encoding/base32: add DecodeString and EncodeToString helper methods.

This makes encoding/base32 be consistent with encoding/base64.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5615053

src/pkg/encoding/base32/base32.go

@@ -125,6 +125,13 @@ func (enc *Encoding) Encode(dst, src []byte) {
 	}
 }
 
+// EncodeToString returns the base32 encoding of src.
+func (enc *Encoding) EncodeToString(src []byte) string {
+	buf := make([]byte, enc.EncodedLen(len(src)))
+	enc.Encode(buf, src)
+	return string(buf)
+}
+
 type encoder struct {
 	err  error
 	enc  *Encoding
@@ -298,6 +305,13 @@ func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
 	return
 }
 
+// DecodeString returns the bytes represented by the base32 string s.
+func (enc *Encoding) DecodeString(s string) ([]byte, error) {
+	dbuf := make([]byte, enc.DecodedLen(len(s)))
+	n, err := enc.Decode(dbuf, []byte(s))
+	return dbuf[:n], err
+}
+
 type decoder struct {
 	err    error
 	enc    *Encoding

src/pkg/encoding/base32/base32_test.go

@@ -51,9 +51,8 @@ func testEqual(t *testing.T, msg string, args ...interface{}) bool {
 
 func TestEncode(t *testing.T) {
 	for _, p := range pairs {
-		buf := make([]byte, StdEncoding.EncodedLen(len(p.decoded)))
-		StdEncoding.Encode(buf, []byte(p.decoded))
-		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, string(buf), p.encoded)
+		got := StdEncoding.EncodeToString([]byte(p.decoded))
+		testEqual(t, "Encode(%q) = %q, want %q", p.decoded, got, p.encoded)
 	}
 }
 
@@ -99,6 +98,10 @@ func TestDecode(t *testing.T) {
 		testEqual(t, "Decode(%q) = %q, want %q", p.encoded,
 			string(dbuf[0:count]),
 			p.decoded)
+
+		dbuf, err = StdEncoding.DecodeString(p.encoded)
+		testEqual(t, "DecodeString(%q) = error %v, want %v", p.encoded, err, error(nil))
+		testEqual(t, "DecodeString(%q) = %q, want %q", string(dbuf), p.decoded)
 	}
 }