From d8cf87949991c0ee5ef504af4bb398cce524deaf Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 11:41:27 +0300
Subject: [PATCH 01/11] dao: deduplicate DeleteBlock, no functional changes

---
 pkg/core/dao/dao.go | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index b6f6d3829..cd4221e1b 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -375,7 +375,10 @@ func (dao *Simple) makeStorageItemKey(id int32, key []byte) []byte {
 
 // GetBlock returns Block by the given hash if it exists in the store.
 func (dao *Simple) GetBlock(hash util.Uint256) (*block.Block, error) {
-	key := dao.makeExecutableKey(hash)
+	return dao.getBlock(dao.makeExecutableKey(hash))
+}
+
+func (dao *Simple) getBlock(key []byte) (*block.Block, error) {
 	b, err := dao.Store.Get(key)
 	if err != nil {
 		return nil, err
@@ -659,16 +662,8 @@ func (dao *Simple) StoreAsBlock(block *block.Block, aer1 *state.AppExecResult, a
 // using private MemCached instance here.
 func (dao *Simple) DeleteBlock(h util.Uint256) error {
 	key := dao.makeExecutableKey(h)
-	bs, err := dao.Store.Get(key)
-	if err != nil {
-		return err
-	}
 
-	r := io.NewBinReaderFromBuf(bs)
-	if r.ReadB() != storage.ExecBlock {
-		return errors.New("internal DB inconsistency")
-	}
-	b, err := block.NewTrimmedFromReader(dao.Version.StateRootInHeader, r)
+	b, err := dao.getBlock(key)
 	if err != nil {
 		return err
 	}

From b60d4ff19177bf0c8137dab50ce3d43090431ccc Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 11:55:06 +0300
Subject: [PATCH 02/11] dao: deduplicate header->KV conversion

---
 pkg/core/blockchain.go | 16 +++++-----------
 pkg/core/dao/dao.go    | 27 ++++++++++++++++++++-------
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index b629a0373..9d127721f 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -932,7 +932,6 @@ func (bc *Blockchain) addHeaders(verify bool, headers ...*block.Header) error {
 		}
 	}
 
-	buf := io.NewBufBinWriter()
 	bc.headerHashesLock.Lock()
 	defer bc.headerHashesLock.Unlock()
 	oldlen := len(bc.headerHashes)
@@ -941,21 +940,16 @@ func (bc *Blockchain) addHeaders(verify bool, headers ...*block.Header) error {
 		if int(h.Index) != len(bc.headerHashes) {
 			continue
 		}
-		bc.headerHashes = append(bc.headerHashes, h.Hash())
-		buf.WriteB(storage.ExecBlock)
-		h.EncodeBinary(buf.BinWriter)
-		buf.BinWriter.WriteB(0)
-		if buf.Err != nil {
-			return buf.Err
+		err = batch.StoreHeader(h)
+		if err != nil {
+			return err
 		}
-
-		key := storage.AppendPrefix(storage.DataExecutable, h.Hash().BytesBE())
-		batch.Store.Put(key, buf.Bytes())
-		buf.Reset()
+		bc.headerHashes = append(bc.headerHashes, h.Hash())
 		lastHeader = h
 	}
 
 	if oldlen != len(bc.headerHashes) {
+		buf := io.NewBufBinWriter()
 		for int(lastHeader.Index)-headerBatchCount >= int(bc.storedHeaderCount) {
 			buf.WriteArray(bc.headerHashes[bc.storedHeaderCount : bc.storedHeaderCount+headerBatchCount])
 			if buf.Err != nil {
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index cd4221e1b..a69ac0355 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -668,14 +668,10 @@ func (dao *Simple) DeleteBlock(h util.Uint256) error {
 		return err
 	}
 
-	w := dao.getDataBuf()
-	w.WriteB(storage.ExecBlock)
-	b.Header.EncodeBinary(w.BinWriter)
-	w.BinWriter.WriteB(0)
-	if w.Err != nil {
-		return w.Err
+	err = dao.storeHeader(key, &b.Header)
+	if err != nil {
+		return err
 	}
-	dao.Store.Put(key, w.Bytes())
 
 	for _, tx := range b.Transactions {
 		copy(key[1:], tx.Hash().BytesBE())
@@ -692,6 +688,23 @@ func (dao *Simple) DeleteBlock(h util.Uint256) error {
 	return nil
 }
 
+// StoreHeader saves block header into the store.
+func (dao *Simple) StoreHeader(h *block.Header) error {
+	return dao.storeHeader(dao.makeExecutableKey(h.Hash()), h)
+}
+
+func (dao *Simple) storeHeader(key []byte, h *block.Header) error {
+	buf := dao.getDataBuf()
+	buf.WriteB(storage.ExecBlock)
+	h.EncodeBinary(buf.BinWriter)
+	buf.BinWriter.WriteB(0)
+	if buf.Err != nil {
+		return buf.Err
+	}
+	dao.Store.Put(key, buf.Bytes())
+	return nil
+}
+
 // StoreAsCurrentBlock stores a hash of the given block with prefix
 // SYSCurrentBlock. It can reuse given buffer for the purpose of value
 // serialization.

