core, trie: replace state caches with trie journal

9 files changed, 350 insertions, 586 deletions

diff --git a/trie/arc.go b/trie/arc.go
deleted file mode 100644
index fc7a3259f..000000000
--- a/trie/arc.go
+++ /dev/null
@@ -1,206 +0,0 @@
-// Copyright (c) 2015 Hans Alexander Gugel <alexander.gugel@gmail.com>
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-// This file contains a modified version of package arc from
-// https://github.com/alexanderGugel/arc
-//
-// It implements the ARC (Adaptive Replacement Cache) algorithm as detailed in
-// https://www.usenix.org/legacy/event/fast03/tech/full_papers/megiddo/megiddo.pdf
-
-package trie
-
-import (
-	"container/list"
-	"sync"
-)
-
-type arc struct {
-	p     int
-	c     int
-	t1    *list.List
-	b1    *list.List
-	t2    *list.List
-	b2    *list.List
-	cache map[string]*entry
-	mutex sync.Mutex
-}
-
-type entry struct {
-	key   hashNode
-	value node
-	ll    *list.List
-	el    *list.Element
-}
-
-// newARC returns a new Adaptive Replacement Cache with the
-// given capacity.
-func newARC(c int) *arc {
-	return &arc{
-		c:     c,
-		t1:    list.New(),
-		b1:    list.New(),
-		t2:    list.New(),
-		b2:    list.New(),
-		cache: make(map[string]*entry, c),
-	}
-}
-
-// Clear clears the cache
-func (a *arc) Clear() {
-	a.mutex.Lock()
-	defer a.mutex.Unlock()
-	a.p = 0
-	a.t1 = list.New()
-	a.b1 = list.New()
-	a.t2 = list.New()
-	a.b2 = list.New()
-	a.cache = make(map[string]*entry, a.c)
-}
-
-// Put inserts a new key-value pair into the cache.
-// This optimizes future access to this entry (side effect).
-func (a *arc) Put(key hashNode, value node) bool {
-	a.mutex.Lock()
-	defer a.mutex.Unlock()
-	ent, ok := a.cache[string(key)]
-	if ok != true {
-		ent = &entry{key: key, value: value}
-		a.req(ent)
-		a.cache[string(key)] = ent
-	} else {
-		ent.value = value
-		a.req(ent)
-	}
-	return ok
-}
-
-// Get retrieves a previously via Set inserted entry.
-// This optimizes future access to this entry (side effect).
-func (a *arc) Get(key hashNode) (value node, ok bool) {
-	a.mutex.Lock()
-	defer a.mutex.Unlock()
-	ent, ok := a.cache[string(key)]
-	if ok {
-		a.req(ent)
-		return ent.value, ent.value != nil
-	}
-	return nil, false
-}
-
-func (a *arc) req(ent *entry) {
-	if ent.ll == a.t1 || ent.ll == a.t2 {
-		// Case I
-		ent.setMRU(a.t2)
-	} else if ent.ll == a.b1 {
-		// Case II
-		// Cache Miss in t1 and t2
-
-		// Adaptation
-		var d int
-		if a.b1.Len() >= a.b2.Len() {
-			d = 1
-		} else {
-			d = a.b2.Len() / a.b1.Len()
-		}
-		a.p = a.p + d
-		if a.p > a.c {
-			a.p = a.c
-		}
-
-		a.replace(ent)
-		ent.setMRU(a.t2)
-	} else if ent.ll == a.b2 {
-		// Case III
-		// Cache Miss in t1 and t2
-
-		// Adaptation
-		var d int
-		if a.b2.Len() >= a.b1.Len() {
-			d = 1
-		} else {
-			d = a.b1.Len() / a.b2.Len()
-		}
-		a.p = a.p - d
-		if a.p < 0 {
-			a.p = 0
-		}
-
-		a.replace(ent)
-		ent.setMRU(a.t2)
-	} else if ent.ll == nil {
-		// Case IV
-
-		if a.t1.Len()+a.b1.Len() == a.c {
-			// Case A
-			if a.t1.Len() < a.c {
-				a.delLRU(a.b1)
-				a.replace(ent)
-			} else {
-				a.delLRU(a.t1)
-			}
-		} else if a.t1.Len()+a.b1.Len() < a.c {
-			// Case B
-			if a.t1.Len()+a.t2.Len()+a.b1.Len()+a.b2.Len() >= a.c {
-				if a.t1.Len()+a.t2.Len()+a.b1.Len()+a.b2.Len() == 2*a.c {
-					a.delLRU(a.b2)
-				}
-				a.replace(ent)
-			}
-		}
-
-		ent.setMRU(a.t1)
-	}
-}
-
-func (a *arc) delLRU(list *list.List) {
-	lru := list.Back()
-	list.Remove(lru)
-	delete(a.cache, string(lru.Value.(*entry).key))
-}
-
-func (a *arc) replace(ent *entry) {
-	if a.t1.Len() > 0 && ((a.t1.Len() > a.p) || (ent.ll == a.b2 && a.t1.Len() == a.p)) {
-		lru := a.t1.Back().Value.(*entry)
-		lru.value = nil
-		lru.setMRU(a.b1)
-	} else {
-		lru := a.t2.Back().Value.(*entry)
-		lru.value = nil
-		lru.setMRU(a.b2)
-	}
-}
-
-func (e *entry) setLRU(list *list.List) {
-	e.detach()
-	e.ll = list
-	e.el = e.ll.PushBack(e)
-}
-
-func (e *entry) setMRU(list *list.List) {
-	e.detach()
-	e.ll = list
-	e.el = e.ll.PushFront(e)
-}
-
-func (e *entry) detach() {
-	if e.ll != nil {
-		e.ll.Remove(e.el)
-	}
-}
diff --git a/trie/hasher.go b/trie/hasher.go
new file mode 100644
index 000000000..87e02fb85
--- /dev/null
