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77 lines
1.6 KiB
77 lines
1.6 KiB
package p2p
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import (
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"sync"
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)
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/*
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PeerSet is a special structure for keeping a table of peers.
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Iteration over the peers is super fast and thread-safe.
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*/
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type PeerSet struct {
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mtx sync.Mutex
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lookup map[string]*peerSetItem
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list []*Peer
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}
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type peerSetItem struct {
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peer *Peer
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index int
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}
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func NewPeerSet() *PeerSet {
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return &PeerSet{
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lookup: make(map[string]*peerSetItem),
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list: make([]*Peer, 0, 256),
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}
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}
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func (ps *PeerSet) Add(peer *Peer) bool {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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addr := peer.RemoteAddress().String()
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if ps.lookup[addr] != nil {
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return false
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}
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index := len(ps.list)
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// Appending is safe even with other goroutines
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// iterating over the ps.list slice.
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ps.list = append(ps.list, peer)
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ps.lookup[addr] = &peerSetItem{peer, index}
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return true
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}
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func (ps *PeerSet) Remove(peer *Peer) {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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addr := peer.RemoteAddress().String()
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item := ps.lookup[addr]
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if item == nil {
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return
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}
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index := item.index
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// Copy the list but without the last element.
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// (we must copy because we're mutating the list)
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newList := make([]*Peer, len(ps.list)-1)
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copy(newList, ps.list)
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// If it's the last peer, that's an easy special case.
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if index == len(ps.list)-1 {
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ps.list = newList
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return
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}
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// Move the last item from ps.list to "index" in list.
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lastPeer := ps.list[len(ps.list)-1]
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lastPeerAddr := lastPeer.RemoteAddress().String()
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lastPeerItem := ps.lookup[lastPeerAddr]
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newList[index] = lastPeer
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lastPeerItem.index = index
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ps.list = newList
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delete(ps.lookup, addr)
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}
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// threadsafe list of peers.
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func (ps *PeerSet) List() []*Peer {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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return ps.list
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}
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