102 lines
2.3 KiB
Go
102 lines
2.3 KiB
Go
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package cache
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import (
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"container/list"
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"sync"
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"gopkg.in/src-d/go-git.v4/plumbing"
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)
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// ObjectLRU implements an object cache with an LRU eviction policy and a
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// maximum size (measured in object size).
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type ObjectLRU struct {
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MaxSize FileSize
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actualSize FileSize
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ll *list.List
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cache map[interface{}]*list.Element
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mut sync.Mutex
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}
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// NewObjectLRU creates a new ObjectLRU with the given maximum size. The maximum
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// size will never be exceeded.
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func NewObjectLRU(maxSize FileSize) *ObjectLRU {
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return &ObjectLRU{MaxSize: maxSize}
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}
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// NewObjectLRUDefault creates a new ObjectLRU with the default cache size.
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func NewObjectLRUDefault() *ObjectLRU {
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return &ObjectLRU{MaxSize: DefaultMaxSize}
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}
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// Put puts an object into the cache. If the object is already in the cache, it
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// will be marked as used. Otherwise, it will be inserted. A single object might
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// be evicted to make room for the new object.
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func (c *ObjectLRU) Put(obj plumbing.EncodedObject) {
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c.mut.Lock()
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defer c.mut.Unlock()
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if c.cache == nil {
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c.actualSize = 0
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c.cache = make(map[interface{}]*list.Element, 1000)
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c.ll = list.New()
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}
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objSize := FileSize(obj.Size())
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key := obj.Hash()
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if ee, ok := c.cache[key]; ok {
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oldObj := ee.Value.(plumbing.EncodedObject)
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// in this case objSize is a delta: new size - old size
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objSize -= FileSize(oldObj.Size())
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c.ll.MoveToFront(ee)
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ee.Value = obj
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} else {
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if objSize > c.MaxSize {
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return
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}
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ee := c.ll.PushFront(obj)
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c.cache[key] = ee
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}
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c.actualSize += objSize
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for c.actualSize > c.MaxSize {
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last := c.ll.Back()
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if last == nil {
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c.actualSize = 0
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break
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}
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lastObj := last.Value.(plumbing.EncodedObject)
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lastSize := FileSize(lastObj.Size())
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c.ll.Remove(last)
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delete(c.cache, lastObj.Hash())
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c.actualSize -= lastSize
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}
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}
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// Get returns an object by its hash. It marks the object as used. If the object
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// is not in the cache, (nil, false) will be returned.
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func (c *ObjectLRU) Get(k plumbing.Hash) (plumbing.EncodedObject, bool) {
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c.mut.Lock()
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defer c.mut.Unlock()
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ee, ok := c.cache[k]
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if !ok {
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return nil, false
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}
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c.ll.MoveToFront(ee)
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return ee.Value.(plumbing.EncodedObject), true
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}
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// Clear the content of this object cache.
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func (c *ObjectLRU) Clear() {
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c.mut.Lock()
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defer c.mut.Unlock()
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c.ll = nil
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c.cache = nil
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c.actualSize = 0
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}
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