trie: add Path to MissingNodeError

The light client trie iterator needs to know the path of the node that's
missing so it can retrieve a proof for it. NodeIterator.Path is not
sufficient because it is updated when the node is resolved and actually
visited by the iterator.

Also remove unused fields. They were added a long time ago before we
knew which fields would be needed for the light client.

trie/errors.go

@@ -23,24 +23,13 @@ import (
 )
 
 // MissingNodeError is returned by the trie functions (TryGet, TryUpdate, TryDelete)
-// in the case where a trie node is not present in the local database. Contains
+// in the case where a trie node is not present in the local database. It contains
-// information necessary for retrieving the missing node through an ODR service.
+// information necessary for retrieving the missing node.
-//
-// NodeHash is the hash of the missing node
-//
-// RootHash is the original root of the trie that contains the node
-//
-// PrefixLen is the nibble length of the key prefix that leads from the root to
-// the missing node
-//
-// SuffixLen is the nibble length of the remaining part of the key that hints on
-// which further nodes should also be retrieved (can be zero when there are no
-// such hints in the error message)
 type MissingNodeError struct {
-	RootHash, NodeHash   common.Hash
+	NodeHash common.Hash // hash of the missing node
-	PrefixLen, SuffixLen int
+	Path     []byte      // hex-encoded path to the missing node
 }
 
 func (err *MissingNodeError) Error() string {
-	return fmt.Sprintf("Missing trie node %064x", err.NodeHash)
+	return fmt.Sprintf("missing trie node %x (path %x)", err.NodeHash, err.Path)
 }

trie/iterator.go

@@ -221,7 +221,7 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
 		if root != emptyRoot {
 			state.hash = root
 		}
-		err := state.resolve(it.trie)
+		err := state.resolve(it.trie, nil)
 		return state, nil, nil, err
 	}
 	if !descend {
@@ -238,8 +238,8 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
 		}
 		state, path, ok := it.nextChild(parent, ancestor)
 		if ok {
-			if err := state.resolve(it.trie); err != nil {
+			if err := state.resolve(it.trie, path); err != nil {
-				return parent, &parent.index, it.path, err
+				return parent, &parent.index, path, err
 			}
 			return state, &parent.index, path, nil
 		}
@@ -249,9 +249,9 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
 	return nil, nil, nil, iteratorEnd
 }
 
-func (st *nodeIteratorState) resolve(tr *Trie) error {
+func (st *nodeIteratorState) resolve(tr *Trie, path []byte) error {
 	if hash, ok := st.node.(hashNode); ok {
-		resolved, err := tr.resolveHash(hash, nil, nil)
+		resolved, err := tr.resolveHash(hash, path)
 		if err != nil {
 			return err
 		}

trie/proof.go

@@ -58,7 +58,7 @@ func (t *Trie) Prove(key []byte) []rlp.RawValue {
 			nodes = append(nodes, n)
 		case hashNode:
 			var err error
-			tn, err = t.resolveHash(n, nil, nil)
+			tn, err = t.resolveHash(n, nil)
 			if err != nil {
 				log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
 				return nil

trie/trie.go

@@ -116,7 +116,7 @@ func New(root common.Hash, db Database) (*Trie, error) {
 		if db == nil {
 			panic("trie.New: cannot use existing root without a database")
 		}
-		rootnode, err := trie.resolveHash(root[:], nil, nil)
+		rootnode, err := trie.resolveHash(root[:], nil)
 		if err != nil {
 			return nil, err
 		}
@@ -180,7 +180,7 @@ func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode
 		}
 		return value, n, didResolve, err
 	case hashNode:
-		child, err := t.resolveHash(n, key[:pos], key[pos:])
+		child, err := t.resolveHash(n, key[:pos])
 		if err != nil {
 			return nil, n, true, err
 		}
@@ -283,7 +283,7 @@ func (t *Trie) insert(n node, prefix, key []byte, value node) (bool, node, error
 		// We've hit a part of the trie that isn't loaded yet. Load
 		// the node and insert into it. This leaves all child nodes on
 		// the path to the value in the trie.
-		rn, err := t.resolveHash(n, prefix, key)
+		rn, err := t.resolveHash(n, prefix)
 		if err != nil {
 			return false, nil, err
 		}
@@ -388,7 +388,7 @@ func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
 				// shortNode{..., shortNode{...}}.  Since the entry
 				// might not be loaded yet, resolve it just for this
 				// check.
-				cnode, err := t.resolve(n.Children[pos], prefix, []byte{byte(pos)})
+				cnode, err := t.resolve(n.Children[pos], prefix)
 				if err != nil {
 					return false, nil, err
 				}
@@ -414,7 +414,7 @@ func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
 		// We've hit a part of the trie that isn't loaded yet. Load
 		// the node and delete from it. This leaves all child nodes on
 		// the path to the value in the trie.
-		rn, err := t.resolveHash(n, prefix, key)
+		rn, err := t.resolveHash(n, prefix)
 		if err != nil {
 			return false, nil, err
 		}
@@ -436,24 +436,19 @@ func concat(s1 []byte, s2 ...byte) []byte {
 	return r
 }
 
-func (t *Trie) resolve(n node, prefix, suffix []byte) (node, error) {
+func (t *Trie) resolve(n node, prefix []byte) (node, error) {
 	if n, ok := n.(hashNode); ok {
-		return t.resolveHash(n, prefix, suffix)
+		return t.resolveHash(n, prefix)
 	}
 	return n, nil
 }
 
-func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
+func (t *Trie) resolveHash(n hashNode, prefix []byte) (node, error) {
 	cacheMissCounter.Inc(1)
 
 	enc, err := t.db.Get(n)
 	if err != nil || enc == nil {
-		return nil, &MissingNodeError{
+		return nil, &MissingNodeError{NodeHash: common.BytesToHash(n), Path: prefix}
-			RootHash:  t.originalRoot,
-			NodeHash:  common.BytesToHash(n),
-			PrefixLen: len(prefix),
-			SuffixLen: len(suffix),
-		}
 	}
 	dec := mustDecodeNode(n, enc, t.cachegen)
 	return dec, nil