chord-1.go

// fingerEntry represents a single finger table entry
type fingerEntry struct {
   Id   []byte         // ID hash of (n + 2^i) mod (2^m)
   Node *internal.Node 
}

func newFingerTable(node *internal.Node, m int) fingerTable {
   ft := make([]*fingerEntry, m)
   for i := range ft {
    ft[i] = newFingerEntry(fingerID(node.Id, i, m), node)
   }
  return ft
}

// newFingerEntry returns an allocated new finger entry with the attributes set
func newFingerEntry(id []byte, node *internal.Node) *fingerEntry {
   return &fingerEntry{
    Id:   id,
    Node: node,
   }
}

// Computes the offset by (n + 2^i) mod (2^m)
func fingerID(n []byte, i int, m int) []byte {
   // Convert the ID to a bigint
   idInt := (&big.Int{}).SetBytes(n)

   // Get the offset
   two := big.NewInt(2)
   offset := big.Int{}
   offset.Exp(two, big.NewInt(int64(i)), nil)

   // Sum
   sum := big.Int{}
   sum.Add(idInt, &offset)

   // Get the ceiling
   ceil := big.Int{}
   ceil.Exp(two, big.NewInt(int64(m)), nil)

   // Apply the mod
   idInt.Mod(&sum, &ceil)
   // Add together
   return idInt.Bytes()
}