Merge pull request #21 from multiformats/kevina/map

Enhance Multibase

.travis.yml

@@ -4,7 +4,7 @@ os:
 language: go
 
 go:
-    - 1.8.3
+    - 1.10.2
 
 install:
     - go get -u github.com/whyrusleeping/gx

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

@@ -0,0 +1,33 @@
+package multibase
+
+import (
+	"testing"
+)
+
+func TestInvalidPrefix(t *testing.T) {
+	_, err := NewEncoder('q')
+	if err == nil {
+		t.Error("expected failure")
+	}
+}
+
+func TestPrefix(t *testing.T) {
+	for str, base := range Encodings {
+		prefix, err := NewEncoder(base)
+		if err != nil {
+			t.Fatalf("NewEncoder(%c) failed: %v", base, err)
+		}
+		str1, err := Encode(base, sampleBytes)
+		if err != nil {
+			t.Fatal(err)
+		}
+		str2 := prefix.Encode(sampleBytes)
+		if str1 != str2 {
+			t.Errorf("encoded string mismatch: %s != %s", str1, str2)
+		}
+		_, err = EncoderByName(str)
+		if err != nil {
+			t.Fatalf("NewEncoder(%s) failed: %v", str, err)
+		}
+	}
+}

multibase.go

@@ -12,7 +12,8 @@ import (
 // Encoding identifies the type of base-encoding that a multibase is carrying.
 type Encoding int
 
-// These are the supported encodings
+// These are the encodings specified in the standard, not are all
+// supported yet
 const (
 	Identity          = 0x00
 	Base1             = '1'
@@ -37,6 +38,48 @@ const (
 	Base64urlPad      = 'U'
 )
 
+// Encodigs is a map of the supported encoding, unsupported encoding
+// specified in standard are left out
+var Encodings = map[string]Encoding{
+	"identity":          0x00,
+	"base16":            'f',
+	"base16upper":       'F',
+	"base32":            'b',
+	"base32upper":       'B',
+	"base32pad":         'c',
+	"base32padupper":    'C',
+	"base32hex":         'v',
+	"base32hexupper":    'V',
+	"base32hexpad":      't',
+	"base32hexpadupper": 'T',
+	"base58flickr":      'Z',
+	"base58btc":         'z',
+	"base64":            'm',
+	"base64url":         'u',
+	"base64pad":         'M',
+	"base64urlpad":      'U',
+}
+
+var EncodingToStr = map[Encoding]string{
+	0x00: "identity",
+	'f':  "base16",
+	'F':  "base16upper",
+	'b':  "base32",
+	'B':  "base32upper",
+	'c':  "base32pad",
+	'C':  "base32padupper",
+	'v':  "base32hex",
+	'V':  "base32hexupper",
+	't':  "base32hexpad",
+	'T':  "base32hexpadupper",
+	'Z':  "base58flickr",
+	'z':  "base58btc",
+	'm':  "base64",
+	'u':  "base64url",
+	'M':  "base64pad",
+	'U':  "base64urlpad",
+}
+
 // ErrUnsupportedEncoding is returned when the selected encoding is not known or
 // implemented.
 var ErrUnsupportedEncoding = fmt.Errorf("selected encoding not supported")

multibase_test.go

@@ -6,6 +6,21 @@ import (
 	"testing"
 )
 
+func TestMap(t *testing.T) {
+	for s,e := range Encodings {
+		s2 := EncodingToStr[e]
+		if s != s2 {
+			t.Errorf("round trip failed on encoding map: %s != %s", s, s2)
+		}
+	}
+	for e,s := range EncodingToStr {
+		e2 := Encodings[s]
+		if e != e2 {
+			t.Errorf("round trip failed on encoding map: '%c' != '%c'", e, e2)
+		}
+	}
+}
+
 var sampleBytes = []byte("Decentralize everything!!!")
 var encodedSamples = map[Encoding]string{
 	Identity:          string(0x00) + "Decentralize everything!!!",