From 5402e654d13991acfa5f4e4e863028cde7e4202a Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 13:18:00 +0300
Subject: [PATCH 03/11] core: don't create useless DAO layer in GetTestVM

We're already wrapping in interop.NewContext.
---
 pkg/core/blockchain.go | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 9d127721f..00690e6be 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -2140,8 +2140,7 @@ func (bc *Blockchain) GetEnrollments() ([]state.Validator, error) {
 
 // GetTestVM returns an interop context with VM set up for a test run.
 func (bc *Blockchain) GetTestVM(t trigger.Type, tx *transaction.Transaction, b *block.Block) *interop.Context {
-	d := bc.dao.GetPrivate()
-	systemInterop := bc.newInteropContext(t, d, b, tx)
+	systemInterop := bc.newInteropContext(t, bc.dao, b, tx)
 	vm := systemInterop.SpawnVM()
 	vm.SetPriceGetter(systemInterop.GetPrice)
 	vm.LoadToken = contract.LoadToken(systemInterop)

From e864768c885974b549cbd0195533f0def54a2365 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:18:56 +0300
Subject: [PATCH 04/11] dao: simplify NewPrivate

---
 pkg/core/dao/dao.go | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index a69ac0355..ec9c44dce 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -68,17 +68,13 @@ func (dao *Simple) GetWrapped() *Simple {
 // GetPrivate returns new DAO instance with another layer of private
 // MemCachedStore around the current DAO Store.
 func (dao *Simple) GetPrivate() *Simple {
-	st := storage.NewPrivateMemCachedStore(dao.Store)
-	d := newSimple(st, dao.Version.StateRootInHeader, dao.Version.P2PSigExtensions)
-	d.Version = dao.Version
-	if dao.keyBuf != nil { // This one is private.
-		d.keyBuf = dao.keyBuf // Thus we can reuse its buffer.
-	} else {
+	d := &Simple{}
+	*d = *dao                                             // Inherit everything...
+	d.Store = storage.NewPrivateMemCachedStore(dao.Store) // except storage, wrap another layer.
+	if d.keyBuf == nil {
 		d.keyBuf = make([]byte, 0, 1+4+storage.MaxStorageKeyLen) // Prefix, uint32, key.
 	}
-	if dao.dataBuf != nil { // This one is private.
-		d.dataBuf = dao.dataBuf // Thus we can reuse its buffer.
-	} else {
+	if dao.dataBuf == nil {
 		d.dataBuf = io.NewBufBinWriter()
 	}
 	return d

From 1ca918e6310f73fd44454c8ed68f42979cd64a5f Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:24:45 +0300
Subject: [PATCH 05/11] dao: delay buffer creation until it's needed

Verification contexts don't ever touch the storage, so these allocations can
be avoided for them.
---
 pkg/core/dao/dao.go | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index ec9c44dce..37e8a8d6d 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -31,6 +31,7 @@ var (
 type Simple struct {
 	Version Version
 	Store   *storage.MemCachedStore
+	private bool
 	keyBuf  []byte
 	dataBuf *io.BufBinWriter
 }
@@ -71,12 +72,7 @@ func (dao *Simple) GetPrivate() *Simple {
 	d := &Simple{}
 	*d = *dao                                             // Inherit everything...
 	d.Store = storage.NewPrivateMemCachedStore(dao.Store) // except storage, wrap another layer.
-	if d.keyBuf == nil {
-		d.keyBuf = make([]byte, 0, 1+4+storage.MaxStorageKeyLen) // Prefix, uint32, key.
-	}
-	if dao.dataBuf == nil {
-		d.dataBuf = io.NewBufBinWriter()
-	}
+	d.private = true
 	return d
 }
 
@@ -748,14 +744,20 @@ func (dao *Simple) StoreAsTransaction(tx *transaction.Transaction, index uint32,
 }
 
 func (dao *Simple) getKeyBuf(len int) []byte {
-	if dao.keyBuf != nil { // Private DAO.
+	if dao.private {
+		if dao.keyBuf == nil {
+			dao.keyBuf = make([]byte, 0, 1+4+storage.MaxStorageKeyLen) // Prefix, uint32, key.
+		}
 		return dao.keyBuf[:len] // Should have enough capacity.
 	}
 	return make([]byte, len)
 }
 
 func (dao *Simple) getDataBuf() *io.BufBinWriter {
-	if dao.dataBuf != nil {
+	if dao.private {
+		if dao.dataBuf == nil {
+			dao.dataBuf = io.NewBufBinWriter()
+		}
 		dao.dataBuf.Reset()
 		return dao.dataBuf
 	}

From 600da6909c411ce4130e3ceee7c1778b633f44bd Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:35:17 +0300
Subject: [PATCH 06/11] storage: put uint32 into keys using in big endianness

