From e7687d620db59fc31893ff9faada43246b043bcc Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 6 Dec 2019 17:40:47 +0300
Subject: [PATCH 1/3] io: simplify WriteBytes()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Which speeds it up at least twofold for a typical 32-bytes write (and that's
for a very naïve test that allocates new BufBinWriter on every iteration):

pkg: github.com/CityOfZion/neo-go/pkg/io
BenchmarkWriteBytes-8           10000000               124 ns/op
BenchmarkWriteBytesOld-8         5000000               251 ns/op
---
 pkg/io/binaryWriter.go  | 7 +++++--
 pkg/io/binaryrw_test.go | 5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/pkg/io/binaryWriter.go b/pkg/io/binaryWriter.go
index b5aee0d0c..16e9dfc77 100644
--- a/pkg/io/binaryWriter.go
+++ b/pkg/io/binaryWriter.go
@@ -95,13 +95,16 @@ func (w *BinWriter) WriteVarUint(val uint64) {
 
 // WriteBytes writes a variable byte into the underlying io.Writer without prefix.
 func (w *BinWriter) WriteBytes(b []byte) {
-	w.WriteLE(b)
+	if w.Err != nil {
+		return
+	}
+	_, w.Err = w.w.Write(b)
 }
 
 // WriteVarBytes writes a variable length byte array into the underlying io.Writer.
 func (w *BinWriter) WriteVarBytes(b []byte) {
 	w.WriteVarUint(uint64(len(b)))
-	w.WriteLE(b)
+	w.WriteBytes(b)
 }
 
 // WriteString writes a variable length string into the underlying io.Writer.
diff --git a/pkg/io/binaryrw_test.go b/pkg/io/binaryrw_test.go
index 6a6278e1e..19a8c2a55 100644
--- a/pkg/io/binaryrw_test.go
+++ b/pkg/io/binaryrw_test.go
@@ -210,6 +210,11 @@ func TestWriteBytes(t *testing.T) {
 	buf := bw.Bytes()
 	assert.Equal(t, 4, len(buf))
 	assert.Equal(t, byte(0xde), buf[0])
+
+	bw = NewBufBinWriter()
+	bw.Err = errors.New("smth bad")
+	bw.WriteBytes(bin)
+	assert.Equal(t, 0, bw.Len())
 }
 
 type testSerializable uint16

From 844491d36598b9af2e4de08e52b312c43eb01b78 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 6 Dec 2019 18:22:21 +0300
Subject: [PATCH 2/3] *: use more efficient WriteBytes where appropriate

Before this patch on block import we could easily be spending more than 6
seconds out of 30 in Uint256 encoding for UnspentBalance, now it's completely
off the radar.
---
 pkg/compiler/emit.go               |  2 +-
 pkg/consensus/commit.go            |  2 +-
 pkg/consensus/payload.go           |  4 ++--
 pkg/consensus/prepare_request.go   |  2 +-
 pkg/consensus/prepare_response.go  |  2 +-
 pkg/consensus/recovery_message.go  |  4 ++--
 pkg/core/account_state.go          |  4 ++--
 pkg/core/asset_state.go            |  8 ++++----
 pkg/core/block.go                  |  4 ++--
 pkg/core/block_base.go             |  8 ++++----
 pkg/core/header.go                 |  2 +-
 pkg/core/notification_event.go     |  4 ++--
 pkg/core/spent_coin_state.go       |  2 +-
 pkg/core/transaction/input.go      |  2 +-
 pkg/core/transaction/output.go     |  4 ++--
 pkg/core/transaction/register.go   |  2 +-
 pkg/core/unspent_coin_state.go     |  2 +-
 pkg/network/message.go             |  2 +-
 pkg/network/payload/address.go     |  2 +-
 pkg/network/payload/getblocks.go   |  2 +-
 pkg/smartcontract/param_context.go |  2 +-
 pkg/util/uint256.go                |  2 +-
 pkg/vm/serialization.go            | 12 ++++++------
 23 files changed, 40 insertions(+), 40 deletions(-)

diff --git a/pkg/compiler/emit.go b/pkg/compiler/emit.go
index a73b59475..56cffb237 100644
--- a/pkg/compiler/emit.go
+++ b/pkg/compiler/emit.go
@@ -19,7 +19,7 @@ func emit(w *io.BinWriter, instr opcode.Opcode, b []byte) {
 
