common/prque: generic priority queue (#26290)

* common, core, eth, les, trie: make prque generic

* les/vflux/server: fixed issues in priorityPool

* common, core, eth, les, trie: make priority also generic in prque

* les/flowcontrol: add test case for priority accumulator overflow

* les/flowcontrol: avoid priority value overflow

* common/prque: use int priority in some tests

No need to convert to int64 when we can just change the type used by the
queue.

* common/prque: remove comment about int64 range

---------

Co-authored-by: Zsolt Felfoldi <zsfelfoldi@gmail.com>
Co-authored-by: Felix Lange <fjl@twurst.com>

common/prque/prque.go

@@ -19,65 +19,59 @@ package prque
 
 import (
 	"container/heap"
+
+	"golang.org/x/exp/constraints"
 )
 
 // Priority queue data structure.
-type Prque struct {
-	cont *sstack
+type Prque[P constraints.Ordered, V any] struct {
+	cont *sstack[P, V]
 }
 
 // New creates a new priority queue.
-func New(setIndex SetIndexCallback) *Prque {
-	return &Prque{newSstack(setIndex, false)}
-}
-
-// NewWrapAround creates a new priority queue with wrap-around priority handling.
-func NewWrapAround(setIndex SetIndexCallback) *Prque {
-	return &Prque{newSstack(setIndex, true)}
+func New[P constraints.Ordered, V any](setIndex SetIndexCallback[V]) *Prque[P, V] {
+	return &Prque[P, V]{newSstack[P, V](setIndex)}
 }
 
 // Pushes a value with a given priority into the queue, expanding if necessary.
-func (p *Prque) Push(data interface{}, priority int64) {
-	heap.Push(p.cont, &item{data, priority})
+func (p *Prque[P, V]) Push(data V, priority P) {
+	heap.Push(p.cont, &item[P, V]{data, priority})
 }
 
 // Peek returns the value with the greatest priority but does not pop it off.
-func (p *Prque) Peek() (interface{}, int64) {
+func (p *Prque[P, V]) Peek() (V, P) {
 	item := p.cont.blocks[0][0]
 	return item.value, item.priority
 }
 
 // Pops the value with the greatest priority off the stack and returns it.
 // Currently no shrinking is done.
-func (p *Prque) Pop() (interface{}, int64) {
-	item := heap.Pop(p.cont).(*item)
+func (p *Prque[P, V]) Pop() (V, P) {
+	item := heap.Pop(p.cont).(*item[P, V])
 	return item.value, item.priority
 }
 
 // Pops only the item from the queue, dropping the associated priority value.
-func (p *Prque) PopItem() interface{} {
-	return heap.Pop(p.cont).(*item).value
+func (p *Prque[P, V]) PopItem() V {
+	return heap.Pop(p.cont).(*item[P, V]).value
 }
 
 // Remove removes the element with the given index.
-func (p *Prque) Remove(i int) interface{} {
-	if i < 0 {
-		return nil
-	}
-	return heap.Remove(p.cont, i)
+func (p *Prque[P, V]) Remove(i int) V {
+	return heap.Remove(p.cont, i).(*item[P, V]).value
 }
 
 // Checks whether the priority queue is empty.
-func (p *Prque) Empty() bool {
+func (p *Prque[P, V]) Empty() bool {
 	return p.cont.Len() == 0
 }
 
 // Returns the number of element in the priority queue.
-func (p *Prque) Size() int {
+func (p *Prque[P, V]) Size() int {
 	return p.cont.Len()
 }
 
 // Clears the contents of the priority queue.
-func (p *Prque) Reset() {
-	*p = *New(p.cont.setIndex)
+func (p *Prque[P, V]) Reset() {
+	*p = *New[P, V](p.cont.setIndex)
 }