+++ b/trie/hasher.go
@@ -0,0 +1,157 @@
+// 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 trie
+
+import (
+	"bytes"
+	"hash"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+type hasher struct {
+	tmp *bytes.Buffer
+	sha hash.Hash
+}
+
+// hashers live in a global pool.
+var hasherPool = sync.Pool{
+	New: func() interface{} {
+		return &hasher{tmp: new(bytes.Buffer), sha: sha3.NewKeccak256()}
+	},
+}
+
+func newHasher() *hasher {
+	return hasherPool.Get().(*hasher)
+}
+
+func returnHasherToPool(h *hasher) {
+	hasherPool.Put(h)
+}
+
+// hash collapses a node down into a hash node, also returning a copy of the
+// original node initialzied with the computed hash to replace the original one.
+func (h *hasher) hash(n node, db DatabaseWriter, force bool) (node, node, error) {
+	// If we're not storing the node, just hashing, use avaialble cached data
+	if hash, dirty := n.cache(); hash != nil && (db == nil || !dirty) {
+		return hash, n, nil
+	}
+	// Trie not processed yet or needs storage, walk the children
+	collapsed, cached, err := h.hashChildren(n, db)
+	if err != nil {
+		return hashNode{}, n, err
+	}
+	hashed, err := h.store(collapsed, db, force)
+	if err != nil {
+		return hashNode{}, n, err
+	}
+	// Cache the hash and RLP blob of the ndoe for later reuse
+	if hash, ok := hashed.(hashNode); ok && !force {
+		switch cached := cached.(type) {
+		case shortNode:
+			cached.hash = hash
+			if db != nil {
+				cached.dirty = false
+			}
+			return hashed, cached, nil
+		case fullNode:
+			cached.hash = hash
+			if db != nil {
+				cached.dirty = false
+			}
+			return hashed, cached, nil
+		}
+	}
+	return hashed, cached, nil
+}
+
+// hashChildren replaces the children of a node with their hashes if the encoded
+// size of the child is larger than a hash, returning the collapsed node as well
+// as a replacement for the original node with the child hashes cached in.
+func (h *hasher) hashChildren(original node, db DatabaseWriter) (node, node, error) {
+	var err error
+
+	switch n := original.(type) {
+	case shortNode:
+		// Hash the short node's child, caching the newly hashed subtree
+		cached := n
+		cached.Key = common.CopyBytes(cached.Key)
+
+		n.Key = compactEncode(n.Key)
+		if _, ok := n.Val.(valueNode); !ok {
+			if n.Val, cached.Val, err = h.hash(n.Val, db, false); err != nil {
+				return n, original, err
+			}
+		}
+		if n.Val == nil {
+			n.Val = valueNode(nil) // Ensure that nil children are encoded as empty strings.
+		}
+		return n, cached, nil
+
+	case fullNode:
+		// Hash the full node's children, caching the newly hashed subtrees
+		cached := fullNode{dirty: n.dirty}
+
+		for i := 0; i < 16; i++ {
+			if n.Children[i] != nil {
+				if n.Children[i], cached.Children[i], err = h.hash(n.Children[i], db, false); err != nil {
+					return n, original, err
+				}
+			} else {
+				n.Children[i] = valueNode(nil) // Ensure that nil children are encoded as empty strings.
+			}
+		}
+		cached.Children[16] = n.Children[16]
+		if n.Children[16] == nil {
+			n.Children[16] = valueNode(nil)
+		}
+		return n, cached, nil
+
+	default:
+		// Value and hash nodes don't have children so they're left as were
+		return n, original, nil
+	}
+}
+
+func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
+	// Don't store hashes or empty nodes.
+	if _, isHash := n.(hashNode); n == nil || isHash {
+		return n, nil
+	}
+	// Generate the RLP encoding of the node
+	h.tmp.Reset()
+	if err := rlp.Encode(h.tmp, n); err != nil {
+		panic("encode error: " + err.Error())
+	}
+	if h.tmp.Len() < 32 && !force {
+		return n, nil // Nodes smaller than 32 bytes are stored inside their parent
+	}
+	// Larger nodes are replaced by their hash and stored in the database.
+	hash, _ := n.cache()
+	if hash == nil {
+		h.sha.Reset()
+		h.sha.Write(h.tmp.Bytes())
+		hash = hashNode(h.sha.Sum(nil))
+	}
+	if db != nil {
+		return hash, db.Put(hash, h.tmp.Bytes())
+	}
+	return hash, nil
+}
diff --git a/trie/iterator.go b/trie/iterator.go
index 88c4cee7f..8cad51aff 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -16,18 +16,13 @@
 
 package trie
 
-import (
-	"bytes"
-	"fmt"
+import "github.com/ethereum/go-ethereum/common"
 
