1 files changed, 295 insertions, 0 deletions
diff --git a/swarm/storage/feed/handler.go b/swarm/storage/feed/handler.go
new file mode 100644
index 000000000..9e2640282
--- /dev/null
+++ b/swarm/storage/feed/handler.go
@@ -0,0 +1,295 @@
+// Copyright 2018 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/>.
+
+// Handler is the API for feeds
+// It enables creating, updating, syncing and retrieving feed updates and their data
+package feed
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/swarm/storage/feed/lookup"
+
+	"github.com/ethereum/go-ethereum/swarm/log"
+	"github.com/ethereum/go-ethereum/swarm/storage"
+)
+
+type Handler struct {
+	chunkStore      *storage.NetStore
+	HashSize        int
+	cache           map[uint64]*cacheEntry
+	cacheLock       sync.RWMutex
+	storeTimeout    time.Duration
+	queryMaxPeriods uint32
+}
+
+// HandlerParams pass parameters to the Handler constructor NewHandler
+// Signer and TimestampProvider are mandatory parameters
+type HandlerParams struct {
+}
+
+// hashPool contains a pool of ready hashers
+var hashPool sync.Pool
+
+// init initializes the package and hashPool
+func init() {
+	hashPool = sync.Pool{
+		New: func() interface{} {
+			return storage.MakeHashFunc(feedsHashAlgorithm)()
+		},
+	}
+}
+
+// NewHandler creates a new Swarm feeds API
+func NewHandler(params *HandlerParams) *Handler {
+	fh := &Handler{
+		cache: make(map[uint64]*cacheEntry),
+	}
+
+	for i := 0; i < hasherCount; i++ {
+		hashfunc := storage.MakeHashFunc(feedsHashAlgorithm)()
+		if fh.HashSize == 0 {
+			fh.HashSize = hashfunc.Size()
+		}
+		hashPool.Put(hashfunc)
+	}
+
+	return fh
+}
+
+// SetStore sets the store backend for the Swarm feeds API
+func (h *Handler) SetStore(store *storage.NetStore) {
+	h.chunkStore = store
+}
+
+// Validate is a chunk validation method
+// If it looks like a feed update, the chunk address is checked against the userAddr of the update's signature
+// It implements the storage.ChunkValidator interface
+func (h *Handler) Validate(chunkAddr storage.Address, data []byte) bool {
+	dataLength := len(data)
+	if dataLength < minimumSignedUpdateLength {
+		return false
+	}
+
+	// check if it is a properly formatted update chunk with
+	// valid signature and proof of ownership of the feed it is trying
+	// to update
+
+	// First, deserialize the chunk
+	var r Request
+	if err := r.fromChunk(chunkAddr, data); err != nil {
+		log.Debug("Invalid feed update chunk", "addr", chunkAddr.Hex(), "err", err.Error())
+		return false
+	}
+
+	// Verify signatures and that the signer actually owns the feed
+	// If it fails, it means either the signature is not valid, data is corrupted
+	// or someone is trying to update someone else's feed.
+	if err := r.Verify(); err != nil {
+		log.Debug("Invalid feed update signature", "err", err)
+		return false
+	}
+
+	return true
+}
+
+// GetContent retrieves the data payload of the last synced update of the feed
+func (h *Handler) GetContent(feed *Feed) (storage.Address, []byte, error) {
+	if feed == nil {
+		return nil, nil, NewError(ErrInvalidValue, "feed is nil")
+	}
+	feedUpdate := h.get(feed)
+	if feedUpdate == nil {
+		return nil, nil, NewError(ErrNotFound, "feed update not cached")
+	}
+	return feedUpdate.lastKey, feedUpdate.data, nil
+}
+
+// NewRequest prepares a Request structure with all the necessary information to
+// just add the desired data and sign it.
+// The resulting structure can then be signed and passed to Handler.Update to be verified and sent
+func (h *Handler) NewRequest(ctx context.Context, feed *Feed) (request *Request, err error) {
+	if feed == nil {
+		return nil, NewError(ErrInvalidValue, "feed cannot be nil")
+	}
+
+	now := TimestampProvider.Now().Time
+	request = new(Request)
+	request.Header.Version = ProtocolVersion
+
+	query := NewQueryLatest(feed, lookup.NoClue)
+
+	feedUpdate, err := h.Lookup(ctx, query)
+	if err != nil {
+		if err.(*Error).code != ErrNotFound {
+			return nil, err
+		}
+		// not finding updates means that there is a network error
+		// or that the feed really does not have updates
+	}
+
+	request.Feed = *feed
+
+	// if we already have an update, then find next epoch
+	if feedUpdate != nil {
+		request.Epoch = lookup.GetNextEpoch(feedUpdate.Epoch, now)
+	} else {
+		request.Epoch = lookup.GetFirstEpoch(now)
+	}
+
+	return request, nil
+}
+
+// Lookup retrieves a specific or latest feed update
+// Lookup works differently depending on the configuration of `query`
+// See the `query` documentation and helper functions:
+// `NewQueryLatest` and `NewQuery`
+func (h *Handler) Lookup(ctx context.Context, query *Query) (*cacheEntry, error) {
+
+	timeLimit := query.TimeLimit
+	if timeLimit == 0 { // if time limit is set to zero, the user wants to get the latest update
+		timeLimit = TimestampProvider.Now().Time
+	}
+
+	if query.Hint == lookup.NoClue { // try to use our cache
+		entry := h.get(&query.Feed)
+		if entry != nil && entry.Epoch.Time <= timeLimit { // avoid bad hints
+			query.Hint = entry.Epoch
+		}
+	}
+
+	// we can't look for anything without a store
+	if h.chunkStore == nil {
+		return nil, NewError(ErrInit, "Call Handler.SetStore() before performing lookups")
+	}
+
+	var id ID
+	id.Feed = query.Feed
+	var readCount int
+
+	// Invoke the lookup engine.