Which allows to iterate over the contents easily.
---
 pkg/core/blockchain.go    |  2 +-
 pkg/core/dao/dao.go       | 23 ++++-------------------
 pkg/core/storage/store.go |  2 +-
 3 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 00690e6be..751d916bf 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -46,7 +46,7 @@ import (
 // Tuning parameters.
 const (
 	headerBatchCount = 2000
-	version          = "0.2.3"
+	version          = "0.2.4"
 
 	defaultInitialGAS                      = 52000000_00000000
 	defaultGCPeriod                        = 10000
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index 37e8a8d6d..23ca3bb68 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -6,7 +6,6 @@ import (
 	"encoding/binary"
 	"errors"
 	iocore "io"
-	"sort"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
@@ -506,33 +505,19 @@ func (dao *Simple) GetStateSyncCurrentBlockHeight() (uint32, error) {
 // GetHeaderHashes returns a sorted list of header hashes retrieved from
 // the given underlying store.
 func (dao *Simple) GetHeaderHashes() ([]util.Uint256, error) {
-	hashMap := make(map[uint32][]util.Uint256)
+	var hashes = make([]util.Uint256, 0)
+
 	dao.Store.Seek(storage.SeekRange{
 		Prefix: storage.IXHeaderHashList.Bytes(),
 	}, func(k, v []byte) bool {
-		storedCount := binary.LittleEndian.Uint32(k[1:])
-		hashes, err := read2000Uint256Hashes(v)
+		newHashes, err := read2000Uint256Hashes(v)
 		if err != nil {
 			panic(err)
 		}
-		hashMap[storedCount] = hashes
+		hashes = append(hashes, newHashes...)
 		return true
 	})
 
-	var (
-		hashes     = make([]util.Uint256, 0, len(hashMap))
-		sortedKeys = make([]uint32, 0, len(hashMap))
-	)
-
-	for k := range hashMap {
-		sortedKeys = append(sortedKeys, k)
-	}
-	sort.Slice(sortedKeys, func(i, j int) bool { return sortedKeys[i] < sortedKeys[j] })
-
-	for _, key := range sortedKeys {
-		hashes = append(hashes[:key], hashMap[key]...)
-	}
-
 	return hashes, nil
 }
 
diff --git a/pkg/core/storage/store.go b/pkg/core/storage/store.go
index 8d4bfad9d..b6cfe80bf 100644
--- a/pkg/core/storage/store.go
+++ b/pkg/core/storage/store.go
@@ -125,7 +125,7 @@ func AppendPrefix(k KeyPrefix, b []byte) []byte {
 //   AppendPrefixInt(SYSCurrentHeader, 10001)
 func AppendPrefixInt(k KeyPrefix, n int) []byte {
 	b := make([]byte, 4)
-	binary.LittleEndian.PutUint32(b, uint32(n))
+	binary.BigEndian.PutUint32(b, uint32(n))
 	return AppendPrefix(k, b)
 }
 

From de2579ec0793645229afbc36765ed4d94f2a26e0 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:38:51 +0300
Subject: [PATCH 07/11] dao: put contract IDs into keys using big endianness

We don't have a need to iterate over them at the moment, but since we're
changing the DB format in the next release anyway let's add this ability also,
just in case.
---
 pkg/core/blockchain.go | 2 +-
 pkg/core/dao/dao.go    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 751d916bf..28e7715f4 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -46,7 +46,7 @@ import (
 // Tuning parameters.
 const (
 	headerBatchCount = 2000
-	version          = "0.2.4"
+	version          = "0.2.5"
 
 	defaultInitialGAS                      = 52000000_00000000
 	defaultGCPeriod                        = 10000
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index 23ca3bb68..505e589dc 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -99,7 +99,7 @@ func (dao *Simple) putWithBuffer(entity io.Serializable, key []byte, buf *io.Buf
 func (dao *Simple) makeContractIDKey(id int32) []byte {
 	key := dao.getKeyBuf(5)
 	key[0] = byte(storage.STContractID)
-	binary.LittleEndian.PutUint32(key[1:], uint32(id))
+	binary.BigEndian.PutUint32(key[1:], uint32(id))
 	return key
 }
 

From d2db58d7481acb8b4a317487c8719850279a5aa6 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:54:05 +0300
Subject: [PATCH 08/11] dao: move header hash store logic out of the core

Which allows for more efficient buffer use along the way.
---
 pkg/core/blockchain.go | 11 ++++-------
 pkg/core/dao/dao.go    | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 28e7715f4..346905870 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -949,15 +949,12 @@ func (bc *Blockchain) addHeaders(verify bool, headers ...*block.Header) error {
 	}
 
 	if oldlen != len(bc.headerHashes) {
-		buf := io.NewBufBinWriter()
 		for int(lastHeader.Index)-headerBatchCount >= int(bc.storedHeaderCount) {
-			buf.WriteArray(bc.headerHashes[bc.storedHeaderCount : bc.storedHeaderCount+headerBatchCount])
-			if buf.Err != nil {
-				return buf.Err
+			err = batch.StoreHeaderHashes(bc.headerHashes[bc.storedHeaderCount:bc.storedHeaderCount+headerBatchCount],
+				bc.storedHeaderCount)
+			if err != nil {
+				return err
 			}
-
-			key := storage.AppendPrefixInt(storage.IXHeaderHashList, int(bc.storedHeaderCount))
-			batch.Store.Put(key, buf.Bytes())
 			bc.storedHeaderCount += headerBatchCount
 		}
 
