98 lines
2.3 KiB
Go
98 lines
2.3 KiB
Go
package ccache
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import (
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"strings"
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"sync"
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"time"
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)
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type bucket struct {
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sync.RWMutex
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lookup map[string]*Item
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}
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func (b *bucket) itemCount() int {
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b.RLock()
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defer b.RUnlock()
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return len(b.lookup)
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}
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func (b *bucket) get(key string) *Item {
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b.RLock()
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defer b.RUnlock()
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return b.lookup[key]
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}
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func (b *bucket) set(key string, value interface{}, duration time.Duration) (*Item, *Item) {
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expires := time.Now().Add(duration).UnixNano()
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item := newItem(key, value, expires)
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b.Lock()
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existing := b.lookup[key]
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b.lookup[key] = item
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b.Unlock()
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return item, existing
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}
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func (b *bucket) delete(key string) *Item {
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b.Lock()
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item := b.lookup[key]
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delete(b.lookup, key)
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b.Unlock()
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return item
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}
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// This is an expensive operation, so we do what we can to optimize it and limit
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// the impact it has on concurrent operations. Specifically, we:
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// 1 - Do an initial iteration to collect matches. This allows us to do the
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// "expensive" prefix check (on all values) using only a read-lock
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// 2 - Do a second iteration, under write lock, for the matched results to do
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// the actual deletion
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// Also, this is the only place where the Bucket is aware of cache detail: the
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// deletables channel. Passing it here lets us avoid iterating over matched items
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// again in the cache. Further, we pass item to deletables BEFORE actually removing
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// the item from the map. I'm pretty sure this is 100% fine, but it is unique.
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// (We do this so that the write to the channel is under the read lock and not the
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// write lock)
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func (b *bucket) deleteFunc(matches func(key string, item interface{}) bool, deletables chan *Item) int {
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lookup := b.lookup
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b.RLock()
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l := len(lookup)
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b.RUnlock()
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items := make([]*Item, 0, l/10)
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b.RLock()
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for key, item := range lookup {
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if matches(key, item) {
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deletables <- item
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items = append(items, item)
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}
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}
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b.RUnlock()
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if len(items) == 0 {
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// avoid the write lock if we can
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return 0
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}
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b.Lock()
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for _, item := range items {
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delete(lookup, item.key)
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}
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b.Unlock()
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return len(items)
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}
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func (b *bucket) deletePrefix(prefix string, deletables chan *Item) int {
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return b.deleteFunc(func(key string, item interface{}) bool {
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return strings.HasPrefix(key, prefix)
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}, deletables)
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}
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func (b *bucket) clear() {
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b.Lock()
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b.lookup = make(map[string]*Item)
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b.Unlock()
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}
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