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// Copyright 2017-present The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package types contains types shared between packages in Hugo.
package types
import (
"slices"
"sync"
)
// EvictingQueue is a queue which automatically evicts elements from the head of
// the queue when attempting to add new elements onto the queue and it is full.
// This queue orders elements LIFO (last-in-first-out). It throws away duplicates.
type EvictingQueue[T comparable] struct {
size int
vals []T
set map[T]bool
mu sync.Mutex
zero T
}
// NewEvictingQueue creates a new queue with the given size.
func NewEvictingQueue[T comparable](size int) *EvictingQueue[T] {
return &EvictingQueue[T]{size: size, set: make(map[T]bool)}
}
// Add adds a new string to the tail of the queue if it's not already there.
func (q *EvictingQueue[T]) Add(v T) *EvictingQueue[T] {
q.mu.Lock()
if q.set[v] {
q.mu.Unlock()
return q
}
if len(q.set) == q.size {
// Full
delete(q.set, q.vals[0])
q.vals = slices.Delete(q.vals, 0, 1)
}
q.set[v] = true
q.vals = append(q.vals, v)
q.mu.Unlock()
return q
}
func (q *EvictingQueue[T]) Len() int {
if q == nil {
return 0
}
q.mu.Lock()
defer q.mu.Unlock()
return len(q.vals)
}
// Contains returns whether the queue contains v.
func (q *EvictingQueue[T]) Contains(v T) bool {
if q == nil {
return false
}
q.mu.Lock()
defer q.mu.Unlock()
return q.set[v]
}
// Peek looks at the last element added to the queue.
func (q *EvictingQueue[T]) Peek() T {
q.mu.Lock()
l := len(q.vals)
if l == 0 {
q.mu.Unlock()
return q.zero
}
elem := q.vals[l-1]
q.mu.Unlock()
return elem
}
// PeekAll looks at all the elements in the queue, with the newest first.
func (q *EvictingQueue[T]) PeekAll() []T {
if q == nil {
return nil
}
q.mu.Lock()
vals := make([]T, len(q.vals))
copy(vals, q.vals)
q.mu.Unlock()
for i, j := 0, len(vals)-1; i < j; i, j = i+1, j-1 {
vals[i], vals[j] = vals[j], vals[i]
}
return vals
}
// PeekAllSet returns PeekAll as a set.
func (q *EvictingQueue[T]) PeekAllSet() map[T]bool {
all := q.PeekAll()
set := make(map[T]bool)
for _, v := range all {
set[v] = true
}
return set
}
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