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index 505e589dc..af781d713 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -590,6 +590,25 @@ func read2000Uint256Hashes(b []byte) ([]util.Uint256, error) {
 	return hashes, nil
 }
 
+func (dao *Simple) mkHeaderHashKey(h uint32) []byte {
+	b := dao.getKeyBuf(1 + 4)
+	b[0] = byte(storage.IXHeaderHashList)
+	binary.BigEndian.PutUint32(b[1:], h)
+	return b
+}
+
+// StoreHeaderHashes pushes a batch of header hashes into the store.
+func (dao *Simple) StoreHeaderHashes(hashes []util.Uint256, height uint32) error {
+	key := dao.mkHeaderHashKey(height)
+	buf := dao.getDataBuf()
+	buf.WriteArray(hashes)
+	if buf.Err != nil {
+		return buf.Err
+	}
+	dao.Store.Put(key, buf.Bytes())
+	return nil
+}
+
 // HasTransaction returns nil if the given store does not contain the given
 // Transaction hash. It returns an error in case if transaction is in chain
 // or in the list of conflicting transactions.

From 522229d731ff375e79681f7ec6212d7b3a20f007 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 14:59:59 +0300
Subject: [PATCH 09/11] storage: drop AppendPrefix/AppendPrefixInt APIs

We're not using them anymore and they allocate.
---
 pkg/core/blockchain_test.go    |  4 +++-
 pkg/core/storage/store.go      | 18 ----------------
 pkg/core/storage/store_test.go | 39 ----------------------------------
 3 files changed, 3 insertions(+), 58 deletions(-)

diff --git a/pkg/core/blockchain_test.go b/pkg/core/blockchain_test.go
index 14c687a19..079b4efd3 100644
--- a/pkg/core/blockchain_test.go
+++ b/pkg/core/blockchain_test.go
@@ -124,8 +124,10 @@ func TestAddBlock(t *testing.T) {
 	_, err = bc.persist(false)
 	require.NoError(t, err)
 
+	key := make([]byte, 1+util.Uint256Size)
+	key[0] = byte(storage.DataExecutable)
 	for _, block := range blocks {
-		key := storage.AppendPrefix(storage.DataExecutable, block.Hash().BytesBE())
+		copy(key[1:], block.Hash().BytesBE())
 		_, err := bc.dao.Store.Get(key)
 		require.NoErrorf(t, err, "block %s not persisted", block.Hash())
 	}
diff --git a/pkg/core/storage/store.go b/pkg/core/storage/store.go
index b6cfe80bf..0812a5f08 100644
--- a/pkg/core/storage/store.go
+++ b/pkg/core/storage/store.go
@@ -1,7 +1,6 @@
 package storage
 
 import (
-	"encoding/binary"
 	"errors"
 	"fmt"
 
@@ -112,23 +111,6 @@ func (k KeyPrefix) Bytes() []byte {
 	return []byte{byte(k)}
 }
 
-// AppendPrefix appends byteslice b to the given KeyPrefix.
-// AppendKeyPrefix(SYSVersion, []byte{0x00, 0x01}).
-func AppendPrefix(k KeyPrefix, b []byte) []byte {
-	dest := make([]byte, len(b)+1)
-	dest[0] = byte(k)
-	copy(dest[1:], b)
-	return dest
-}
-
-// AppendPrefixInt append int n to the given KeyPrefix.
-//   AppendPrefixInt(SYSCurrentHeader, 10001)
-func AppendPrefixInt(k KeyPrefix, n int) []byte {
-	b := make([]byte, 4)
-	binary.BigEndian.PutUint32(b, uint32(n))
-	return AppendPrefix(k, b)
-}
-
 func seekRangeToPrefixes(sr SeekRange) *util.Range {
 	var (
 		rang  *util.Range
diff --git a/pkg/core/storage/store_test.go b/pkg/core/storage/store_test.go
index a07b97ece..7191e46ad 100644
--- a/pkg/core/storage/store_test.go
+++ b/pkg/core/storage/store_test.go
@@ -3,48 +3,9 @@ package storage
 import (
 	"testing"
 
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-var (
-	prefixes = []KeyPrefix{
-		DataExecutable,
-		DataMPT,
-		STStorage,
-		IXHeaderHashList,
-		SYSCurrentBlock,
-		SYSCurrentHeader,
-		SYSVersion,
-	}
-
-	expected = []uint8{
-		0x01,
-		0x03,
-		0x70,
-		0x80,
-		0xc0,
-		0xc1,
-		0xf0,
-	}
-)
-
-func TestAppendPrefix(t *testing.T) {
-	for i := 0; i < len(expected); i++ {
-		value := []byte{0x01, 0x02}
-		prefix := AppendPrefix(prefixes[i], value)
-		assert.Equal(t, KeyPrefix(expected[i]), KeyPrefix(prefix[0]))
-	}
-}
-
-func TestAppendPrefixInt(t *testing.T) {
-	for i := 0; i < len(expected); i++ {
-		value := 2000
-		prefix := AppendPrefixInt(prefixes[i], value)
-		assert.Equal(t, KeyPrefix(expected[i]), KeyPrefix(prefix[0]))
-	}
-}
-
 func TestBatchToOperations(t *testing.T) {
 	b := &MemBatch{
 		Put: []KeyValueExists{

