light: implemented odr-capable trie and state structures

10 files changed, 1091 insertions, 15 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
+	}
+}
diff --git a/light/state.go b/light/state.go
new file mode 100644
index 000000000..e18f9cdc5
--- /dev/null
+++ b/light/state.go
@@ -0,0 +1,275 @@
+// 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 (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"golang.org/x/net/context"
+)
+
+// StartingNonce determines the default nonce when new accounts are being created.
+var StartingNonce uint64
+
+// LightState is a memory representation of a state.
+// This version is ODR capable, caching only the already accessed part of the
+// state, retrieving unknown parts on-demand from the ODR backend. Changes are
+// never stored in the local database, only in the memory objects.
+type LightState struct {
+	odr  OdrBackend
+	trie *LightTrie
+
+	stateObjects map[string]*StateObject
+}
+
+// NewLightState creates a new LightState with the specified root.
+// Note that the creation of a light state is always successful, even if the
+// root is non-existent. In that case, ODR retrieval will always be unsuccessful
+// and every operation will return with an error or wait for the context to be
+// cancelled.
+func NewLightState(root common.Hash, odr OdrBackend) *LightState {
+	tr := NewLightTrie(root, odr, true)
+	return &LightState{
+		odr:          odr,
+		trie:         tr,
+		stateObjects: make(map[string]*StateObject),
+	}
+}
+
+// HasAccount returns true if an account exists at the given address
+func (self *LightState) HasAccount(ctx context.Context, addr common.Address) (bool, error) {
+	so, err := self.GetStateObject(ctx, addr)
+	return so != nil, err
+}
+
+// GetBalance retrieves the balance from the given address or 0 if the account does
+// not exist
+func (self *LightState) GetBalance(ctx context.Context, addr common.Address) (*big.Int, error) {
+	stateObject, err := self.GetStateObject(ctx, addr)
+	if err != nil {
+		return common.Big0, err
+	}
+	if stateObject != nil {
+		return stateObject.balance, nil
+	}
+
+	return common.Big0, nil
+}
+
+// GetNonce returns the nonce at the given address or 0 if the account does
+// not exist
+func (self *LightState) GetNonce(ctx context.Context, addr common.Address) (uint64, error) {
+	stateObject, err := self.GetStateObject(ctx, addr)
+	if err != nil {
+		return 0, err
+	}
+	if stateObject != nil {
+		return stateObject.nonce, nil
+	}
+	return 0, nil
+}
+
+// GetCode returns the contract code at the given address or nil if the account
+// does not exist
+func (self *LightState) GetCode(ctx context.Context, addr common.Address) ([]byte, error) {
+	stateObject, err := self.GetStateObject(ctx, addr)
+	if err != nil {
+		return nil, err
+	}
+	if stateObject != nil {
+		return stateObject.code, nil
+	}
+	return nil, nil
+}
+
+// GetState returns the contract storage value at storage address b from the
+// contract address a or common.Hash{} if the account does not exist
+func (self *LightState) GetState(ctx context.Context, a common.Address, b common.Hash) (common.Hash, error) {
+	stateObject, err := self.GetStateObject(ctx, a)
+	if err == nil && stateObject != nil {
+		return stateObject.GetState(ctx, b)
+	}
+	return common.Hash{}, err
+}
+
+// IsDeleted returns true if the given account has been marked for deletion
+// or false if the account does not exist
+func (self *LightState) IsDeleted(ctx context.Context, addr common.Address) (bool, error) {
+	stateObject, err := self.GetStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		return stateObject.remove, nil
