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99 lines
2.5 KiB
Go
99 lines
2.5 KiB
Go
// Licensed to the LF AI & Data foundation under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cache
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import (
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"container/list"
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)
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// lruCache is a LRU cache.
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type lruCache struct {
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cache *cache
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cap int64
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ls list.List
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}
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// init initializes cache list.
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func (l *lruCache) init(c *cache, cap int64) {
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l.cache = c
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l.cap = cap
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l.ls.Init()
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}
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// write adds new entry to the cache and returns evicted entry if necessary.
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func (l *lruCache) write(en *entry) *entry {
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// Fast path
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if en.accessList != nil {
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// Entry existed, update its status instead.
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l.markAccess(en)
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return nil
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}
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// Try to add new entry to the list
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cen := l.cache.getOrSet(en)
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if cen == nil {
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// Brand new entry, add to the LRU list.
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en.accessList = l.ls.PushFront(en)
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} else {
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// Entry has already been added, update its value instead.
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cen.setValue(en.getValue())
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cen.setWriteTime(en.getWriteTime())
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if cen.accessList == nil {
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// Entry is loaded to the cache but not yet registered.
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cen.accessList = l.ls.PushFront(cen)
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} else {
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l.markAccess(cen)
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}
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}
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if l.cap > 0 && int64(l.ls.Len()) > l.cap {
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// Remove the last element when capacity exceeded.
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en = getEntry(l.ls.Back())
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return l.remove(en)
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}
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return nil
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}
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// access updates cache entry for a get.
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func (l *lruCache) access(en *entry) {
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if en.accessList != nil {
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l.markAccess(en)
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}
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}
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// markAccess marks the element has just been accessed.
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// en.accessList must not be null.
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func (l *lruCache) markAccess(en *entry) {
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l.ls.MoveToFront(en.accessList)
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}
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// remove an entry from the cache.
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func (l *lruCache) remove(en *entry) *entry {
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if en.accessList == nil {
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// Already deleted
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return nil
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}
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l.cache.delete(en)
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l.ls.Remove(en.accessList)
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en.accessList = nil
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return en
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}
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// iterate walks through all lists by access time.
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func (l *lruCache) iterate(fn func(en *entry) bool) {
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iterateListFromBack(&l.ls, fn)
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}
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