package native import ( "errors" "fmt" "math" "math/big" "github.com/nspcc-dev/neo-go/pkg/core/dao" "github.com/nspcc-dev/neo-go/pkg/core/interop" "github.com/nspcc-dev/neo-go/pkg/core/interop/contract" "github.com/nspcc-dev/neo-go/pkg/core/interop/runtime" "github.com/nspcc-dev/neo-go/pkg/core/state" "github.com/nspcc-dev/neo-go/pkg/encoding/bigint" "github.com/nspcc-dev/neo-go/pkg/smartcontract" "github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag" "github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest" "github.com/nspcc-dev/neo-go/pkg/util" "github.com/nspcc-dev/neo-go/pkg/vm/stackitem" ) // prefixAccount is the standard prefix used to store account data. const prefixAccount = 20 // makeAccountKey creates a key from account script hash. func makeAccountKey(h util.Uint160) []byte { return makeUint160Key(prefixAccount, h) } // nep17TokenNative represents NEP-17 token contract. type nep17TokenNative struct { interop.ContractMD symbol string decimals int64 factor int64 incBalance func(*interop.Context, util.Uint160, *state.StorageItem, *big.Int, *big.Int) error balFromBytes func(item *state.StorageItem) (*big.Int, error) } // totalSupplyKey is the key used to store totalSupply value. var totalSupplyKey = []byte{11} func (c *nep17TokenNative) Metadata() *interop.ContractMD { return &c.ContractMD } func newNEP17Native(name string, id int32) *nep17TokenNative { n := &nep17TokenNative{ContractMD: *interop.NewContractMD(name, id)} n.Manifest.SupportedStandards = []string{manifest.NEP17StandardName} desc := newDescriptor("symbol", smartcontract.StringType) md := newMethodAndPrice(n.Symbol, 0, callflag.NoneFlag) n.AddMethod(md, desc) desc = newDescriptor("decimals", smartcontract.IntegerType) md = newMethodAndPrice(n.Decimals, 0, callflag.NoneFlag) n.AddMethod(md, desc) desc = newDescriptor("totalSupply", smartcontract.IntegerType) md = newMethodAndPrice(n.TotalSupply, 1<<15, callflag.ReadStates) n.AddMethod(md, desc) desc = newDescriptor("balanceOf", smartcontract.IntegerType, manifest.NewParameter("account", smartcontract.Hash160Type)) md = newMethodAndPrice(n.balanceOf, 1<<15, callflag.ReadStates) n.AddMethod(md, desc) transferParams := []manifest.Parameter{ manifest.NewParameter("from", smartcontract.Hash160Type), manifest.NewParameter("to", smartcontract.Hash160Type), manifest.NewParameter("amount", smartcontract.IntegerType), } desc = newDescriptor("transfer", smartcontract.BoolType, append(transferParams, manifest.NewParameter("data", smartcontract.AnyType))..., ) md = newMethodAndPrice(n.Transfer, 1<<17, callflag.States|callflag.AllowCall|callflag.AllowNotify) md.StorageFee = 50 n.AddMethod(md, desc) n.AddEvent("Transfer", transferParams...) return n } func (c *nep17TokenNative) Initialize(_ *interop.Context) error { return nil } func (c *nep17TokenNative) Symbol(_ *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewByteArray([]byte(c.symbol)) } func (c *nep17TokenNative) Decimals(_ *interop.Context, _ []stackitem.Item) stackitem.Item { return stackitem.NewBigInteger(big.NewInt(c.decimals)) } func (c *nep17TokenNative) TotalSupply(ic *interop.Context, _ []stackitem.Item) stackitem.Item { _, supply := c.getTotalSupply(ic.DAO) return stackitem.NewBigInteger(supply) } func (c *nep17TokenNative) getTotalSupply(d *dao.Simple) (state.StorageItem, *big.Int) { si := d.GetStorageItem(c.ID, totalSupplyKey) if si == nil { si = []byte{} } return si, bigint.FromBytes(si) } func (c *nep17TokenNative) saveTotalSupply(d *dao.Simple, si state.StorageItem, supply *big.Int) { si = state.StorageItem(bigint.ToPreallocatedBytes(supply, si)) d.PutStorageItem(c.ID, totalSupplyKey, si) } func (c *nep17TokenNative) Transfer(ic *interop.Context, args []stackitem.Item) stackitem.Item { from := toUint160(args[0]) to := toUint160(args[1]) amount := toBigInt(args[2]) err := c.TransferInternal(ic, from, to, amount, args[3]) return stackitem.NewBool(err == nil) } func addrToStackItem(u *util.Uint160) stackitem.Item { if u == nil { return stackitem.Null{} } return stackitem.NewByteArray(u.BytesBE()) } func (c *nep17TokenNative) postTransfer(ic *interop.Context, from, to *util.Uint160, amount *big.Int, data stackitem.Item, callOnPayment bool) { c.emitTransfer(ic, from, to, amount) if to == nil || !callOnPayment { return } cs, err := ic.GetContract(*to) if err != nil { return } fromArg := stackitem.Item(stackitem.Null{}) if from != nil { fromArg = stackitem.NewByteArray((*from).BytesBE()) } args := []stackitem.Item{ fromArg, stackitem.NewBigInteger(amount), data, } if err := contract.CallFromNative(ic, c.Hash, cs, manifest.MethodOnNEP17Payment, args, false); err != nil { panic(err) } } func (c *nep17TokenNative) emitTransfer(ic *interop.Context, from, to *util.Uint160, amount *big.Int) { ne := state.NotificationEvent{ ScriptHash: c.Hash, Name: "Transfer", Item: stackitem.NewArray([]stackitem.Item{ addrToStackItem(from), addrToStackItem(to), stackitem.NewBigInteger(amount), }), } ic.Notifications = append(ic.Notifications, ne) } // updateAccBalance adds specified amount to the acc's balance. If requiredBalance // is set and amount is 0, then acc's balance is checked against requiredBalance. func (c *nep17TokenNative) updateAccBalance(ic *interop.Context, acc util.Uint160, amount *big.Int, requiredBalance *big.Int) error { key := makeAccountKey(acc) si := ic.DAO.GetStorageItem(c.ID, key) if si == nil { if amount.Sign() < 0 { return errors.New("insufficient funds") } if amount.Sign() == 0 { // it's OK to transfer 0 if the balance 0, no need to put si to the storage return nil } si = state.StorageItem{} } err := c.incBalance(ic, acc, &si, amount, requiredBalance) if err != nil { if si != nil && amount.Sign() <= 0 { ic.DAO.PutStorageItem(c.ID, key, si) } return err } if si == nil { ic.DAO.DeleteStorageItem(c.ID, key) } else { ic.DAO.PutStorageItem(c.ID, key, si) } return nil } // TransferInternal transfers NEO between accounts. func (c *nep17TokenNative) TransferInternal(ic *interop.Context, from, to util.Uint160, amount *big.Int, data stackitem.Item) error { if amount.Sign() == -1 { return errors.New("negative amount") } caller := ic.VM.GetCallingScriptHash() if caller.Equals(util.Uint160{}) || !from.Equals(caller) { ok, err := runtime.CheckHashedWitness(ic, from) if err != nil { return err } else if !ok { return errors.New("invalid signature") } } isEmpty := from.Equals(to) || amount.Sign() == 0 inc := amount if isEmpty { inc = big.NewInt(0) } else { inc = new(big.Int).Neg(inc) } if err := c.updateAccBalance(ic, from, inc, amount); err != nil { return err } if !isEmpty { if err := c.updateAccBalance(ic, to, amount, nil); err != nil { return err } } c.postTransfer(ic, &from, &to, amount, data, true) return nil } func (c *nep17TokenNative) balanceOf(ic *interop.Context, args []stackitem.Item) stackitem.Item { h := toUint160(args[0]) return stackitem.NewBigInteger(c.balanceOfInternal(ic.DAO, h)) } func (c *nep17TokenNative) balanceOfInternal(d *dao.Simple, h util.Uint160) *big.Int { key := makeAccountKey(h) si := d.GetStorageItem(c.ID, key) if si == nil { return big.NewInt(0) } balance, err := c.balFromBytes(&si) if err != nil { panic(fmt.Errorf("can not deserialize balance state: %w", err)) } return balance } func (c *nep17TokenNative) mint(ic *interop.Context, h util.Uint160, amount *big.Int, callOnPayment bool) { if amount.Sign() == 0 { return } c.addTokens(ic, h, amount) c.postTransfer(ic, nil, &h, amount, stackitem.Null{}, callOnPayment) } func (c *nep17TokenNative) burn(ic *interop.Context, h util.Uint160, amount *big.Int) { if amount.Sign() == 0 { return } amount.Neg(amount) c.addTokens(ic, h, amount) amount.Neg(amount) c.postTransfer(ic, &h, nil, amount, stackitem.Null{}, false) } func (c *nep17TokenNative) addTokens(ic *interop.Context, h util.Uint160, amount *big.Int) { if amount.Sign() == 0 { return } key := makeAccountKey(h) si := ic.DAO.GetStorageItem(c.ID, key) if si == nil { si = state.StorageItem{} } if err := c.incBalance(ic, h, &si, amount, nil); err != nil { panic(err) } if si == nil { ic.DAO.DeleteStorageItem(c.ID, key) } else { ic.DAO.PutStorageItem(c.ID, key, si) } buf, supply := c.getTotalSupply(ic.DAO) supply.Add(supply, amount) c.saveTotalSupply(ic.DAO, buf, supply) } func newDescriptor(name string, ret smartcontract.ParamType, ps ...manifest.Parameter) *manifest.Method { if len(ps) == 0 { ps = []manifest.Parameter{} } return &manifest.Method{ Name: name, Parameters: ps, ReturnType: ret, } } func newMethodAndPrice(f interop.Method, cpuFee int64, flags callflag.CallFlag) *interop.MethodAndPrice { return &interop.MethodAndPrice{ Func: f, CPUFee: cpuFee, RequiredFlags: flags, } } func toBigInt(s stackitem.Item) *big.Int { bi, err := s.TryInteger() if err != nil { panic(err) } return bi } func toUint160(s stackitem.Item) util.Uint160 { buf, err := s.TryBytes() if err != nil { panic(err) } u, err := util.Uint160DecodeBytesBE(buf) if err != nil { panic(err) } return u } func toUint32(s stackitem.Item) uint32 { bigInt := toBigInt(s) if !bigInt.IsUint64() { panic("bigint is not an uint64") } uint64Value := bigInt.Uint64() if uint64Value > math.MaxUint32 { panic("bigint does not fit into uint32") } return uint32(uint64Value) }