core/state: access trie through Database interface, track errors (#14589)

With this commit, core/state's access to the underlying key/value database is
mediated through an interface. Database errors are tracked in StateDB and
returned by CommitTo or the new Error method.

Motivation for this change: We can remove the light client's duplicated copy of
core/state. The light client now supports node iteration, so tracing and storage
enumeration can work with the light client (not implemented in this commit).

light/trie_test.go

@@ -0,0 +1,83 @@
+// Copyright 2017 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"
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+func TestNodeIterator(t *testing.T) {
+	var (
+		fulldb, _  = ethdb.NewMemDatabase()
+		lightdb, _ = ethdb.NewMemDatabase()
+		gspec      = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
+		genesis    = gspec.MustCommit(fulldb)
+	)
+	gspec.MustCommit(lightdb)
+	blockchain, _ := core.NewBlockChain(fulldb, params.TestChainConfig, ethash.NewFullFaker(), new(event.TypeMux), vm.Config{})
+	gchain, _ := core.GenerateChain(params.TestChainConfig, genesis, fulldb, 4, testChainGen)
+	if _, err := blockchain.InsertChain(gchain); err != nil {
+		panic(err)
+	}
+
+	ctx := context.Background()
+	odr := &testOdr{sdb: fulldb, ldb: lightdb}
+	head := blockchain.CurrentHeader()
+	lightTrie, _ := NewStateDatabase(ctx, head, odr).OpenTrie(head.Root)
+	fullTrie, _ := state.NewDatabase(fulldb).OpenTrie(head.Root)
+	if err := diffTries(fullTrie, lightTrie); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func diffTries(t1, t2 state.Trie) error {
+	i1 := trie.NewIterator(t1.NodeIterator(nil))
+	i2 := trie.NewIterator(t2.NodeIterator(nil))
+	for i1.Next() && i2.Next() {
+		if !bytes.Equal(i1.Key, i2.Key) {
+			spew.Dump(i2)
+			return fmt.Errorf("tries have different keys %x, %x", i1.Key, i2.Key)
+		}
+		if !bytes.Equal(i2.Value, i2.Value) {
+			return fmt.Errorf("tries differ at key %x", i1.Key)
+		}
+	}
+	switch {
+	case i1.Err != nil:
+		return fmt.Errorf("full trie iterator error: %v", i1.Err)
+	case i2.Err != nil:
+		return fmt.Errorf("light trie iterator error: %v", i1.Err)
+	case i1.Next():
+		return fmt.Errorf("full trie iterator has more k/v pairs")
+	case i2.Next():
+		return fmt.Errorf("light trie iterator has more k/v pairs")
+	}
+	return nil
+}