 // emitOpcode emits a single VM Instruction the given buffer.
 func emitOpcode(w *io.BinWriter, instr opcode.Opcode) {
-	w.WriteLE(byte(instr))
+	w.WriteBytes([]byte{byte(instr)})
 }
 
 // emitBool emits a bool type the given buffer.
diff --git a/pkg/consensus/commit.go b/pkg/consensus/commit.go
index e5d0e0fb9..da20be00f 100644
--- a/pkg/consensus/commit.go
+++ b/pkg/consensus/commit.go
@@ -18,7 +18,7 @@ var _ payload.Commit = (*commit)(nil)
 
 // EncodeBinary implements io.Serializable interface.
 func (c *commit) EncodeBinary(w *io.BinWriter) {
-	w.WriteBE(c.signature)
+	w.WriteBytes(c.signature[:])
 }
 
 // DecodeBinary implements io.Serializable interface.
diff --git a/pkg/consensus/payload.go b/pkg/consensus/payload.go
index fce529568..f7ad50a07 100644
--- a/pkg/consensus/payload.go
+++ b/pkg/consensus/payload.go
@@ -162,7 +162,7 @@ func (p *Payload) SetHeight(h uint32) {
 // EncodeBinaryUnsigned writes payload to w excluding signature.
 func (p Payload) EncodeBinaryUnsigned(w *io.BinWriter) {
 	w.WriteLE(p.version)
-	w.WriteBE(p.prevHash[:])
+	w.WriteBytes(p.prevHash[:])
 	w.WriteLE(p.height)
 	w.WriteLE(p.validatorIndex)
 	w.WriteLE(p.timestamp)
@@ -254,7 +254,7 @@ func (p *Payload) DecodeBinary(r *io.BinReader) {
 
 // EncodeBinary implements io.Serializable interface.
 func (m *message) EncodeBinary(w *io.BinWriter) {
-	w.WriteLE(byte(m.Type))
+	w.WriteBytes([]byte{byte(m.Type)})
 	w.WriteLE(m.ViewNumber)
 	m.payload.EncodeBinary(w)
 }
diff --git a/pkg/consensus/prepare_request.go b/pkg/consensus/prepare_request.go
index 6966de0f5..ef98e6512 100644
--- a/pkg/consensus/prepare_request.go
+++ b/pkg/consensus/prepare_request.go
@@ -22,7 +22,7 @@ var _ payload.PrepareRequest = (*prepareRequest)(nil)
 func (p *prepareRequest) EncodeBinary(w *io.BinWriter) {
 	w.WriteLE(p.timestamp)
 	w.WriteLE(p.nonce)
-	w.WriteBE(p.nextConsensus[:])
+	w.WriteBytes(p.nextConsensus[:])
 	w.WriteArray(p.transactionHashes)
 	p.minerTx.EncodeBinary(w)
 }
diff --git a/pkg/consensus/prepare_response.go b/pkg/consensus/prepare_response.go
index 8d338bc62..760b9475c 100644
--- a/pkg/consensus/prepare_response.go
+++ b/pkg/consensus/prepare_response.go
@@ -15,7 +15,7 @@ var _ payload.PrepareResponse = (*prepareResponse)(nil)
 
 // EncodeBinary implements io.Serializable interface.
 func (p *prepareResponse) EncodeBinary(w *io.BinWriter) {
-	w.WriteBE(p.preparationHash[:])
+	w.WriteBytes(p.preparationHash[:])
 }
 
 // DecodeBinary implements io.Serializable interface.
diff --git a/pkg/consensus/recovery_message.go b/pkg/consensus/recovery_message.go
index 3a01a168e..aaa1a91f6 100644
--- a/pkg/consensus/recovery_message.go
+++ b/pkg/consensus/recovery_message.go
@@ -79,7 +79,7 @@ func (m *recoveryMessage) EncodeBinary(w *io.BinWriter) {
 			w.WriteVarUint(0)
 		} else {
 			w.WriteVarUint(util.Uint256Size)
-			w.WriteBE(m.preparationHash[:])
+			w.WriteBytes(m.preparationHash[:])
 		}
 	}
 