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/logger"
-	"github.com/ethereum/go-ethereum/logger/glog"
-)
-
-// Iterator is a key-value trie iterator to traverse the data contents.
+// Iterator is a key-value trie iterator that traverses a Trie.
 type Iterator struct {
-	trie *Trie
+	trie   *Trie
+	nodeIt *NodeIterator
+	keyBuf []byte
 
 	Key   []byte // Current data key on which the iterator is positioned on
 	Value []byte // Current data value on which the iterator is positioned on
@@ -35,119 +30,45 @@ type Iterator struct {
 
 // NewIterator creates a new key-value iterator.
 func NewIterator(trie *Trie) *Iterator {
-	return &Iterator{trie: trie, Key: nil}
-}
-
-// Next moves the iterator forward with one key-value entry.
-func (self *Iterator) Next() bool {
-	isIterStart := false
-	if self.Key == nil {
-		isIterStart = true
-		self.Key = make([]byte, 32)
+	return &Iterator{
+		trie:   trie,
+		nodeIt: NewNodeIterator(trie),
+		keyBuf: make([]byte, 0, 64),
+		Key:    nil,
 	}
-
-	key := remTerm(compactHexDecode(self.Key))
-	k := self.next(self.trie.root, key, isIterStart)
-
-	self.Key = []byte(decodeCompact(k))
-
-	return len(k) > 0
 }
 
-func (self *Iterator) next(node interface{}, key []byte, isIterStart bool) []byte {
-	if node == nil {
-		return nil
-	}
-
-	switch node := node.(type) {
-	case fullNode:
-		if len(key) > 0 {
-			k := self.next(node.Children[key[0]], key[1:], isIterStart)
-			if k != nil {
-				return append([]byte{key[0]}, k...)
-			}
-		}
-
-		var r byte
-		if len(key) > 0 {
-			r = key[0] + 1
-		}
-
-		for i := r; i < 16; i++ {
-			k := self.key(node.Children[i])
-			if k != nil {
-				return append([]byte{i}, k...)
-			}
+// Next moves the iterator forward one key-value entry.
+func (it *Iterator) Next() bool {
+	for it.nodeIt.Next() {
+		if it.nodeIt.Leaf {
+			it.Key = it.makeKey()
+			it.Value = it.nodeIt.LeafBlob
+			return true
 		}
-
-	case shortNode:
-		k := remTerm(node.Key)
-		if vnode, ok := node.Val.(valueNode); ok {
-			switch bytes.Compare([]byte(k), key) {
-			case 0:
-				if isIterStart {
-					self.Value = vnode
-					return k
-				}
-			case 1:
-				self.Value = vnode
-				return k
-			}
-		} else {
-			cnode := node.Val
-
-			var ret []byte
-			skey := key[len(k):]
-			if bytes.HasPrefix(key, k) {
-				ret = self.next(cnode, skey, isIterStart)
-			} else if bytes.Compare(k, key[:len(k)]) > 0 {
-				return self.key(node)
-			}
-
-			if ret != nil {
-				return append(k, ret...)
-			}
-		}
-
-	case hashNode:
-		rn, err := self.trie.resolveHash(node, nil, nil)
-		if err != nil && glog.V(logger.Error) {
-			glog.Errorf("Unhandled trie error: %v", err)
-		}
-		return self.next(rn, key, isIterStart)
 	}
-	return nil
+	it.Key = nil
+	it.Value = nil
+	return false
 }
 
-func (self *Iterator) key(node interface{}) []byte {
-	switch node := node.(type) {
-	case shortNode:
-		// Leaf node
-		k := remTerm(node.Key)
-		if vnode, ok := node.Val.(valueNode); ok {
-			self.Value = vnode
-			return k
-		}
-		return append(k, self.key(node.Val)...)
-	case fullNode:
-		if node.Children[16] != nil {
-			self.Value = node.Children[16].(valueNode)
-			return []byte{16}
-		}
-		for i := 0; i < 16; i++ {
-			k := self.key(node.Children[i])
-			if k != nil {
-				return append([]byte{byte(i)}, k...)
+func (it *Iterator) makeKey() []byte {
+	key := it.keyBuf[:0]
+	for _, se := range it.nodeIt.stack {
+		switch node := se.node.(type) {
+		case fullNode:
+			if se.child <= 16 {
+				key = append(key, byte(se.child))
+			}
+		case shortNode:
+			if hasTerm(node.Key) {
+				key = append(key, node.Key[:len(node.Key)-1]...)
+			} else {
+				key = append(key, node.Key...)
 			}
 		}
-	case hashNode:
-		rn, err := self.trie.resolveHash(node, nil, nil)
-		if err != nil && glog.V(logger.Error) {
-			glog.Errorf("Unhandled trie error: %v", err)
-		}
-		return self.key(rn)
 	}
-	return nil
+	return decodeCompact(key)
 }
 
