package nep17 import ( "github.com/nspcc-dev/neo-go/pkg/interop" "github.com/nspcc-dev/neo-go/pkg/interop/runtime" "github.com/nspcc-dev/neo-go/pkg/interop/storage" "github.com/nspcc-dev/neo-go/pkg/interop/util" ) // Token holds all token info type Token struct { // Token name Name string // Ticker symbol Symbol string // Amount of decimals Decimals int // Token owner address Owner []byte // Total tokens * multiplier TotalSupply int // Storage key for circulation value CirculationKey string } // getIntFromDB is a helper that checks for nil result of storage.Get and returns // zero as the default value. func getIntFromDB(ctx storage.Context, key []byte) int { var res int val := storage.Get(ctx, key) if val != nil { res = val.(int) } return res } // GetSupply gets the token totalSupply value from VM storage func (t Token) GetSupply(ctx storage.Context) int { return getIntFromDB(ctx, []byte(t.CirculationKey)) } // BalanceOf gets the token balance of a specific address func (t Token) BalanceOf(ctx storage.Context, holder []byte) int { return getIntFromDB(ctx, holder) } // Transfer token from one user to another func (t Token) Transfer(ctx storage.Context, from, to interop.Hash160, amount int, data interface{}) bool { amountFrom := t.CanTransfer(ctx, from, to, amount) if amountFrom == -1 { return false } if amountFrom == 0 { storage.Delete(ctx, from) } if amountFrom > 0 { diff := amountFrom - amount storage.Put(ctx, from, diff) } amountTo := getIntFromDB(ctx, to) totalAmountTo := amountTo + amount storage.Put(ctx, to, totalAmountTo) runtime.Notify("Transfer", from, to, amount) return true } // CanTransfer returns the amount it can transfer func (t Token) CanTransfer(ctx storage.Context, from []byte, to []byte, amount int) int { if len(to) != 20 || !IsUsableAddress(from) { return -1 } amountFrom := getIntFromDB(ctx, from) if amountFrom < amount { return -1 } // Tell Transfer the result is equal - special case since it uses Delete if amountFrom == amount { return 0 } // return amountFrom value back to Transfer, reduces extra Get return amountFrom } // IsUsableAddress checks if the sender is either the correct NEO address or SC address func IsUsableAddress(addr []byte) bool { if len(addr) == 20 { if runtime.CheckWitness(addr) { return true } // Check if a smart contract is calling scripthash callingScriptHash := runtime.GetCallingScriptHash() if util.Equals(callingScriptHash, addr) { return true } } return false } // Mint initial supply of tokens func (t Token) Mint(ctx storage.Context, to interop.Hash160) bool { if !IsUsableAddress(t.Owner) { return false } minted := storage.Get(ctx, []byte("minted")) if minted != nil && minted.(bool) == true { return false } storage.Put(ctx, to, t.TotalSupply) storage.Put(ctx, []byte("minted"), true) storage.Put(ctx, []byte(t.CirculationKey), t.TotalSupply) var from interop.Hash160 runtime.Notify("Transfer", from, to, t.TotalSupply) return true }