encoding/base32: handle NoPadding when using buffered encoding in Close

This changes makes encoder.Close aware of how many bytes to write if there
is any data left in the buffer.

Fixes #25295

Change-Id: I4138891359935509cb561c453b8059ba2b9e576b
GitHub-Last-Rev: f374096d2f3cae8635506074f59e1cd440c14844
GitHub-Pull-Request: golang/go#25316
Reviewed-on: https://go-review.googlesource.com/112515
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/encoding/base32/base32.go

@@ -244,8 +244,9 @@ func (e *encoder) Close() error {
 	// If there's anything left in the buffer, flush it out
 	if e.err == nil && e.nbuf > 0 {
 		e.enc.Encode(e.out[0:], e.buf[0:e.nbuf])
+		encodedLen := e.enc.EncodedLen(e.nbuf)
 		e.nbuf = 0
-		_, e.err = e.w.Write(e.out[0:8])
+		_, e.err = e.w.Write(e.out[0:encodedLen])
 	}
 	return e.err
 }

src/encoding/base32/base32_test.go

@@ -658,3 +658,31 @@ func TestEncodedDecodedLen(t *testing.T) {
 		})
 	}
 }
+
+func TestWithoutPaddingClose(t *testing.T) {
+	encodings := []*Encoding{
+		StdEncoding,
+		StdEncoding.WithPadding(NoPadding),
+	}
+
+	for _, encoding := range encodings {
+		for _, testpair := range pairs {
+
+			var buf bytes.Buffer
+			encoder := NewEncoder(encoding, &buf)
+			encoder.Write([]byte(testpair.decoded))
+			encoder.Close()
+
+			expected := testpair.encoded
+			if encoding.padChar == NoPadding {
+				expected = strings.Replace(expected, "=", "", -1)
+			}
+
+			res := buf.String()
+
+			if res != expected {
+				t.Errorf("Expected %s got %s; padChar=%d", expected, res, encoding.padChar)
+			}
+		}
+	}
+}