From 7223caf36953efd597303f3c7cd7a2aa91831c6c Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 15:04:57 +0300
Subject: [PATCH 10/11] dao: improve PutCurrentHeader logic

Move serialization out of the core.
---
 pkg/core/blockchain.go | 11 ++---------
 pkg/core/dao/dao.go    |  7 +++++--
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 346905870..624b9932c 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -325,7 +325,7 @@ func (bc *Blockchain) init() error {
 			return err
 		}
 		bc.headerHashes = []util.Uint256{genesisBlock.Hash()}
-		bc.dao.PutCurrentHeader(hashAndIndexToBytes(genesisBlock.Hash(), genesisBlock.Index))
+		bc.dao.PutCurrentHeader(genesisBlock.Hash(), genesisBlock.Index)
 		if err := bc.stateRoot.Init(0); err != nil {
 			return fmt.Errorf("can't init MPT: %w", err)
 		}
@@ -958,7 +958,7 @@ func (bc *Blockchain) addHeaders(verify bool, headers ...*block.Header) error {
 			bc.storedHeaderCount += headerBatchCount
 		}
 
-		batch.Store.Put(storage.SYSCurrentHeader.Bytes(), hashAndIndexToBytes(lastHeader.Hash(), lastHeader.Index))
+		batch.PutCurrentHeader(lastHeader.Hash(), lastHeader.Index)
 		updateHeaderHeightMetric(len(bc.headerHashes) - 1)
 		if _, err = batch.Persist(); err != nil {
 			return err
@@ -2299,13 +2299,6 @@ func (bc *Blockchain) ManagementContractHash() util.Uint160 {
 	return bc.contracts.Management.Hash
 }
 
-func hashAndIndexToBytes(h util.Uint256, index uint32) []byte {
-	buf := io.NewBufBinWriter()
-	buf.WriteBytes(h.BytesLE())
-	buf.WriteU32LE(index)
-	return buf.Bytes()
-}
-
 func (bc *Blockchain) newInteropContext(trigger trigger.Type, d *dao.Simple, block *block.Block, tx *transaction.Transaction) *interop.Context {
 	ic := interop.NewContext(trigger, bc, d, bc.contracts.Management.GetContract, bc.contracts.Contracts, block, tx, bc.log)
 	ic.Functions = systemInterops
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index af781d713..4b7520d45 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -559,8 +559,11 @@ func (dao *Simple) PutVersion(v Version) {
 }
 
 // PutCurrentHeader stores current header.
-func (dao *Simple) PutCurrentHeader(hashAndIndex []byte) {
-	dao.Store.Put(storage.SYSCurrentHeader.Bytes(), hashAndIndex)
+func (dao *Simple) PutCurrentHeader(h util.Uint256, index uint32) {
+	buf := dao.getDataBuf()
+	buf.WriteBytes(h.BytesLE())
+	buf.WriteU32LE(index)
+	dao.Store.Put(storage.SYSCurrentHeader.Bytes(), buf.Bytes())
 }
 
 // PutStateSyncPoint stores current state synchronisation point P.

From 7d6f08733710f4919d3440e77e14285e937361ed Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 18 Feb 2022 15:19:57 +0300
Subject: [PATCH 11/11] storage: drop (KeyPrefix).Bytes() API

It allocates and most of the time we can avoid that.
---
 pkg/core/blockchain.go            |  4 ++--
 pkg/core/blockchain_test.go       | 19 +++++++++-------
 pkg/core/dao/dao.go               | 36 ++++++++++++++++++-------------
 pkg/core/dao/dao_test.go          |  4 ++--
 pkg/core/statesync/module_test.go |  4 ++--
 pkg/core/statesync_test.go        |  4 ++--
 pkg/core/storage/store.go         |  5 -----
 7 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 624b9932c..1d51823f8 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -406,7 +406,7 @@ func (bc *Blockchain) init() error {
 	}
 
 	// Check whether StateJump stage is in the storage and continue interrupted state jump if so.
-	jumpStage, err := bc.dao.Store.Get(storage.SYSStateJumpStage.Bytes())
+	jumpStage, err := bc.dao.Store.Get([]byte{byte(storage.SYSStateJumpStage)})
 	if err == nil {
 		if !(bc.GetConfig().P2PStateExchangeExtensions && bc.GetConfig().RemoveUntraceableBlocks) {
 			return errors.New("state jump was not completed, but P2PStateExchangeExtensions are disabled or archival node capability is on. " +
@@ -500,7 +500,7 @@ func (bc *Blockchain) jumpToStateInternal(p uint32, stage stateJumpStage) error
 
 	bc.log.Info("jumping to state sync point", zap.Uint32("state sync point", p))
 
