Remove "magical" NewPrefix function, rename Prefix to Encoder.

encoder.go

@@ -0,0 +1,53 @@
+package multibase
+
+import (
+	"fmt"
+)
+
+// Encoder is a multibase encoding that is verified to be supported and
+// supports an Encode method that does not return an error
+type Encoder struct {
+	enc Encoding
+}
+
+// NewEncoder create a new Encoder from an Encoding
+func NewEncoder(base Encoding) (Encoder, error) {
+	_, ok := EncodingToStr[base]
+	if !ok {
+		return Encoder{-1}, fmt.Errorf("Unsupported multibase encoding: %d", base)
+	}
+	return Encoder{base}, 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) {
+	var base Encoding
+	ok := true
+	if len(str) == 0 {
+		return Encoder{-1}, fmt.Errorf("Empty multibase encoding")
+	} else if len(str) == 1 {
+		base = Encoding(str[0])
+		_, ok = EncodingToStr[base]
+	} else {
+		base, ok = Encodings[str]
+	}
+	if !ok {
+		return Encoder{-1}, fmt.Errorf("Unsupported multibase encoding: %s", str)
+	}
+	return Encoder{base}, nil
+}
+
+func (p Encoder) Encoding() Encoding {
+	return p.enc
+}
+
+// Encode encodes the multibase using the given Encoder.
+func (p Encoder) Encode(data []byte) string {
+	str, err := Encode(p.enc, data)
+	if err != nil {
+		// should not happen
+		panic(err)
+	}
+	return str
+}

encoder_test.go

@@ -5,24 +5,17 @@ import (
 )
 
 func TestInvalidPrefix(t *testing.T) {
-	_, err := NewPrefix('q')
+	_, err := NewEncoder('q')
 	if err == nil {
 		t.Error("expected failure")
 	}
 }
 
 func TestPrefix(t *testing.T) {
-	prefix,err := NewPrefix(nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if prefix.Encoding() != Base58BTC {
-		t.Error("unexpected default encoding")
-	}
 	for str, base := range Encodings {
-		prefix,err = NewPrefix(base)
+		prefix, err := NewEncoder(base)
 		if err != nil {
-			t.Fatalf("NewPrefix(%c) failed: %v", base, err)
+			t.Fatalf("NewEncoder(%c) failed: %v", base, err)
 		}
 		str1, err := Encode(base, sampleBytes)
 		if err != nil {
@@ -32,9 +25,9 @@ func TestPrefix(t *testing.T) {
 		if str1 != str2 {
 			t.Errorf("encoded string mismatch: %s != %s", str1, str2)
 		}
-		_, err = NewPrefix(str)
+		_, err = EncoderByName(str)
 		if err != nil {
-			t.Fatalf("NewPrefix(%s) failed: %v", str, err)
+			t.Fatalf("NewEncoder(%s) failed: %v", str, err)
 		}
 	}
 }

prefix.go

@@ -1,64 +0,0 @@
-package multibase
-
-import (
-	"fmt"
-)
-
-// Prefix is a multibase encoding that is verified to be supported and
-// supports an Encode method that does not return an error
-type Prefix struct {
-	enc Encoding
-}
-
-// NewPrefix create a new Prefix type from either an Encoding or a
-// string.  If nil or an empty string the default base (currently
-// Base58BTC) will be used.
-func NewPrefix(e interface{}) (Prefix, error) {
-	base := Encoding(Base58BTC)
-	switch v := e.(type) {
-	case byte:
-		base = Encoding(v)
-	case rune:
-		base = Encoding(v)
-	case int:
-		base = Encoding(v)
-	case Encoding:
-		base = v
-	case string:
-		ok := true
-		// note: if empty string use default value
-		if len(v) == 1 {
-			base = Encoding(v[0])
-			_, ok = EncodingToStr[base]
-		} else if len(v) > 1 {
-			base, ok = Encodings[v]
-		}
-		if !ok {
-			return Prefix{-1}, fmt.Errorf("Unsupported multibase encoding: %s", v)
-		}
-		return Prefix{base}, nil
-	case nil:
-		/* use default value */
-	default:
-		return Prefix{-1}, fmt.Errorf("Unsupported parameter type.")
-	}
-	_, ok := EncodingToStr[base]
-	if !ok {
-		return Prefix{-1}, fmt.Errorf("Unsupported multibase encoding: %d", base)
-	}
-	return Prefix{base}, nil
-}
-
-func (p Prefix) Encoding() Encoding {
-	return p.enc
-}
-
-// Encode encodes the multibase using the given Prefix.  
-func (p Prefix) Encode(data []byte) string {
-	str, err := Encode(p.enc, data)
-	if err != nil {
-		// should not happen
-		panic(err)
-	}
-	return str
-}