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package kademlia
import ( "math/bits" "strconv")
const ( alpha = 3 // 'alpha', max parallalel calls
B = 20 // 'B', 160 bits, ID length
KBucketSize = 20 // 'K', bucket size
)
type ListedNode struct { ID ID Addr string}
type Kademlia struct { ID ID KBuckets [B * 8][]ListedNode}
func NewKademliaTable(id ID) *Kademlia { return &Kademlia{ ID: id, }}
func (kad Kademlia) String() string { r := "Node ID: " + kad.ID.String() + ", KBuckets:\n" for i, kb := range kad.KBuckets { if len(kb) > 0 { r += " KBucket " + strconv.Itoa(i) + "\n" for _, e := range kb { r += " " + e.ID.String() + "\n" } } } return r}
func (kad Kademlia) KBucket(o ID) int { d := kad.ID.Distance(o) return kBucketByDistance(d[:])
}
func kBucketByDistance(b []byte) int { for i := 0; i < B; i++ { for a := b[i] ^ 0; a != 0; a &= a - 1 { return (B-1-i)*8 + (7 - bits.TrailingZeros8(bits.Reverse8(uint8(a)))) } } return (B*8 - 1) - (B*8 - 1)}
func (kad *Kademlia) Update(o ListedNode) { k := kad.KBucket(o.ID) kb := kad.KBuckets[k] if len(kb) >= KBucketSize { // if n.KBuckets[k] is alrady full, perform ping of the first element
kad.Ping(k, o) return } // check that is not already in the list
exist, pos := existsInListedNodes(kad.KBuckets[k], o) if exist { // update position of o to the bottom
kad.KBuckets[k] = moveToBottom(kad.KBuckets[k], pos) return } // not exists, add it to the kBucket
kad.KBuckets[k] = append(kad.KBuckets[k], o) return}
func (kad *Kademlia) Ping(k int, o ListedNode) { // TODO when rpc layer is done
// ping the n.KBuckets[k][0] (using goroutine)
// if no response (timeout), delete it and add 'o'
// n.KBuckets[k][0] = o
}
func existsInListedNodes(lns []ListedNode, ln ListedNode) (bool, int) { for i, v := range lns { if v.ID.Equal(ln.ID) { return true, i } } return false, 0}
func moveToBottom(kb []ListedNode, k int) []ListedNode { e := kb[k] kb = append(kb[:k], kb[k+1:]...) kb = append(kb[:], e) return kb}
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