Factor out XDR en/decoding

xdr/reader.go

@@ -0,0 +1,65 @@
+package xdr
+
+import "io"
+
+type Reader struct {
+	r   io.Reader
+	tot uint64
+	err error
+	b   [8]byte
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		r: r,
+	}
+}
+
+func (r *Reader) ReadString() string {
+	return string(r.ReadBytes(nil))
+}
+
+func (r *Reader) ReadBytes(dst []byte) []byte {
+	if r.err != nil {
+		return nil
+	}
+	l := int(r.ReadUint32())
+	if r.err != nil {
+		return nil
+	}
+	if l+pad(l) > len(dst) {
+		dst = make([]byte, l+pad(l))
+	} else {
+		dst = dst[:l+pad(l)]
+	}
+	_, r.err = io.ReadFull(r.r, dst)
+	r.tot += uint64(l + pad(l))
+	return dst[:l]
+}
+
+func (r *Reader) ReadUint32() uint32 {
+	if r.err != nil {
+		return 0
+	}
+	_, r.err = io.ReadFull(r.r, r.b[:4])
+	r.tot += 8
+	return uint32(r.b[3]) | uint32(r.b[2])<<8 | uint32(r.b[1])<<16 | uint32(r.b[0])<<24
+}
+
+func (r *Reader) ReadUint64() uint64 {
+	if r.err != nil {
+		return 0
+	}
+	_, r.err = io.ReadFull(r.r, r.b[:8])
+	r.tot += 8
+	return uint64(r.b[7]) | uint64(r.b[6])<<8 | uint64(r.b[5])<<16 | uint64(r.b[4])<<24 |
+		uint64(r.b[3])<<32 | uint64(r.b[2])<<40 | uint64(r.b[1])<<48 | uint64(r.b[0])<<56
+}
+
+func (r *Reader) Tot() uint64 {
+	return r.tot
+}
+
+func (r *Reader) Err() error {
+	return r.err
+}