+	// The callback will be called every time the lookup algorithm needs to guess
+	requestPtr, err := lookup.Lookup(timeLimit, query.Hint, func(epoch lookup.Epoch, now uint64) (interface{}, error) {
+		readCount++
+		id.Epoch = epoch
+		ctx, cancel := context.WithTimeout(ctx, defaultRetrieveTimeout)
+		defer cancel()
+
+		chunk, err := h.chunkStore.Get(ctx, id.Addr())
+		if err != nil { // TODO: check for catastrophic errors other than chunk not found
+			return nil, nil
+		}
+
+		var request Request
+		if err := request.fromChunk(chunk.Address(), chunk.Data()); err != nil {
+			return nil, nil
+		}
+		if request.Time <= timeLimit {
+			return &request, nil
+		}
+		return nil, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	log.Info(fmt.Sprintf("Feed lookup finished in %d lookups", readCount))
+
+	request, _ := requestPtr.(*Request)
+	if request == nil {
+		return nil, NewError(ErrNotFound, "no feed updates found")
+	}
+	return h.updateCache(request)
+
+}
+
+// update feed updates cache with specified content
+func (h *Handler) updateCache(request *Request) (*cacheEntry, error) {
+
+	updateAddr := request.Addr()
+	log.Trace("feed cache update", "topic", request.Topic.Hex(), "updateaddr", updateAddr, "epoch time", request.Epoch.Time, "epoch level", request.Epoch.Level)
+
+	feedUpdate := h.get(&request.Feed)
+	if feedUpdate == nil {
+		feedUpdate = &cacheEntry{}
+		h.set(&request.Feed, feedUpdate)
+	}
+
+	// update our rsrcs entry map
+	feedUpdate.lastKey = updateAddr
+	feedUpdate.Update = request.Update
+	feedUpdate.Reader = bytes.NewReader(feedUpdate.data)
+	return feedUpdate, nil
+}
+
+// Update publishes a feed update
+// Note that a feed update cannot span chunks, and thus has a MAX NET LENGTH 4096, INCLUDING update header data and signature.
+// This results in a max payload of `maxUpdateDataLength` (check update.go for more details)
+// An error will be returned if the total length of the chunk payload will exceed this limit.
+// Update can only check if the caller is trying to overwrite the very last known version, otherwise it just puts the update
+// on the network.
+func (h *Handler) Update(ctx context.Context, r *Request) (updateAddr storage.Address, err error) {
+
+	// we can't update anything without a store
+	if h.chunkStore == nil {
+		return nil, NewError(ErrInit, "Call Handler.SetStore() before updating")
+	}
+
+	feedUpdate := h.get(&r.Feed)
+	if feedUpdate != nil && feedUpdate.Epoch.Equals(r.Epoch) { // This is the only cheap check we can do for sure
+		return nil, NewError(ErrInvalidValue, "A former update in this epoch is already known to exist")
+	}
+
+	chunk, err := r.toChunk() // Serialize the update into a chunk. Fails if data is too big
+	if err != nil {
+		return nil, err
+	}
+
+	// send the chunk
+	h.chunkStore.Put(ctx, chunk)
+	log.Trace("feed update", "updateAddr", r.idAddr, "epoch time", r.Epoch.Time, "epoch level", r.Epoch.Level, "data", chunk.Data())
+	// update our feed updates map cache entry if the new update is older than the one we have, if we have it.
+	if feedUpdate != nil && r.Epoch.After(feedUpdate.Epoch) {
+		feedUpdate.Epoch = r.Epoch
+		feedUpdate.data = make([]byte, len(r.data))
+		feedUpdate.lastKey = r.idAddr
+		copy(feedUpdate.data, r.data)
+		feedUpdate.Reader = bytes.NewReader(feedUpdate.data)
+	}
+
+	return r.idAddr, nil
+}
+
+// Retrieves the feed update cache value for the given nameHash
+func (h *Handler) get(feed *Feed) *cacheEntry {
+	mapKey := feed.mapKey()
+	h.cacheLock.RLock()
+	defer h.cacheLock.RUnlock()
+	feedUpdate := h.cache[mapKey]
+	return feedUpdate
+}
+
+// Sets the feed update cache value for the given feed
+func (h *Handler) set(feed *Feed, feedUpdate *cacheEntry) {
+	mapKey := feed.mapKey()
+	h.cacheLock.Lock()
+	defer h.cacheLock.Unlock()
+	h.cache[mapKey] = feedUpdate
+}