triedb/pathdb: implement iterator in the history index

triedb/pathdb/history_index.go

@@ -20,7 +20,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"sort"
 
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -119,30 +118,34 @@ func (r *indexReader) refresh() error {
 	return nil
 }
 
+// newIterator creates an iterator for traversing the index entries.
+func (r *indexReader) newIterator() *indexIterator {
+	return newIndexIterator(r.descList, func(id uint32) (*blockReader, error) {
+		br, ok := r.readers[id]
+		if !ok {
+			var err error
+			br, err = newBlockReader(readStateIndexBlock(r.state, r.db, id))
+			if err != nil {
+				return nil, err
+			}
+			r.readers[id] = br
+		}
+		return br, nil
+	})
+}
+
 // readGreaterThan locates the first element that is greater than the specified
 // id. If no such element is found, MaxUint64 is returned.
 func (r *indexReader) readGreaterThan(id uint64) (uint64, error) {
-	index := sort.Search(len(r.descList), func(i int) bool {
-		return id < r.descList[i].max
-	})
-	if index == len(r.descList) {
+	it := r.newIterator()
+	found := it.SeekGT(id)
+	if err := it.Error(); err != nil {
+		return 0, err
+	}
+	if !found {
 		return math.MaxUint64, nil
 	}
-	desc := r.descList[index]
-
-	br, ok := r.readers[desc.id]
-	if !ok {
-		var err error
-		blob := readStateIndexBlock(r.state, r.db, desc.id)
-		br, err = newBlockReader(blob)
-		if err != nil {
-			return 0, err
-		}
-		r.readers[desc.id] = br
-	}
-	// The supplied ID is not greater than block.max, ensuring that an element
-	// satisfying the condition can be found.
-	return br.readGreaterThan(id)
+	return it.ID(), nil
 }
 
 // indexWriter is responsible for writing index data for a specific state (either

triedb/pathdb/history_index_block.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"sort"
 )
 
 const (
@@ -164,58 +163,15 @@ func newBlockReader(blob []byte) (*blockReader, error) {
 // readGreaterThan locates the first element in the block that is greater than
 // the specified value. If no such element is found, MaxUint64 is returned.
 func (br *blockReader) readGreaterThan(id uint64) (uint64, error) {
-	var err error
-	index := sort.Search(len(br.restarts), func(i int) bool {
-		item, n := binary.Uvarint(br.data[br.restarts[i]:])
-		if n <= 0 {
-			err = fmt.Errorf("failed to decode item at restart %d", br.restarts[i])
-		}
-		return item > id
-	})
-	if err != nil {
+	it := newBlockIterator(br.data, br.restarts)
+	found := it.SeekGT(id)
+	if err := it.Error(); err != nil {
 		return 0, err
 	}
-	if index == 0 {
-		item, _ := binary.Uvarint(br.data[br.restarts[0]:])
-		return item, nil
-	}
-	var (
-		start  int
-		limit  int
-		result uint64
-	)
-	if index == len(br.restarts) {
-		// The element being searched falls within the last restart section,
-		// there is no guarantee such element can be found.
-		start = int(br.restarts[len(br.restarts)-1])
-		limit = len(br.data)
-	} else {
-		// The element being searched falls within the non-last restart section,
-		// such element can be found for sure.
-		start = int(br.restarts[index-1])
-		limit = int(br.restarts[index])
-	}
-	pos := start
-	for pos < limit {
-		x, n := binary.Uvarint(br.data[pos:])
-		if pos == start {
-			result = x
-		} else {
-			result += x
-		}
-		if result > id {
-			return result, nil
-		}
-		pos += n
-	}
-	// The element which is greater than specified id is not found.
-	if index == len(br.restarts) {
+	if !found {
 		return math.MaxUint64, nil
 	}
-	// The element which is the first one greater than the specified id
-	// is exactly the one located at the restart point.
-	item, _ := binary.Uvarint(br.data[br.restarts[index]:])
-	return item, nil
+	return it.ID(), nil
 }
 