 // nodeIteratorState represents the iteration state at one particular node of the
@@ -199,25 +120,27 @@ func (it *NodeIterator) Next() bool {
 
 // step moves the iterator to the next node of the trie.
 func (it *NodeIterator) step() error {
-	// Abort if we reached the end of the iteration
 	if it.trie == nil {
+		// Abort if we reached the end of the iteration
 		return nil
 	}
-	// Initialize the iterator if we've just started, or pop off the old node otherwise
 	if len(it.stack) == 0 {
-		// Always start with a collapsed root
+		// Initialize the iterator if we've just started.
 		root := it.trie.Hash()
-		it.stack = append(it.stack, &nodeIteratorState{node: hashNode(root[:]), child: -1})
-		if it.stack[0].node == nil {
-			return fmt.Errorf("root node missing: %x", it.trie.Hash())
+		state := &nodeIteratorState{node: it.trie.root, child: -1}
+		if root != emptyRoot {
+			state.hash = root
 		}
+		it.stack = append(it.stack, state)
 	} else {
+		// Continue iterating at the previous node otherwise.
 		it.stack = it.stack[:len(it.stack)-1]
 		if len(it.stack) == 0 {
 			it.trie = nil
 			return nil
 		}
 	}
+
 	// Continue iteration to the next child
 	for {
 		parent := it.stack[len(it.stack)-1]
@@ -232,7 +155,12 @@ func (it *NodeIterator) step() error {
 			}
 			for parent.child++; parent.child < len(node.Children); parent.child++ {
 				if current := node.Children[parent.child]; current != nil {
-					it.stack = append(it.stack, &nodeIteratorState{node: current, parent: ancestor, child: -1})
+					it.stack = append(it.stack, &nodeIteratorState{
+						hash:   common.BytesToHash(node.hash),
+						node:   current,
+						parent: ancestor,
+						child:  -1,
+					})
 					break
 				}
 			}
@@ -242,7 +170,12 @@ func (it *NodeIterator) step() error {
 				break
 			}
 			parent.child++
-			it.stack = append(it.stack, &nodeIteratorState{node: node.Val, parent: ancestor, child: -1})
+			it.stack = append(it.stack, &nodeIteratorState{
+				hash:   common.BytesToHash(node.hash),
+				node:   node.Val,
+				parent: ancestor,
+				child:  -1,
+			})
 		} else if hash, ok := parent.node.(hashNode); ok {
 			// Hash node, resolve the hash child from the database, then the node itself
 			if parent.child >= 0 {
@@ -254,7 +187,12 @@ func (it *NodeIterator) step() error {
 			if err != nil {
 				return err
 			}
-			it.stack = append(it.stack, &nodeIteratorState{hash: common.BytesToHash(hash), node: node, parent: ancestor, child: -1})
+			it.stack = append(it.stack, &nodeIteratorState{
+				hash:   common.BytesToHash(hash),
+				node:   node,
+				parent: ancestor,
+				child:  -1,
+			})
 		} else {
 			break
 		}
diff --git a/trie/iterator_test.go b/trie/iterator_test.go
index dc8276116..2bcc3700e 100644
--- a/trie/iterator_test.go
+++ b/trie/iterator_test.go
@@ -34,21 +34,60 @@ func TestIterator(t *testing.T) {
 		{"dog", "puppy"},
 		{"somethingveryoddindeedthis is", "myothernodedata"},
 	}
-	v := make(map[string]bool)
+	all := make(map[string]string)
 	for _, val := range vals {
-		v[val.k] = false
+		all[val.k] = val.v
 		trie.Update([]byte(val.k), []byte(val.v))
 	}
 	trie.Commit()
 
+	found := make(map[string]string)
 	it := NewIterator(trie)
 	for it.Next() {
-		v[string(it.Key)] = true
+		found[string(it.Key)] = string(it.Value)
 	}
 