+	}
+	return false, err
+}
+
+/*
+ * SETTERS
+ */
+
+// AddBalance adds the given amount to the balance of the specified account
+func (self *LightState) AddBalance(ctx context.Context, addr common.Address, amount *big.Int) error {
+	stateObject, err := self.GetOrNewStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		stateObject.AddBalance(amount)
+	}
+	return err
+}
+
+// SetNonce sets the nonce of the specified account
+func (self *LightState) SetNonce(ctx context.Context, addr common.Address, nonce uint64) error {
+	stateObject, err := self.GetOrNewStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		stateObject.SetNonce(nonce)
+	}
+	return err
+}
+
+// SetCode sets the contract code at the specified account
+func (self *LightState) SetCode(ctx context.Context, addr common.Address, code []byte) error {
+	stateObject, err := self.GetOrNewStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		stateObject.SetCode(code)
+	}
+	return err
+}
+
+// SetState sets the storage value at storage address key of the account addr
+func (self *LightState) SetState(ctx context.Context, addr common.Address, key common.Hash, value common.Hash) error {
+	stateObject, err := self.GetOrNewStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		stateObject.SetState(key, value)
+	}
+	return err
+}
+
+// Delete marks an account to be removed and clears its balance
+func (self *LightState) Delete(ctx context.Context, addr common.Address) (bool, error) {
+	stateObject, err := self.GetOrNewStateObject(ctx, addr)
+	if err == nil && stateObject != nil {
+		stateObject.MarkForDeletion()
+		stateObject.balance = new(big.Int)
+
+		return true, nil
+	}
+
+	return false, err
+}
+
+//
+// Get, set, new state object methods
+//
+
+// GetStateObject returns the state object of the given account or nil if the
+// account does not exist
+func (self *LightState) GetStateObject(ctx context.Context, addr common.Address) (stateObject *StateObject, err error) {
+	stateObject = self.stateObjects[addr.Str()]
+	if stateObject != nil {
+		if stateObject.deleted {
+			stateObject = nil
+		}
+		return stateObject, nil
+	}
+	data, err := self.trie.Get(ctx, addr[:])
+	if err != nil {
+		return nil, err
+	}
+	if len(data) == 0 {
+		return nil, nil
+	}
+
+	stateObject, err = DecodeObject(ctx, addr, self.odr, []byte(data))
+	if err != nil {
+		return nil, err
+	}
+
+	self.SetStateObject(stateObject)
+
+	return stateObject, nil
+}
+
+// SetStateObject sets the state object of the given account
+func (self *LightState) SetStateObject(object *StateObject) {
+	self.stateObjects[object.Address().Str()] = object
+}
+
+// GetOrNewStateObject returns the state object of the given account or creates a
+// new one if the account does not exist
+func (self *LightState) GetOrNewStateObject(ctx context.Context, addr common.Address) (*StateObject, error) {
+	stateObject, err := self.GetStateObject(ctx, addr)
+	if err == nil && (stateObject == nil || stateObject.deleted) {
+		stateObject, err = self.CreateStateObject(ctx, addr)
+	}
+	return stateObject, err
+}
+
+// newStateObject creates a state object whether it exists in the state or not
+func (self *LightState) newStateObject(addr common.Address) *StateObject {
+	if glog.V(logger.Core) {
+		glog.Infof("(+) %x\n", addr)
+	}
+
+	stateObject := NewStateObject(addr, self.odr)
+	stateObject.SetNonce(StartingNonce)
+	self.stateObjects[addr.Str()] = stateObject
+
+	return stateObject
+}
+
+// CreateStateObject creates creates a new state object and takes ownership.
