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simple.go
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simple.go
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package mcache
import (
"container/heap"
"context"
"sync"
"time"
)
type SimpleCache struct {
clock Clock
items map[string]simpleItem
pq simplepq
cap int
sync.Mutex
}
func (c *SimpleCache) Init(clock Clock, capacity int) {
c.clock = clock
c.items = make(map[string]simpleItem, capacity)
c.pq = make(simplepq, 0, capacity)
c.cap = capacity
}
func (c *SimpleCache) Set(ctx context.Context, key string, val interface{}, ttl time.Duration) error {
c.Lock()
defer c.Unlock()
value := deref(val)
var entry = simpleEntry{
key: key,
}
item, ok := c.items[key]
if ttl > 0 {
item.expireAt = c.clock.Now().Add(ttl)
} else {
item.expireAt = c.clock.Now().Add(defaultExpiredAt)
}
if ok {
item.value = value
entry.priority = item.expireAt.UnixNano()
c.pq.update(entry.index)
} else {
c.evict(ctx, 1)
item.value = value
item.index = c.pq.Len()
c.items[key] = item
entry.item = &item
entry.priority = item.expireAt.UnixNano()
heap.Push(&c.pq, entry)
}
return nil
}
func (c *SimpleCache) Get(ctx context.Context, key string) (interface{}, error) {
c.Lock()
defer c.Unlock()
item, ok := c.items[key]
if ok {
if !item.IsExpired(c.clock) {
return item.value, nil
}
c.remove(ctx, key)
return nil, KeyExpiredError
}
return nil, KeyNotFoundError
}
func (c *SimpleCache) Exists(ctx context.Context, key string) bool {
c.Lock()
defer c.Unlock()
item, ok := c.items[key]
if !ok {
return false
}
if item.IsExpired(c.clock) {
c.remove(ctx, key)
return false
}
return true
}
func (c *SimpleCache) Remove(ctx context.Context, key string) bool {
c.Lock()
defer c.Unlock()
return c.remove(ctx, key)
}
func (c *SimpleCache) Evict(ctx context.Context, count int) {
c.Lock()
defer c.Unlock()
c.evict(ctx, count)
}
func (c *SimpleCache) remove(ctx context.Context, key string) bool {
item, ok := c.items[key]
if ok {
heap.Remove(&c.pq, item.index)
delete(c.items, key)
return true
}
return false
}
func (c *SimpleCache) evict(ctx context.Context, count int) {
if len(c.items) < c.cap {
return
}
cnt := 0
now := c.clock.Now()
if n := c.pq.Len(); n > 0 {
entry := c.pq[0]
item := c.items[entry.key]
if now.After(item.expireAt) {
heap.Pop(&c.pq)
delete(c.items, entry.key)
cnt++
}
}
for k, v := range c.items {
if cnt >= count {
return
}
heap.Remove(&c.pq, v.index)
delete(c.items, k)
cnt++
}
}
type simpleItem struct {
value interface{}
expireAt time.Time
index int
}
func (si simpleItem) IsExpired(clock Clock) bool {
return si.expireAt.Before(clock.Now())
}
type simpleEntry struct {
key string
item *simpleItem
priority int64
index int
}
type simplepq []simpleEntry
func (pq simplepq) Len() int { return len(pq) }
func (pq simplepq) Less(i, j int) bool {
return pq[i].priority < pq[j].priority
}
func (pq simplepq) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
pq[i].index = i
pq[i].item.index = i
pq[j].index = j
pq[j].item.index = j
}
func (pq *simplepq) Push(x interface{}) {
n := len(*pq)
entry := x.(simpleEntry)
entry.index = n
*pq = append(*pq, entry)
}
func (pq *simplepq) Pop() interface{} {
old := *pq
n := len(old)
entry := old[0]
entry.index = -1
*pq = old[1:n]
return entry
}
func (pq *simplepq) update(index int) {
heap.Fix(pq, index)
}