100 lines
2.1 KiB
Go
100 lines
2.1 KiB
Go
|
package lrucache
|
||
|
|
|
||
|
|
import (
|
||
|
|
"hash/crc32"
|
||
|
|
"sync"
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
// hashCode hashes a string to a unique hashcode.
|
||
|
|
//
|
||
|
|
// crc32 returns a uint32, but for our use we need
|
||
|
|
// and non negative integer. Here we cast to an integer
|
||
|
|
// and invert it if the result is negative.
|
||
|
|
func hashCode(s string) (hc int) {
|
||
|
|
hc = int(crc32.ChecksumIEEE([]byte(s)))
|
||
|
|
if hc >= 0 {
|
||
|
|
return hc
|
||
|
|
}
|
||
|
|
if -hc >= 0 {
|
||
|
|
return -hc
|
||
|
|
}
|
||
|
|
// hc == MinInt
|
||
|
|
return hc
|
||
|
|
}
|
||
|
|
|
||
|
|
// SyncCache - concurrent cache structure
|
||
|
|
type SyncCache struct {
|
||
|
|
locks []sync.Mutex
|
||
|
|
caches []*LRUCache
|
||
|
|
mask int
|
||
|
|
timeout int64
|
||
|
|
}
|
||
|
|
|
||
|
|
type scValue struct {
|
||
|
|
Value interface{}
|
||
|
|
ts int64
|
||
|
|
}
|
||
|
|
|
||
|
|
func nextPowOf2(cap int) int {
|
||
|
|
if cap < 2 {
|
||
|
|
return 2
|
||
|
|
}
|
||
|
|
if cap&(cap-1) == 0 {
|
||
|
|
return cap
|
||
|
|
}
|
||
|
|
cap |= cap >> 1
|
||
|
|
cap |= cap >> 2
|
||
|
|
cap |= cap >> 4
|
||
|
|
cap |= cap >> 8
|
||
|
|
cap |= cap >> 16
|
||
|
|
return cap + 1
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewSyncCache - create sync cache
|
||
|
|
// `capacity` is lru cache length of each bucket
|
||
|
|
// store `capacity * bucket` count of element in SyncCache at most
|
||
|
|
// `timeout` is in seconds
|
||
|
|
func NewSyncCache(capacity int, bucket int, timeout int64) *SyncCache {
|
||
|
|
size := nextPowOf2(bucket)
|
||
|
|
sc := SyncCache{make([]sync.Mutex, size), make([]*LRUCache, size), size - 1, timeout}
|
||
|
|
for i := range sc.caches {
|
||
|
|
sc.caches[i] = New(capacity)
|
||
|
|
}
|
||
|
|
return &sc
|
||
|
|
}
|
||
|
|
|
||
|
|
// Put - put a cache item into sync cache
|
||
|
|
func (sc *SyncCache) Put(key string, value interface{}) {
|
||
|
|
idx := hashCode(key) & sc.mask
|
||
|
|
sc.locks[idx].Lock()
|
||
|
|
sc.caches[idx].Put(key, &scValue{value, time.Now().Unix()})
|
||
|
|
sc.locks[idx].Unlock()
|
||
|
|
}
|
||
|
|
|
||
|
|
// Get - get value of key from sync cache with result
|
||
|
|
func (sc *SyncCache) Get(key string) (interface{}, bool) {
|
||
|
|
idx := hashCode(key) & sc.mask
|
||
|
|
sc.locks[idx].Lock()
|
||
|
|
v, b := sc.caches[idx].Get(key)
|
||
|
|
if !b {
|
||
|
|
sc.locks[idx].Unlock()
|
||
|
|
return nil, false
|
||
|
|
}
|
||
|
|
if time.Now().Unix()-v.(*scValue).ts >= sc.timeout {
|
||
|
|
sc.caches[idx].Delete(key)
|
||
|
|
sc.locks[idx].Unlock()
|
||
|
|
return nil, false
|
||
|
|
}
|
||
|
|
sc.locks[idx].Unlock()
|
||
|
|
return v.(*scValue).Value, b
|
||
|
|
}
|
||
|
|
|
||
|
|
// Delete - delete item by key from sync cache
|
||
|
|
func (sc *SyncCache) Delete(key string) {
|
||
|
|
idx := hashCode(key) & sc.mask
|
||
|
|
sc.locks[idx].Lock()
|
||
|
|
sc.caches[idx].Delete(key)
|
||
|
|
sc.locks[idx].Unlock()
|
||
|
|
}
|