+// This is different from "NewStateObject"
+func (self *LightState) CreateStateObject(ctx context.Context, addr common.Address) (*StateObject, error) {
+	// Get previous (if any)
+	so, err := self.GetStateObject(ctx, addr)
+	if err != nil {
+		return nil, err
+	}
+	// Create a new one
+	newSo := self.newStateObject(addr)
+
+	// If it existed set the balance to the new account
+	if so != nil {
+		newSo.balance = so.balance
+	}
+
+	return newSo, nil
+}
+
+//
+// Setting, copying of the state methods
+//
+
+// Copy creates a copy of the state
+func (self *LightState) Copy() *LightState {
+	// ignore error - we assume state-to-be-copied always exists
+	state := NewLightState(common.Hash{}, self.odr)
+	state.trie = self.trie
+	for k, stateObject := range self.stateObjects {
+		state.stateObjects[k] = stateObject.Copy()
+	}
+
+	return state
+}
+
+// Set copies the contents of the given state onto this state, overwriting
+// its contents
+func (self *LightState) Set(state *LightState) {
+	self.trie = state.trie
+	self.stateObjects = state.stateObjects
+}
diff --git a/light/state_object.go b/light/state_object.go
new file mode 100644
index 000000000..7660c3883
--- /dev/null
+++ b/light/state_object.go
@@ -0,0 +1,267 @@
+// Copyright 2014 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 (
+	"bytes"
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/rlp"
+	"golang.org/x/net/context"
+)
+
+var emptyCodeHash = crypto.Sha3(nil)
+
+// Code represents a contract code in binary form
+type Code []byte
+
+// String returns a string representation of the code
+func (self Code) String() string {
+	return string(self) //strings.Join(Disassemble(self), " ")
+}
+
+// Storage is a memory map cache of a contract storage
+type Storage map[string]common.Hash
+
+// String returns a string representation of the storage cache
+func (self Storage) String() (str string) {
+	for key, value := range self {
+		str += fmt.Sprintf("%X : %X\n", key, value)
+	}
+
+	return
+}
+
+// Copy copies the contents of a storage cache
+func (self Storage) Copy() Storage {
+	cpy := make(Storage)
+	for key, value := range self {
+		cpy[key] = value
+	}
+
+	return cpy
+}
+
+// StateObject is a memory representation of an account or contract and its storage.
+// This version is ODR capable, caching only the already accessed part of the
+// storage, retrieving unknown parts on-demand from the ODR backend. Changes are
+// never stored in the local database, only in the memory objects.
+type StateObject struct {
+	odr  OdrBackend
+	trie *LightTrie
+
+	// Address belonging to this account
+	address common.Address
+	// The balance of the account
+	balance *big.Int
+	// The nonce of the account
+	nonce uint64
+	// The code hash if code is present (i.e. a contract)
+	codeHash []byte
+	// The code for this account
+	code Code
+	// Temporarily initialisation code
+	initCode Code
+	// Cached storage (flushed when updated)
+	storage Storage
+
+	// Mark for deletion
+	// When an object is marked for deletion it will be delete from the trie
+	// during the "update" phase of the state transition
+	remove  bool
+	deleted bool
+	dirty   bool
+}
+
+// NewStateObject creates a new StateObject of the specified account address
+func NewStateObject(address common.Address, odr OdrBackend) *StateObject {
+	object := &StateObject{
+		odr:      odr,
+		address:  address,
+		balance:  new(big.Int),
+		dirty:    true,
+		codeHash: emptyCodeHash,
+		storage:  make(Storage),
+	}
+	object.trie = NewLightTrie(common.Hash{}, odr, true)
+	return object
+}
+
+// MarkForDeletion marks an account to be removed
