Initial commit.

uniuri.go

@@ -0,0 +1,55 @@
+// Package uniuri generates random strings good for use in URIs to identify
+// unique objects.
+//
+// Example usage:
+//
+//	s := uniuri.New() // s is now "apHCJBl7L1OmC57n"
+//
+// A standard string created by New() is 16 bytes in length and consists of
+// Latin upper and lowercase letters, and numbers (from the set of 62 allowed
+// characters), which means that it has ~95 bits of entropy. To get more
+// entropy, you can use NewLen(UUIDLen), which returns 20-byte string, giving
+// ~119 bits of entropy, or any other desired length.
+//
+// Functions read from crypto/rand random source, and panic if they fail to
+// read from it.
+package uniuri
+
+import "crypto/rand"
+
+const (
+	// Standard length of uniuri string to achive ~95 bits of entropy.
+	StdLen = 16
+	// Length of uniurl string to achive ~119 bits of entropy, closest
+	// to what can be losslessly converted to UUIDv4 (122 bits).
+	UUIDLen = 20
+)
+
+// Standard characters allowed in uniuri string.
+var StdChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890")
+
+// New returns a new random string with the standard length and standard
+// characters.
+func New() string {
+	return NewLenChars(StdLen, StdChars)
+}
+
+// NewLen returns a new random string with the provided length and standard
+// characters.
+func NewLen(length int) string {
+	return NewLenChars(length, StdChars)
+}
+
+// NewLenChars returns a new random string with the provided length and byte
+// slice of allowed characters (maximum 256).
+func NewLenChars(length int, chars []byte) string {
+	b := make([]byte, length)
+	if _, err := rand.Reader.Read(b); err != nil {
+		panic("error reading from random source: " + err.String())
+	}
+	alen := byte(len(chars))
+	for i, c := range b {
+		b[i] = chars[c%alen]
+	}
+	return string(b)
+}