Decode(buff, bytes.NewBufferString(in).Bytes())
	neg := false
	if err == nil {
		buff = buff[0:n]
		if buff[0]&0x80 == 0x80 {
			neg = true
			buff[0] &= 0x7f
		}
		b.SetBytes(buff)
		// In case the passed in big was negative...
		b.Abs(b)
		if neg {
			b.Neg(b)
		}
	}
	return
}
Esempio n. 2
0
// a.convertTo(t) converts the value of the analyzed expression a,
// which must be a constant, ideal number, to a new analyzed
// expression with a constant value of type t.
//
// TODO(austin) Rename to resolveIdeal or something?
func (a *expr) convertTo(t Type) *expr {
	if !a.t.isIdeal() {
		log.Panicf("attempted to convert from %v, expected ideal", a.t)
	}

	var rat *big.Rat

	// XXX(Spec)  The spec says "It is erroneous".
	//
	// It is an error to assign a value with a non-zero fractional
	// part to an integer, or if the assignment would overflow or
	// underflow, or in general if the value cannot be represented
	// by the type of the variable.
	switch a.t {
	case IdealFloatType:
		rat = a.asIdealFloat()()
		if t.isInteger() && !rat.IsInt() {
			a.diag("constant %v truncated to integer", rat.FloatString(6))
			return nil
		}
	case IdealIntType:
		i := a.asIdealInt()()
		rat = new(big.Rat).SetInt(i)
	default:
		log.Panicf("unexpected ideal type %v", a.t)
	}

	// Check bounds
	if t, ok := t.lit().(BoundedType); ok {
		if rat.Cmp(t.minVal()) < 0 {
			a.diag("constant %v underflows %v", rat.FloatString(6), t)
			return nil
		}
		if rat.Cmp(t.maxVal()) > 0 {
			a.diag("constant %v overflows %v", rat.FloatString(6), t)
			return nil
		}
	}

	// Convert rat to type t.
	res := a.newExpr(t, a.desc)
	switch t := t.lit().(type) {
	case *uintType:
		n, d := rat.Num(), rat.Denom()
		f := new(big.Int).Quo(n, d)
		f = f.Abs(f)
		v := uint64(f.Int64())
		res.eval = func(*Thread) uint64 { return v }
	case *intType:
		n, d := rat.Num(), rat.Denom()
		f := new(big.Int).Quo(n, d)
		v := f.Int64()
		res.eval = func(*Thread) int64 { return v }
	case *idealIntType:
		n, d := rat.Num(), rat.Denom()
		f := new(big.Int).Quo(n, d)
		res.eval = func() *big.Int { return f }
	case *floatType:
		n, d := rat.Num(), rat.Denom()
		v := float64(n.Int64()) / float64(d.Int64())
		res.eval = func(*Thread) float64 { return v }
	case *idealFloatType:
		res.eval = func() *big.Rat { return rat }
	default:
		log.Panicf("cannot convert to type %T", t)
	}

	return res
}