-	for k, found := range v {
-		if !found {
-			t.Error("iterator didn't find", k)
+	for k, v := range all {
+		if found[k] != v {
+			t.Errorf("iterator value mismatch for %s: got %q want %q", k, found[k], v)
+		}
+	}
+}
+
+type kv struct {
+	k, v []byte
+	t    bool
+}
+
+func TestIteratorLargeData(t *testing.T) {
+	trie := newEmpty()
+	vals := make(map[string]*kv)
+
+	for i := byte(0); i < 255; i++ {
+		value := &kv{common.LeftPadBytes([]byte{i}, 32), []byte{i}, false}
+		value2 := &kv{common.LeftPadBytes([]byte{10, i}, 32), []byte{i}, false}
+		trie.Update(value.k, value.v)
+		trie.Update(value2.k, value2.v)
+		vals[string(value.k)] = value
+		vals[string(value2.k)] = value2
+	}
+
+	it := NewIterator(trie)
+	for it.Next() {
+		vals[string(it.Key)].t = true
+	}
+
+	var untouched []*kv
+	for _, value := range vals {
+		if !value.t {
+			untouched = append(untouched, value)
+		}
+	}
+
+	if len(untouched) > 0 {
+		t.Errorf("Missed %d nodes", len(untouched))
+		for _, value := range untouched {
+			t.Error(value)
 		}
 	}
 }
diff --git a/trie/proof.go b/trie/proof.go
index 5135de047..116c13a1b 100644
--- a/trie/proof.go
+++ b/trie/proof.go
@@ -70,15 +70,13 @@ func (t *Trie) Prove(key []byte) []rlp.RawValue {
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}
 	}
-	if t.hasher == nil {
-		t.hasher = newHasher()
-	}
+	hasher := newHasher()
 	proof := make([]rlp.RawValue, 0, len(nodes))
 	for i, n := range nodes {
 		// Don't bother checking for errors here since hasher panics
 		// if encoding doesn't work and we're not writing to any database.
-		n, _, _ = t.hasher.hashChildren(n, nil)
-		hn, _ := t.hasher.store(n, nil, false)
+		n, _, _ = hasher.hashChildren(n, nil)
+		hn, _ := hasher.store(n, nil, false)
 		if _, ok := hn.(hashNode); ok || i == 0 {
 			// If the node's database encoding is a hash (or is the
 			// root node), it becomes a proof element.
diff --git a/trie/secure_trie.go b/trie/secure_trie.go
index 1d027c102..efe875bc8 100644
--- a/trie/secure_trie.go
+++ b/trie/secure_trie.go
@@ -17,10 +17,7 @@
 package trie
 
 import (
-	"hash"
-
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 )
@@ -38,11 +35,9 @@ var secureKeyPrefix = []byte("secure-key-")
 //
 // SecureTrie is not safe for concurrent use.
 type SecureTrie struct {
-	*Trie
-
-	hash        hash.Hash
+	trie        Trie
 	hashKeyBuf  []byte
-	secKeyBuf   []byte
+	secKeyBuf   [200]byte
 	secKeyCache map[string][]byte
 }
 
@@ -61,7 +56,7 @@ func NewSecure(root common.Hash, db Database) (*SecureTrie, error) {
 		return nil, err
 	}
 	return &SecureTrie{
-		Trie:        trie,
+		trie:        *trie,
 		secKeyCache: make(map[string][]byte),
 	}, nil
 }
@@ -80,7 +75,7 @@ func (t *SecureTrie) Get(key []byte) []byte {
 // The value bytes must not be modified by the caller.
 // If a node was not found in the database, a MissingNodeError is returned.
 func (t *SecureTrie) TryGet(key []byte) ([]byte, error) {
-	return t.Trie.TryGet(t.hashKey(key))
+	return t.trie.TryGet(t.hashKey(key))
 }
 
 // Update associates key with value in the trie. Subsequent calls to
@@ -105,7 +100,7 @@ func (t *SecureTrie) Update(key, value []byte) {
 // If a node was not found in the database, a MissingNodeError is returned.
 func (t *SecureTrie) TryUpdate(key, value []byte) error {
 	hk := t.hashKey(key)
-	err := t.Trie.TryUpdate(hk, value)
+	err := t.trie.TryUpdate(hk, value)
 	if err != nil {
 		return err
 	}
@@ -125,7 +120,7 @@ func (t *SecureTrie) Delete(key []byte) {
 func (t *SecureTrie) TryDelete(key []byte) error {
 	hk := t.hashKey(key)
 	delete(t.secKeyCache, string(hk))
-	return t.Trie.TryDelete(hk)
+	return t.trie.TryDelete(hk)
 }
 
 // GetKey returns the sha3 preimage of a hashed key that was
@@ -134,7 +129,7 @@ func (t *SecureTrie) GetKey(shaKey []byte) []byte {
 	if key, ok := t.secKeyCache[string(shaKey)]; ok {
 		return key
 	}
-	key, _ := t.Trie.db.Get(t.secKey(shaKey))
+	key, _ := t.trie.db.Get(t.secKey(shaKey))
 	return key
 }
 
