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// Copyright 2024 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 maps
import (
"sync"
)
// Cache is a simple thread safe cache backed by a map.
type Cache[K comparable, T any] struct {
m map[K]T
hasBeenInitialized bool
sync.RWMutex
}
// NewCache creates a new Cache.
func NewCache[K comparable, T any]() *Cache[K, T] {
return &Cache[K, T]{m: make(map[K]T)}
}
// Delete deletes the given key from the cache.
// If c is nil, this method is a no-op.
func (c *Cache[K, T]) Get(key K) (T, bool) {
if c == nil {
var zero T
return zero, false
}
c.RLock()
v, found := c.get(key)
c.RUnlock()
return v, found
}
func (c *Cache[K, T]) get(key K) (T, bool) {
v, found := c.m[key]
return v, found
}
// GetOrCreate gets the value for the given key if it exists, or creates it if not.
func (c *Cache[K, T]) GetOrCreate(key K, create func() (T, error)) (T, error) {
c.RLock()
v, found := c.m[key]
c.RUnlock()
if found {
return v, nil
}
c.Lock()
defer c.Unlock()
v, found = c.m[key]
if found {
return v, nil
}
v, err := create()
if err != nil {
return v, err
}
c.m[key] = v
return v, nil
}
// InitAndGet initializes the cache if not already done and returns the value for the given key.
// The init state will be reset on Reset or Drain.
func (c *Cache[K, T]) InitAndGet(key K, init func(get func(key K) (T, bool), set func(key K, value T)) error) (T, error) {
var v T
c.RLock()
if !c.hasBeenInitialized {
c.RUnlock()
if err := func() error {
c.Lock()
defer c.Unlock()
// Double check in case another goroutine has initialized it in the meantime.
if !c.hasBeenInitialized {
err := init(c.get, c.set)
if err != nil {
return err
}
c.hasBeenInitialized = true
}
return nil
}(); err != nil {
return v, err
}
// Reacquire the read lock.
c.RLock()
}
v = c.m[key]
c.RUnlock()
return v, nil
}
// Set sets the given key to the given value.
func (c *Cache[K, T]) Set(key K, value T) {
c.Lock()
c.set(key, value)
c.Unlock()
}
func (c *Cache[K, T]) set(key K, value T) {
c.m[key] = value
}
// ForEeach calls the given function for each key/value pair in the cache.
func (c *Cache[K, T]) ForEeach(f func(K, T)) {
c.RLock()
defer c.RUnlock()
for k, v := range c.m {
f(k, v)
}
}
func (c *Cache[K, T]) Drain() map[K]T {
c.Lock()
m := c.m
c.m = make(map[K]T)
c.hasBeenInitialized = false
c.Unlock()
return m
}
func (c *Cache[K, T]) Len() int {
c.RLock()
defer c.RUnlock()
return len(c.m)
}
func (c *Cache[K, T]) Reset() {
c.Lock()
c.m = make(map[K]T)
c.hasBeenInitialized = false
c.Unlock()
}
// SliceCache is a simple thread safe cache backed by a map.
type SliceCache[T any] struct {
m map[string][]T
sync.RWMutex
}
func NewSliceCache[T any]() *SliceCache[T] {
return &SliceCache[T]{m: make(map[string][]T)}
}
func (c *SliceCache[T]) Get(key string) ([]T, bool) {
c.RLock()
v, found := c.m[key]
c.RUnlock()
return v, found
}
func (c *SliceCache[T]) Append(key string, values ...T) {
c.Lock()
c.m[key] = append(c.m[key], values...)
c.Unlock()
}
func (c *SliceCache[T]) Reset() {
c.Lock()
c.m = make(map[string][]T)
c.Unlock()
}
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