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95 lines
2.5 KiB
95 lines
2.5 KiB
//
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// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
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//
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// Permission to use, copy, modify, and distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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package main
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import (
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"reflect"
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"sync"
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"time"
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)
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type cacheFiller func(key interface{}) (interface{}, bool)
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type cacheOptions struct {
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Filler interface{}
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Duration time.Duration
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}
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type Cache struct {
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cache map[interface{}]interface{}
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filler cacheFiller
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lock sync.Mutex
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stale time.Time
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duration time.Duration
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}
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func cacheNew(options cacheOptions) *Cache {
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c := new(Cache)
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c.cache = make(map[interface{}]interface{})
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fillfn := options.Filler
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ftype := reflect.TypeOf(fillfn)
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if ftype.Kind() != reflect.Func {
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panic("cache filler is not function")
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}
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if ftype.NumIn() != 1 || ftype.NumOut() != 2 {
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panic("cache filler has wrong argument count")
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}
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c.filler = func(key interface{}) (interface{}, bool) {
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vfn := reflect.ValueOf(fillfn)
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args := []reflect.Value{reflect.ValueOf(key)}
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rv := vfn.Call(args)
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return rv[0].Interface(), rv[1].Bool()
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}
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if options.Duration != 0 {
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c.duration = options.Duration
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c.stale = time.Now().Add(c.duration)
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}
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return c
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}
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func (cache *Cache) Get(key interface{}, value interface{}) bool {
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cache.lock.Lock()
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defer cache.lock.Unlock()
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if !cache.stale.IsZero() && cache.stale.Before(time.Now()) {
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cache.stale = time.Now().Add(cache.duration)
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cache.cache = make(map[interface{}]interface{})
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}
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v, ok := cache.cache[key]
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if !ok {
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v, ok = cache.filler(key)
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if ok {
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cache.cache[key] = v
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}
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}
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if ok {
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ptr := reflect.ValueOf(v)
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reflect.ValueOf(value).Elem().Set(ptr)
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}
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return ok
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}
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func (cache *Cache) Clear(key interface{}) {
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cache.lock.Lock()
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defer cache.lock.Unlock()
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delete(cache.cache, key)
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}
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func (cache *Cache) Flush() {
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cache.lock.Lock()
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defer cache.lock.Unlock()
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cache.cache = make(map[interface{}]interface{})
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}
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