From 2170058ef98bc1e5186780d59e0a4512ef4b7cce Mon Sep 17 00:00:00 2001
From: Kevin Atkinson <k@kevina.org>
Date: Fri, 31 Aug 2018 18:17:03 -0400
Subject: [PATCH] Add CheckEncoding function.

---
 encoder.go      | 21 +++++++++++++++------
 encoder_test.go |  7 +++++++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/encoder.go b/encoder.go
index 9323b57..f4d35a1 100644
--- a/encoder.go
+++ b/encoder.go
@@ -10,17 +10,26 @@ type Encoder struct {
 	enc Encoding
 }
 
-// NewEncoder create a new Encoder from an Encoding.  It will panic is
-// the encoding is invalid.  To check for a valid encoding use the
-// EncodingToStr map.
+// NewEncoder create a new Encoder from an Encoding.  It will panic if
+// the encoding is invalid.  To check for a valid encoding use
+// CheckEncoding.
 func NewEncoder(base Encoding) Encoder {
-	_, ok := EncodingToStr[base]
-	if !ok {
-		panic(fmt.Errorf("Unsupported multibase encoding: %d", base))
+	err := CheckEncoding(base)
+	if err != nil {
+		panic(err)
 	}
 	return Encoder{base}
 }
 
+// CheckEncoding checks that an encoding is valid
+func CheckEncoding(base Encoding) error {
+	_, ok := EncodingToStr[base]
+	if !ok {
+		return fmt.Errorf("Unsupported multibase encoding: %d", base)
+	}
+	return nil
+}
+
 // EncoderByName creates an encoder from a string, the string can
 // either be the multibase name or single character multibase prefix
 func EncoderByName(str string) (Encoder, error) {
diff --git a/encoder_test.go b/encoder_test.go
index 6274e44..39f1009 100644
--- a/encoder_test.go
+++ b/encoder_test.go
@@ -4,6 +4,13 @@ import (
 	"testing"
 )
 
+func TestInvalidEncoding(t *testing.T) {
+	err := CheckEncoding(Encoding('q'))
+	if err == nil {
+		t.Errorf("CheckEncoding('q') expected failure")
+	}
+}
+
 func TestInvalidName(t *testing.T) {
 	values := []string{"invalid", "", "q"}
 	for _, val := range values {