@@ -115,7 +115,7 @@ func (p *commitCompact) DecodeBinary(r *io.BinReader) {
 func (p *commitCompact) EncodeBinary(w *io.BinWriter) {
 	w.WriteLE(p.ViewNumber)
 	w.WriteLE(p.ValidatorIndex)
-	w.WriteBE(p.Signature)
+	w.WriteBytes(p.Signature[:])
 	w.WriteVarBytes(p.InvocationScript)
 }
 
diff --git a/pkg/core/account_state.go b/pkg/core/account_state.go
index f2779340c..30ca2bc35 100644
--- a/pkg/core/account_state.go
+++ b/pkg/core/account_state.go
@@ -121,13 +121,13 @@ func (s *AccountState) DecodeBinary(br *io.BinReader) {
 // EncodeBinary encodes AccountState to the given BinWriter.
 func (s *AccountState) EncodeBinary(bw *io.BinWriter) {
 	bw.WriteLE(s.Version)
-	bw.WriteLE(s.ScriptHash)
+	bw.WriteBytes(s.ScriptHash[:])
 	bw.WriteLE(s.IsFrozen)
 	bw.WriteArray(s.Votes)
 
 	bw.WriteVarUint(uint64(len(s.Balances)))
 	for k, v := range s.Balances {
-		bw.WriteLE(k)
+		bw.WriteBytes(k[:])
 		bw.WriteArray(v)
 	}
 }
diff --git a/pkg/core/asset_state.go b/pkg/core/asset_state.go
index 8f883a467..10dd5902a 100644
--- a/pkg/core/asset_state.go
+++ b/pkg/core/asset_state.go
@@ -73,19 +73,19 @@ func (a *AssetState) DecodeBinary(br *io.BinReader) {
 
 // EncodeBinary implements Serializable interface.
 func (a *AssetState) EncodeBinary(bw *io.BinWriter) {
-	bw.WriteLE(a.ID)
+	bw.WriteBytes(a.ID[:])
 	bw.WriteLE(a.AssetType)
 	bw.WriteString(a.Name)
 	bw.WriteLE(a.Amount)
 	bw.WriteLE(a.Available)
 	bw.WriteLE(a.Precision)
 	bw.WriteLE(a.FeeMode)
-	bw.WriteLE(a.FeeAddress)
+	bw.WriteBytes(a.FeeAddress[:])
 
 	a.Owner.EncodeBinary(bw)
 
-	bw.WriteLE(a.Admin)
-	bw.WriteLE(a.Issuer)
+	bw.WriteBytes(a.Admin[:])
+	bw.WriteBytes(a.Issuer[:])
 	bw.WriteLE(a.Expiration)
 	bw.WriteLE(a.IsFrozen)
 }
diff --git a/pkg/core/block.go b/pkg/core/block.go
index f02fb425f..2dabbcba5 100644
--- a/pkg/core/block.go
+++ b/pkg/core/block.go
@@ -111,12 +111,12 @@ func NewBlockFromTrimmedBytes(b []byte) (*Block, error) {
 func (b *Block) Trim() ([]byte, error) {
 	buf := io.NewBufBinWriter()
 	b.encodeHashableFields(buf.BinWriter)
-	buf.WriteLE(uint8(1))
+	buf.WriteBytes([]byte{1})
 	b.Script.EncodeBinary(buf.BinWriter)
 
 	buf.WriteVarUint(uint64(len(b.Transactions)))
 	for _, tx := range b.Transactions {
-		buf.WriteLE(tx.Hash())
+		tx.Hash().EncodeBinary(buf.BinWriter)
 	}
 	if buf.Err != nil {
 		return nil, buf.Err
diff --git a/pkg/core/block_base.go b/pkg/core/block_base.go
index dfbc6cd15..e4a4bd64f 100644
--- a/pkg/core/block_base.go
+++ b/pkg/core/block_base.go
@@ -87,7 +87,7 @@ func (b *BlockBase) DecodeBinary(br *io.BinReader) {
 // EncodeBinary implements Serializable interface
 func (b *BlockBase) EncodeBinary(bw *io.BinWriter) {
 	b.encodeHashableFields(bw)
-	bw.WriteLE(uint8(1))
+	bw.WriteBytes([]byte{1})
 	b.Script.EncodeBinary(bw)
 }
 