+func (self *StateObject) MarkForDeletion() {
+	self.remove = true
+	self.dirty = true
+
+	if glog.V(logger.Core) {
+		glog.Infof("%x: #%d %v X\n", self.Address(), self.nonce, self.balance)
+	}
+}
+
+// getAddr gets the storage value at the given address from the trie
+func (c *StateObject) getAddr(ctx context.Context, addr common.Hash) (common.Hash, error) {
+	var ret []byte
+	val, err := c.trie.Get(ctx, addr[:])
+	if err != nil {
+		return common.Hash{}, err
+	}
+	rlp.DecodeBytes(val, &ret)
+	return common.BytesToHash(ret), nil
+}
+
+// Storage returns the storage cache object of the account
+func (self *StateObject) Storage() Storage {
+	return self.storage
+}
+
+// GetState returns the storage value at the given address from either the cache
+// or the trie
+func (self *StateObject) GetState(ctx context.Context, key common.Hash) (common.Hash, error) {
+	strkey := key.Str()
+	value, exists := self.storage[strkey]
+	if !exists {
+		var err error
+		value, err = self.getAddr(ctx, key)
+		if err != nil {
+			return common.Hash{}, err
+		}
+		if (value != common.Hash{}) {
+			self.storage[strkey] = value
+		}
+	}
+
+	return value, nil
+}
+
+// SetState sets the storage value at the given address
+func (self *StateObject) SetState(k, value common.Hash) {
+	self.storage[k.Str()] = value
+	self.dirty = true
+}
+
+// AddBalance adds the given amount to the account balance
+func (c *StateObject) AddBalance(amount *big.Int) {
+	c.SetBalance(new(big.Int).Add(c.balance, amount))
+
+	if glog.V(logger.Core) {
+		glog.Infof("%x: #%d %v (+ %v)\n", c.Address(), c.nonce, c.balance, amount)
+	}
+}
+
+// SubBalance subtracts the given amount from the account balance
+func (c *StateObject) SubBalance(amount *big.Int) {
+	c.SetBalance(new(big.Int).Sub(c.balance, amount))
+
+	if glog.V(logger.Core) {
+		glog.Infof("%x: #%d %v (- %v)\n", c.Address(), c.nonce, c.balance, amount)
+	}
+}
+
+// SetBalance sets the account balance to the given amount
+func (c *StateObject) SetBalance(amount *big.Int) {
+	c.balance = amount
+	c.dirty = true
+}
+
+// Copy creates a copy of the state object
+func (self *StateObject) Copy() *StateObject {
+	stateObject := NewStateObject(self.Address(), self.odr)
+	stateObject.balance.Set(self.balance)
+	stateObject.codeHash = common.CopyBytes(self.codeHash)
+	stateObject.nonce = self.nonce
+	stateObject.trie = self.trie
+	stateObject.code = common.CopyBytes(self.code)
+	stateObject.initCode = common.CopyBytes(self.initCode)
+	stateObject.storage = self.storage.Copy()
+	stateObject.remove = self.remove
+	stateObject.dirty = self.dirty
+	stateObject.deleted = self.deleted
+
+	return stateObject
+}
+
+//
+// Attribute accessors
+//
+
+// Balance returns the account balance
+func (self *StateObject) Balance() *big.Int {
+	return self.balance
+}
+
+// Address returns the address of the contract/account
+func (c *StateObject) Address() common.Address {
+	return c.address
+}
+
+// Code returns the contract code
+func (self *StateObject) Code() []byte {
+	return self.code
+}
+
+// SetCode sets the contract code
+func (self *StateObject) SetCode(code []byte) {
+	self.code = code
+	self.codeHash = crypto.Sha3(code)
+	self.dirty = true
+}
+
+// SetNonce sets the account nonce
+func (self *StateObject) SetNonce(nonce uint64) {
+	self.nonce = nonce
+	self.dirty = true
+}
+
+// Nonce returns the account nonce
+func (self *StateObject) Nonce() uint64 {
+	return self.nonce
+}
+
+// Encoding
+
+type extStateObject struct {
+	Nonce    uint64
+	Balance  *big.Int
+	Root     common.Hash
+	CodeHash []byte
+}
+
+// DecodeObject decodes an RLP-encoded state object.