@@ -144,7 +139,23 @@ func (t *SecureTrie) GetKey(shaKey []byte) []byte {
 // Committing flushes nodes from memory. Subsequent Get calls will load nodes
 // from the database.
 func (t *SecureTrie) Commit() (root common.Hash, err error) {
-	return t.CommitTo(t.db)
+	return t.CommitTo(t.trie.db)
+}
+
+func (t *SecureTrie) Hash() common.Hash {
+	return t.trie.Hash()
+}
+
+func (t *SecureTrie) Root() []byte {
+	return t.trie.Root()
+}
+
+func (t *SecureTrie) Iterator() *Iterator {
+	return t.trie.Iterator()
+}
+
+func (t *SecureTrie) NodeIterator() *NodeIterator {
+	return NewNodeIterator(&t.trie)
 }
 
 // CommitTo writes all nodes and the secure hash pre-images to the given database.
@@ -162,27 +173,26 @@ func (t *SecureTrie) CommitTo(db DatabaseWriter) (root common.Hash, err error) {
 		}
 		t.secKeyCache = make(map[string][]byte)
 	}
-	n, clean, err := t.hashRoot(db)
-	if err != nil {
-		return (common.Hash{}), err
-	}
-	t.root = clean
-	return common.BytesToHash(n.(hashNode)), nil
+	return t.trie.CommitTo(db)
 }
 
+// secKey returns the database key for the preimage of key, as an ephemeral buffer.
+// The caller must not hold onto the return value because it will become
+// invalid on the next call to hashKey or secKey.
 func (t *SecureTrie) secKey(key []byte) []byte {
-	t.secKeyBuf = append(t.secKeyBuf[:0], secureKeyPrefix...)
-	t.secKeyBuf = append(t.secKeyBuf, key...)
-	return t.secKeyBuf
+	buf := append(t.secKeyBuf[:0], secureKeyPrefix...)
+	buf = append(buf, key...)
+	return buf
 }
 
+// hashKey returns the hash of key as an ephemeral buffer.
+// The caller must not hold onto the return value because it will become
+// invalid on the next call to hashKey or secKey.
 func (t *SecureTrie) hashKey(key []byte) []byte {
-	if t.hash == nil {
-		t.hash = sha3.NewKeccak256()
-		t.hashKeyBuf = make([]byte, 32)
-	}
-	t.hash.Reset()
-	t.hash.Write(key)
-	t.hashKeyBuf = t.hash.Sum(t.hashKeyBuf[:0])
-	return t.hashKeyBuf
+	h := newHasher()
+	h.sha.Reset()
+	h.sha.Write(key)
+	buf := h.sha.Sum(t.hashKeyBuf[:0])
+	returnHasherToPool(h)
+	return buf
 }
diff --git a/trie/sync_test.go b/trie/sync_test.go
index a81f7650e..a763dc564 100644
--- a/trie/sync_test.go
+++ b/trie/sync_test.go
@@ -51,9 +51,6 @@ func makeTestTrie() (ethdb.Database, *Trie, map[string][]byte) {
 	}
 	trie.Commit()
 
-	// Remove any potentially cached data from the test trie creation
-	globalCache.Clear()
-
 	// Return the generated trie
 	return db, trie, content
 }
@@ -61,9 +58,6 @@ func makeTestTrie() (ethdb.Database, *Trie, map[string][]byte) {
 // checkTrieContents cross references a reconstructed trie with an expected data
 // content map.
 func checkTrieContents(t *testing.T, db Database, root []byte, content map[string][]byte) {
-	// Remove any potentially cached data from the trie synchronisation
-	globalCache.Clear()
-
 	// Check root availability and trie contents
 	trie, err := New(common.BytesToHash(root), db)
 	if err != nil {
@@ -81,9 +75,6 @@ func checkTrieContents(t *testing.T, db Database, root []byte, content map[strin
 
 // checkTrieConsistency checks that all nodes in a trie are indeed present.
 func checkTrieConsistency(db Database, root common.Hash) error {
-	// Remove any potentially cached data from the test trie creation or previous checks
-	globalCache.Clear()
-
 	// Create and iterate a trie rooted in a subnode
 	trie, err := New(root, db)
 	if err != nil {
diff --git a/trie/trie.go b/trie/trie.go
index a530e7b2a..93e189e2e 100644
--- a/trie/trie.go
+++ b/trie/trie.go
@@ -20,22 +20,14 @@ package trie
 import (
 	"bytes"
 	"fmt"
-	"hash"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
-	"github.com/ethereum/go-ethereum/crypto/sha3"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
-	"github.com/ethereum/go-ethereum/rlp"
 )
 
-const defaultCacheCapacity = 800
-
 var (
-	// The global cache stores decoded trie nodes by hash as they get loaded.
-	globalCache = newARC(defaultCacheCapacity)
-
 	// This is the known root hash of an empty trie.
 	emptyRoot = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
 
@@ -43,11 +35,6 @@ var (
 	emptyState = crypto.Keccak256Hash(nil)
 )
 
-// ClearGlobalCache clears the global trie cache
-func ClearGlobalCache() {
-	globalCache.Clear()
-}
-
 // Database must be implemented by backing stores for the trie.
 type Database interface {
 	DatabaseWriter
@@ -72,7 +59,6 @@ type Trie struct {
 	root         node
 	db           Database
 	originalRoot common.Hash
-	*hasher
 }
 