@@ -116,12 +116,12 @@ func (b *BlockBase) createHash() {
 // see Hash() for more information about the fields.
 func (b *BlockBase) encodeHashableFields(bw *io.BinWriter) {
 	bw.WriteLE(b.Version)
-	bw.WriteLE(b.PrevHash)
-	bw.WriteLE(b.MerkleRoot)
+	bw.WriteBytes(b.PrevHash[:])
+	bw.WriteBytes(b.MerkleRoot[:])
 	bw.WriteLE(b.Timestamp)
 	bw.WriteLE(b.Index)
 	bw.WriteLE(b.ConsensusData)
-	bw.WriteLE(b.NextConsensus)
+	bw.WriteBytes(b.NextConsensus[:])
 }
 
 // decodeHashableFields decodes the fields used for hashing.
diff --git a/pkg/core/header.go b/pkg/core/header.go
index a33f0a0af..e21ce70ed 100644
--- a/pkg/core/header.go
+++ b/pkg/core/header.go
@@ -29,5 +29,5 @@ func (h *Header) DecodeBinary(r *io.BinReader) {
 // EncodeBinary implements Serializable interface.
 func (h *Header) EncodeBinary(w *io.BinWriter) {
 	h.BlockBase.EncodeBinary(w)
-	w.WriteLE(uint8(0))
+	w.WriteBytes([]byte{0})
 }
diff --git a/pkg/core/notification_event.go b/pkg/core/notification_event.go
index 850642557..63774ee7d 100644
--- a/pkg/core/notification_event.go
+++ b/pkg/core/notification_event.go
@@ -57,7 +57,7 @@ func getAppExecResultFromStore(s storage.Store, hash util.Uint256) (*AppExecResu
 
 // EncodeBinary implements the Serializable interface.
 func (ne NotificationEvent) EncodeBinary(w *io.BinWriter) {
-	w.WriteLE(ne.ScriptHash)
+	w.WriteBytes(ne.ScriptHash[:])
 	vm.EncodeBinaryStackItem(ne.Item, w)
 }
 
@@ -69,7 +69,7 @@ func (ne *NotificationEvent) DecodeBinary(r *io.BinReader) {
 
 // EncodeBinary implements the Serializable interface.
 func (aer *AppExecResult) EncodeBinary(w *io.BinWriter) {
-	w.WriteLE(aer.TxHash)
+	w.WriteBytes(aer.TxHash[:])
 	w.WriteArray(aer.Events)
 }
 
diff --git a/pkg/core/spent_coin_state.go b/pkg/core/spent_coin_state.go
index 84973df26..f72943707 100644
--- a/pkg/core/spent_coin_state.go
+++ b/pkg/core/spent_coin_state.go
@@ -93,7 +93,7 @@ func (s *SpentCoinState) DecodeBinary(br *io.BinReader) {
 
 // EncodeBinary implements Serializable interface.
 func (s *SpentCoinState) EncodeBinary(bw *io.BinWriter) {
-	bw.WriteLE(s.txHash)
+	bw.WriteBytes(s.txHash[:])
 	bw.WriteLE(s.txHeight)
 	bw.WriteVarUint(uint64(len(s.items)))
 	for k, v := range s.items {
diff --git a/pkg/core/transaction/input.go b/pkg/core/transaction/input.go
index f5e25dcc7..27d895afc 100644
--- a/pkg/core/transaction/input.go
+++ b/pkg/core/transaction/input.go
@@ -22,6 +22,6 @@ func (in *Input) DecodeBinary(br *io.BinReader) {
 
 // EncodeBinary implements Serializable interface.
 func (in *Input) EncodeBinary(bw *io.BinWriter) {
-	bw.WriteLE(in.PrevHash)
+	bw.WriteBytes(in.PrevHash[:])
 	bw.WriteLE(in.PrevIndex)
 }
diff --git a/pkg/core/transaction/output.go b/pkg/core/transaction/output.go
index d0ad24006..1e31fa92a 100644
--- a/pkg/core/transaction/output.go
+++ b/pkg/core/transaction/output.go
@@ -42,9 +42,9 @@ func (out *Output) DecodeBinary(br *io.BinReader) {
 
