➕ Added password validator

vendor/github.com/lane-c-wagner/go-password-validator/entropy.go

@@ -0,0 +1,47 @@
+package passwordvalidator
+
+import (
+	"math"
+)
+
+// GetEntropy returns the entropy in bits for the given password
+// See the ReadMe for more information
+func GetEntropy(password string) float64 {
+	return getEntropy(password)
+}
+
+func getEntropy(password string) float64 {
+	base := getBase(password)
+	length := getLength(password)
+
+	// calculate log2(base^length)
+	return logPow(float64(base), length, 2)
+}
+
+func logX(base, n float64) float64 {
+	if base == 0 {
+		return 0
+	}
+	// change of base formulae
+	return math.Log2(n) / math.Log2(base)
+}
+
+func logBaseTo2(base, n float64) float64 {
+	if base == 0 {
+		return 0
+	}
+	// change of base formulae
+	return math.Log2(n) / math.Log2(base)
+}
+
+// logPow calculates log_base(x^y)
+// without leaving logspace for each multiplication step
+// this makes it take less space in memory
+func logPow(expBase float64, pow int, logBase float64) float64 {
+	// logb (MN) = logb M + logb N
+	total := 0.0
+	for i := 0; i < pow; i++ {
+		total += logX(logBase, expBase)
+	}
+	return total
+}