state: use big.Int for NEP5 balances and transfer amounts

In general, NEP5 contracts are not limited to int64. And we have an example
of pnWETH Flamingo token now (with 18 decimals) that easily overflows int64,
so for correctness we need to store big.Int.

And as TransferLog is shared for different purposes I've decided to not make
it variable-length on Neo 2.

pkg/core/blockchain.go

@@ -3,6 +3,7 @@ package core
 import (
 	"fmt"
 	"math"
+	"math/big"
 	"sort"
 	"sync"
 	"sync/atomic"
@@ -944,20 +945,23 @@ func (bc *Blockchain) processNEP5Transfer(cache *dao.Cached, transfer *state.NEP
 			return
 		}
 		bs := balances.Trackers[transfer.Asset]
-		bs.Balance -= transfer.Amount
+		if bs.Balance == nil {
-		if bs.Balance != 0 {
+			return
+		}
+		bs.Balance.Sub(bs.Balance, transfer.Amount)
+		if bs.Balance.Sign() > 0 {
 			bs.LastUpdatedBlock = transfer.Block
 			balances.Trackers[transfer.Asset] = bs
 		} else {
 			delete(balances.Trackers, transfer.Asset)
 		}
 
-		transfer.Amount = -transfer.Amount
+		transfer.Amount.Neg(transfer.Amount)
 		isBig, err := cache.AppendNEP5Transfer(transfer.From, balances.NextTransferBatch, transfer)
 		if err != nil {
 			return
 		}
-		transfer.Amount = -transfer.Amount
+		transfer.Amount.Neg(transfer.Amount)
 		if isBig {
 			balances.NextTransferBatch++
 		}
@@ -971,7 +975,10 @@ func (bc *Blockchain) processNEP5Transfer(cache *dao.Cached, transfer *state.NEP
 			return
 		}
 		bs := balances.Trackers[transfer.Asset]
-		bs.Balance += transfer.Amount
+		if bs.Balance == nil {
+			bs.Balance = new(big.Int)
+		}
+		bs.Balance.Add(bs.Balance, transfer.Amount)
 		bs.LastUpdatedBlock = transfer.Block
 		balances.Trackers[transfer.Asset] = bs
 

pkg/core/state/nep5.go

@@ -13,7 +13,7 @@ import (
 // NEP5Tracker contains info about a single account in a NEP5 contract.
 type NEP5Tracker struct {
 	// Balance is the current balance of the account.
-	Balance int64
+	Balance *big.Int
 	// LastUpdatedBlock is a number of block when last `transfer` to or from the
 	// account occured.
 	LastUpdatedBlock uint32
@@ -25,7 +25,7 @@ type TransferLog struct {
 }
 
 // NEP5TransferSize is a size of a marshaled NEP5Transfer struct in bytes.
-const NEP5TransferSize = util.Uint160Size*3 + 8 + 4 + 4 + util.Uint256Size + 4
+const NEP5TransferSize = util.Uint160Size*3 + amountSize + 4 + 4 + util.Uint256Size + 4
 
 // NEP5Transfer represents a single NEP5 Transfer event.
 type NEP5Transfer struct {
@@ -37,7 +37,7 @@ type NEP5Transfer struct {
 	To util.Uint160
 	// Amount is the amount of tokens transferred.
 	// It is negative when tokens are sent and positive if they are received.
-	Amount int64
+	Amount *big.Int
 	// Block is a number of block when the event occured.
 	Block uint32
 	// Timestamp is the timestamp of the block where transfer occured.
@@ -48,6 +48,8 @@ type NEP5Transfer struct {
 	Index uint32
 }
 
+const amountSize = 32
+
 // NEP5Balances is a map of the NEP5 contract hashes
 // to the corresponding structures.
 type NEP5Balances struct {
@@ -143,13 +145,13 @@ func (lg *TransferLog) Size() int {
 
 // EncodeBinary implements io.Serializable interface.
 func (t *NEP5Tracker) EncodeBinary(w *io.BinWriter) {
-	w.WriteU64LE(uint64(t.Balance))
+	w.WriteVarBytes(emit.IntToBytes(t.Balance))
 	w.WriteU32LE(t.LastUpdatedBlock)
 }
 
 // DecodeBinary implements io.Serializable interface.
 func (t *NEP5Tracker) DecodeBinary(r *io.BinReader) {
-	t.Balance = int64(r.ReadU64LE())
+	t.Balance = emit.BytesToInt(r.ReadVarBytes(amountSize))
 	t.LastUpdatedBlock = r.ReadU32LE()
 }
 
@@ -194,7 +196,7 @@ func NEP5TransferFromNotification(ne NotificationEvent, txHash util.Uint256, hei
 		Asset:     ne.ScriptHash,
 		From:      fromAddr,
 		To:        toAddr,
-		Amount:    amount.Int64(),
+		Amount:    amount,
 		Block:     height,
 		Timestamp: time,
 		Tx:        txHash,
@@ -212,7 +214,19 @@ func (t *NEP5Transfer) EncodeBinary(w *io.BinWriter) {
 	w.WriteBytes(t.To[:])
 	w.WriteU32LE(t.Block)
 	w.WriteU32LE(t.Timestamp)
-	w.WriteU64LE(uint64(t.Amount))
+	am := emit.IntToBytes(t.Amount)
+	if len(am) > amountSize {
+		panic("bad integer length")
+	}
+	fillerLen := amountSize - len(am)
+	w.WriteBytes(am)
+	var filler byte
+	if t.Amount.Sign() < 0 {
+		filler = 0xff
+	}
+	for i := 0; i < fillerLen; i++ {
+		w.WriteB(filler)
+	}
 	w.WriteU32LE(t.Index)
 }
 