 type blockWriter struct {

triedb/pathdb/history_index_iterator.go

@@ -0,0 +1,359 @@
+// Copyright 2025 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 pathdb
+
+import (
+	"encoding/binary"
+	"fmt"
+	"sort"
+)
+
+// HistoryIndexIterator is an iterator to traverse the history indices.
+type HistoryIndexIterator interface {
+	// SeekGT moves the iterator to the first element whose id is greater than
+	// the given number. It returns whether such element exists.
+	SeekGT(id uint64) bool
+
+	// Next moves the iterator to the next element. If the iterator has been
+	// exhausted, and boolean with false should be returned.
+	Next() bool
+
+	// ID returns the id of the element where the iterator is positioned at.
+	ID() uint64
+
+	// Error returns any accumulated error. Exhausting all the elements is not
+	// considered to be an error.
+	Error() error
+}
+
+// blockIterator is the iterator to traverse the indices within a single block.
+type blockIterator struct {
+	// immutable fields
+	data     []byte   // Reference to the data segment within the block reader
+	restarts []uint16 // Offsets pointing to the restart sections within the data
+
+	// mutable fields
+	id         uint64 // ID of the element at the iterators current position
+	dataPtr    int    // Current read position within the data slice
+	restartPtr int    // Index of the restart section where the iterator is currently positioned
+	exhausted  bool   // Flag whether the iterator has been exhausted
+	err        error  // Accumulated error during the traversal
+}
+
+func newBlockIterator(data []byte, restarts []uint16) *blockIterator {
+	it := &blockIterator{
+		data:     data,     // hold the slice directly with no deep copy
+		restarts: restarts, // hold the slice directly with no deep copy
+	}
+	it.reset()
+	return it
+}
+
+func (it *blockIterator) set(dataPtr int, restartPtr int, id uint64) {
+	it.id = id
+	it.dataPtr = dataPtr
+	it.restartPtr = restartPtr
+	it.exhausted = dataPtr == len(it.data)
+}
+
+func (it *blockIterator) setErr(err error) {
+	if it.err != nil {
+		return
+	}
+	it.err = err
+}
+
+func (it *blockIterator) reset() {
+	it.id = 0
+	it.dataPtr = -1
+	it.restartPtr = -1
+	it.exhausted = false
+	it.err = nil
+
+	// Mark the iterator as exhausted if the associated index block is empty
+	if len(it.data) == 0 || len(it.restarts) == 0 {
+		it.exhausted = true
+	}
+}
+
+// SeekGT moves the iterator to the first element whose id is greater than the
+// given number. It returns whether such element exists.
+//
+// Note, this operation will unset the exhausted status and subsequent traversal
+// is allowed.
+func (it *blockIterator) SeekGT(id uint64) bool {
+	if it.err != nil {
+		return false
+	}
+	var err error
+	index := sort.Search(len(it.restarts), func(i int) bool {
+		item, n := binary.Uvarint(it.data[it.restarts[i]:])
+		if n <= 0 {
+			err = fmt.Errorf("failed to decode item at restart %d", it.restarts[i])
+		}
+		return item > id
+	})
+	if err != nil {
+		it.setErr(err)
+		return false
+	}
+	if index == 0 {
