1 files changed, 98 insertions, 0 deletions
diff --git a/light/odr.go b/light/odr.go
new file mode 100644
index 000000000..5ed4f2325
--- /dev/null
+++ b/light/odr.go
@@ -0,0 +1,98 @@
+// Copyright 2015 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 light implements on-demand retrieval capable state and chain objects
+// for the Ethereum Light Client.
+package light
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/rlp"
+	"golang.org/x/net/context"
+)
+
+// OdrBackend is an interface to a backend service that handles odr retrievals
+type OdrBackend interface {
+	Database() ethdb.Database
+	Retrieve(ctx context.Context, req OdrRequest) error
+}
+
+// OdrRequest is an interface for retrieval requests
+type OdrRequest interface {
+	StoreResult(db ethdb.Database)
+}
+
+// TrieRequest is the ODR request type for state/storage trie entries
+type TrieRequest struct {
+	OdrRequest
+	root  common.Hash
+	key   []byte
+	proof []rlp.RawValue
+}
+
+// StoreResult stores the retrieved data in local database
+func (req *TrieRequest) StoreResult(db ethdb.Database) {
+	storeProof(db, req.proof)
+}
+
+// storeProof stores the new trie nodes obtained from a merkle proof in the database
+func storeProof(db ethdb.Database, proof []rlp.RawValue) {
+	for _, buf := range proof {
+		hash := crypto.Sha3(buf)
+		val, _ := db.Get(hash)
+		if val == nil {
+			db.Put(hash, buf)
+		}
+	}
+}
+
+// NodeDataRequest is the ODR request type for node data (used for retrieving contract code)
+type NodeDataRequest struct {
+	OdrRequest
+	hash common.Hash
+	data []byte
+}
+
+// GetData returns the retrieved node data after a successful request
+func (req *NodeDataRequest) GetData() []byte {
+	return req.data
+}
+
+// StoreResult stores the retrieved data in local database
+func (req *NodeDataRequest) StoreResult(db ethdb.Database) {
+	db.Put(req.hash[:], req.GetData())
+}
+
+var sha3_nil = crypto.Sha3Hash(nil)
+
+// retrieveNodeData tries to retrieve node data with the given hash from the network
+func retrieveNodeData(ctx context.Context, odr OdrBackend, hash common.Hash) ([]byte, error) {
+	if hash == sha3_nil {
+		return nil, nil
+	}
+	res, _ := odr.Database().Get(hash[:])
+	if res != nil {
+		return res, nil
+	}
+	r := &NodeDataRequest{hash: hash}
+	if err := odr.Retrieve(ctx, r); err != nil {
+		return nil, err
+	} else {
+		return r.GetData(), nil
+	}
+}