chore: vendor

vendor/github.com/cloudflare/circl/math/mlsbset/power.go

@@ -0,0 +1,64 @@
+package mlsbset
+
+import "fmt"
+
+// Power is a valid exponent produced by the MLSBSet encoding algorithm.
+type Power struct {
+	set Encoder // parameters of code.
+	s   []int32 // set of signs.
+	b   []int32 // set of digits.
+	c   int     // carry is {0,1}.
+}
+
+// Exp is calculates x^k, where x is a predetermined element of a group G.
+func (p *Power) Exp(G Group) EltG {
+	a, b := G.Identity(), G.NewEltP()
+	for e := int(p.set.p.E - 1); e >= 0; e-- {
+		G.Sqr(a)
+		for v := uint(0); v < p.set.p.V; v++ {
+			sgnElt, idElt := p.Digit(v, uint(e))
+			G.Lookup(b, v, sgnElt, idElt)
+			G.Mul(a, b)
+		}
+	}
+	if p.set.IsExtended() && p.c == 1 {
+		G.Mul(a, G.ExtendedEltP())
+	}
+	return a
+}
+
+// Digit returns the (v,e)-th digit and its sign.
+func (p *Power) Digit(v, e uint) (sgn, dig int32) {
+	sgn = p.bit(0, v, e)
+	dig = 0
+	for i := p.set.p.W - 1; i > 0; i-- {
+		dig = 2*dig + p.bit(i, v, e)
+	}
+	mask := dig >> 31
+	dig = (dig + mask) ^ mask
+	return sgn, dig
+}
+
+// bit returns the (w,v,e)-th bit of the code.
+func (p *Power) bit(w, v, e uint) int32 {
+	if !(w < p.set.p.W &&
+		v < p.set.p.V &&
+		e < p.set.p.E) {
+		panic(fmt.Errorf("indexes outside (%v,%v,%v)", w, v, e))
+	}
+	if w == 0 {
+		return p.s[p.set.p.E*v+e]
+	}
+	return p.b[p.set.p.D*(w-1)+p.set.p.E*v+e]
+}
+
+func (p *Power) String() string {
+	dig := ""
+	for j := uint(0); j < p.set.p.V; j++ {
+		for i := uint(0); i < p.set.p.E; i++ {
+			s, d := p.Digit(j, i)
+			dig += fmt.Sprintf("(%2v,%2v) = %+2v %+2v\n", j, i, s, d)
+		}
+	}
+	return fmt.Sprintf("len: %v\ncarry: %v\ndigits:\n%v", len(p.b)+len(p.s), p.c, dig)
+}