+		item, n := binary.Uvarint(it.data[it.restarts[0]:])
+
+		// If the restart size is 1, then the restart pointer shouldn't be 0.
+		// It's not practical and should be denied in the first place.
+		it.set(int(it.restarts[0])+n, 0, item)
+		return true
+	}
+	var (
+		start        int
+		limit        int
+		restartIndex int // The restart section being searched below
+	)
+	if index == len(it.restarts) {
+		// The element being searched falls within the last restart section,
+		// there is no guarantee such element can be found.
+		start = int(it.restarts[len(it.restarts)-1])
+		limit = len(it.data)
+		restartIndex = len(it.restarts) - 1
+	} else {
+		// The element being searched falls within the non-last restart section,
+		// such element can be found for sure.
+		start = int(it.restarts[index-1])
+		limit = int(it.restarts[index])
+		restartIndex = index - 1
+	}
+	var (
+		result uint64
+		pos    = start
+	)
+	for pos < limit {
+		x, n := binary.Uvarint(it.data[pos:])
+		if n <= 0 {
+			it.setErr(fmt.Errorf("failed to decode item at pos %d", pos))
+			return false
+		}
+		if pos == start {
+			result = x
+		} else {
+			result += x
+		}
+		pos += n
+
+		if result > id {
+			if pos == limit {
+				it.set(pos, restartIndex+1, result)
+			} else {
+				it.set(pos, restartIndex, result)
+			}
+			return true
+		}
+	}
+	// The element which is greater than specified id is not found.
+	if index == len(it.restarts) {
+		it.reset()
+		return false
+	}
+	// The element which is the first one greater than the specified id
+	// is exactly the one located at the restart point.
+	item, n := binary.Uvarint(it.data[it.restarts[index]:])
+	it.set(int(it.restarts[index])+n, index, item)
+	return true
+}
+
+func (it *blockIterator) init() {
+	if it.dataPtr != -1 {
+		return
+	}
+	it.dataPtr = 0
+	it.restartPtr = 0
+}
+
+// Next implements the HistoryIndexIterator, moving the iterator to the next
+// element. If the iterator has been exhausted, and boolean with false should
+// be returned.
+func (it *blockIterator) Next() bool {
+	if it.exhausted || it.err != nil {
+		return false
+	}
+	it.init()
+
+	// Decode the next element pointed by the iterator
+	v, n := binary.Uvarint(it.data[it.dataPtr:])
+	if n <= 0 {
+		it.setErr(fmt.Errorf("failed to decode item at pos %d", it.dataPtr))
+		return false
+	}
+
+	var val uint64
+	if it.dataPtr == int(it.restarts[it.restartPtr]) {
+		val = v
+	} else {
+		val = it.id + v
+	}
+
+	// Move to the next restart section if the data pointer crosses the boundary
+	nextRestartPtr := it.restartPtr
+	if it.restartPtr < len(it.restarts)-1 && it.dataPtr+n == int(it.restarts[it.restartPtr+1]) {
+		nextRestartPtr = it.restartPtr + 1
+	}
+	it.set(it.dataPtr+n, nextRestartPtr, val)
+
+	return true
+}
+
+// ID implements HistoryIndexIterator, returning the id of the element where the
+// iterator is positioned at.
+func (it *blockIterator) ID() uint64 {
+	return it.id
+}
+
+// Error implements HistoryIndexIterator, returning any accumulated error.
+// Exhausting all the elements is not considered to be an error.