+func DecodeObject(ctx context.Context, address common.Address, odr OdrBackend, data []byte) (*StateObject, error) {
+	var (
+		obj = &StateObject{address: address, odr: odr, storage: make(Storage)}
+		ext extStateObject
+		err error
+	)
+	if err = rlp.DecodeBytes(data, &ext); err != nil {
+		return nil, err
+	}
+	obj.trie = NewLightTrie(ext.Root, odr, true)
+	if !bytes.Equal(ext.CodeHash, emptyCodeHash) {
+		if obj.code, err = retrieveNodeData(ctx, obj.odr, common.BytesToHash(ext.CodeHash)); err != nil {
+			return nil, fmt.Errorf("can't find code for hash %x: %v", ext.CodeHash, err)
+		}
+	}
+	obj.nonce = ext.Nonce
+	obj.balance = ext.Balance
+	obj.codeHash = ext.CodeHash
+	return obj, nil
+}
\ No newline at end of file
diff --git a/light/state_test.go b/light/state_test.go
new file mode 100644
index 000000000..2c2e6daea
--- /dev/null
+++ b/light/state_test.go
@@ -0,0 +1,269 @@
+// 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 (
+	"bytes"
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/trie"
+	"golang.org/x/net/context"
+)
+
+type testOdr struct {
+	OdrBackend
+	sdb, ldb ethdb.Database
+}
+
+func (odr *testOdr) Database() ethdb.Database {
+	return odr.ldb
+}
+
+func (odr *testOdr) Retrieve(ctx context.Context, req OdrRequest) error {
+	switch req := req.(type) {
+	case *TrieRequest:
+		t, _ := trie.New(req.root, odr.sdb)
+		req.proof = t.Prove(req.key)
+		trie.ClearGlobalCache()
+	case *NodeDataRequest:
+		req.data, _ = odr.sdb.Get(req.hash[:])
+	}
+	req.StoreResult(odr.ldb)
+	return nil
+}
+
+func makeTestState() (common.Hash, ethdb.Database) {
+	sdb, _ := ethdb.NewMemDatabase()
+	st, _ := state.New(common.Hash{}, sdb)
+	for i := byte(0); i < 100; i++ {
+		so := st.GetOrNewStateObject(common.Address{i})
+		for j := byte(0); j < 100; j++ {
+			val := common.Hash{i, j}
+			so.SetState(common.Hash{j}, val)
+			so.SetNonce(100)
+		}
+		so.AddBalance(big.NewInt(int64(i)))
+		so.SetCode([]byte{i, i, i})
+		so.Update()
+		st.UpdateStateObject(so)
+	}
+	root, _ := st.Commit()
+	return root, sdb
+}
+
+func TestLightStateOdr(t *testing.T) {
+	root, sdb := makeTestState()
+	ldb, _ := ethdb.NewMemDatabase()
+	odr := &testOdr{sdb: sdb, ldb: ldb}
+	ls := NewLightState(root, odr)
+	ctx := context.Background()
+	trie.ClearGlobalCache()
+
+	for i := byte(0); i < 100; i++ {
+		addr := common.Address{i}
+		err := ls.AddBalance(ctx, addr, big.NewInt(1000))
+		if err != nil {
+			t.Fatalf("Error adding balance to acc[%d]: %v", i, err)
+		}
+		err = ls.SetState(ctx, addr, common.Hash{100}, common.Hash{i, 100})
+		if err != nil {
+			t.Fatalf("Error setting storage of acc[%d]: %v", i, err)
+		}
+	}
+
+	addr := common.Address{100}
+	_, err := ls.CreateStateObject(ctx, addr)
+	if err != nil {
+		t.Fatalf("Error creating state object: %v", err)
+	}
+	err = ls.SetCode(ctx, addr, []byte{100, 100, 100})
+	if err != nil {
+		t.Fatalf("Error setting code: %v", err)
+	}
+	err = ls.AddBalance(ctx, addr, big.NewInt(1100))
+	if err != nil {
+		t.Fatalf("Error adding balance to acc[100]: %v", err)
+	}
+	for j := byte(0); j < 101; j++ {