 // EncodeBinary implements Serializable interface.
 func (out *Output) EncodeBinary(bw *io.BinWriter) {
-	bw.WriteLE(out.AssetID)
+	bw.WriteBytes(out.AssetID[:])
 	bw.WriteLE(out.Amount)
-	bw.WriteLE(out.ScriptHash)
+	bw.WriteBytes(out.ScriptHash[:])
 }
 
 // MarshalJSON implements the Marshaler interface.
diff --git a/pkg/core/transaction/register.go b/pkg/core/transaction/register.go
index e8d754eb3..cccb6f769 100644
--- a/pkg/core/transaction/register.go
+++ b/pkg/core/transaction/register.go
@@ -50,5 +50,5 @@ func (tx *RegisterTX) EncodeBinary(bw *io.BinWriter) {
 	bw.WriteLE(tx.Amount)
 	bw.WriteLE(tx.Precision)
 	bw.WriteBytes(tx.Owner.Bytes())
-	bw.WriteLE(tx.Admin)
+	bw.WriteBytes(tx.Admin[:])
 }
diff --git a/pkg/core/unspent_coin_state.go b/pkg/core/unspent_coin_state.go
index a7b566fd8..dd391c66a 100644
--- a/pkg/core/unspent_coin_state.go
+++ b/pkg/core/unspent_coin_state.go
@@ -92,7 +92,7 @@ func (u UnspentCoins) commit(store storage.Store) error {
 func (s *UnspentCoinState) EncodeBinary(bw *io.BinWriter) {
 	bw.WriteVarUint(uint64(len(s.states)))
 	for _, state := range s.states {
-		bw.WriteLE(byte(state))
+		bw.WriteBytes([]byte{byte(state)})
 	}
 }
 
diff --git a/pkg/network/message.go b/pkg/network/message.go
index 2807e22de..9459079ff 100644
--- a/pkg/network/message.go
+++ b/pkg/network/message.go
@@ -213,7 +213,7 @@ func (m *Message) decodePayload(br *io.BinReader) error {
 // Encode encodes a Message to any given BinWriter.
 func (m *Message) Encode(br *io.BinWriter) error {
 	br.WriteLE(m.Magic)
-	br.WriteLE(m.Command)
+	br.WriteBytes(m.Command[:])
 	br.WriteLE(m.Length)
 	br.WriteLE(m.Checksum)
 	if m.Payload != nil {
diff --git a/pkg/network/payload/address.go b/pkg/network/payload/address.go
index 0daee4456..c8a4f9ece 100644
--- a/pkg/network/payload/address.go
+++ b/pkg/network/payload/address.go
@@ -39,7 +39,7 @@ func (p *AddressAndTime) DecodeBinary(br *io.BinReader) {
 func (p *AddressAndTime) EncodeBinary(bw *io.BinWriter) {
 	bw.WriteLE(p.Timestamp)
 	bw.WriteLE(p.Services)
-	bw.WriteBE(p.IP)
+	bw.WriteBytes(p.IP[:])
 	bw.WriteBE(p.Port)
 }
 
diff --git a/pkg/network/payload/getblocks.go b/pkg/network/payload/getblocks.go
index 8701a1df0..5c5caaebc 100644
--- a/pkg/network/payload/getblocks.go
+++ b/pkg/network/payload/getblocks.go
@@ -30,5 +30,5 @@ func (p *GetBlocks) DecodeBinary(br *io.BinReader) {
 // EncodeBinary implements Serializable interface.
 func (p *GetBlocks) EncodeBinary(bw *io.BinWriter) {
 	bw.WriteArray(p.HashStart)
-	bw.WriteLE(p.HashStop)
+	bw.WriteBytes(p.HashStop[:])
 }
diff --git a/pkg/smartcontract/param_context.go b/pkg/smartcontract/param_context.go
index ad509f17d..97158844b 100644
--- a/pkg/smartcontract/param_context.go
+++ b/pkg/smartcontract/param_context.go
@@ -80,7 +80,7 @@ func (pt ParamType) MarshalJSON() ([]byte, error) {
 
 // EncodeBinary implements io.Serializable interface.
 func (pt ParamType) EncodeBinary(w *io.BinWriter) {
-	w.WriteLE(pt)
+	w.WriteBytes([]byte{byte(pt)})
 }
 