+func (it *blockIterator) Error() error { return it.err }
+
+// blockLoader defines the method to retrieve the specific block for reading.
+type blockLoader func(id uint32) (*blockReader, error)
+
+// indexIterator is an iterator to traverse the history indices belonging to the
+// specific state entry.
+type indexIterator struct {
+	// immutable fields
+	descList []*indexBlockDesc
+	loader   blockLoader
+
+	// mutable fields
+	blockIt   *blockIterator
+	blockPtr  int
+	exhausted bool
+	err       error
+}
+
+func newIndexIterator(descList []*indexBlockDesc, loader blockLoader) *indexIterator {
+	it := &indexIterator{
+		descList: descList,
+		loader:   loader,
+	}
+	it.reset()
+	return it
+}
+
+func (it *indexIterator) setErr(err error) {
+	if it.err != nil {
+		return
+	}
+	it.err = err
+}
+
+func (it *indexIterator) reset() {
+	it.blockIt = nil
+	it.blockPtr = -1
+	it.exhausted = false
+	it.err = nil
+
+	if len(it.descList) == 0 {
+		it.exhausted = true
+	}
+}
+
+func (it *indexIterator) open(blockPtr int) error {
+	id := it.descList[blockPtr].id
+	br, err := it.loader(id)
+	if err != nil {
+		return err
+	}
+	it.blockIt = newBlockIterator(br.data, br.restarts)
+	it.blockPtr = blockPtr
+	return nil
+}
+
+// SeekGT moves the iterator to the first element whose id is greater than the
+// given number. It returns whether such element exists.
+//
+// Note, this operation will unset the exhausted status and subsequent traversal
+// is allowed.
+func (it *indexIterator) SeekGT(id uint64) bool {
+	if it.err != nil {
+		return false
+	}
+	index := sort.Search(len(it.descList), func(i int) bool {
+		return id < it.descList[i].max
+	})
+	if index == len(it.descList) {
+		return false
+	}
+	it.exhausted = false
+
+	if it.blockIt == nil || it.blockPtr != index {
+		if err := it.open(index); err != nil {
+			it.setErr(err)
+			return false
+		}
+	}
+	return it.blockIt.SeekGT(id)
+}
+
+func (it *indexIterator) init() error {
+	if it.blockIt != nil {
+		return nil
+	}
+	return it.open(0)
+}
+
+// Next implements the HistoryIndexIterator, moving the iterator to the next
+// element. If the iterator has been exhausted, and boolean with false should
+// be returned.
+func (it *indexIterator) Next() bool {
+	if it.exhausted || it.err != nil {
+		return false
+	}
+	if err := it.init(); err != nil {
+		it.setErr(err)
+		return false
+	}
+
+	if it.blockIt.Next() {
+		return true
+	}
+	if it.blockPtr == len(it.descList)-1 {
+		it.exhausted = true
+		return false
+	}
+	if err := it.open(it.blockPtr + 1); err != nil {
+		it.setErr(err)
+		return false
+	}
+	return it.blockIt.Next()
+}
+
+// Error implements HistoryIndexIterator, returning any accumulated error.
+// Exhausting all the elements is not considered to be an error.
+func (it *indexIterator) Error() error {
+	if it.err != nil {
+		return it.err
+	}
+	if it.blockIt != nil {
+		return it.blockIt.Error()
+	}
+	return nil
+}
+
+// ID implements HistoryIndexIterator, returning the id of the element where the
+// iterator is positioned at.
+func (it *indexIterator) ID() uint64 {
+	return it.blockIt.ID()
+}

