added some dhcp4 packet functions and generic byte reading functions

haza.go

@@ -1,5 +1,9 @@
 package haza
 
+import "bytes"
+import "encoding/binary"
+import "io"
+import "net"
 import "sync"
 import "unsafe"
 
@@ -75,3 +79,46 @@ func Ntoh32(v uint32) uint32 {
 	if _is_big_endian { return v }
 	return ((v >> 24) & 0xFF) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | ((v << 24) & 0xFF000000)
 }
+
+// ---------------------------------------------------------
+type ByteReader struct {
+	r *bytes.Reader
+}
+
+func NewByteReader(b []byte) *ByteReader {
+	return &ByteReader{ r: bytes.NewReader(b) }
+}
+
+func (br* ByteReader) ReadByte() (byte, error) {
+	return br.r.ReadByte()
+}
+
+func (br* ByteReader) ReadUint16() (uint16, error) {
+	var v uint16
+	var err error
+	err = binary.Read(br.r, binary.BigEndian, &v)
+	if err != nil { return 0, err }
+	return v, nil
+}
+
+func (br* ByteReader) ReadUint32() (uint32, error) {
+	var v uint32
+	var err error
+	err = binary.Read(br.r, binary.BigEndian, &v)
+	if err != nil { return 0, err }
+	return v, nil
+}
+
+func (br* ByteReader) ReadIp4() (net.IP, error) {
+	var buf [4]byte
+	var err error
+	_, err = io.ReadFull(br.r, buf[:])
+	if err != nil { return nil, err }
+	return net.IP(buf[:]), nil
+}
+
+func (br *ByteReader) ReadAllBytes(buf []byte) error {
+	var err error
+	_, err = io.ReadFull(br.r, buf)
+	return err
+}