-	jumpStageKey := storage.SYSStateJumpStage.Bytes()
+	jumpStageKey := []byte{byte(storage.SYSStateJumpStage)}
 	switch stage {
 	case none:
 		bc.dao.Store.Put(jumpStageKey, []byte{byte(stateJumpStarted)})
diff --git a/pkg/core/blockchain_test.go b/pkg/core/blockchain_test.go
index 079b4efd3..39710482f 100644
--- a/pkg/core/blockchain_test.go
+++ b/pkg/core/blockchain_test.go
@@ -1853,7 +1853,9 @@ func TestBlockchain_InitWithIncompleteStateJump(t *testing.T) {
 	if bcSpout.dao.Version.StoragePrefix == tempPrefix {
 		tempPrefix = storage.STStorage
 	}
-	bcSpout.dao.Store.Seek(storage.SeekRange{Prefix: bcSpout.dao.Version.StoragePrefix.Bytes()}, func(k, v []byte) bool {
+	bPrefix := make([]byte, 1)
+	bPrefix[0] = byte(bcSpout.dao.Version.StoragePrefix)
+	bcSpout.dao.Store.Seek(storage.SeekRange{Prefix: bPrefix}, func(k, v []byte) bool {
 		key := slice.Copy(k)
 		key[0] = byte(tempPrefix)
 		value := slice.Copy(v)
@@ -1880,34 +1882,35 @@ func TestBlockchain_InitWithIncompleteStateJump(t *testing.T) {
 		c.ProtocolConfiguration.KeepOnlyLatestState = true
 	}
 	// manually store statejump stage to check statejump recover process
+	bPrefix[0] = byte(storage.SYSStateJumpStage)
 	t.Run("invalid RemoveUntraceableBlocks setting", func(t *testing.T) {
-		bcSpout.dao.Store.Put(storage.SYSStateJumpStage.Bytes(), []byte{byte(stateJumpStarted)})
+		bcSpout.dao.Store.Put(bPrefix, []byte{byte(stateJumpStarted)})
 		checkNewBlockchainErr(t, func(c *config.Config) {
 			boltCfg(c)
 			c.ProtocolConfiguration.RemoveUntraceableBlocks = false
 		}, bcSpout.dao.Store, true)
 	})
 	t.Run("invalid state jump stage format", func(t *testing.T) {
-		bcSpout.dao.Store.Put(storage.SYSStateJumpStage.Bytes(), []byte{0x01, 0x02})
+		bcSpout.dao.Store.Put(bPrefix, []byte{0x01, 0x02})
 		checkNewBlockchainErr(t, boltCfg, bcSpout.dao.Store, true)
 	})
 	t.Run("missing state sync point", func(t *testing.T) {
-		bcSpout.dao.Store.Put(storage.SYSStateJumpStage.Bytes(), []byte{byte(stateJumpStarted)})
+		bcSpout.dao.Store.Put(bPrefix, []byte{byte(stateJumpStarted)})
 		checkNewBlockchainErr(t, boltCfg, bcSpout.dao.Store, true)
 	})
 	t.Run("invalid state sync point", func(t *testing.T) {
-		bcSpout.dao.Store.Put(storage.SYSStateJumpStage.Bytes(), []byte{byte(stateJumpStarted)})
+		bcSpout.dao.Store.Put(bPrefix, []byte{byte(stateJumpStarted)})
 		point := make([]byte, 4)
 		binary.LittleEndian.PutUint32(point, uint32(len(bcSpout.headerHashes)))
-		bcSpout.dao.Store.Put(storage.SYSStateSyncPoint.Bytes(), point)
+		bcSpout.dao.Store.Put([]byte{byte(storage.SYSStateSyncPoint)}, point)
 		checkNewBlockchainErr(t, boltCfg, bcSpout.dao.Store, true)
 	})
 	for _, stage := range []stateJumpStage{stateJumpStarted, newStorageItemsAdded, genesisStateRemoved, 0x03} {
 		t.Run(fmt.Sprintf("state jump stage %d", stage), func(t *testing.T) {
-			bcSpout.dao.Store.Put(storage.SYSStateJumpStage.Bytes(), []byte{byte(stage)})
+			bcSpout.dao.Store.Put(bPrefix, []byte{byte(stage)})
 			point := make([]byte, 4)
 			binary.LittleEndian.PutUint32(point, uint32(stateSyncPoint))
-			bcSpout.dao.Store.Put(storage.SYSStateSyncPoint.Bytes(), point)
+			bcSpout.dao.Store.Put([]byte{byte(storage.SYSStateSyncPoint)}, point)
 			shouldFail := stage == 0x03 // unknown stage
 			checkNewBlockchainErr(t, spountCfg, bcSpout.dao.Store, shouldFail)
 		})
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index 4b7520d45..cae2622d6 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -448,12 +448,18 @@ func (v *Version) Bytes() []byte {
 	return append([]byte(v.Value), '\x00', byte(v.StoragePrefix), mask)
 }
 
+func (dao *Simple) mkKeyPrefix(k storage.KeyPrefix) []byte {
+	b := dao.getKeyBuf(1)
+	b[0] = byte(k)
+	return b
+}
+
 // GetVersion attempts to get the current version stored in the
 // underlying store.
 func (dao *Simple) GetVersion() (Version, error) {
 	var version Version
 
