package native import ( "errors" "math/big" "github.com/nspcc-dev/neo-go/pkg/core/interop" "github.com/nspcc-dev/neo-go/pkg/core/state" "github.com/nspcc-dev/neo-go/pkg/smartcontract" "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" "github.com/nspcc-dev/neo-go/pkg/vm/emit" ) // 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 { k := make([]byte, util.Uint160Size+1) k[0] = prefixAccount copy(k[1:], h.BytesBE()) return k } // nep5TokenNative represents NEP-5 token contract. type nep5TokenNative struct { interop.ContractMD name string symbol string decimals int64 factor int64 onPersist func(*interop.Context) error incBalance func(*interop.Context, util.Uint160, *state.StorageItem, *big.Int) error } // totalSupplyKey is the key used to store totalSupply value. var totalSupplyKey = []byte{11} func (c *nep5TokenNative) Metadata() *interop.ContractMD { return &c.ContractMD } var _ interop.Contract = (*nep5TokenNative)(nil) func newNEP5Native(name string) *nep5TokenNative { n := &nep5TokenNative{ContractMD: *interop.NewContractMD(name)} desc := newDescriptor("name", smartcontract.StringType) md := newMethodAndPrice(n.Name, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("symbol", smartcontract.StringType) md = newMethodAndPrice(n.Symbol, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("decimals", smartcontract.IntegerType) md = newMethodAndPrice(n.Decimals, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("totalSupply", smartcontract.IntegerType) md = newMethodAndPrice(n.TotalSupply, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("balanceOf", smartcontract.IntegerType, manifest.NewParameter("account", smartcontract.Hash160Type)) md = newMethodAndPrice(n.balanceOf, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, true) desc = newDescriptor("transfer", smartcontract.BoolType, manifest.NewParameter("from", smartcontract.Hash160Type), manifest.NewParameter("to", smartcontract.Hash160Type), manifest.NewParameter("amount", smartcontract.IntegerType), ) md = newMethodAndPrice(n.Transfer, 1, smartcontract.NoneFlag) n.AddMethod(md, desc, false) n.AddEvent("Transfer", desc.Parameters...) return n } func (c *nep5TokenNative) Initialize(_ *interop.Context) error { return nil } func (c *nep5TokenNative) Name(_ *interop.Context, _ []vm.StackItem) vm.StackItem { return vm.NewByteArrayItem([]byte(c.name)) } func (c *nep5TokenNative) Symbol(_ *interop.Context, _ []vm.StackItem) vm.StackItem { return vm.NewByteArrayItem([]byte(c.symbol)) } func (c *nep5TokenNative) Decimals(_ *interop.Context, _ []vm.StackItem) vm.StackItem { return vm.NewBigIntegerItem(big.NewInt(c.decimals)) } func (c *nep5TokenNative) TotalSupply(ic *interop.Context, _ []vm.StackItem) vm.StackItem { return vm.NewBigIntegerItem(c.getTotalSupply(ic)) } func (c *nep5TokenNative) getTotalSupply(ic *interop.Context) *big.Int { si := ic.DAO.GetStorageItem(c.Hash, totalSupplyKey) if si == nil { return big.NewInt(0) } return emit.BytesToInt(si.Value) } func (c *nep5TokenNative) saveTotalSupply(ic *interop.Context, supply *big.Int) error { si := &state.StorageItem{Value: emit.IntToBytes(supply)} return ic.DAO.PutStorageItem(c.Hash, totalSupplyKey, si) } func (c *nep5TokenNative) Transfer(ic *interop.Context, args []vm.StackItem) vm.StackItem { from := toUint160(args[0]) to := toUint160(args[1]) amount := toBigInt(args[2]) err := c.transfer(ic, from, to, amount) return vm.NewBoolItem(err == nil) } func addrToStackItem(u *util.Uint160) vm.StackItem { if u == nil { return vm.NullItem{} } return vm.NewByteArrayItem(u.BytesBE()) } func (c *nep5TokenNative) emitTransfer(ic *interop.Context, from, to *util.Uint160, amount *big.Int) { ne := state.NotificationEvent{ ScriptHash: c.Hash, Item: vm.NewArrayItem([]vm.StackItem{ vm.NewByteArrayItem([]byte("Transfer")), addrToStackItem(from), addrToStackItem(to), vm.NewBigIntegerItem(amount), }), } ic.Notifications = append(ic.Notifications, ne) } func (c *nep5TokenNative) transfer(ic *interop.Context, from, to util.Uint160, amount *big.Int) error { if amount.Sign() == -1 { return errors.New("negative amount") } keyFrom := makeAccountKey(from) siFrom := ic.DAO.GetStorageItem(c.Hash, keyFrom) if siFrom == nil { return errors.New("insufficient funds") } isEmpty := from.Equals(to) || amount.Sign() == 0 inc := amount if isEmpty { inc = big.NewInt(0) } if err := c.incBalance(ic, from, siFrom, inc); err != nil { return err } if err := ic.DAO.PutStorageItem(c.Hash, keyFrom, siFrom); err != nil { return err } if !isEmpty { keyTo := makeAccountKey(to) siTo := ic.DAO.GetStorageItem(c.Hash, keyTo) if siTo == nil { siTo = new(state.StorageItem) } if err := c.incBalance(ic, to, siTo, amount); err != nil { return err } if err := ic.DAO.PutStorageItem(c.Hash, keyTo, siTo); err != nil { return err } } c.emitTransfer(ic, &from, &to, amount) return nil } func (c *nep5TokenNative) balanceOf(ic *interop.Context, args []vm.StackItem) vm.StackItem { h := toUint160(args[0]) bs, err := ic.DAO.GetNEP5Balances(h) if err != nil { panic(err) } balance := bs.Trackers[c.Hash].Balance return vm.NewBigIntegerItem(big.NewInt(balance)) } func (c *nep5TokenNative) mint(ic *interop.Context, h util.Uint160, amount *big.Int) { c.addTokens(ic, h, amount) c.emitTransfer(ic, nil, &h, amount) } func (c *nep5TokenNative) burn(ic *interop.Context, h util.Uint160, amount *big.Int) { amount = new(big.Int).Neg(amount) c.addTokens(ic, h, amount) c.emitTransfer(ic, &h, nil, amount) } func (c *nep5TokenNative) addTokens(ic *interop.Context, h util.Uint160, amount *big.Int) { if sign := amount.Sign(); sign == -1 { panic("negative amount") } else if sign == 0 { return } key := makeAccountKey(h) si := ic.DAO.GetStorageItem(c.Hash, key) if si == nil { si = new(state.StorageItem) } if err := c.incBalance(ic, h, si, amount); err != nil { panic(err) } if err := ic.DAO.PutStorageItem(c.Hash, key, si); err != nil { panic(err) } supply := c.getTotalSupply(ic) supply.Add(supply, amount) err := c.saveTotalSupply(ic, supply) if err != nil { panic(err) } } func (c *nep5TokenNative) OnPersist(ic *interop.Context) error { return c.onPersist(ic) } func newDescriptor(name string, ret smartcontract.ParamType, ps ...manifest.Parameter) *manifest.Method { return &manifest.Method{ Name: name, Parameters: ps, ReturnType: ret, } } func newMethodAndPrice(f interop.Method, price int64, flags smartcontract.CallFlag) *interop.MethodAndPrice { return &interop.MethodAndPrice{ Func: f, Price: price, RequiredFlags: flags, } } func toBigInt(s vm.StackItem) *big.Int { bi, err := s.TryInteger() if err != nil { panic(err) } return bi } func toUint160(s vm.StackItem) util.Uint160 { buf, err := s.TryBytes() if err != nil { panic(err) } u, err := util.Uint160DecodeBytesBE(buf) if err != nil { panic(err) } return u }