+		err = ls.SetState(ctx, addr, common.Hash{j}, common.Hash{100, j})
+		if err != nil {
+			t.Fatalf("Error setting storage of acc[100]: %v", err)
+		}
+	}
+	err = ls.SetNonce(ctx, addr, 100)
+	if err != nil {
+		t.Fatalf("Error setting nonce for acc[100]: %v", err)
+	}
+
+	for i := byte(0); i < 101; i++ {
+		addr := common.Address{i}
+
+		bal, err := ls.GetBalance(ctx, addr)
+		if err != nil {
+			t.Fatalf("Error getting balance of acc[%d]: %v", i, err)
+		}
+		if bal.Int64() != int64(i)+1000 {
+			t.Fatalf("Incorrect balance at acc[%d]: expected %v, got %v", i, int64(i)+1000, bal.Int64())
+		}
+
+		nonce, err := ls.GetNonce(ctx, addr)
+		if err != nil {
+			t.Fatalf("Error getting nonce of acc[%d]: %v", i, err)
+		}
+		if nonce != 100 {
+			t.Fatalf("Incorrect nonce at acc[%d]: expected %v, got %v", i, 100, nonce)
+		}
+
+		code, err := ls.GetCode(ctx, addr)
+		exp := []byte{i, i, i}
+		if err != nil {
+			t.Fatalf("Error getting code of acc[%d]: %v", i, err)
+		}
+		if !bytes.Equal(code, exp) {
+			t.Fatalf("Incorrect code at acc[%d]: expected %v, got %v", i, exp, code)
+		}
+
+		for j := byte(0); j < 101; j++ {
+			exp := common.Hash{i, j}
+			val, err := ls.GetState(ctx, addr, common.Hash{j})
+			if err != nil {
+				t.Fatalf("Error retrieving acc[%d].storage[%d]: %v", i, j, err)
+			}
+			if val != exp {
+				t.Fatalf("Retrieved wrong value from acc[%d].storage[%d]: expected %04x, got %04x", i, j, exp, val)
+			}
+		}
+	}
+}
+
+func TestLightStateSetCopy(t *testing.T) {
+	root, sdb := makeTestState()
+	ldb, _ := ethdb.NewMemDatabase()
+	odr := &testOdr{sdb: sdb, ldb: ldb}
+	ls := NewLightState(root, odr)
+	ctx := context.Background()
+	trie.ClearGlobalCache()
+
+	for i := byte(0); i < 100; i++ {
+		addr := common.Address{i}
+		err := ls.AddBalance(ctx, addr, big.NewInt(1000))
+		if err != nil {
+			t.Fatalf("Error adding balance to acc[%d]: %v", i, err)
+		}
+		err = ls.SetState(ctx, addr, common.Hash{100}, common.Hash{i, 100})
+		if err != nil {
+			t.Fatalf("Error setting storage of acc[%d]: %v", i, err)
+		}
+	}
+
+	ls2 := ls.Copy()
+
+	for i := byte(0); i < 100; i++ {
+		addr := common.Address{i}
+		err := ls2.AddBalance(ctx, addr, big.NewInt(1000))
+		if err != nil {
+			t.Fatalf("Error adding balance to acc[%d]: %v", i, err)
+		}
+		err = ls2.SetState(ctx, addr, common.Hash{100}, common.Hash{i, 200})
+		if err != nil {
+			t.Fatalf("Error setting storage of acc[%d]: %v", i, err)
+		}
+	}
+
+	lsx := ls.Copy()
+	ls.Set(ls2)
+	ls2.Set(lsx)
+
+	for i := byte(0); i < 100; i++ {
+		addr := common.Address{i}
+		// check balance in ls
+		bal, err := ls.GetBalance(ctx, addr)
+		if err != nil {
+			t.Fatalf("Error getting balance to acc[%d]: %v", i, err)
+		}
+		if bal.Int64() != int64(i)+2000 {
+			t.Fatalf("Incorrect balance at ls.acc[%d]: expected %v, got %v", i, int64(i)+1000, bal.Int64())
+		}
+		// check balance in ls2
+		bal, err = ls2.GetBalance(ctx, addr)
+		if err != nil {
+			t.Fatalf("Error getting balance to acc[%d]: %v", i, err)
+		}
+		if bal.Int64() != int64(i)+1000 {
+			t.Fatalf("Incorrect balance at ls.acc[%d]: expected %v, got %v", i, int64(i)+1000, bal.Int64())