-	data, err := dao.Store.Get(storage.SYSVersion.Bytes())
+	data, err := dao.Store.Get(dao.mkKeyPrefix(storage.SYSVersion))
 	if err == nil {
 		err = version.FromBytes(data)
 	}
@@ -463,7 +469,7 @@ func (dao *Simple) GetVersion() (Version, error) {
 // GetCurrentBlockHeight returns the current block height found in the
 // underlying store.
 func (dao *Simple) GetCurrentBlockHeight() (uint32, error) {
-	b, err := dao.Store.Get(storage.SYSCurrentBlock.Bytes())
+	b, err := dao.Store.Get(dao.mkKeyPrefix(storage.SYSCurrentBlock))
 	if err != nil {
 		return 0, err
 	}
@@ -474,7 +480,7 @@ func (dao *Simple) GetCurrentBlockHeight() (uint32, error) {
 // the underlying store.
 func (dao *Simple) GetCurrentHeaderHeight() (i uint32, h util.Uint256, err error) {
 	var b []byte
-	b, err = dao.Store.Get(storage.SYSCurrentHeader.Bytes())
+	b, err = dao.Store.Get(dao.mkKeyPrefix(storage.SYSCurrentHeader))
 	if err != nil {
 		return
 	}
@@ -485,7 +491,7 @@ func (dao *Simple) GetCurrentHeaderHeight() (i uint32, h util.Uint256, err error
 
 // GetStateSyncPoint returns current state synchronisation point P.
 func (dao *Simple) GetStateSyncPoint() (uint32, error) {
-	b, err := dao.Store.Get(storage.SYSStateSyncPoint.Bytes())
+	b, err := dao.Store.Get(dao.mkKeyPrefix(storage.SYSStateSyncPoint))
 	if err != nil {
 		return 0, err
 	}
@@ -495,7 +501,7 @@ func (dao *Simple) GetStateSyncPoint() (uint32, error) {
 // GetStateSyncCurrentBlockHeight returns current block height stored during state
 // synchronisation process.
 func (dao *Simple) GetStateSyncCurrentBlockHeight() (uint32, error) {
-	b, err := dao.Store.Get(storage.SYSStateSyncCurrentBlockHeight.Bytes())
+	b, err := dao.Store.Get(dao.mkKeyPrefix(storage.SYSStateSyncCurrentBlockHeight))
 	if err != nil {
 		return 0, err
 	}
@@ -508,7 +514,7 @@ func (dao *Simple) GetHeaderHashes() ([]util.Uint256, error) {
 	var hashes = make([]util.Uint256, 0)
 
 	dao.Store.Seek(storage.SeekRange{
-		Prefix: storage.IXHeaderHashList.Bytes(),
+		Prefix: dao.mkKeyPrefix(storage.IXHeaderHashList),
 	}, func(k, v []byte) bool {
 		newHashes, err := read2000Uint256Hashes(v)
 		if err != nil {
@@ -555,7 +561,7 @@ func (dao *Simple) GetTransaction(hash util.Uint256) (*transaction.Transaction,
 // PutVersion stores the given version in the underlying store.
 func (dao *Simple) PutVersion(v Version) {
 	dao.Version = v
-	dao.Store.Put(storage.SYSVersion.Bytes(), v.Bytes())
+	dao.Store.Put(dao.mkKeyPrefix(storage.SYSVersion), v.Bytes())
 }
 
 // PutCurrentHeader stores current header.
@@ -563,21 +569,21 @@ func (dao *Simple) PutCurrentHeader(h util.Uint256, index uint32) {
 	buf := dao.getDataBuf()
 	buf.WriteBytes(h.BytesLE())
 	buf.WriteU32LE(index)
-	dao.Store.Put(storage.SYSCurrentHeader.Bytes(), buf.Bytes())
+	dao.Store.Put(dao.mkKeyPrefix(storage.SYSCurrentHeader), buf.Bytes())
 }
 
 // PutStateSyncPoint stores current state synchronisation point P.
 func (dao *Simple) PutStateSyncPoint(p uint32) {
-	buf := dao.getKeyBuf(4) // It's very small, no point in using BufBinWriter.
-	binary.LittleEndian.PutUint32(buf, p)
-	dao.Store.Put(storage.SYSStateSyncPoint.Bytes(), buf)
+	buf := dao.getDataBuf()
+	buf.WriteU32LE(p)
+	dao.Store.Put(dao.mkKeyPrefix(storage.SYSStateSyncPoint), buf.Bytes())
 }
 
 // PutStateSyncCurrentBlockHeight stores current block height during state synchronisation process.
 func (dao *Simple) PutStateSyncCurrentBlockHeight(h uint32) {
-	buf := dao.getKeyBuf(4) // It's very small, no point in using BufBinWriter.
-	binary.LittleEndian.PutUint32(buf, h)
-	dao.Store.Put(storage.SYSStateSyncCurrentBlockHeight.Bytes(), buf)
+	buf := dao.getDataBuf()
+	buf.WriteU32LE(h)
+	dao.Store.Put(dao.mkKeyPrefix(storage.SYSStateSyncCurrentBlockHeight), buf.Bytes())
 }
 
 // read2000Uint256Hashes attempts to read 2000 Uint256 hashes from
@@ -712,7 +718,7 @@ func (dao *Simple) StoreAsCurrentBlock(block *block.Block) {
 	h := block.Hash()
 	h.EncodeBinary(buf.BinWriter)
 	buf.WriteU32LE(block.Index)
-	dao.Store.Put(storage.SYSCurrentBlock.Bytes(), buf.Bytes())
+	dao.Store.Put(dao.mkKeyPrefix(storage.SYSCurrentBlock), buf.Bytes())
 }
 
