1 files changed, 193 insertions, 0 deletions
diff --git a/swarm/storage/localstore/subscription_pull.go b/swarm/storage/localstore/subscription_pull.go
new file mode 100644
index 000000000..a18f0915d
--- /dev/null
+++ b/swarm/storage/localstore/subscription_pull.go
@@ -0,0 +1,193 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package localstore
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/swarm/shed"
+	"github.com/ethereum/go-ethereum/swarm/storage"
+)
+
+// SubscribePull returns a channel that provides chunk addresses and stored times from pull syncing index.
+// Pull syncing index can be only subscribed to a particular proximity order bin. If since
+// is not nil, the iteration will start from the first item stored after that timestamp. If until is not nil,
+// only chunks stored up to this timestamp will be send to the channel, and the returned channel will be
+// closed. The since-until interval is open on the left and closed on the right (since,until]. Returned stop
+// function will terminate current and further iterations without errors, and also close the returned channel.
+// Make sure that you check the second returned parameter from the channel to stop iteration when its value
+// is false.
+func (db *DB) SubscribePull(ctx context.Context, bin uint8, since, until *ChunkDescriptor) (c <-chan ChunkDescriptor, stop func()) {
+	chunkDescriptors := make(chan ChunkDescriptor)
+	trigger := make(chan struct{}, 1)
+
+	db.pullTriggersMu.Lock()
+	if _, ok := db.pullTriggers[bin]; !ok {
+		db.pullTriggers[bin] = make([]chan struct{}, 0)
+	}
+	db.pullTriggers[bin] = append(db.pullTriggers[bin], trigger)
+	db.pullTriggersMu.Unlock()
+
+	// send signal for the initial iteration
+	trigger <- struct{}{}
+
+	stopChan := make(chan struct{})
+	var stopChanOnce sync.Once
+
+	// used to provide information from the iterator to
+	// stop subscription when until chunk descriptor is reached
+	var errStopSubscription = errors.New("stop subscription")
+
+	go func() {
+		// close the returned ChunkDescriptor channel at the end to
+		// signal that the subscription is done
+		defer close(chunkDescriptors)
+		// sinceItem is the Item from which the next iteration
+		// should start. The first iteration starts from the first Item.
+		var sinceItem *shed.Item
+		if since != nil {
+			sinceItem = &shed.Item{
+				Address:        since.Address,
+				StoreTimestamp: since.StoreTimestamp,
+			}
+		}
+		for {
+			select {
+			case <-trigger:
+				// iterate until:
+				// - last index Item is reached
+				// - subscription stop is called
+				// - context is done
+				err := db.pullIndex.Iterate(func(item shed.Item) (stop bool, err error) {
+					select {
+					case chunkDescriptors <- ChunkDescriptor{
+						Address:        item.Address,
+						StoreTimestamp: item.StoreTimestamp,
+					}:
+						// until chunk descriptor is sent
+						// break the iteration
+						if until != nil &&
+							(item.StoreTimestamp >= until.StoreTimestamp ||
+								bytes.Equal(item.Address, until.Address)) {
+							return true, errStopSubscription
+						}
+						// set next iteration start item
+						// when its chunk is successfully sent to channel
+						sinceItem = &item
+						return false, nil
+					case <-stopChan:
+						// gracefully stop the iteration
+						// on stop
+						return true, nil
+					case <-db.close:
+						// gracefully stop the iteration
+						// on database close
+						return true, nil
+					case <-ctx.Done():
+						return true, ctx.Err()
+					}
+				}, &shed.IterateOptions{
+					StartFrom: sinceItem,
+					// sinceItem was sent as the last Address in the previous
+					// iterator call, skip it in this one
+					SkipStartFromItem: true,
+					Prefix:            []byte{bin},
+				})
+				if err != nil {
+					if err == errStopSubscription {
+						// stop subscription without any errors
+						// if until is reached
+						return
+					}
+					log.Error("localstore pull subscription iteration", "bin", bin, "since", since, "until", until, "err", err)
+					return
+				}
+			case <-stopChan:
+				// terminate the subscription
+				// on stop
+				return
+			case <-db.close:
+				// terminate the subscription
+				// on database close
+				return
+			case <-ctx.Done():
+				err := ctx.Err()
+				if err != nil {
+					log.Error("localstore pull subscription", "bin", bin, "since", since, "until", until, "err", err)
+				}
+				return
+			}
+		}
+	}()
+
+	stop = func() {
+		stopChanOnce.Do(func() {
+			close(stopChan)
+		})
+
+		db.pullTriggersMu.Lock()
+		defer db.pullTriggersMu.Unlock()
+
+		for i, t := range db.pullTriggers[bin] {
+			if t == trigger {
+				db.pullTriggers[bin] = append(db.pullTriggers[bin][:i], db.pullTriggers[bin][i+1:]...)
+				break
+			}
+		}
+	}
+
+	return chunkDescriptors, stop
+}
+
+// ChunkDescriptor holds information required for Pull syncing. This struct
+// is provided by subscribing to pull index.
+type ChunkDescriptor struct {
+	Address        storage.Address
+	StoreTimestamp int64
+}
+
+func (c *ChunkDescriptor) String() string {
+	if c == nil {
+		return "none"
+	}
+	return fmt.Sprintf("%s stored at %v", c.Address.Hex(), c.StoreTimestamp)
+}
+
+// triggerPullSubscriptions is used internally for starting iterations
+// on Pull subscriptions for a particular bin. When new item with address
+// that is in particular bin for DB's baseKey is added to pull index
+// this function should be called.
+func (db *DB) triggerPullSubscriptions(bin uint8) {
+	db.pullTriggersMu.RLock()
+	triggers, ok := db.pullTriggers[bin]
+	db.pullTriggersMu.RUnlock()
+	if !ok {
+		return
+	}
+
+	for _, t := range triggers {
+		select {
+		case t <- struct{}{}:
+		default:
+		}
+	}
+}