Create peermap.go, add documentation

tracker/models/peermap.go

@@ -0,0 +1,163 @@
+// Copyright 2014 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 models
+
+import (
+	"net"
+	"sync"
+
+	"github.com/chihaya/chihaya/stats"
+)
+
+// PeerMap is a thread-safe map from PeerKeys to Peers.
+type PeerMap struct {
+	peers map[PeerKey]Peer
+	sync.RWMutex
+}
+
+// NewPeerMap initializes the map for a new PeerMap.
+func NewPeerMap() PeerMap {
+	return PeerMap{
+		peers: make(map[PeerKey]Peer),
+	}
+}
+
+// Contains is true if a peer is contained with a PeerMap.
+func (pm *PeerMap) Contains(pk PeerKey) (exists bool) {
+	pm.RLock()
+	defer pm.RUnlock()
+
+	_, exists = pm.peers[pk]
+
+	return
+}
+
+// LookUp is a thread-safe read from a PeerMap.
+func (pm *PeerMap) LookUp(pk PeerKey) (peer Peer, exists bool) {
+	pm.RLock()
+	defer pm.RUnlock()
+
+	peer, exists = pm.peers[pk]
+
+	return
+}
+
+// Put is a thread-safe write to a PeerMap.
+func (pm *PeerMap) Put(p Peer) {
+	pm.Lock()
+	defer pm.Unlock()
+
+	pm.peers[p.Key()] = p
+}
+
+// Delete is a thread-safe delete from a PeerMap.
+func (pm *PeerMap) Delete(pk PeerKey) {
+	pm.Lock()
+	defer pm.Unlock()
+
+	delete(pm.peers, pk)
+}
+
+// Len returns the number of peers within a PeerMap.
+func (pm *PeerMap) Len() int {
+	pm.RLock()
+	defer pm.RUnlock()
+
+	return len(pm.peers)
+}
+
+// Purge iterates over all of the peers within a PeerMap and deletes them if
+// they are older than the provided time.
+func (pm *PeerMap) Purge(unixtime int64) {
+	pm.Lock()
+	defer pm.Unlock()
+
+	for key, peer := range pm.peers {
+		if peer.LastAnnounce <= unixtime {
+			delete(pm.peers, key)
+			stats.RecordPeerEvent(stats.ReapedSeed, peer.HasIPv6())
+		}
+	}
+}
+
+// AppendPeers adds peers to given IPv4 or IPv6 lists.
+func (pm *PeerMap) AppendPeers(ipv4s, ipv6s PeerList, ann *Announce, wanted int) (PeerList, PeerList) {
+	if ann.Config.PreferredSubnet {
+		return pm.AppendSubnetPeers(ipv4s, ipv6s, ann, wanted)
+	}
+
+	pm.Lock()
+	defer pm.Unlock()
+
+	count := 0
+	for _, peer := range pm.peers {
+		if count >= wanted {
+			break
+		} else if peersEquivalent(&peer, ann.Peer) {
+			continue
+		}
+
+		if ann.HasIPv6() && peer.HasIPv6() {
+			ipv6s = append(ipv6s, peer)
+			count++
+		} else if peer.HasIPv4() {
+			ipv4s = append(ipv4s, peer)
+			count++
+		}
+	}
+
+	return ipv4s, ipv6s
+}
+
+// AppendSubnetPeers is an alternative version of AppendPeers used when the
+// config variable PreferredSubnet is enabled.
+func (pm *PeerMap) AppendSubnetPeers(ipv4s, ipv6s PeerList, ann *Announce, wanted int) (PeerList, PeerList) {
+	var subnetIPv4 net.IPNet
+	var subnetIPv6 net.IPNet
+
+	if ann.HasIPv4() {
+		subnetIPv4 = net.IPNet{ann.IPv4, net.CIDRMask(ann.Config.PreferredIPv4Subnet, 32)}
+	}
+
+	if ann.HasIPv6() {
+		subnetIPv6 = net.IPNet{ann.IPv6, net.CIDRMask(ann.Config.PreferredIPv6Subnet, 128)}
+	}
+
+	pm.Lock()
+	defer pm.Unlock()
+
+	// Iterate over the peers twice: first add only peers in the same subnet and
+	// if we still need more peers grab ones that haven't already been added.
+	count := 0
+	for _, checkInSubnet := range [2]bool{true, false} {
+		for _, peer := range pm.peers {
+			if count >= wanted {
+				break
+			}
+
+			inSubnet4 := peer.HasIPv4() && subnetIPv4.Contains(peer.IP)
+			inSubnet6 := peer.HasIPv6() && subnetIPv6.Contains(peer.IP)
+
+			if peersEquivalent(&peer, ann.Peer) || checkInSubnet != (inSubnet4 || inSubnet6) {
+				continue
+			}
+
+			if ann.HasIPv6() && peer.HasIPv6() {
+				ipv6s = append(ipv6s, peer)
+				count++
+			} else if peer.HasIPv4() {
+				ipv4s = append(ipv4s, peer)
+				count++
+			}
+		}
+	}
+
+	return ipv4s, ipv6s
+}
+
+// peersEquivalent checks if two peers represent the same entity.
+func peersEquivalent(a, b *Peer) bool {
+	return a.ID == b.ID || a.UserID != 0 && a.UserID == b.UserID
+}