pkg: added random string, peer

pkg/random/peer.go

@@ -0,0 +1,74 @@
+// Copyright 2016 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
+package random
+
+import (
+	"math/rand"
+	"net"
+
+	"github.com/chihaya/chihaya"
+)
+
+// Peer generates a random chihaya.Peer.
+//
+// prefix is the prefix to use for the peer ID. If len(prefix) > 20, it will be
+// truncated to 20 characters. If len(prefix) < 20, it will be padded with an
+// alphanumeric random string to have 20 characters.
+//
+// v6 indicates whether an IPv6 address should be generated.
+// Regardless of the length of the generated IP address, its bytes will have
+// values in [1,254].
+//
+// minPort and maxPort describe the range for the randomly generated port, where
+// minPort <= port < maxPort.
+// minPort and maxPort will be checked and altered so that
+// 1 <= minPort <= maxPort <= 65536.
+// If minPort == maxPort, port will be set to minPort.
+func Peer(r *rand.Rand, prefix string, v6 bool, minPort, maxPort int) chihaya.Peer {
+	var (
+		port uint16
+		ip   net.IP
+	)
+
+	if minPort <= 0 {
+		minPort = 1
+	}
+	if maxPort > 65536 {
+		maxPort = 65536
+	}
+	if maxPort < minPort {
+		maxPort = minPort
+	}
+	if len(prefix) > 20 {
+		prefix = prefix[:20]
+	}
+
+	if minPort == maxPort {
+		port = uint16(minPort)
+	} else {
+		port = uint16(r.Int63()%int64(maxPort-minPort)) + uint16(minPort)
+	}
+
+	if v6 {
+		b := make([]byte, 16)
+		ip = net.IP(b)
+	} else {
+		b := make([]byte, 4)
+		ip = net.IP(b)
+	}
+
+	for i := range ip {
+		b := r.Intn(254) + 1
+		ip[i] = byte(b)
+	}
+
+	prefix = prefix + AlphaNumericString(r, 20-len(prefix))
+
+	return chihaya.Peer{
+		ID:   chihaya.PeerID(prefix),
+		Port: port,
+		IP:   ip,
+	}
+}