3 files changed, 31 insertions, 6 deletions
diff --git a/src/pkg/encoding/binary/binary.go b/src/pkg/encoding/binary/binary.go
index f3466b9af..a5694876a 100644
--- a/src/pkg/encoding/binary/binary.go
+++ b/src/pkg/encoding/binary/binary.go
@@ -133,6 +133,7 @@ func (bigEndian) GoString() string { return "binary.BigEndian" }
 // When reading into structs, the field data for fields with
 // blank (_) field names is skipped; i.e., blank field names
 // may be used for padding.
+// When reading into a struct, all non-blank fields must be exported.
 func Read(r io.Reader, order ByteOrder, data interface{}) error {
 	// Fast path for basic types and slices.
 	if n := intDataSize(data); n != 0 {
diff --git a/src/pkg/encoding/binary/binary_test.go b/src/pkg/encoding/binary/binary_test.go
index fdfee7d87..c80c90383 100644
--- a/src/pkg/encoding/binary/binary_test.go
+++ b/src/pkg/encoding/binary/binary_test.go
@@ -111,7 +111,7 @@ func checkResult(t *testing.T, dir string, order ByteOrder, err error, have, wan
 
 func testRead(t *testing.T, order ByteOrder, b []byte, s1 interface{}) {
 	var s2 Struct
-	err := Read(bytes.NewBuffer(b), order, &s2)
+	err := Read(bytes.NewReader(b), order, &s2)
 	checkResult(t, "Read", order, err, s2, s1)
 }
 
@@ -131,7 +131,7 @@ func TestBigEndianPtrWrite(t *testing.T) { testWrite(t, BigEndian, big, &s) }
 
 func TestReadSlice(t *testing.T) {
 	slice := make([]int32, 2)
-	err := Read(bytes.NewBuffer(src), BigEndian, slice)
+	err := Read(bytes.NewReader(src), BigEndian, slice)
 	checkResult(t, "ReadSlice", BigEndian, err, slice, res)
 }
 
@@ -265,6 +265,30 @@ func TestBlankFields(t *testing.T) {
 	}
 }
 
+// An attempt to read into a struct with an unexported field will
+// panic.  This is probably not the best choice, but at this point
+// anything else would be an API change.
+
+type Unexported struct {
+	a int32
+}
+
+func TestUnexportedRead(t *testing.T) {
+	var buf bytes.Buffer
+	u1 := Unexported{a: 1}
+	if err := Write(&buf, LittleEndian, &u1); err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		if recover() == nil {
+			t.Fatal("did not panic")
+		}
+	}()
+	var u2 Unexported
+	Read(&buf, LittleEndian, &u2)
+}
+
 type byteSliceReader struct {
 	remain []byte
 }
diff --git a/src/pkg/encoding/binary/varint_test.go b/src/pkg/encoding/binary/varint_test.go
index 9476bd5fb..ca411ecbd 100644
--- a/src/pkg/encoding/binary/varint_test.go
+++ b/src/pkg/encoding/binary/varint_test.go
@@ -35,7 +35,7 @@ func testVarint(t *testing.T, x int64) {
 		t.Errorf("Varint(%d): got n = %d; want %d", x, m, n)
 	}
 
-	y, err := ReadVarint(bytes.NewBuffer(buf))
+	y, err := ReadVarint(bytes.NewReader(buf))
 	if err != nil {
 		t.Errorf("ReadVarint(%d): %s", x, err)
 	}
@@ -55,7 +55,7 @@ func testUvarint(t *testing.T, x uint64) {
 		t.Errorf("Uvarint(%d): got n = %d; want %d", x, m, n)
 	}
 
-	y, err := ReadUvarint(bytes.NewBuffer(buf))
+	y, err := ReadUvarint(bytes.NewReader(buf))
 	if err != nil {
 		t.Errorf("ReadUvarint(%d): %s", x, err)
 	}
@@ -114,7 +114,7 @@ func TestBufferTooSmall(t *testing.T) {
 			t.Errorf("Uvarint(%v): got x = %d, n = %d", buf, x, n)
 		}
 
-		x, err := ReadUvarint(bytes.NewBuffer(buf))
+		x, err := ReadUvarint(bytes.NewReader(buf))
 		if x != 0 || err != io.EOF {
 			t.Errorf("ReadUvarint(%v): got x = %d, err = %s", buf, x, err)
 		}
@@ -127,7 +127,7 @@ func testOverflow(t *testing.T, buf []byte, n0 int, err0 error) {
 		t.Errorf("Uvarint(%v): got x = %d, n = %d; want 0, %d", buf, x, n, n0)
 	}
 
-	x, err := ReadUvarint(bytes.NewBuffer(buf))
+	x, err := ReadUvarint(bytes.NewReader(buf))
 	if x != 0 || err != err0 {
 		t.Errorf("ReadUvarint(%v): got x = %d, err = %s; want 0, %s", buf, x, err, err0)
 	}