 // StoreAsTransaction stores given TX as DataTransaction. It also stores transactions
diff --git a/pkg/core/dao/dao_test.go b/pkg/core/dao/dao_test.go
index feb2e2055..6583319e7 100644
--- a/pkg/core/dao/dao_test.go
+++ b/pkg/core/dao/dao_test.go
@@ -132,14 +132,14 @@ func TestGetVersion(t *testing.T) {
 
 	t.Run("invalid", func(t *testing.T) {
 		dao := NewSimple(storage.NewMemoryStore(), false, false)
-		dao.Store.Put(storage.SYSVersion.Bytes(), []byte("0.1.2\x00x"))
+		dao.Store.Put([]byte{byte(storage.SYSVersion)}, []byte("0.1.2\x00x"))
 
 		_, err := dao.GetVersion()
 		require.Error(t, err)
 	})
 	t.Run("old format", func(t *testing.T) {
 		dao := NewSimple(storage.NewMemoryStore(), false, false)
-		dao.Store.Put(storage.SYSVersion.Bytes(), []byte("0.1.2"))
+		dao.Store.Put([]byte{byte(storage.SYSVersion)}, []byte("0.1.2"))
 
 		version, err := dao.GetVersion()
 		require.NoError(t, err)
diff --git a/pkg/core/statesync/module_test.go b/pkg/core/statesync/module_test.go
index 79e24a8ba..6894f0593 100644
--- a/pkg/core/statesync/module_test.go
+++ b/pkg/core/statesync/module_test.go
@@ -32,7 +32,7 @@ func TestModule_PR2019_discussion_r689629704(t *testing.T) {
 		nodes         = make(map[util.Uint256][]byte)
 		expectedItems []storage.KeyValue
 	)
-	expectedStorage.Seek(storage.SeekRange{Prefix: storage.DataMPT.Bytes()}, func(k, v []byte) bool {
+	expectedStorage.Seek(storage.SeekRange{Prefix: []byte{byte(storage.DataMPT)}}, func(k, v []byte) bool {
 		key := slice.Copy(k)
 		value := slice.Copy(v)
 		expectedItems = append(expectedItems, storage.KeyValue{
@@ -96,7 +96,7 @@ func TestModule_PR2019_discussion_r689629704(t *testing.T) {
 
 	// Compare resulting storage items and refcounts.
 	var actualItems []storage.KeyValue
-	expectedStorage.Seek(storage.SeekRange{Prefix: storage.DataMPT.Bytes()}, func(k, v []byte) bool {
+	expectedStorage.Seek(storage.SeekRange{Prefix: []byte{byte(storage.DataMPT)}}, func(k, v []byte) bool {
 		key := slice.Copy(k)
 		value := slice.Copy(v)
 		actualItems = append(actualItems, storage.KeyValue{
diff --git a/pkg/core/statesync_test.go b/pkg/core/statesync_test.go
index 9da8e5f2b..2be3b01a9 100644
--- a/pkg/core/statesync_test.go
+++ b/pkg/core/statesync_test.go
@@ -423,7 +423,7 @@ func TestStateSyncModule_RestoreBasicChain(t *testing.T) {
 	// compare storage states
 	fetchStorage := func(bc *Blockchain) []storage.KeyValue {
 		var kv []storage.KeyValue
-		bc.dao.Store.Seek(storage.SeekRange{Prefix: bc.dao.Version.StoragePrefix.Bytes()}, func(k, v []byte) bool {
+		bc.dao.Store.Seek(storage.SeekRange{Prefix: []byte{byte(bc.dao.Version.StoragePrefix)}}, func(k, v []byte) bool {
 			key := slice.Copy(k)
 			value := slice.Copy(v)
 			if key[0] == byte(storage.STTempStorage) {
@@ -444,7 +444,7 @@ func TestStateSyncModule_RestoreBasicChain(t *testing.T) {
 	// no temp items should be left
 	require.Eventually(t, func() bool {
 		var haveItems bool
-		bcBolt.dao.Store.Seek(storage.SeekRange{Prefix: storage.STStorage.Bytes()}, func(_, _ []byte) bool {
+		bcBolt.dao.Store.Seek(storage.SeekRange{Prefix: []byte{byte(storage.STStorage)}}, func(_, _ []byte) bool {
 			haveItems = true
 			return false
 		})
diff --git a/pkg/core/storage/store.go b/pkg/core/storage/store.go
index 0812a5f08..4d2b1a550 100644
--- a/pkg/core/storage/store.go
+++ b/pkg/core/storage/store.go
@@ -106,11 +106,6 @@ type (
 	KeyPrefix uint8
 )
 
-// Bytes returns the bytes representation of KeyPrefix.
-func (k KeyPrefix) Bytes() []byte {
-	return []byte{byte(k)}
-}
-
 func seekRangeToPrefixes(sr SeekRange) *util.Range {
 	var (
 		rang  *util.Range