mirror of https://github.com/tikv/client-go.git
147 lines
3.3 KiB
Go
147 lines
3.3 KiB
Go
// Copyright 2023 TiKV Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package client
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import "container/heap"
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// Item is the interface that all entries in a priority queue must implement.
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type Item interface {
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priority() uint64
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// isCanceled returns true if the item is canceled by the caller.
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isCanceled() bool
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}
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// entry is an entry in a priority queue.
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//type entry struct {
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// entry Item
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//}
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// prioritySlice implements heap.Interface and holds Entries.
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type prioritySlice []Item
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// Len returns the length of the priority queue.
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func (ps prioritySlice) Len() int {
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return len(ps)
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}
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// Less compares two entries in the priority queue.
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// The higher priority entry is the one with the lower value.
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func (ps prioritySlice) Less(i, j int) bool {
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return ps[i].priority() > ps[j].priority()
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}
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// Swap swaps two entries in the priority queue.
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func (ps prioritySlice) Swap(i, j int) {
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ps[i], ps[j] = ps[j], ps[i]
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}
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// Push adds an entry to the priority queue.
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func (ps *prioritySlice) Push(x interface{}) {
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item := x.(Item)
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*ps = append(*ps, item)
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}
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// Pop removes the highest priority entry from the priority queue.
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func (ps *prioritySlice) Pop() interface{} {
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old := *ps
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n := len(old)
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item := old[n-1]
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*ps = old[0 : n-1]
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return item
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}
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// PriorityQueue is a priority queue.
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type PriorityQueue struct {
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ps prioritySlice
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}
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// NewPriorityQueue creates a new priority queue.
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func NewPriorityQueue() *PriorityQueue {
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return &PriorityQueue{}
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}
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// Len returns the length of the priority queue.
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func (pq *PriorityQueue) Len() int {
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return pq.ps.Len()
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}
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// Push adds an entry to the priority queue.
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func (pq *PriorityQueue) Push(item Item) {
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heap.Push(&pq.ps, item)
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}
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// pop removes the highest priority entry from the priority queue.
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func (pq *PriorityQueue) pop() Item {
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e := heap.Pop(&pq.ps)
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if e == nil {
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return nil
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}
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return e.(Item)
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}
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// Take returns the highest priority entries from the priority queue.
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func (pq *PriorityQueue) Take(n int) []Item {
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if n <= 0 {
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return nil
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}
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if n >= pq.Len() {
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ret := pq.ps
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pq.ps = pq.ps[:0]
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return ret
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} else {
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ret := make([]Item, n)
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for i := 0; i < n; i++ {
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ret[i] = pq.pop()
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}
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return ret
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}
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}
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func (pq *PriorityQueue) highestPriority() uint64 {
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if pq.Len() == 0 {
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return 0
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}
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return pq.ps[0].priority()
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}
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// all returns all entries in the priority queue not ensure the priority.
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func (pq *PriorityQueue) all() []Item {
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items := make([]Item, 0, pq.Len())
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for i := 0; i < pq.Len(); i++ {
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items = append(items, pq.ps[i])
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}
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return items
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}
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// clean removes all canceled entries from the priority queue.
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func (pq *PriorityQueue) clean() {
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for i := 0; i < pq.Len(); {
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if pq.ps[i].isCanceled() {
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heap.Remove(&pq.ps, i)
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continue
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}
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i++
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}
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}
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// reset clear all entry in the queue.
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func (pq *PriorityQueue) reset() {
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for i := 0; i < pq.Len(); i++ {
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pq.ps[i] = nil
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}
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pq.ps = pq.ps[:0]
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}
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