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79 lines
1.7 KiB
Go
79 lines
1.7 KiB
Go
package main
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import (
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"container/list"
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)
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/* TODO: work on efficiency. use our own lower level data structure? */
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/* FixedMap:
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* A fixed size map that pushes the last
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* used value from the stack if size limit
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* is reached.
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*/
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type FixedMap struct {
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Map map[string]*MapElement
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List *list.List
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Size int
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}
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/* MapElement:
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* Simple structure to wrap pointer to list
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* element and stored map value together.
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*/
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type MapElement struct {
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Element *list.Element
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Value *File
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}
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func NewFixedMap(size int) *FixedMap {
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return &FixedMap{
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make(map[string]*MapElement),
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list.New(),
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size,
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}
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}
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/* Get file in map for key, or nil */
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func (fm *FixedMap) Get(key string) *File {
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elem, ok := fm.Map[key]
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if ok {
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/* And that's an LRU implementation folks! */
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fm.List.MoveToFront(elem.Element)
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return elem.Value
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} else {
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return nil
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}
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}
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/* Put file in map as key, pushing out last file if size limit reached */
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func (fm *FixedMap) Put(key string, value *File) {
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element := fm.List.PushFront(key)
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fm.Map[key] = &MapElement{ element, value }
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if fm.List.Len() > fm.Size {
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/* We're at capacity! SIR! */
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element = fm.List.Back()
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/* We don't check here as we know this is ALWAYS a string */
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key, _ := element.Value.(string)
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/* Finally delete the map entry and list element! */
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delete(fm.Map, key)
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fm.List.Remove(element)
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}
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}
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/* Try delete element, else do nothing */
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func (fm *FixedMap) Remove(key string) {
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elem, ok := fm.Map[key]
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if !ok {
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/* We don't have this key, return */
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return
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}
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/* Remove the selected element */
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delete(fm.Map, key)
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fm.List.Remove(elem.Element)
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}
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