 // New creates a trie with an existing root node from db.
@@ -118,32 +104,50 @@ func (t *Trie) Get(key []byte) []byte {
 // If a node was not found in the database, a MissingNodeError is returned.
 func (t *Trie) TryGet(key []byte) ([]byte, error) {
 	key = compactHexDecode(key)
-	pos := 0
-	tn := t.root
-	for pos < len(key) {
-		switch n := tn.(type) {
-		case shortNode:
-			if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
-				return nil, nil
-			}
-			tn = n.Val
-			pos += len(n.Key)
-		case fullNode:
-			tn = n.Children[key[pos]]
-			pos++
-		case nil:
-			return nil, nil
-		case hashNode:
-			var err error
-			tn, err = t.resolveHash(n, key[:pos], key[pos:])
-			if err != nil {
-				return nil, err
-			}
-		default:
-			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
+	value, newroot, didResolve, err := t.tryGet(t.root, key, 0)
+	if err == nil && didResolve {
+		t.root = newroot
+	}
+	return value, err
+}
+
+func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode node, didResolve bool, err error) {
+	switch n := (origNode).(type) {
+	case nil:
+		return nil, nil, false, nil
+	case valueNode:
+		return n, n, false, nil
+	case shortNode:
+		if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
+			// key not found in trie
+			return nil, n, false, nil
+		}
+		value, newnode, didResolve, err = t.tryGet(n.Val, key, pos+len(n.Key))
+		if err == nil && didResolve {
+			n.Val = newnode
+			return value, n, didResolve, err
+		} else {
+			return value, origNode, didResolve, err
+		}
+	case fullNode:
+		child := n.Children[key[pos]]
+		value, newnode, didResolve, err = t.tryGet(child, key, pos+1)
+		if err == nil && didResolve {
+			n.Children[key[pos]] = newnode
+			return value, n, didResolve, err
+		} else {
+			return value, origNode, didResolve, err
+		}
+	case hashNode:
+		child, err := t.resolveHash(n, key[:pos], key[pos:])
+		if err != nil {
+			return nil, n, true, err
 		}
+		value, newnode, _, err := t.tryGet(child, key, pos)
+		return value, newnode, true, err
+	default:
+		panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
 	}
-	return tn.(valueNode), nil
 }
 
 // Update associates key with value in the trie. Subsequent calls to
@@ -410,9 +414,6 @@ func (t *Trie) resolve(n node, prefix, suffix []byte) (node, error) {
 }
 
 func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
-	if v, ok := globalCache.Get(n); ok {
-		return v, nil
-	}
 	enc, err := t.db.Get(n)
 	if err != nil || enc == nil {
 		return nil, &MissingNodeError{
@@ -424,9 +425,6 @@ func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
 		}
 	}
 	dec := mustDecodeNode(n, enc)
-	if dec != nil {
-		globalCache.Put(n, dec)
-	}
 	return dec, nil
 }
 
