Split: added split method

codec.go

@@ -67,6 +67,30 @@ func bytesToString(b []byte) (ret string, err error) {
 	return s, nil
 }
 
+func bytesSplit(b []byte) (ret [][]byte, err error) {
+	// panic handler, in case we try accessing bytes incorrectly.
+	defer func() {
+		if e := recover(); e != nil {
+			ret = [][]byte{}
+			err = e.(error)
+		}
+	}()
+
+	ret = [][]byte{}
+	for len(b) > 0 {
+		p := ProtocolWithCode(int(b[0]))
+		if p == nil {
+			return [][]byte{}, fmt.Errorf("no protocol with code %d", b[0])
+		}
+
+		length := 1 + (p.Size / 8)
+		ret = append(ret, b[:length])
+		b = b[length:]
+	}
+
+	return ret, nil
+}
+
 func addressStringToBytes(p *Protocol, s string) []byte {
 	switch p.Code {
 

interface.go

@@ -39,4 +39,10 @@ type Multiaddr interface {
 	//      /ip4/1.2.3.4/tcp/80 decapsulate /ip4/1.2.3.4 = /tcp/80
 	//
 	Decapsulate(Multiaddr) Multiaddr
+
+	// Split returns the sub-address portions of this multiaddr.
+	//
+	//   m, _ := NewMultiaddr("/ip4/1.2.3.4/tcp/1234")
+	//   m.Split() -> [/ip4/1.2.3.4, /tcp/1234]
+	Split() []Multiaddr
 }

multiaddr.go

@@ -108,3 +108,19 @@ func (m *multiaddr) Decapsulate(o Multiaddr) Multiaddr {
 	}
 	return ma
 }
+
+// Split returns the sub-address portions of this multiaddr.
+func (m *multiaddr) Split() []Multiaddr {
+	split, err := bytesSplit(m.bytes)
+	if err != nil {
+		panic(fmt.Errorf("invalid multiaddr %s", m.String()))
+	}
+
+	addrs := make([]Multiaddr, len(split))
+	for i, addr := range split {
+		c := make([]byte, len(addr))
+		copy(c, addr)
+		addrs[i] = &multiaddr{bytes: c}
+	}
+	return addrs
+}

multiaddr_test.go

@@ -91,6 +91,45 @@ func TestBytesToString(t *testing.T) {
 	testString("/ip4/127.0.0.1/udp/1234", "047f0000011104d2")
 }
 
+func TestBytesSplit(t *testing.T) {
+
+	testString := func(s string, res []string) {
+		m, err := NewMultiaddr(s)
+		if err != nil {
+			t.Error("failed to convert", s)
+		}
+
+		split := m.Split()
+		if len(split) != len(res) {
+			t.Error("not enough split components", split)
+			return
+		}
+
+		for i, a := range split {
+			if a.String() != res[i] {
+				t.Errorf("split component failed: %s != %s", a, res[i])
+			}
+		}
+
+		// modifying underlying bytes is fine.
+		m2 := m.(*multiaddr)
+		for i := range m2.bytes {
+			m2.bytes[i] = 0
+		}
+
+		for i, a := range split {
+			if a.String() != res[i] {
+				t.Errorf("split component failed: %s != %s", a, res[i])
+			}
+		}
+
+	}
+
+	testString("/ip4/1.2.3.4/udp/1234", []string{"/ip4/1.2.3.4", "/udp/1234"})
+	testString("/ip4/1.2.3.4/tcp/1/ip4/2.3.4.5/udp/2",
+		[]string{"/ip4/1.2.3.4", "/tcp/1", "/ip4/2.3.4.5", "/udp/2"})
+}
+
 func TestProtocols(t *testing.T) {
 	m, err := NewMultiaddr("/ip4/127.0.0.1/udp/1234")
 	if err != nil {