diff options
Diffstat (limited to 'common/types/evictingqueue.go')
-rw-r--r-- | common/types/evictingqueue.go | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/common/types/evictingqueue.go b/common/types/evictingqueue.go new file mode 100644 index 000000000..152dc4c41 --- /dev/null +++ b/common/types/evictingqueue.go @@ -0,0 +1,89 @@ +// 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 ( + "sync" +) + +// EvictingStringQueue 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. +// Note: This queue currently does not contain any remove (poll etc.) methods. +type EvictingStringQueue struct { + size int + vals []string + set map[string]bool + mu sync.Mutex +} + +// NewEvictingStringQueue creates a new queue with the given size. +func NewEvictingStringQueue(size int) *EvictingStringQueue { + return &EvictingStringQueue{size: size, set: make(map[string]bool)} +} + +// Add adds a new string to the tail of the queue if it's not already there. +func (q *EvictingStringQueue) Add(v string) { + q.mu.Lock() + if q.set[v] { + q.mu.Unlock() + return + } + + if len(q.set) == q.size { + // Full + delete(q.set, q.vals[0]) + q.vals = append(q.vals[:0], q.vals[1:]...) + } + q.set[v] = true + q.vals = append(q.vals, v) + q.mu.Unlock() +} + +// Peek looks at the last element added to the queue. +func (q *EvictingStringQueue) Peek() string { + q.mu.Lock() + l := len(q.vals) + if l == 0 { + q.mu.Unlock() + return "" + } + 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 *EvictingStringQueue) PeekAll() []string { + q.mu.Lock() + vals := make([]string, 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 *EvictingStringQueue) PeekAllSet() map[string]bool { + all := q.PeekAll() + set := make(map[string]bool) + for _, v := range all { + set[v] = true + } + + return set +} |