 // DecodeBinary implements io.Serializable interface.
diff --git a/pkg/util/uint256.go b/pkg/util/uint256.go
index 76d69c468..0f3a20fbf 100644
--- a/pkg/util/uint256.go
+++ b/pkg/util/uint256.go
@@ -98,7 +98,7 @@ func (u Uint256) CompareTo(other Uint256) int { return bytes.Compare(u[:], other
 
 // EncodeBinary implements io.Serializable interface.
 func (u Uint256) EncodeBinary(w *io.BinWriter) {
-	w.WriteBE(u)
+	w.WriteBytes(u[:])
 }
 
 // DecodeBinary implements io.Serializable interface.
diff --git a/pkg/vm/serialization.go b/pkg/vm/serialization.go
index 5434e8b5a..8f155a8d6 100644
--- a/pkg/vm/serialization.go
+++ b/pkg/vm/serialization.go
@@ -43,13 +43,13 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 
 	switch t := item.(type) {
 	case *ByteArrayItem:
-		w.WriteLE(byte(byteArrayT))
+		w.WriteBytes([]byte{byte(byteArrayT)})
 		w.WriteVarBytes(t.value)
 	case *BoolItem:
-		w.WriteLE(byte(booleanT))
+		w.WriteBytes([]byte{byte(booleanT)})
 		w.WriteLE(t.value)
 	case *BigIntegerItem:
-		w.WriteLE(byte(integerT))
+		w.WriteBytes([]byte{byte(integerT)})
 		w.WriteVarBytes(t.Bytes())
 	case *InteropItem:
 		w.Err = errors.New("not supported")
@@ -58,9 +58,9 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 
 		_, isArray := t.(*ArrayItem)
 		if isArray {
-			w.WriteLE(byte(arrayT))
+			w.WriteBytes([]byte{byte(arrayT)})
 		} else {
-			w.WriteLE(byte(structT))
+			w.WriteBytes([]byte{byte(structT)})
 		}
 
 		arr := t.Value().([]StackItem)
@@ -71,7 +71,7 @@ func serializeItemTo(item StackItem, w *io.BinWriter, seen map[StackItem]bool) {
 	case *MapItem:
 		seen[item] = true
 
-		w.WriteLE(byte(mapT))
+		w.WriteBytes([]byte{byte(mapT)})
 		w.WriteVarUint(uint64(len(t.value)))
 		for k, v := range t.value {
 			serializeItemTo(v, w, seen)

From 9992a980076351e70fd094cd995243ebd6181826 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 6 Dec 2019 18:44:28 +0300
Subject: [PATCH 3/3] core: optimize balance utxo removal

One of my samples had 8 (out of 30) seconds spent here, but values of 100ms
are more typical. After this change it becomes invisible.
---
 pkg/core/blockchain.go | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 87d219125..bb84c083e 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -402,16 +402,17 @@ func (bc *Blockchain) storeBlock(block *Block) error {
 				if balancesLen <= 1 {
 					delete(account.Balances, prevTXOutput.AssetID)
 				} else {
-					var gotTx bool
-					for index, balance := range account.Balances[prevTXOutput.AssetID] {
-						if !gotTx && balance.Tx.Equals(input.PrevHash) && balance.Index == input.PrevIndex {
-							gotTx = true
-						}
-						if gotTx && index+1 < balancesLen {
-							account.Balances[prevTXOutput.AssetID][index] = account.Balances[prevTXOutput.AssetID][index+1]
+					var index = -1
+					for i, balance := range account.Balances[prevTXOutput.AssetID] {
+						if balance.Tx.Equals(input.PrevHash) && balance.Index == input.PrevIndex {
+							index = i
+							break
 						}
 					}
-					account.Balances[prevTXOutput.AssetID] = account.Balances[prevTXOutput.AssetID][:balancesLen-1]
+					if index >= 0 {
+						copy(account.Balances[prevTXOutput.AssetID][index:], account.Balances[prevTXOutput.AssetID][index+1:])
+						account.Balances[prevTXOutput.AssetID] = account.Balances[prevTXOutput.AssetID][:balancesLen-1]
+					}
 				}
 			}
 		}