formalize token munging code

irc/utils/crypto_test.go

@@ -47,8 +47,37 @@ func TestTokenCompare(t *testing.T) {
 	}
 }
 
+func TestMunging(t *testing.T) {
+	count := 131072
+	set := make(map[string]bool)
+	var token string
+	for i := 0; i < count; i++ {
+		token = GenerateSecretToken()
+		set[token] = true
+	}
+	// all tokens generated thus far should be unique
+	assertEqual(len(set), count, t)
+
+	// iteratively munge the last generated token an additional `count` times
+	mungedToken := token
+	for i := 0; i < count; i++ {
+		mungedToken = MungeSecretToken(mungedToken)
+		assertEqual(len(mungedToken), len(token), t)
+		set[mungedToken] = true
+	}
+	// munged tokens should not collide with generated tokens, or each other
+	assertEqual(len(set), count*2, t)
+}
+
 func BenchmarkGenerateSecretToken(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		GenerateSecretToken()
 	}
 }
+
+func BenchmarkMungeSecretToken(b *testing.B) {
+	t := GenerateSecretToken()
+	for i := 0; i < b.N; i++ {
+		t = MungeSecretToken(t)
+	}
+}