2 files changed, 31 insertions, 2 deletions
diff --git a/src/pkg/encoding/ascii85/ascii85.go b/src/pkg/encoding/ascii85/ascii85.go
index e2afc5871..60da304b5 100644
--- a/src/pkg/encoding/ascii85/ascii85.go
+++ b/src/pkg/encoding/ascii85/ascii85.go
@@ -281,6 +281,18 @@ func (d *decoder) Read(p []byte) (n int, err error) {
 				d.nbuf = copy(d.buf[0:], d.buf[nsrc:d.nbuf])
 				continue // copy out and return
 			}
+			if ndst == 0 && d.err == nil {
+				// Special case: input buffer is mostly filled with non-data bytes.
+				// Filter out such bytes to make room for more input.
+				off := 0
+				for i := 0; i < d.nbuf; i++ {
+					if d.buf[i] > ' ' {
+						d.buf[off] = d.buf[i]
+						off++
+					}
+				}
+				d.nbuf = off
+			}
 		}
 
 		// Out of input, out of decoded output.  Check errors.
diff --git a/src/pkg/encoding/ascii85/ascii85_test.go b/src/pkg/encoding/ascii85/ascii85_test.go
index 42cf7e80e..aad199b4f 100644
--- a/src/pkg/encoding/ascii85/ascii85_test.go
+++ b/src/pkg/encoding/ascii85/ascii85_test.go
@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"io"
 	"io/ioutil"
+	"strings"
 	"testing"
 )
 
@@ -16,6 +17,11 @@ type testpair struct {
 }
 
 var pairs = []testpair{
+	// Encode returns 0 when len(src) is 0
+	{
+		"",
+		"",
+	},
 	// Wikipedia example
 	{
 		"Man is distinguished, not only by his reason, but by this singular passion from " +
@@ -110,7 +116,7 @@ func TestDecode(t *testing.T) {
 
 func TestDecoder(t *testing.T) {
 	for _, p := range pairs {
-		decoder := NewDecoder(bytes.NewBufferString(p.encoded))
+		decoder := NewDecoder(strings.NewReader(p.encoded))
 		dbuf, err := ioutil.ReadAll(decoder)
 		if err != nil {
 			t.Fatal("Read failed", err)
@@ -125,7 +131,7 @@ func TestDecoder(t *testing.T) {
 
 func TestDecoderBuffering(t *testing.T) {
 	for bs := 1; bs <= 12; bs++ {
-		decoder := NewDecoder(bytes.NewBufferString(bigtest.encoded))
+		decoder := NewDecoder(strings.NewReader(bigtest.encoded))
 		buf := make([]byte, len(bigtest.decoded)+12)
 		var total int
 		for total = 0; total < len(bigtest.decoded); {
@@ -191,3 +197,14 @@ func TestBig(t *testing.T) {
 		t.Errorf("Decode(Encode(%d-byte string)) failed at offset %d", n, i)
 	}
 }
+
+func TestDecoderInternalWhitespace(t *testing.T) {
+	s := strings.Repeat(" ", 2048) + "z"
+	decoded, err := ioutil.ReadAll(NewDecoder(strings.NewReader(s)))
+	if err != nil {
+		t.Errorf("Decode gave error %v", err)
+	}
+	if want := []byte("\000\000\000\000"); !bytes.Equal(want, decoded) {
+		t.Errorf("Decode failed: got %v, want %v", decoded, want)
+	}
+}