Adding upstream version 1.0.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

store.go

@@ -0,0 +1,117 @@
+// Copyright 2011 Dmitry Chestnykh. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package captcha
+
+import (
+	"container/list"
+	"sync"
+	"time"
+)
+
+// An object implementing Store interface can be registered with SetCustomStore
+// function to handle storage and retrieval of captcha ids and solutions for
+// them, replacing the default memory store.
+//
+// It is the responsibility of an object to delete expired and used captchas
+// when necessary (for example, the default memory store collects them in Set
+// method after the certain amount of captchas has been stored.)
+type Store interface {
+	// Set sets the digits for the captcha id.
+	Set(id string, digits []byte)
+
+	// Get returns stored digits for the captcha id. Clear indicates
+	// whether the captcha must be deleted from the store.
+	Get(id string, clear bool) (digits []byte)
+}
+
+// expValue stores timestamp and id of captchas. It is used in the list inside
+// memoryStore for indexing generated captchas by timestamp to enable garbage
+// collection of expired captchas.
+type idByTimeValue struct {
+	timestamp time.Time
+	id        string
+}
+
+// memoryStore is an internal store for captcha ids and their values.
+type memoryStore struct {
+	sync.RWMutex
+	digitsByID map[string][]byte
+	idByTime   *list.List
+	// Number of items stored since last collection.
+	numStored int
+	// Number of saved items that triggers collection.
+	collectNum int
+	// Expiration time of captchas.
+	expiration time.Duration
+}
+
+// NewMemoryStore returns a new standard memory store for captchas with the
+// given collection threshold and expiration time (duration). The returned
+// store must be registered with SetCustomStore to replace the default one.
+func NewMemoryStore(collectNum int, expiration time.Duration) Store {
+	s := new(memoryStore)
+	s.digitsByID = make(map[string][]byte)
+	s.idByTime = list.New()
+	s.collectNum = collectNum
+	s.expiration = expiration
+	return s
+}
+
+func (s *memoryStore) Set(id string, digits []byte) {
+	s.Lock()
+	s.digitsByID[id] = digits
+	s.idByTime.PushBack(idByTimeValue{time.Now(), id})
+	s.numStored++
+	if s.numStored <= s.collectNum {
+		s.Unlock()
+		return
+	}
+	s.Unlock()
+	go s.collect()
+}
+
+func (s *memoryStore) Get(id string, clear bool) (digits []byte) {
+	if !clear {
+		// When we don't need to clear captcha, acquire read lock.
+		s.RLock()
+		defer s.RUnlock()
+	} else {
+		s.Lock()
+		defer s.Unlock()
+	}
+	digits, ok := s.digitsByID[id]
+	if !ok {
+		return
+	}
+	if clear {
+		delete(s.digitsByID, id)
+		// XXX(dchest) Index (s.idByTime) will be cleaned when
+		// collecting expired captchas.  Can't clean it here, because
+		// we don't store reference to expValue in the map.
+		// Maybe store it?
+	}
+	return
+}
+
+func (s *memoryStore) collect() {
+	now := time.Now()
+	s.Lock()
+	defer s.Unlock()
+	s.numStored = 0
+	for e := s.idByTime.Front(); e != nil; {
+		ev, ok := e.Value.(idByTimeValue)
+		if !ok {
+			return
+		}
+		if ev.timestamp.Add(s.expiration).Before(now) {
+			delete(s.digitsByID, ev.id)
+			next := e.Next()
+			s.idByTime.Remove(e)
+			e = next
+		} else {
+			return
+		}
+	}
+}