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89 lines
2.8 KiB
89 lines
2.8 KiB
2 years ago
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// Copyright 2022 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package lru
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import (
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"math"
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"sync"
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"github.com/ethereum/go-ethereum/common"
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"github.com/hashicorp/golang-lru/simplelru"
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)
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// SizeConstrainedLRU is a wrapper around simplelru.LRU. The simplelru.LRU is capable
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// of item-count constraints, but is not capable of enforcing a byte-size constraint,
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// hence this wrapper.
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// OBS: This cache assumes that items are content-addressed: keys are unique per content.
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// In other words: two Add(..) with the same key K, will always have the same value V.
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type SizeConstrainedLRU struct {
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size uint64
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maxSize uint64
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lru *simplelru.LRU
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lock sync.RWMutex
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}
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// NewSizeConstrainedLRU creates a new SizeConstrainedLRU.
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func NewSizeConstrainedLRU(max uint64) *SizeConstrainedLRU {
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lru, err := simplelru.NewLRU(math.MaxInt, nil)
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if err != nil {
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panic(err)
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}
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return &SizeConstrainedLRU{
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size: 0,
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maxSize: max,
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lru: lru,
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}
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}
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// Add adds a value to the cache. Returns true if an eviction occurred.
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// OBS: This cache assumes that items are content-addressed: keys are unique per content.
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// In other words: two Add(..) with the same key K, will always have the same value V.
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// OBS: The value is _not_ copied on Add, so the caller must not modify it afterwards.
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func (c *SizeConstrainedLRU) Add(key common.Hash, value []byte) (evicted bool) {
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c.lock.Lock()
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defer c.lock.Unlock()
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// Unless it is already present, might need to evict something.
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// OBS: If it is present, we still call Add internally to bump the recentness.
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if !c.lru.Contains(key) {
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targetSize := c.size + uint64(len(value))
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for targetSize > c.maxSize {
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evicted = true
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_, v, ok := c.lru.RemoveOldest()
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if !ok {
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// list is now empty. Break
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break
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}
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targetSize -= uint64(len(v.([]byte)))
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}
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c.size = targetSize
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}
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c.lru.Add(key, value)
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return evicted
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}
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// Get looks up a key's value from the cache.
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func (c *SizeConstrainedLRU) Get(key common.Hash) []byte {
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c.lock.RLock()
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defer c.lock.RUnlock()
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if v, ok := c.lru.Get(key); ok {
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return v.([]byte)
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}
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return nil
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}
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