triedb/pathdb/history_index_iterator_test.go

@@ -0,0 +1,297 @@
+// Copyright 2025 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 pathdb
+
+import (
+	"errors"
+	"fmt"
+	"math/rand"
+	"sort"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+func makeTestIndexBlock(count int) ([]byte, []uint64) {
+	var (
+		marks    = make(map[uint64]bool)
+		elements []uint64
+	)
+	bw, _ := newBlockWriter(nil, newIndexBlockDesc(0))
+	for i := 0; i < count; i++ {
+		n := uint64(rand.Uint32())
+		if marks[n] {
+			continue
+		}
+		marks[n] = true
+		elements = append(elements, n)
+	}
+	sort.Slice(elements, func(i, j int) bool { return elements[i] < elements[j] })
+
+	for i := 0; i < len(elements); i++ {
+		bw.append(elements[i])
+	}
+	data := bw.finish()
+
+	return data, elements
+}
+
+func makeTestIndexBlocks(db ethdb.KeyValueStore, stateIdent stateIdent, count int) []uint64 {
+	var (
+		marks    = make(map[uint64]bool)
+		elements []uint64
+	)
+	for i := 0; i < count; i++ {
+		n := uint64(rand.Uint32())
+		if marks[n] {
+			continue
+		}
+		marks[n] = true
+		elements = append(elements, n)
+	}
+	sort.Slice(elements, func(i, j int) bool { return elements[i] < elements[j] })
+
+	iw, _ := newIndexWriter(db, stateIdent)
+	for i := 0; i < len(elements); i++ {
+		iw.append(elements[i])
+	}
+	batch := db.NewBatch()
+	iw.finish(batch)
+	batch.Write()
+
+	return elements
+}
+
+func checkSeekGT(it HistoryIndexIterator, input uint64, exp bool, expVal uint64) error {
+	found := it.SeekGT(input)
+	if it.Error() != nil {
+		return it.Error()
+	}
+	if !exp {
+		if found {
+			return fmt.Errorf("unexpected returned value: %d", it.ID())
+		}
+		return nil
+	}
+	if !found {
+		return fmt.Errorf("element grearter than %d is not found", input)
+	}
+	if it.ID() != expVal {
+		return fmt.Errorf("unexpected returned value, want: %d, got: %d", expVal, it.ID())
+	}
+	return nil
+}
+
+func checkNext(it HistoryIndexIterator, values []uint64) error {
+	for _, value := range values {
+		if !it.Next() {
+			return errors.New("iterator is exhausted")
+		}
+		if it.ID() != value {
+			return fmt.Errorf("unexpected iterator ID, want: %v, got: %v", value, it.ID())
+		}
+	}
+	if it.Next() {
+		return errors.New("iterator is not exhausted yet")
+	}
+	return it.Error()
+}
+
+func TestBlockIteratorSeekGT(t *testing.T) {
+	/* 0-size index block is not allowed
+
+	data, elements := makeTestIndexBlock(0)
+	testBlockIterator(t, data, elements)
+	*/
+
+	data, elements := makeTestIndexBlock(1)
+	testBlockIterator(t, data, elements)
+
+	data, elements = makeTestIndexBlock(indexBlockRestartLen)
+	testBlockIterator(t, data, elements)
+
+	data, elements = makeTestIndexBlock(3 * indexBlockRestartLen)
+	testBlockIterator(t, data, elements)
+
+	data, elements = makeTestIndexBlock(indexBlockEntriesCap)
+	testBlockIterator(t, data, elements)
+}
+
+func testBlockIterator(t *testing.T, data []byte, elements []uint64) {
+	br, err := newBlockReader(data)
+	if err != nil {
+		t.Fatalf("Failed to open the block for reading, %v", err)
+	}
+	it := newBlockIterator(br.data, br.restarts)
+
+	for i := 0; i < 128; i++ {
+		var input uint64
+		if rand.Intn(2) == 0 {
+			input = elements[rand.Intn(len(elements))]
+		} else {
+			input = uint64(rand.Uint32())
+		}
+		index := sort.Search(len(elements), func(i int) bool {
+			return elements[i] > input
+		})
+		var (
+			exp     bool
+			expVal  uint64
+			remains []uint64
+		)
+		if index == len(elements) {
+			exp = false
+		} else {
+			exp = true
+			expVal = elements[index]
+			if index < len(elements) {
+				remains = elements[index+1:]
+			}
+		}
+		if err := checkSeekGT(it, input, exp, expVal); err != nil {
+			t.Fatal(err)
+		}
+		if exp {
+			if err := checkNext(it, remains); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+}
