DHT: Starting with the fork, initially only the hash table.

The distributed part follows.

dht/Node.go

@@ -0,0 +1,110 @@
+/*
+File Name:  Node.go
+Copyright:  2021 Peernet s.r.o.
+Author:     Peter Kleissner
+*/
+
+package dht
+
+import (
+	"bytes"
+	"math/big"
+	"time"
+)
+
+// Node is the over-the-wire representation of a node
+type Node struct {
+	// ID is the unique identifier
+	ID []byte
+
+	// LastSeen when was this node last considered seen by the DHT
+	LastSeen time.Time
+}
+
+// nodeList is used in order to sort a list of arbitrary nodes against a
+// comparator. These nodes are sorted by xor distance
+type shortList struct {
+	// Nodes are a list of nodes to be compared
+	Nodes []Node
+
+	// Comparator is the ID to compare to
+	Comparator []byte
+}
+
+func areNodesEqual(n1 *Node, n2 *Node, allowNilID bool) bool {
+	if n1 == nil || n2 == nil {
+		return false
+	}
+	if !allowNilID {
+		if n1.ID == nil || n2.ID == nil {
+			return false
+		}
+		if bytes.Compare(n1.ID, n2.ID) != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+func (n *shortList) RemoveNode(node Node) {
+	for i := 0; i < n.Len(); i++ {
+		if bytes.Compare(n.Nodes[i].ID, node.ID) == 0 {
+			n.Nodes = append(n.Nodes[:i], n.Nodes[i+1:]...)
+			return
+		}
+	}
+}
+
+func (n *shortList) AppendUniqueNodes(nodes ...Node) {
+	for _, vv := range nodes {
+		exists := false
+		for _, v := range n.Nodes {
+			if bytes.Compare(v.ID, vv.ID) == 0 {
+				exists = true
+			}
+		}
+		if !exists {
+			n.Nodes = append(n.Nodes, vv)
+		}
+	}
+}
+
+func (n *shortList) AppendUnique(nodes ...Node) {
+	for _, vv := range nodes {
+		exists := false
+		for _, v := range n.Nodes {
+			if bytes.Compare(v.ID, vv.ID) == 0 {
+				exists = true
+			}
+		}
+		if !exists {
+			n.Nodes = append(n.Nodes, vv)
+		}
+	}
+}
+
+func (n *shortList) Len() int {
+	return len(n.Nodes)
+}
+
+func (n *shortList) Swap(i, j int) {
+	n.Nodes[i], n.Nodes[j] = n.Nodes[j], n.Nodes[i]
+}
+
+func (n *shortList) Less(i, j int) bool {
+	iDist := getDistance(n.Nodes[i].ID, n.Comparator)
+	jDist := getDistance(n.Nodes[j].ID, n.Comparator)
+
+	if iDist.Cmp(jDist) == -1 {
+		return true
+	}
+
+	return false
+}
+
+func getDistance(id1 []byte, id2 []byte) *big.Int {
+	buf1 := new(big.Int).SetBytes(id1)
+	buf2 := new(big.Int).SetBytes(id2)
+	result := new(big.Int).Xor(buf1, buf2)
+	return result
+}