@@ -224,6 +238,8 @@ func (t *NEP5Transfer) DecodeBinary(r *io.BinReader) {
 	r.ReadBytes(t.To[:])
 	t.Block = r.ReadU32LE()
 	t.Timestamp = r.ReadU32LE()
-	t.Amount = int64(r.ReadU64LE())
+	amount := make([]byte, amountSize)
+	r.ReadBytes(amount)
+	t.Amount = emit.BytesToInt(amount)
 	t.Index = r.ReadU32LE()
 }

pkg/core/state/nep5_test.go

@@ -1,6 +1,7 @@
 package state
 
 import (
+	"math/big"
 	"math/rand"
 	"testing"
 	"time"
@@ -41,7 +42,7 @@ func TestNEP5TransferLog_Append(t *testing.T) {
 
 func TestNEP5Tracker_EncodeBinary(t *testing.T) {
 	expected := &NEP5Tracker{
-		Balance:          int64(rand.Uint64()),
+		Balance:          big.NewInt(int64(rand.Uint64())),
 		LastUpdatedBlock: rand.Uint32(),
 	}
 
@@ -53,7 +54,7 @@ func TestNEP5Transfer_DecodeBinary(t *testing.T) {
 		Asset:     util.Uint160{1, 2, 3},
 		From:      util.Uint160{5, 6, 7},
 		To:        util.Uint160{8, 9, 10},
-		Amount:    42,
+		Amount:    big.NewInt(42),
 		Block:     12345,
 		Timestamp: 54321,
 		Tx:        util.Uint256{8, 5, 3},
@@ -70,7 +71,7 @@ func TestNEP5TransferSize(t *testing.T) {
 
 func randomTransfer(r *rand.Rand) *NEP5Transfer {
 	return &NEP5Transfer{
-		Amount: int64(r.Uint64()),
+		Amount: big.NewInt(int64(r.Uint64())),
 		Block:  r.Uint32(),
 		Asset:  random.Uint160(),
 		From:   random.Uint160(),

pkg/rpc/server/server.go

@@ -771,7 +771,7 @@ func (s *Server) getNEP5Balances(ps request.Params) (interface{}, *response.Erro
 	}
 	if as != nil {
 		for h, bal := range as.Trackers {
-			amount := strconv.FormatInt(bal.Balance, 10)
+			amount := bal.Balance.String()
 			bs.Balances = append(bs.Balances, result.NEP5Balance{
 				Asset:       h,
 				Amount:      amount,
@@ -824,14 +824,15 @@ func (s *Server) getNEP5Transfers(ps request.Params) (interface{}, *response.Err
 
 			NotifyIndex: tr.Index,
 		}
-		if tr.Amount > 0 { // token was received
+		if tr.Amount.Sign() > 0 { // token was received
-			transfer.Amount = strconv.FormatInt(tr.Amount, 10)
+			transfer.Amount = tr.Amount.String()
 			if !tr.From.Equals(util.Uint160{}) {
 				transfer.Address = address.Uint160ToString(tr.From)
 			}
 			bs.Received = append(bs.Received, transfer)
 		} else {
-			transfer.Amount = strconv.FormatInt(-tr.Amount, 10)
+			tr.Amount.Neg(tr.Amount)
+			transfer.Amount = tr.Amount.String()
 			if !tr.To.Equals(util.Uint160{}) {
 				transfer.Address = address.Uint160ToString(tr.To)
 			}
@@ -888,12 +889,14 @@ func uint160ToString(u util.Uint160) string {
 func appendNEP5ToTransferTx(transfer *result.TransferTx, nepTr *state.NEP5Transfer) {
 	var event result.TransferTxEvent
 	event.Asset = nepTr.Asset.StringLE()
-	if nepTr.Amount > 0 { // token was received
+	if nepTr.Amount.Sign() > 0 { // token was received
-		event.Value = strconv.FormatInt(nepTr.Amount, 10)
+		event.Value = nepTr.Amount.String()
 		event.Type = "receive"
 		event.Address = uint160ToString(nepTr.From)
 	} else {
-		event.Value = strconv.FormatInt(-nepTr.Amount, 10)
+		nepTr.Amount.Neg(nepTr.Amount)
+		event.Value = nepTr.Amount.String()
+		nepTr.Amount.Neg(nepTr.Amount)
 		event.Type = "send"
 		event.Address = uint160ToString(nepTr.To)
 	}
@@ -1327,7 +1330,7 @@ func (s *Server) getBlockTransferTx(ps request.Params) (interface{}, *response.E
 					Asset: nepTr.Asset.StringLE(),
 					From:  uint160ToString(nepTr.From),
 					To:    uint160ToString(nepTr.To),
-					Value: strconv.FormatInt(nepTr.Amount, 10),
+					Value: nepTr.Amount.String(),
 				})
 				index++
 			}