fix bug for large counts: used a one-byte buffer.

R=rsc
CC=golang-dev
https://golang.org/cl/174082

src/pkg/gob/decoder.go

@@ -23,7 +23,7 @@ type Decoder struct {
 	state		*decodeState;					// reads data from in-memory buffer
 	countState	*decodeState;					// reads counts from wire
 	buf		[]byte;
-	oneByte		[]byte;
+	countBuf	[9]byte;	// counts may be uint64s (unlikely!), require 9 bytes
 }
 
 // NewDecoder returns a new decoder that reads from the io.Reader.
@@ -34,7 +34,6 @@ func NewDecoder(r io.Reader) *Decoder {
 	dec.state = newDecodeState(nil);	// buffer set in Decode(); rest is unimportant
 	dec.decoderCache = make(map[reflect.Type]map[typeId]**decEngine);
 	dec.ignorerCache = make(map[typeId]**decEngine);
-	dec.oneByte = make([]byte, 1);
 
 	return dec;
 }
@@ -73,7 +72,7 @@ func (dec *Decoder) Decode(e interface{}) os.Error {
 	for {
 		// Read a count.
 		var nbytes uint64;
-		nbytes, dec.state.err = decodeUintReader(dec.r, dec.oneByte);
+		nbytes, dec.state.err = decodeUintReader(dec.r, dec.countBuf[0:]);
 		if dec.state.err != nil {
 			break
 		}