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119 lines
2.7 KiB
119 lines
2.7 KiB
package p2p
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import (
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"sync"
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)
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// IPeerSet has a (immutable) subset of the methods of PeerSet.
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type IPeerSet interface {
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Has(key string) bool
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Get(key string) Peer
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List() []Peer
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Size() int
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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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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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// NewPeerSet creates a new peerSet with a list of initial capacity of 256 items.
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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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// Add adds the peer to the PeerSet.
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// It returns ErrSwitchDuplicatePeer if the peer is already present.
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func (ps *PeerSet) Add(peer Peer) error {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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if ps.lookup[peer.Key()] != nil {
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return ErrSwitchDuplicatePeer
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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[peer.Key()] = &peerSetItem{peer, index}
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return nil
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}
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// Has returns true iff the PeerSet contains
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// the peer referred to by this peerKey.
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func (ps *PeerSet) Has(peerKey string) bool {
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ps.mtx.Lock()
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_, ok := ps.lookup[peerKey]
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ps.mtx.Unlock()
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return ok
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}
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// Get looks up a peer by the provided peerKey.
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func (ps *PeerSet) Get(peerKey string) Peer {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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item, ok := ps.lookup[peerKey]
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if ok {
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return item.peer
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} else {
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return nil
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}
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}
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// Remove discards peer by its Key, if the peer was previously memoized.
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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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item := ps.lookup[peer.Key()]
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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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// Create a new copy of the list but with one less item.
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// (we must copy because we'll be 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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delete(ps.lookup, peer.Key())
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return
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}
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// Replace the popped item with the last item in the old list.
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lastPeer := ps.list[len(ps.list)-1]
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lastPeerKey := lastPeer.Key()
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lastPeerItem := ps.lookup[lastPeerKey]
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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, peer.Key())
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}
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// Size returns the number of unique items in the peerSet.
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func (ps *PeerSet) Size() int {
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ps.mtx.Lock()
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defer ps.mtx.Unlock()
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return len(ps.list)
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}
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// List returns the 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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