swarm: plan bee for content storage and distribution on web3

This change imports the Swarm protocol codebase. Compared to the 'swarm'
branch, a few mostly cosmetic changes had to be made:

* The various redundant log message prefixes are gone.
* All files now have LGPLv3 license headers.
* Minor code changes were needed to please go vet and make the tests
  pass on Windows.
* Further changes were required to adapt to the go-ethereum develop
  branch and its new Go APIs.

Some code has not (yet) been brought over:

* swarm/cmd/bzzhash: will reappear as cmd/bzzhash later
* swarm/cmd/bzzup.sh: will be reimplemented in cmd/bzzup
* swarm/cmd/makegenesis: will reappear somehow
* swarm/examples/album: will move to a separate repository
* swarm/examples/filemanager: ditto
* swarm/examples/files: will not be merged
* swarm/test/*: will not be merged
* swarm/services/swear: will reappear as contracts/swear when needed

swarm/storage/localstore.go

@@ -0,0 +1,74 @@
+// Copyright 2016 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 storage
+
+import (
+	"encoding/binary"
+)
+
+// LocalStore is a combination of inmemory db over a disk persisted db
+// implements a Get/Put with fallback (caching) logic using any 2 ChunkStores
+type LocalStore struct {
+	memStore ChunkStore
+	DbStore  ChunkStore
+}
+
+// This constructor uses MemStore and DbStore as components
+func NewLocalStore(hash Hasher, params *StoreParams) (*LocalStore, error) {
+	dbStore, err := NewDbStore(params.ChunkDbPath, hash, params.DbCapacity, params.Radius)
+	if err != nil {
+		return nil, err
+	}
+	return &LocalStore{
+		memStore: NewMemStore(dbStore, params.CacheCapacity),
+		DbStore:  dbStore,
+	}, nil
+}
+
+// LocalStore is itself a chunk store
+// unsafe, in that the data is not integrity checked
+func (self *LocalStore) Put(chunk *Chunk) {
+	chunk.dbStored = make(chan bool)
+	self.memStore.Put(chunk)
+	if chunk.wg != nil {
+		chunk.wg.Add(1)
+	}
+	go func() {
+		self.DbStore.Put(chunk)
+		if chunk.wg != nil {
+			chunk.wg.Done()
+		}
+	}()
+}
+
+// Get(chunk *Chunk) looks up a chunk in the local stores
+// This method is blocking until the chunk is retrieved
+// so additional timeout may be needed to wrap this call if
+// ChunkStores are remote and can have long latency
+func (self *LocalStore) Get(key Key) (chunk *Chunk, err error) {
+	chunk, err = self.memStore.Get(key)
+	if err == nil {
+		return
+	}
+	chunk, err = self.DbStore.Get(key)
+	if err != nil {
+		return
+	}
+	chunk.Size = int64(binary.LittleEndian.Uint64(chunk.SData[0:8]))
+	self.memStore.Put(chunk)
+	return
+}