+		}
+		// check storage in ls
+		exp := common.Hash{i, 200}
+		val, err := ls.GetState(ctx, addr, common.Hash{100})
+		if err != nil {
+			t.Fatalf("Error retrieving acc[%d].storage[100]: %v", i, err)
+		}
+		if val != exp {
+			t.Fatalf("Retrieved wrong value from acc[%d].storage[100]: expected %04x, got %04x", i, exp, val)
+		}
+		// check storage in ls2
+		exp = common.Hash{i, 100}
+		val, err = ls2.GetState(ctx, addr, common.Hash{100})
+		if err != nil {
+			t.Fatalf("Error retrieving acc[%d].storage[100]: %v", i, err)
+		}
+		if val != exp {
+			t.Fatalf("Retrieved wrong value from acc[%d].storage[100]: expected %04x, got %04x", i, exp, val)
+		}
+	}
+}
+
+func TestLightStateDelete(t *testing.T) {
+	root, sdb := makeTestState()
+	ldb, _ := ethdb.NewMemDatabase()
+	odr := &testOdr{sdb: sdb, ldb: ldb}
+	ls := NewLightState(root, odr)
+	ctx := context.Background()
+	trie.ClearGlobalCache()
+
+	addr := common.Address{42}
+
+	b, err := ls.HasAccount(ctx, addr)
+	if err != nil {
+		t.Fatalf("HasAccount error: %v", err)
+	}
+	if !b {
+		t.Fatalf("HasAccount returned false, expected true")
+	}
+
+	b, err = ls.IsDeleted(ctx, addr)
+	if err != nil {
+		t.Fatalf("IsDeleted error: %v", err)
+	}
+	if b {
+		t.Fatalf("IsDeleted returned true, expected false")
+	}
+
+	ls.Delete(ctx, addr)
+
+	b, err = ls.IsDeleted(ctx, addr)
+	if err != nil {
+		t.Fatalf("IsDeleted error: %v", err)
+	}
+	if !b {
+		t.Fatalf("IsDeleted returned false, expected true")
+	}
+}
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
+}
diff --git a/trie/encoding.go b/trie/encoding.go
index 3c172b843..761bad188 100644
--- a/trie/encoding.go
+++ b/trie/encoding.go
@@ -69,6 +69,27 @@ func compactHexDecode(str []byte) []byte {
 	return nibbles
 }
 
+// compactHexEncode encodes a series of nibbles into a byte array
+func compactHexEncode(nibbles []byte) []byte {
+	nl := len(nibbles)
+	if nl == 0 {
+		return nil
+	}
+	if nibbles[nl-1] == 16 {
+		nl--
+	}
+	l := (nl + 1) / 2
+	var str = make([]byte, l)
+	for i, _ := range str {
+		b := nibbles[i*2] * 16
+		if nl > i*2 {
+			b += nibbles[i*2+1]
+		}
+		str[i] = b
+	}
+	return str
+}
+
 func decodeCompact(key []byte) []byte {
 	l := len(key) / 2
 	var res = make([]byte, l)
diff --git a/trie/encoding_test.go b/trie/encoding_test.go
index 061d48d58..2f125ef2f 100644
--- a/trie/encoding_test.go
+++ b/trie/encoding_test.go
@@ -57,6 +57,12 @@ func (s *TrieEncodingSuite) TestCompactHexDecode(c *checker.C) {
 	c.Assert(res, checker.DeepEquals, exp)
 }
 
+func (s *TrieEncodingSuite) TestCompactHexEncode(c *checker.C) {
+	exp := []byte("verb")
+	res := compactHexEncode([]byte{7, 6, 6, 5, 7, 2, 6, 2, 16})
+	c.Assert(res, checker.DeepEquals, exp)
+}
+
 func (s *TrieEncodingSuite) TestCompactDecode(c *checker.C) {
 	// odd compact decode
 	exp := []byte{1, 2, 3, 4, 5}
diff --git a/trie/errors.go b/trie/errors.go
index a0f58f28f..fd0e6f0a9 100644
--- a/trie/errors.go
+++ b/trie/errors.go
@@ -27,13 +27,23 @@ import (
 // information necessary for retrieving the missing node through an ODR service.
