feat(peers): peer representation and marshalling

pkg/peers/peer.go

@@ -0,0 +1,38 @@
+package peers
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+	"strconv"
+)
+
+// Peer encodes connection information for a peer
+type Peer struct {
+	IP   net.IP
+	Port uint16
+}
+
+// Unmarshal parses peer IP addresses and ports from a buffer
+func Unmarshal(peersBin []byte) ([]Peer, error) {
+	// 4 for IP, 2 for port
+	const peerSize = 6
+	numPeers := len(peersBin) / peerSize
+	if len(peersBin)%peerSize != 0 {
+		err := fmt.Errorf("Received malformed peers")
+		return nil, err
+	}
+
+	peers := make([]Peer, numPeers)
+	for i := 0; i < numPeers; i++ {
+		offset := i * peerSize
+		peers[i].IP = net.IP(peersBin[offset : offset+4])
+		peers[i].Port = binary.BigEndian.Uint16(peersBin[offset+4 : offset+6])
+	}
+
+	return peers, nil
+}
+
+func (p Peer) String() string {
+	return net.JoinHostPort(p.IP.String(), strconv.Itoa(int(p.Port)))
+}

pkg/peers/peer_test.go

@@ -0,0 +1,55 @@
+package peers
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUnmarshall(t *testing.T) {
+	tests := map[string]struct {
+		input  string
+		output []Peer
+		fails  bool
+	}{
+		"correctly parses peers": {
+			input: string([]byte{127, 0, 0, 1, 0x00, 0x50, 1, 1, 1, 1, 0x01, 0xbb}),
+			output: []Peer{
+				{IP: net.IP{127, 0, 0, 1}, Port: 80},
+				{IP: net.IP{1, 1, 1, 1}, Port: 443},
+			},
+		},
+		"not enough bytes in peers": {
+			input:  string([]byte{127, 0, 0, 1, 0x00}),
+			output: nil,
+			fails:  true,
+		},
+	}
+
+	for _, test := range tests {
+		peers, err := Unmarshal([]byte(test.input))
+		if test.fails {
+			assert.NotNil(t, err)
+		} else {
+			assert.Nil(t, err)
+		}
+		assert.Equal(t, test.output, peers)
+	}
+}
+
+func TestString(t *testing.T) {
+	tests := []struct {
+		input  Peer
+		output string
+	}{
+		{
+			input:  Peer{IP: net.IP{127, 0, 0, 1}, Port: 8080},
+			output: "127.0.0.1:8080",
+		},
+	}
+	for _, test := range tests {
+		s := test.input.String()
+		assert.Equal(t, test.output, s)
+	}
+}