98 lines
2.7 KiB
Go
98 lines
2.7 KiB
Go
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package main
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import (
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"container/list"
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"fmt"
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"github.com/btcsuite/btcwire"
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)
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// MruInventoryMap provides a map that is limited to a maximum number of items
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// with eviction for the oldest entry when the limit is exceeded.
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type MruInventoryMap struct {
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invMap map[btcwire.InvVect]*list.Element // nearly O(1) lookups
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invList *list.List // O(1) insert, update, delete
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limit uint
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}
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// String returns the map as a human-readable string.
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func (m MruInventoryMap) String() string {
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return fmt.Sprintf("<%d>%v", m.limit, m.invMap)
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}
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// Exists returns whether or not the passed inventory item is in the map.
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func (m *MruInventoryMap) Exists(iv *btcwire.InvVect) bool {
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if _, exists := m.invMap[*iv]; exists {
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return true
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}
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return false
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}
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// Add adds the passed inventory to the map and handles eviction of the oldest
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// item if adding the new item would exceed the max limit.
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func (m *MruInventoryMap) Add(iv *btcwire.InvVect) {
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// When the limit is zero, nothing can be added to the map, so just
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// return.
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if m.limit == 0 {
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return
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}
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// When the entry already exists move it to the front of the list
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// thereby marking it most recently used.
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if node, exists := m.invMap[*iv]; exists {
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m.invList.MoveToFront(node)
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return
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}
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// Evict the least recently used entry (back of the list) if the the new
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// entry would exceed the size limit for the map. Also reuse the list
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// node so a new one doesn't have to be allocated.
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if uint(len(m.invMap))+1 > m.limit {
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node := m.invList.Back()
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lru, ok := node.Value.(*btcwire.InvVect)
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if !ok {
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return
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}
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// Evict least recently used item.
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delete(m.invMap, *lru)
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// Reuse the list node of the item that was just evicted for the
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// new item.
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node.Value = iv
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m.invList.MoveToFront(node)
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m.invMap[*iv] = node
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return
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}
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// The limit hasn't been reached yet, so just add the new item.
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node := m.invList.PushFront(iv)
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m.invMap[*iv] = node
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return
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}
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// Delete deletes the passed inventory item from the map (if it exists).
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func (m *MruInventoryMap) Delete(iv *btcwire.InvVect) {
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if node, exists := m.invMap[*iv]; exists {
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m.invList.Remove(node)
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delete(m.invMap, *iv)
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}
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}
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// NewMruInventoryMap returns a new inventory map that is limited to the number
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// of entries specified by limit. When the number of entries exceeds the limit,
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// the oldest (least recently used) entry will be removed to make room for the
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// new entry.
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func NewMruInventoryMap(limit uint) *MruInventoryMap {
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m := MruInventoryMap{
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invMap: make(map[btcwire.InvVect]*list.Element),
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invList: list.New(),
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limit: limit,
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}
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return &m
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}
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