 //
 // NodeHash is the hash of the missing node
+//
 // RootHash is the original root of the trie that contains the node
-// KeyPrefix is the prefix that leads from the root to the missing node (hex encoded)
-// KeySuffix (optional) contains the rest of the key we were looking for, gives a
-//  hint on which further nodes should also be retrieved (hex encoded)
+//
+// Key is a binary-encoded key that contains the prefix that leads to the first
+// missing node and optionally a suffix that hints on which further nodes should
+// also be retrieved
+//
+// 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
-	KeyPrefix, KeySuffix []byte
+	Key                  []byte
+	PrefixLen, SuffixLen int
 }
 
 func (err *MissingNodeError) Error() string {
diff --git a/trie/proof.go b/trie/proof.go
index 2e88bb50b..0f9264942 100644
--- a/trie/proof.go
+++ b/trie/proof.go
@@ -17,29 +17,30 @@ import (
 // also included in the last node and can be retrieved by verifying
 // the proof.
 //
-// The returned proof is nil if the trie does not contain a value for key.
-// For existing keys, the proof will have at least one element.
+// If the trie does not contain a value for key, the returned proof
+// contains all nodes of the longest existing prefix of the key
+// (at least the root node), ending with the node that proves the
+// absence of the key.
 func (t *Trie) Prove(key []byte) []rlp.RawValue {
 	// Collect all nodes on the path to key.
 	key = compactHexDecode(key)
 	nodes := []node{}
 	tn := t.root
-	for len(key) > 0 {
+	for len(key) > 0 && tn != nil {
 		switch n := tn.(type) {
 		case shortNode:
 			if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
 				// The trie doesn't contain the key.
-				return nil
+				tn = nil
+			} else {
+				tn = n.Val
+				key = key[len(n.Key):]
 			}
-			tn = n.Val
-			key = key[len(n.Key):]
 			nodes = append(nodes, n)
 		case fullNode:
 			tn = n[key[0]]
 			key = key[1:]
 			nodes = append(nodes, n)
-		case nil:
-			return nil
 		case hashNode:
 			var err error
 			tn, err = t.resolveHash(n, nil, nil)
@@ -93,7 +94,12 @@ func VerifyProof(rootHash common.Hash, key []byte, proof []rlp.RawValue) (value
 		keyrest, cld := get(n, key)
 		switch cld := cld.(type) {
 		case nil:
-			return nil, fmt.Errorf("key mismatch at proof node %d", i)
+			if i != len(proof)-1 {
+				return nil, fmt.Errorf("key mismatch at proof node %d", i)
+			} else {
+				// The trie doesn't contain the key.
+				return nil, nil
+			}
 		case hashNode:
 			key = keyrest
 			wantHash = cld
diff --git a/trie/trie.go b/trie/trie.go
index 717296e27..9dfde4529 100644
--- a/trie/trie.go
+++ b/trie/trie.go
@@ -394,8 +394,9 @@ func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
 		return nil, &MissingNodeError{
 			RootHash:  t.originalRoot,
 			NodeHash:  common.BytesToHash(n),
-			KeyPrefix: prefix,
-			KeySuffix: suffix,
+			Key:       compactHexEncode(append(prefix, suffix...)),
+			PrefixLen: len(prefix),
+			SuffixLen: len(suffix),
 		}
 	}
 	dec := mustDecodeNode(n, enc)