@@ -474,127 +472,7 @@ func (t *Trie) hashRoot(db DatabaseWriter) (node, node, error) {
 	if t.root == nil {
 		return hashNode(emptyRoot.Bytes()), nil, nil
 	}
-	if t.hasher == nil {
-		t.hasher = newHasher()
-	}
-	return t.hasher.hash(t.root, db, true)
-}
-
-type hasher struct {
-	tmp *bytes.Buffer
-	sha hash.Hash
-}
-
-func newHasher() *hasher {
-	return &hasher{tmp: new(bytes.Buffer), sha: sha3.NewKeccak256()}
-}
-
-// hash collapses a node down into a hash node, also returning a copy of the
-// original node initialzied with the computed hash to replace the original one.
-func (h *hasher) hash(n node, db DatabaseWriter, force bool) (node, node, error) {
-	// If we're not storing the node, just hashing, use avaialble cached data
-	if hash, dirty := n.cache(); hash != nil && (db == nil || !dirty) {
-		return hash, n, nil
-	}
-	// Trie not processed yet or needs storage, walk the children
-	collapsed, cached, err := h.hashChildren(n, db)
-	if err != nil {
-		return hashNode{}, n, err
-	}
-	hashed, err := h.store(collapsed, db, force)
-	if err != nil {
-		return hashNode{}, n, err
-	}
-	// Cache the hash and RLP blob of the ndoe for later reuse
-	if hash, ok := hashed.(hashNode); ok && !force {
-		switch cached := cached.(type) {
-		case shortNode:
-			cached.hash = hash
-			if db != nil {
-				cached.dirty = false
-			}
-			return hashed, cached, nil
-		case fullNode:
-			cached.hash = hash
-			if db != nil {
-				cached.dirty = false
-			}
-			return hashed, cached, nil
-		}
-	}
-	return hashed, cached, nil
-}
-
-// hashChildren replaces the children of a node with their hashes if the encoded
-// size of the child is larger than a hash, returning the collapsed node as well
-// as a replacement for the original node with the child hashes cached in.
-func (h *hasher) hashChildren(original node, db DatabaseWriter) (node, node, error) {
-	var err error
-
-	switch n := original.(type) {
-	case shortNode:
-		// Hash the short node's child, caching the newly hashed subtree
-		cached := n
-		cached.Key = common.CopyBytes(cached.Key)
-
-		n.Key = compactEncode(n.Key)
-		if _, ok := n.Val.(valueNode); !ok {
-			if n.Val, cached.Val, err = h.hash(n.Val, db, false); err != nil {
-				return n, original, err
-			}
-		}
-		if n.Val == nil {
-			n.Val = valueNode(nil) // Ensure that nil children are encoded as empty strings.
-		}
-		return n, cached, nil
-
-	case fullNode:
-		// Hash the full node's children, caching the newly hashed subtrees
-		cached := fullNode{dirty: n.dirty}
-
-		for i := 0; i < 16; i++ {
-			if n.Children[i] != nil {
-				if n.Children[i], cached.Children[i], err = h.hash(n.Children[i], db, false); err != nil {
-					return n, original, err
-				}
-			} else {
-				n.Children[i] = valueNode(nil) // Ensure that nil children are encoded as empty strings.
-			}
-		}
-		cached.Children[16] = n.Children[16]
-		if n.Children[16] == nil {
-			n.Children[16] = valueNode(nil)
-		}
-		return n, cached, nil
-
-	default:
-		// Value and hash nodes don't have children so they're left as were
-		return n, original, nil
-	}
-}
-
-func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
-	// Don't store hashes or empty nodes.
-	if _, isHash := n.(hashNode); n == nil || isHash {
-		return n, nil
-	}
-	// Generate the RLP encoding of the node
-	h.tmp.Reset()
-	if err := rlp.Encode(h.tmp, n); err != nil {
-		panic("encode error: " + err.Error())
-	}
-	if h.tmp.Len() < 32 && !force {
-		return n, nil // Nodes smaller than 32 bytes are stored inside their parent
-	}
-	// Larger nodes are replaced by their hash and stored in the database.
-	hash, _ := n.cache()
-	if hash == nil {
-		h.sha.Reset()
-		h.sha.Write(h.tmp.Bytes())
-		hash = hashNode(h.sha.Sum(nil))
-	}
-	if db != nil {
-		return hash, db.Put(hash, h.tmp.Bytes())
-	}
-	return hash, nil
+	h := newHasher()
+	defer returnHasherToPool(h)
+	return h.hash(t.root, db, true)
 }
diff --git a/trie/trie_test.go b/trie/trie_test.go
index 121ba24c1..5a3ea1be9 100644
--- a/trie/trie_test.go
+++ b/trie/trie_test.go
@@ -76,8 +76,6 @@ func TestMissingNode(t *testing.T) {
 	updateString(trie, "123456", "asdfasdfasdfasdfasdfasdfasdfasdf")
 	root, _ := trie.Commit()
 
-	ClearGlobalCache()
-
 	trie, _ = New(root, db)
 	_, err := trie.TryGet([]byte("120000"))
 	if err != nil {
@@ -109,7 +107,6 @@ func TestMissingNode(t *testing.T) {
 	}
 
 	db.Delete(common.FromHex("e1d943cc8f061a0c0b98162830b970395ac9315654824bf21b73b891365262f9"))
-	ClearGlobalCache()
 
 	trie, _ = New(root, db)
 	_, err = trie.TryGet([]byte("120000"))
@@ -362,44 +359,6 @@ func TestLargeValue(t *testing.T) {
 
 }
 
-type kv struct {
-	k, v []byte
-	t    bool
-}
-
-func TestLargeData(t *testing.T) {
-	trie := newEmpty()
-	vals := make(map[string]*kv)
-
-	for i := byte(0); i < 255; i++ {
-		value := &kv{common.LeftPadBytes([]byte{i}, 32), []byte{i}, false}
-		value2 := &kv{common.LeftPadBytes([]byte{10, i}, 32), []byte{i}, false}
-		trie.Update(value.k, value.v)
-		trie.Update(value2.k, value2.v)
-		vals[string(value.k)] = value
-		vals[string(value2.k)] = value2
-	}
-
-	it := NewIterator(trie)
-	for it.Next() {
-		vals[string(it.Key)].t = true
-	}
-
-	var untouched []*kv
-	for _, value := range vals {
-		if !value.t {
-			untouched = append(untouched, value)
-		}
-	}
-
-	if len(untouched) > 0 {
-		t.Errorf("Missed %d nodes", len(untouched))
-		for _, value := range untouched {
-			t.Error(value)
-		}
-	}
-}
-
 func BenchmarkGet(b *testing.B)      { benchGet(b, false) }
 func BenchmarkGetDB(b *testing.B)    { benchGet(b, true) }
 func BenchmarkUpdateBE(b *testing.B) { benchUpdate(b, binary.BigEndian) }