forked from btcsuite/btcd
/
mruinvmap.go
132 lines (113 loc) · 3.44 KB
/
mruinvmap.go
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// Copyright (c) 2013-2015 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package peer
import (
"bytes"
"container/list"
"fmt"
"sync"
"github.com/gcash/bchd/wire"
)
// mruInventoryMap provides a concurrency safe map that is limited to a maximum
// number of items with eviction for the oldest entry when the limit is
// exceeded.
type mruInventoryMap struct {
invMtx sync.Mutex
invMap map[wire.InvVect]*list.Element // nearly O(1) lookups
invList *list.List // O(1) insert, update, delete
limit uint
}
// String returns the map as a human-readable string.
//
// This function is safe for concurrent access.
func (m *mruInventoryMap) String() string {
m.invMtx.Lock()
defer m.invMtx.Unlock()
lastEntryNum := len(m.invMap) - 1
curEntry := 0
buf := bytes.NewBufferString("[")
for iv := range m.invMap {
buf.WriteString(fmt.Sprintf("%v", iv))
if curEntry < lastEntryNum {
buf.WriteString(", ")
}
curEntry++
}
buf.WriteString("]")
return fmt.Sprintf("<%d>%s", m.limit, buf.String())
}
// Exists returns whether or not the passed inventory item is in the map.
//
// This function is safe for concurrent access.
func (m *mruInventoryMap) Exists(iv *wire.InvVect) bool {
m.invMtx.Lock()
defer m.invMtx.Unlock()
_, exists := m.invMap[*iv]
return exists
}
// Add adds the passed inventory to the map and handles eviction of the oldest
// item if adding the new item would exceed the max limit. Adding an existing
// item makes it the most recently used item.
//
// This function is safe for concurrent access.
func (m *mruInventoryMap) Add(iv *wire.InvVect) {
m.invMtx.Lock()
defer m.invMtx.Unlock()
// When the limit is zero, nothing can be added to the map, so just
// return.
if m.limit == 0 {
return
}
// When the entry already exists move it to the front of the list
// thereby marking it most recently used.
if node, exists := m.invMap[*iv]; exists {
m.invList.MoveToFront(node)
return
}
// Evict the least recently used entry (back of the list) if the the new
// entry would exceed the size limit for the map. Also reuse the list
// node so a new one doesn't have to be allocated.
if uint(len(m.invMap))+1 > m.limit {
node := m.invList.Back()
lru, ok := node.Value.(*wire.InvVect)
// Don't panic if assertion failed
if !ok {
return
}
// Evict least recently used item.
delete(m.invMap, *lru)
// Reuse the list node of the item that was just evicted for the
// new item.
node.Value = iv
m.invList.MoveToFront(node)
m.invMap[*iv] = node
return
}
// The limit hasn't been reached yet, so just add the new item.
node := m.invList.PushFront(iv)
m.invMap[*iv] = node
}
// Delete deletes the passed inventory item from the map (if it exists).
//
// This function is safe for concurrent access.
func (m *mruInventoryMap) Delete(iv *wire.InvVect) {
m.invMtx.Lock()
defer m.invMtx.Unlock()
if node, exists := m.invMap[*iv]; exists {
m.invList.Remove(node)
delete(m.invMap, *iv)
}
}
// newMruInventoryMap returns a new inventory map that is limited to the number
// of entries specified by limit. When the number of entries exceeds the limit,
// the oldest (least recently used) entry will be removed to make room for the
// new entry.
func newMruInventoryMap(limit uint) *mruInventoryMap {
m := mruInventoryMap{
invMap: make(map[wire.InvVect]*list.Element),
invList: list.New(),
limit: limit,
}
return &m
}