common/prque: implement LazyQueue

common/prque/lazyqueue.go

@@ -0,0 +1,161 @@
+// CookieJar - A contestant's algorithm toolbox
+// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
+//
+// CookieJar is dual licensed: use of this source code is governed by a BSD
+// license that can be found in the LICENSE file. Alternatively, the CookieJar
+// toolbox may be used in accordance with the terms and conditions contained
+// in a signed written agreement between you and the author(s).
+
+// This is a duplicated and slightly modified version of "gopkg.in/karalabe/cookiejar.v2/collections/LazyQueue".
+
+// Package LazyQueue implements a priority queue data structure supporting arbitrary
+// value types and int64 priorities.
+//
+// If you would like to use a min-priority queue, simply negate the priorities.
+//
+// Internally the queue is based on the standard heap package working on a
+// sortable version of the block based stack.
+package prque
+
+import (
+	"container/heap"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+type (
+	PriorityCallback    func(data interface{}, now mclock.AbsTime) int64
+	MaxPriorityCallback func(data interface{}, until mclock.AbsTime) int64
+)
+
+// Priority queue data structure.
+type LazyQueue struct {
+	clock       mclock.Clock
+	queue       [2]*sstack
+	popQueue    *sstack
+	period      time.Duration
+	maxUntil    mclock.AbsTime
+	indexOffset int
+	setIndex    SetIndexCallback
+	priority    PriorityCallback
+	maxPriority MaxPriorityCallback
+}
+
+// New creates a new priority queue.
+func NewLazyQueue(setIndex SetIndexCallback, priority PriorityCallback, maxPriority MaxPriorityCallback, clock mclock.Clock, period time.Duration) *LazyQueue {
+	q := &LazyQueue{
+		popQueue:    newSstack(nil),
+		setIndex:    setIndex,
+		priority:    priority,
+		maxPriority: maxPriority,
+		clock:       clock,
+		period:      period}
+	q.Reset()
+	q.Refresh()
+	return q
+}
+
+func (q *LazyQueue) Refresh() {
+	q.maxUntil = q.clock.Now() + mclock.AbsTime(q.period)
+	for q.queue[0].Len() != 0 {
+		q.Push(heap.Pop(q.queue[0]).(*item).value)
+	}
+	q.queue[0], q.queue[1] = q.queue[1], q.queue[0]
+	q.indexOffset = 1 - q.indexOffset
+	q.maxUntil += mclock.AbsTime(q.period)
+}
+
+func (q *LazyQueue) setIndex0(data interface{}, index int) {
+	q.setIndex(data, index+index)
+}
+
+func (q *LazyQueue) setIndex1(data interface{}, index int) {
+	q.setIndex(data, index+index+1)
+}
+
+// Pushes a value with a given priority into the queue, expanding if necessary.
+func (q *LazyQueue) Push(data interface{}) {
+	heap.Push(q.queue[1], &item{data, q.maxPriority(data, q.maxUntil)})
+}
+
+func (q *LazyQueue) Update(i int) {
+	q.Push(q.Remove(i))
+}
+
+// Pops the value with the greates priority off the stack and returns it.
+// Currently no shrinking is done.
+func (q *LazyQueue) Pop() (interface{}, int64) {
+	var (
+		resData interface{}
+		resPri  int64
+	)
+	q.MultiPop(func(data interface{}, priority int64) bool {
+		resData = data
+		resPri = priority
+		return false
+	})
+	return resData, resPri
+}
+
+func (q *LazyQueue) peekIndex() int {
+	if q.queue[0].Len() != 0 {
+		if q.queue[1].Len() != 0 && q.queue[1].blocks[0][0].priority > q.queue[0].blocks[0][0].priority {
+			return 1
+		}
+		return 0
+	}
+	if q.queue[1].Len() != 0 {
+		return 1
+	}
+	return -1
+}
+
+func (q *LazyQueue) MultiPop(callback func(data interface{}, priority int64) bool) {
+	now := q.clock.Now()
+	nextIndex := q.peekIndex()
+	for nextIndex != -1 {
+		data := heap.Pop(q.queue[nextIndex]).(*item).value
+		q.popQueue.Push(&item{data, q.priority(data, now)})
+		nextIndex = q.peekIndex()
+		for q.popQueue.Len() != 0 && (nextIndex == -1 || q.queue[nextIndex].blocks[0][0].priority < q.popQueue.blocks[0][0].priority) {
+			i := heap.Pop(q.popQueue).(*item)
+			if !callback(i.value, i.priority) {
+				for q.popQueue.Len() != 0 {
+					q.Push(heap.Pop(q.popQueue).(*item).value)
+				}
+				return
+			}
+		}
+	}
+}
+
+// Pops only the item from the queue, dropping the associated priority value.
+func (q *LazyQueue) PopItem() interface{} {
+	i, _ := q.Pop()
+	return i.(*item).value
+}
+
+// Remove removes the element with the given index.
+func (q *LazyQueue) Remove(i int) interface{} {
+	if i < 0 {
+		return nil
+	}
+	return heap.Remove(q.queue[i&1^q.indexOffset], i>>1)
+}
+
+// Checks whether the priority queue is empty.
+func (q *LazyQueue) Empty() bool {
+	return q.queue[0].Len() == 0 && q.queue[1].Len() == 0
+}
+
+// Returns the number of element in the priority queue.
+func (q *LazyQueue) Size() int {
+	return q.queue[0].Len() + q.queue[1].Len()
+}
+
+// Clears the contents of the priority queue.
+func (q *LazyQueue) Reset() {
+	q.queue[0] = newSstack(q.setIndex0)
+	q.queue[1] = newSstack(q.setIndex1)
+}