first commit

pkg/rand/rand.go

@@ -0,0 +1,80 @@
+package rand
+
+import (
+	"crypto/rand"
+)
+
+var (
+	// stdSource standard source string.
+	stdSource = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+	// stdNumberSource standard number source string.
+	stdNumberSource = "0123456789"
+
+	// 16
+	std16Source = "0123456789abcdef"
+)
+
+// StdSource returns standard source string.
+func StdSource() string {
+	return stdSource
+}
+
+// StdNumberSource returns standard number source string.
+func StdNumberSource() string {
+	return stdNumberSource
+}
+
+func Std16Source() string {
+	return std16Source
+}
+
+// NewString returns a new random string of the provided length, consisting
+// of the standard source string.
+// It panics if source length is wrong (<1 or >256) or rand.Read occurs an error.
+func NewString(length int) string {
+	return NewWithSource(length, StdSource())
+}
+
+// NewNumber returns a new random string of the provided length, consisting
+// of the standard number source string.
+// It panics if source length is wrong (<1 or >256) or rand.Read occurs an error.
+func NewNumber(length int) string {
+	return NewWithSource(length, StdNumberSource())
+}
+
+// NewWithSource returns a new random string of the provided length, consisting
+// of the provided source string.
+// It panics if source length is wrong (<1 or >256) or rand.Read occurs an error.
+func NewWithSource(length int, source string) string {
+	if length == 0 {
+		return ""
+	}
+	sl := len(source)
+	if sl < 1 || sl > 256 {
+		panic("rand: wrong source length")
+	}
+	rbMax := 255 - (256 % sl)
+	b := make([]byte, length)
+	r := make([]byte, length+length/2) // storage for random bytes
+	i := 0
+	for {
+		if _, err := rand.Read(r); err != nil {
+			panic(err)
+		}
+		for _, rb := range r {
+			v := int(rb)
+			if v > rbMax { // skip to avoid modulo bias
+				continue
+			}
+			b[i] = source[v%sl]
+			i++
+			if i == length {
+				return string(b)
+			}
+		}
+	}
+}
+
+func NewAESKey256() string {
+	return NewWithSource(32, Std16Source())
+}