118 lines
3.1 KiB
Go
118 lines
3.1 KiB
Go
// Copyright 2011 Dmitry Chestnykh. All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package captcha
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import (
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"container/list"
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"sync"
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"time"
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)
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// An object implementing Store interface can be registered with SetCustomStore
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// function to handle storage and retrieval of captcha ids and solutions for
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// them, replacing the default memory store.
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//
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// It is the responsibility of an object to delete expired and used captchas
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// when necessary (for example, the default memory store collects them in Set
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// method after the certain amount of captchas has been stored.)
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type Store interface {
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// Set sets the digits for the captcha id.
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Set(id string, digits []byte)
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// Get returns stored digits for the captcha id. Clear indicates
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// whether the captcha must be deleted from the store.
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Get(id string, clear bool) (digits []byte)
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}
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// expValue stores timestamp and id of captchas. It is used in the list inside
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// memoryStore for indexing generated captchas by timestamp to enable garbage
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// collection of expired captchas.
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type idByTimeValue struct {
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timestamp time.Time
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id string
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}
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// memoryStore is an internal store for captcha ids and their values.
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type memoryStore struct {
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sync.RWMutex
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digitsById map[string][]byte
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idByTime *list.List
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// Number of items stored since last collection.
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numStored int
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// Number of saved items that triggers collection.
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collectNum int
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// Expiration time of captchas.
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expiration time.Duration
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}
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// NewMemoryStore returns a new standard memory store for captchas with the
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// given collection threshold and expiration time (duration). The returned
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// store must be registered with SetCustomStore to replace the default one.
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func NewMemoryStore(collectNum int, expiration time.Duration) Store {
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s := new(memoryStore)
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s.digitsById = make(map[string][]byte)
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s.idByTime = list.New()
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s.collectNum = collectNum
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s.expiration = expiration
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return s
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}
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func (s *memoryStore) Set(id string, digits []byte) {
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s.Lock()
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s.digitsById[id] = digits
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s.idByTime.PushBack(idByTimeValue{time.Now(), id})
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s.numStored++
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if s.numStored <= s.collectNum {
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s.Unlock()
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return
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}
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s.Unlock()
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go s.collect()
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}
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func (s *memoryStore) Get(id string, clear bool) (digits []byte) {
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if !clear {
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// When we don't need to clear captcha, acquire read lock.
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s.RLock()
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defer s.RUnlock()
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} else {
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s.Lock()
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defer s.Unlock()
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}
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digits, ok := s.digitsById[id]
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if !ok {
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return
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}
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if clear {
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delete(s.digitsById, id)
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// XXX(dchest) Index (s.idByTime) will be cleaned when
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// collecting expired captchas. Can't clean it here, because
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// we don't store reference to expValue in the map.
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// Maybe store it?
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}
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return
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}
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func (s *memoryStore) collect() {
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now := time.Now()
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s.Lock()
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defer s.Unlock()
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s.numStored = 0
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for e := s.idByTime.Front(); e != nil; {
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ev, ok := e.Value.(idByTimeValue)
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if !ok {
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return
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}
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if ev.timestamp.Add(s.expiration).Before(now) {
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delete(s.digitsById, ev.id)
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next := e.Next()
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s.idByTime.Remove(e)
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e = next
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} else {
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return
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}
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}
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}
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