1 files changed, 123 insertions, 0 deletions
diff --git a/light/trie.go b/light/trie.go
new file mode 100644
index 000000000..e9c96ea48
--- /dev/null
+++ b/light/trie.go
@@ -0,0 +1,123 @@
+// 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
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/trie"
+	"golang.org/x/net/context"
+)
+
+// LightTrie is an ODR-capable wrapper around trie.SecureTrie
+type LightTrie struct {
+	trie         *trie.SecureTrie
+	originalRoot common.Hash
+	odr          OdrBackend
+	db           ethdb.Database
+}
+
+// NewLightTrie creates a new LightTrie instance. It doesn't instantly try to
+// access the db or network and retrieve the root node, it only initializes its
+// encapsulated SecureTrie at the first actual operation.
+func NewLightTrie(root common.Hash, odr OdrBackend, useFakeMap bool) *LightTrie {
+	return &LightTrie{
+		// SecureTrie is initialized before first request
+		originalRoot: root,
+		odr:          odr,
+		db:           odr.Database(),
+	}
+}
+
+// retrieveKey retrieves a single key, returns true and stores nodes in local
+// database if successful
+func (t *LightTrie) retrieveKey(ctx context.Context, key []byte) bool {
+	r := &TrieRequest{root: t.originalRoot, key: key}
+	return t.odr.Retrieve(ctx, r) == nil
+}
+
+// do tries and retries to execute a function until it returns with no error or
+// an error type other than MissingNodeError
+func (t *LightTrie) do(ctx context.Context, fallbackKey []byte, fn func() error) error {
+	err := fn()
+	for err != nil {
+		mn, ok := err.(*trie.MissingNodeError)
+		if !ok {
+			return err
+		}
+
+		var key []byte
+		if mn.PrefixLen+mn.SuffixLen > 0 {
+			key = mn.Key
+		} else {
+			key = fallbackKey
+		}
+		if !t.retrieveKey(ctx, key) {
+			break
+		}
+		err = fn()
+	}
+	return err
+}
+
+// Get returns the value for key stored in the trie.
+// The value bytes must not be modified by the caller.
+func (t *LightTrie) Get(ctx context.Context, key []byte) (res []byte, err error) {
+	err = t.do(ctx, key, func() (err error) {
+		if t.trie == nil {
+			t.trie, err = trie.NewSecure(t.originalRoot, t.db)
+		}
+		if err == nil {
+			res, err = t.trie.TryGet(key)
+		}
+		return
+	})
+	return
+}
+
+// Update associates key with value in the trie. Subsequent calls to
+// Get will return value. If value has length zero, any existing value
+// is deleted from the trie and calls to Get will return nil.
+//
+// The value bytes must not be modified by the caller while they are
+// stored in the trie.
+func (t *LightTrie) Update(ctx context.Context, key, value []byte) (err error) {
+	err = t.do(ctx, key, func() (err error) {
+		if t.trie == nil {
+			t.trie, err = trie.NewSecure(t.originalRoot, t.db)
+		}
+		if err == nil {
+			err = t.trie.TryUpdate(key, value)
+		}
+		return
+	})
+	return
+}
+
+// Delete removes any existing value for key from the trie.
+func (t *LightTrie) Delete(ctx context.Context, key []byte) (err error) {
+	err = t.do(ctx, key, func() (err error) {
+		if t.trie == nil {
+			t.trie, err = trie.NewSecure(t.originalRoot, t.db)
+		}
+		if err == nil {
+			err = t.trie.TryDelete(key)
+		}
+		return
+	})
+	return
+}