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pslice.go
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pslice.go
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package pslice
import (
"github.com/gauss-project/aurorafs/pkg/topology/model"
"sync"
"github.com/gauss-project/aurorafs/pkg/boson"
)
// PSlice maintains a list of addresses, indexing them by their different proximity orders.
type PSlice struct {
peers [][]boson.Address // the slice of peers
baseBytes []byte
mu sync.RWMutex
maxBins int
}
// New creates a new PSlice.
func New(maxBins int, base boson.Address) *PSlice {
return &PSlice{
peers: make([][]boson.Address, maxBins),
baseBytes: base.Bytes(),
maxBins: maxBins,
}
}
// Add a peer at a certain PO.
func (s *PSlice) Add(addrs ...boson.Address) {
s.mu.Lock()
defer s.mu.Unlock()
// bypass unnecessary allocations below if address count is one
if len(addrs) == 1 {
addr := addrs[0]
po := s.po(addr.Bytes())
if e, _ := s.index(addr, po); e {
return
}
s.peers[po] = append(s.peers[po], addr)
return
}
addrPo := make([]uint8, 0, len(addrs))
binChange := make([]int, s.maxBins)
exists := make([]bool, len(addrs))
for i, addr := range addrs {
po := s.po(addr.Bytes())
addrPo = append(addrPo, po)
if e, _ := s.index(addr, po); e {
exists[i] = true
} else {
binChange[po]++
}
}
for i, count := range binChange {
peers := s.peers[i]
if count > 0 && cap(peers) < len(peers)+count {
newPeers := make([]boson.Address, len(peers), len(peers)+count)
copy(newPeers, peers)
s.peers[i] = newPeers
}
}
for i, addr := range addrs {
if exists[i] {
continue
}
po := addrPo[i]
s.peers[po] = append(s.peers[po], addr)
}
}
// iterates over all peers from deepest bin to shallowest.
func (s *PSlice) EachBin(pf model.EachPeerFunc) error {
for i := s.maxBins - 1; i >= 0; i-- {
s.mu.RLock()
peers := s.peers[i]
s.mu.RUnlock()
for _, peer := range peers {
stop, next, err := pf(peer, uint8(i))
if err != nil {
return err
}
if stop {
return nil
}
if next {
break
}
}
}
return nil
}
// EachBinRev iterates over all peers from shallowest bin to deepest.
func (s *PSlice) EachBinRev(pf model.EachPeerFunc) error {
for i := 0; i < s.maxBins; i++ {
s.mu.RLock()
peers := s.peers[i]
s.mu.RUnlock()
for _, peer := range peers {
stop, next, err := pf(peer, uint8(i))
if err != nil {
return err
}
if stop {
return nil
}
if next {
break
}
}
}
return nil
}
func (s *PSlice) BinSize(bin uint8) int {
if int(bin) >= s.maxBins {
return 0
}
s.mu.RLock()
defer s.mu.RUnlock()
return len(s.peers[bin])
}
func (s *PSlice) BinPeers(bin uint8) []boson.Address {
if int(bin) >= s.maxBins {
return nil
}
s.mu.RLock()
defer s.mu.RUnlock()
ret := make([]boson.Address, len(s.peers[bin]))
copy(ret, s.peers[bin])
return ret
}
// Length returns the number of peers in the Pslice.
func (s *PSlice) Length() int {
s.mu.RLock()
defer s.mu.RUnlock()
var ret int
for _, peers := range s.peers {
ret += len(peers)
}
return ret
}
// ShallowestEmpty returns the shallowest empty bin if one exists.
// If such bin does not exists, returns true as bool value.
func (s *PSlice) ShallowestEmpty() (uint8, bool) {
s.mu.RLock()
defer s.mu.RUnlock()
for i, peers := range s.peers {
if len(peers) == 0 {
return uint8(i), false
}
}
return 0, true
}
// Exists checks if a peer exists.
func (s *PSlice) Exists(addr boson.Address) bool {
s.mu.RLock()
defer s.mu.RUnlock()
e, _ := s.index(addr, s.po(addr.Bytes()))
return e
}
// Remove a peer at a certain PO.
func (s *PSlice) Remove(addr boson.Address) {
s.mu.Lock()
defer s.mu.Unlock()
po := s.po(addr.Bytes())
e, i := s.index(addr, po)
if !e {
return
}
// Since order of elements does not matter, the optimized removing process
// below replaces the index to be removed with the last element of the array,
// and shortens the array by one.
// make copy of the bin slice with one fewer element
newLength := len(s.peers[po]) - 1
cpy := make([]boson.Address, newLength)
copy(cpy, s.peers[po][:newLength])
// if the index is the last element, then assign slice and return early
if i == newLength {
s.peers[po] = cpy
return
}
// replace index being removed with last element
lastItem := s.peers[po][newLength]
cpy[i] = lastItem
// assign the copy with the index removed back to the original array
s.peers[po] = cpy
}
func (s *PSlice) po(peer []byte) uint8 {
po := boson.Proximity(s.baseBytes, peer)
if int(po) >= s.maxBins {
return uint8(s.maxBins) - 1
}
return po
}
// index returns if a peer exists and the index in the slice.
func (s *PSlice) index(addr boson.Address, po uint8) (bool, int) {
for i, peer := range s.peers[po] {
if peer.Equal(addr) {
return true, i
}
}
return false, 0
}