+
+func TestIndexIteratorSeekGT(t *testing.T) {
+	ident := newAccountIdent(common.Hash{0x1})
+
+	dbA := rawdb.NewMemoryDatabase()
+	testIndexIterator(t, ident, dbA, makeTestIndexBlocks(dbA, ident, 1))
+
+	dbB := rawdb.NewMemoryDatabase()
+	testIndexIterator(t, ident, dbB, makeTestIndexBlocks(dbB, ident, 3*indexBlockEntriesCap))
+
+	dbC := rawdb.NewMemoryDatabase()
+	testIndexIterator(t, ident, dbC, makeTestIndexBlocks(dbC, ident, indexBlockEntriesCap-1))
+
+	dbD := rawdb.NewMemoryDatabase()
+	testIndexIterator(t, ident, dbD, makeTestIndexBlocks(dbD, ident, indexBlockEntriesCap+1))
+}
+
+func testIndexIterator(t *testing.T, stateIdent stateIdent, db ethdb.Database, elements []uint64) {
+	ir, err := newIndexReader(db, stateIdent)
+	if err != nil {
+		t.Fatalf("Failed to open the index reader, %v", err)
+	}
+	it := newIndexIterator(ir.descList, func(id uint32) (*blockReader, error) {
+		return newBlockReader(readStateIndexBlock(stateIdent, db, id))
+	})
+
+	for i := 0; i < 128; i++ {
+		var input uint64
+		if rand.Intn(2) == 0 {
+			input = elements[rand.Intn(len(elements))]
+		} else {
+			input = uint64(rand.Uint32())
+		}
+		index := sort.Search(len(elements), func(i int) bool {
+			return elements[i] > input
+		})
+		var (
+			exp     bool
+			expVal  uint64
+			remains []uint64
+		)
+		if index == len(elements) {
+			exp = false
+		} else {
+			exp = true
+			expVal = elements[index]
+			if index < len(elements) {
+				remains = elements[index+1:]
+			}
+		}
+		if err := checkSeekGT(it, input, exp, expVal); err != nil {
+			t.Fatal(err)
+		}
+		if exp {
+			if err := checkNext(it, remains); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+}
+
+func TestBlockIteratorTraversal(t *testing.T) {
+	/* 0-size index block is not allowed
+
+	data, elements := makeTestIndexBlock(0)
+	testBlockIterator(t, data, elements)
+	*/
+
+	data, elements := makeTestIndexBlock(1)
+	testBlockIteratorTraversal(t, data, elements)
+
+	data, elements = makeTestIndexBlock(indexBlockRestartLen)
+	testBlockIteratorTraversal(t, data, elements)
+
+	data, elements = makeTestIndexBlock(3 * indexBlockRestartLen)
+	testBlockIteratorTraversal(t, data, elements)
+
+	data, elements = makeTestIndexBlock(indexBlockEntriesCap)
+	testBlockIteratorTraversal(t, data, elements)
+}
+
+func testBlockIteratorTraversal(t *testing.T, data []byte, elements []uint64) {
+	br, err := newBlockReader(data)
+	if err != nil {
+		t.Fatalf("Failed to open the block for reading, %v", err)
+	}
+	it := newBlockIterator(br.data, br.restarts)
+
+	if err := checkNext(it, elements); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestIndexIteratorTraversal(t *testing.T) {
+	ident := newAccountIdent(common.Hash{0x1})
+
+	dbA := rawdb.NewMemoryDatabase()
+	testIndexIteratorTraversal(t, ident, dbA, makeTestIndexBlocks(dbA, ident, 1))
+
+	dbB := rawdb.NewMemoryDatabase()
+	testIndexIteratorTraversal(t, ident, dbB, makeTestIndexBlocks(dbB, ident, 3*indexBlockEntriesCap))
+
+	dbC := rawdb.NewMemoryDatabase()
+	testIndexIteratorTraversal(t, ident, dbC, makeTestIndexBlocks(dbC, ident, indexBlockEntriesCap-1))
+
+	dbD := rawdb.NewMemoryDatabase()
+	testIndexIteratorTraversal(t, ident, dbD, makeTestIndexBlocks(dbD, ident, indexBlockEntriesCap+1))
+}
+
+func testIndexIteratorTraversal(t *testing.T, stateIdent stateIdent, db ethdb.KeyValueReader, elements []uint64) {
+	ir, err := newIndexReader(db, stateIdent)
+	if err != nil {
+		t.Fatalf("Failed to open the index reader, %v", err)
+	}
+	it := newIndexIterator(ir.descList, func(id uint32) (*blockReader, error) {
+		return newBlockReader(readStateIndexBlock(stateIdent, db, id))
+	})
+	if err := checkNext(it, elements); err != nil {
+		t.Fatal(err)
+	}
+}