/
cache.go
138 lines (125 loc) · 2.55 KB
/
cache.go
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package ndn
import (
"container/list"
"crypto/sha256"
"fmt"
"sync"
"time"
"github.com/NDNLink/lpm"
"github.com/NDNLink/tlv"
)
// Cache stores data packet and finds data packet by interest
type Cache interface {
Add(*Data)
Get(*Interest) *Data
}
// NewCache creates a new thread-safe in-memory LRU content store
func NewCache(size int) Cache {
return &cache{
List: list.New(),
size: size,
}
}
type cache struct {
cacheMatcher
*list.List
size int
sync.Mutex
}
type cacheEntry struct {
*Data
time.Time
remove func()
}
func (c *cache) Add(d *Data) {
h := sha256.New()
err := d.WriteTo(tlv.NewWriter(h))
if err != nil {
return
}
digest := lpm.Component(h.Sum(nil))
components := append(d.Name.Components, digest)
key := fmt.Sprintf("%s/%s", d.Name, digest)
c.Lock()
defer c.Unlock()
// check for existing element
if m, ok := c.cacheMatcher.Get(components); ok {
if elem, ok := m[key]; ok {
c.MoveToFront(elem)
return
}
}
// add new element
elem := c.PushFront(cacheEntry{
Data: d,
Time: time.Now(),
remove: func() {
c.UpdateAll(components, func(_ []lpm.Component, m map[string]*list.Element) (map[string]*list.Element, bool) {
delete(m, key)
if len(m) == 0 {
return nil, true
}
return m, false
})
},
})
c.UpdateAll(components, func(_ []lpm.Component, m map[string]*list.Element) (map[string]*list.Element, bool) {
if m == nil {
m = make(map[string]*list.Element)
}
m[key] = elem
return m, false
})
// evict oldest element
if c.Len() <= c.size {
return
}
elem = c.Back()
if elem == nil {
return
}
c.Remove(elem).(cacheEntry).remove()
}
func (c *cache) Get(i *Interest) *Data {
components := i.Name.Components
if len(i.Name.ImplicitDigestSHA256) != 0 {
components = append(components, i.Name.ImplicitDigestSHA256)
}
c.Lock()
defer c.Unlock()
var match *list.Element
m, ok := c.cacheMatcher.Get(components)
if !ok {
return nil
}
for _, elem := range m {
ent := elem.Value.(cacheEntry)
if !i.Selectors.Match(ent.Data, i.Name.Len()) {
continue
}
if i.Selectors.MustBeFresh && ent.MetaInfo.FreshnessPeriod > 0 &&
time.Since(ent.Time) > time.Duration(ent.MetaInfo.FreshnessPeriod)*time.Millisecond {
continue
}
if match == nil {
match = elem
} else {
cmp := ent.Name.Compare(match.Value.(cacheEntry).Name)
switch i.Selectors.ChildSelector {
case 0:
if cmp < 0 {
match = elem
}
case 1:
if cmp > 0 {
match = elem
}
}
}
}
if match != nil {
c.MoveToFront(match)
return match.Value.(cacheEntry).Data
}
return nil
}