Release v0.1.0

vendor/github.com/btcsuite/btcd/peer/mrunoncemap.go

@@ -0,0 +1,125 @@
+// Copyright (c) 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"
+)
+
+// mruNonceMap 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 mruNonceMap struct {
+	mtx       sync.Mutex
+	nonceMap  map[uint64]*list.Element // nearly O(1) lookups
+	nonceList *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 *mruNonceMap) String() string {
+	m.mtx.Lock()
+	defer m.mtx.Unlock()
+
+	lastEntryNum := len(m.nonceMap) - 1
+	curEntry := 0
+	buf := bytes.NewBufferString("[")
+	for nonce := range m.nonceMap {
+		buf.WriteString(fmt.Sprintf("%d", nonce))
+		if curEntry < lastEntryNum {
+			buf.WriteString(", ")
+		}
+		curEntry++
+	}
+	buf.WriteString("]")
+
+	return fmt.Sprintf("<%d>%s", m.limit, buf.String())
+}
+
+// Exists returns whether or not the passed nonce is in the map.
+//
+// This function is safe for concurrent access.
+func (m *mruNonceMap) Exists(nonce uint64) bool {
+	m.mtx.Lock()
+	_, exists := m.nonceMap[nonce]
+	m.mtx.Unlock()
+
+	return exists
+}
+
+// Add adds the passed nonce 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 *mruNonceMap) Add(nonce uint64) {
+	m.mtx.Lock()
+	defer m.mtx.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.nonceMap[nonce]; exists {
+		m.nonceList.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.nonceMap))+1 > m.limit {
+		node := m.nonceList.Back()
+		lru := node.Value.(uint64)
+
+		// Evict least recently used item.
+		delete(m.nonceMap, lru)
+
+		// Reuse the list node of the item that was just evicted for the
+		// new item.
+		node.Value = nonce
+		m.nonceList.MoveToFront(node)
+		m.nonceMap[nonce] = node
+		return
+	}
+
+	// The limit hasn't been reached yet, so just add the new item.
+	node := m.nonceList.PushFront(nonce)
+	m.nonceMap[nonce] = node
+}
+
+// Delete deletes the passed nonce from the map (if it exists).
+//
+// This function is safe for concurrent access.
+func (m *mruNonceMap) Delete(nonce uint64) {
+	m.mtx.Lock()
+	if node, exists := m.nonceMap[nonce]; exists {
+		m.nonceList.Remove(node)
+		delete(m.nonceMap, nonce)
+	}
+	m.mtx.Unlock()
+}
+
+// newMruNonceMap returns a new nonce 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 newMruNonceMap(limit uint) *mruNonceMap {
+	m := mruNonceMap{
+		nonceMap:  make(map[uint64]*list.Element),
+		nonceList: list.New(),
+		limit:     limit,
+	}
+	return &m
+}