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|
package cache
import (
"bytes"
"sync"
"time"
)
type node struct {
Hash uint64
Expiration time.Time
Access uint64
Key []byte
Value []byte
HashNext *node
HashPrev *node
EvictNext *node
EvictPrev *node
}
func (n *node) IsValid() bool {
return n.Expiration.IsZero() || n.Expiration.After(time.Now())
}
func (n *node) TTL() time.Duration {
if n.Expiration.IsZero() {
return 0
} else {
return time.Until(n.Expiration)
}
}
type store struct {
Bucket []node
Length uint64
Cost uint64
Evict node
MaxCost uint64
Policy evictionPolicy
mu sync.Mutex
}
func (s *store) Init() {
s.Clear()
s.Policy.evict = &s.Evict
s.Policy.SetPolicy(PolicyNone)
}
func (s *store) Clear() {
s.mu.Lock()
defer s.mu.Unlock()
s.Bucket = make([]node, 8)
s.Length = 0
s.Cost = 0
s.Evict.EvictNext = &s.Evict
s.Evict.EvictPrev = &s.Evict
}
func lookup(s *store, key []byte) (uint64, uint64) {
hash := hash(key)
return hash % uint64(len(s.Bucket)), hash
}
func lazyInitBucket(n *node) {
if n.HashNext == nil {
n.HashNext = n
n.HashPrev = n
}
}
func (s *store) lookup(key []byte) (*node, uint64, uint64) {
idx, hash := lookup(s, key)
bucket := &s.Bucket[idx]
lazyInitBucket(bucket)
for v := bucket.HashNext; v != bucket; v = v.HashNext {
if bytes.Equal(key, v.Key) {
return v, idx, hash
}
}
return nil, idx, hash
}
func (s *store) get(key []byte) ([]byte, time.Duration, bool) {
v, _, _ := s.lookup(key)
if v != nil {
if !v.IsValid() {
deleteNode(s, v)
return nil, 0, false
}
s.Policy.OnAccess(v)
return v.Value, v.TTL(), true
}
return nil, 0, false
}
func (s *store) Get(key []byte) ([]byte, time.Duration, bool) {
s.mu.Lock()
defer s.mu.Unlock()
return s.get(key)
}
func resize(s *store) {
bucket := make([]node, 2*len(s.Bucket))
for v := s.Evict.EvictNext; v != &s.Evict; v = v.EvictNext {
if !v.IsValid() {
continue
}
idx := v.Hash % uint64(len(bucket))
n := &bucket[idx]
lazyInitBucket(n)
v.HashPrev = n
v.HashNext = v.HashPrev.HashNext
v.HashNext.HashPrev = v
v.HashPrev.HashNext = v
}
s.Bucket = bucket
}
func cleanup(s *store) {
for v := s.Evict.EvictNext; v != &s.Evict; v = v.EvictNext {
if !v.IsValid() {
deleteNode(s, v)
}
}
}
func evict(s *store) bool {
for s.MaxCost != 0 && s.MaxCost < s.Cost {
n := s.Policy.Evict()
if n == nil {
break
}
deleteNode(s, n)
}
return true
}
func (s *store) set(key []byte, value []byte, ttl time.Duration) {
v, idx, hash := s.lookup(key)
if v != nil {
s.Cost = s.Cost + uint64(len(value)) - uint64(len(v.Value))
v.Value = value
v.Expiration = time.Now().Add(ttl)
s.Policy.OnAccess(v)
}
bucket := &s.Bucket[idx]
if float64(s.Length)/float64(len(s.Bucket)) > 0.75 {
resize(s)
//resize may invidate pointer to bucket
bucket = &s.Bucket[idx]
lazyInitBucket(bucket)
}
node := &node{
Hash: hash,
Key: key,
Value: value,
}
if ttl != 0 {
node.Expiration = time.Now().Add(ttl)
}
node.HashPrev = bucket
node.HashNext = node.HashPrev.HashNext
node.HashNext.HashPrev = node
node.HashPrev.HashNext = node
s.Policy.OnInsert(node)
s.Cost = s.Cost + uint64(len(key)) + uint64(len(value))
s.Length = s.Length + 1
}
func (s *store) Set(key []byte, value []byte, ttl time.Duration) {
s.mu.Lock()
defer s.mu.Unlock()
s.set(key, value, ttl)
}
func deleteNode(s *store, v *node) {
v.HashNext.HashPrev = v.HashPrev
v.HashPrev.HashNext = v.HashNext
v.HashNext = nil
v.HashPrev = nil
v.EvictNext.EvictPrev = v.EvictPrev
v.EvictPrev.EvictNext = v.EvictNext
v.EvictNext = nil
v.EvictPrev = nil
s.Cost = s.Cost - (uint64(len(v.Key)) + uint64(len(v.Value)))
s.Length = s.Length - 1
}
func (s *store) delete(key []byte) bool {
v, _, _ := s.lookup(key)
if v != nil {
deleteNode(s, v)
return true
}
return false
}
func (s *store) Delete(key []byte) bool {
s.mu.Lock()
defer s.mu.Unlock()
return s.delete(key)
}
|
