package vm import ( "bytes" "errors" "fmt" "math/big" . "github.com/tendermint/tendermint/common" "github.com/tendermint/tendermint/events" "github.com/tendermint/tendermint/types" "github.com/tendermint/tendermint/vm/sha3" ) var ( ErrUnknownAddress = errors.New("Unknown address") ErrInsufficientBalance = errors.New("Insufficient balance") ErrInvalidJumpDest = errors.New("Invalid jump dest") ErrInsufficientGas = errors.New("Insuffient gas") ErrMemoryOutOfBounds = errors.New("Memory out of bounds") ErrCodeOutOfBounds = errors.New("Code out of bounds") ErrInputOutOfBounds = errors.New("Input out of bounds") ErrCallStackOverflow = errors.New("Call stack overflow") ErrCallStackUnderflow = errors.New("Call stack underflow") ErrDataStackOverflow = errors.New("Data stack overflow") ErrDataStackUnderflow = errors.New("Data stack underflow") ErrInvalidContract = errors.New("Invalid contract") ) type Debug bool const ( dataStackCapacity = 1024 callStackCapacity = 100 // TODO ensure usage. memoryCapacity = 1024 * 1024 // 1 MB dbg Debug = true ) func (d Debug) Printf(s string, a ...interface{}) { if d { fmt.Printf(s, a...) } } type VM struct { appState AppState params Params origin Word256 txid []byte callDepth int evc events.Fireable } func NewVM(appState AppState, params Params, origin Word256, txid []byte) *VM { return &VM{ appState: appState, params: params, origin: origin, callDepth: 0, txid: txid, } } // satisfies events.Eventable func (vm *VM) SetFireable(evc events.Fireable) { vm.evc = evc } // CONTRACT appState is aware of caller and callee, so we can just mutate them. // value: To be transferred from caller to callee. Refunded upon error. // gas: Available gas. No refunds for gas. func (vm *VM) Call(caller, callee *Account, code, input []byte, value uint64, gas *uint64) (output []byte, err error) { if len(code) == 0 { panic("Call() requires code") } if err = transfer(caller, callee, value); err != nil { return } vm.callDepth += 1 output, err = vm.call(caller, callee, code, input, value, gas) vm.callDepth -= 1 exception := "" if err != nil { exception = err.Error() err := transfer(callee, caller, value) if err != nil { panic("Could not return value to caller") } } // if callDepth is 0 the event is fired from ExecTx (along with the Input event) // otherwise, we fire from here. if vm.callDepth != 0 && vm.evc != nil { vm.evc.FireEvent(types.EventStringAccReceive(callee.Address.Postfix(20)), types.EventMsgCall{ &types.CallData{caller.Address.Postfix(20), callee.Address.Postfix(20), input, value, *gas}, vm.origin.Postfix(20), vm.txid, output, exception, }) } return } // Just like Call() but does not transfer 'value' or modify the callDepth. func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, gas *uint64) (output []byte, err error) { dbg.Printf("(%d) (%X) %X (code=%d) gas: %v (d) %X\n", vm.callDepth, caller.Address[:4], callee.Address, len(callee.Code), *gas, input) var ( pc uint64 = 0 stack = NewStack(dataStackCapacity, gas, &err) memory = make([]byte, memoryCapacity) ok = false // convenience ) for { // If there is an error, return if err != nil { return nil, err } var op = codeGetOp(code, pc) dbg.Printf("(pc) %-3d (op) %-14s (st) %-4d ", pc, op.String(), stack.Len()) switch op { case STOP: // 0x00 return nil, nil case ADD: // 0x01 x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) sum := new(big.Int).Add(xb, yb) res := LeftPadWord256(U256(sum).Bytes()) stack.Push(res) dbg.Printf(" %v + %v = %v (%X)\n", xb, yb, sum, res) case MUL: // 0x02 x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) prod := new(big.Int).Mul(xb, yb) res := LeftPadWord256(U256(prod).Bytes()) stack.Push(res) dbg.Printf(" %v * %v = %v (%X)\n", xb, yb, prod, res) case SUB: // 0x03 x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) diff := new(big.Int).Sub(xb, yb) res := LeftPadWord256(U256(diff).Bytes()) stack.Push(res) dbg.Printf(" %v - %v = %v (%X)\n", xb, yb, diff, res) case DIV: // 0x04 x, y := stack.Pop(), stack.Pop() if y.IsZero() { stack.Push(Zero256) dbg.Printf(" %x / %x = %v\n", x, y, 0) } else { xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) div := new(big.Int).Div(xb, yb) res := LeftPadWord256(U256(div).Bytes()) stack.Push(res) dbg.Printf(" %v / %v = %v (%X)\n", xb, yb, div, res) } case SDIV: // 0x05 x, y := stack.Pop(), stack.Pop() if y.IsZero() { stack.Push(Zero256) dbg.Printf(" %x / %x = %v\n", x, y, 0) } else { xb := S256(new(big.Int).SetBytes(x[:])) yb := S256(new(big.Int).SetBytes(y[:])) div := new(big.Int).Div(xb, yb) res := LeftPadWord256(U256(div).Bytes()) stack.Push(res) dbg.Printf(" %v / %v = %v (%X)\n", xb, yb, div, res) } case MOD: // 0x06 x, y := stack.Pop(), stack.Pop() if y.IsZero() { stack.Push(Zero256) dbg.Printf(" %v %% %v = %v\n", x, y, 0) } else { xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) mod := new(big.Int).Mod(xb, yb) res := LeftPadWord256(U256(mod).Bytes()) stack.Push(res) dbg.Printf(" %v %% %v = %v (%X)\n", xb, yb, mod, res) } case SMOD: // 0x07 x, y := stack.Pop(), stack.Pop() if y.IsZero() { stack.Push(Zero256) dbg.Printf(" %v %% %v = %v\n", x, y, 0) } else { xb := S256(new(big.Int).SetBytes(x[:])) yb := S256(new(big.Int).SetBytes(y[:])) mod := new(big.Int).Mod(xb, yb) res := LeftPadWord256(U256(mod).Bytes()) stack.Push(res) dbg.Printf(" %v %% %v = %v (%X)\n", xb, yb, mod, res) } case ADDMOD: // 0x08 x, y, z := stack.Pop(), stack.Pop(), stack.Pop() if z.IsZero() { stack.Push(Zero256) dbg.Printf(" %v %% %v = %v\n", x, y, 0) } else { xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) zb := new(big.Int).SetBytes(z[:]) add := new(big.Int).Add(xb, yb) mod := new(big.Int).Mod(add, zb) res := LeftPadWord256(U256(mod).Bytes()) stack.Push(res) dbg.Printf(" %v + %v %% %v = %v (%X)\n", xb, yb, zb, mod, res) } case MULMOD: // 0x09 x, y, z := stack.Pop(), stack.Pop(), stack.Pop() if z.IsZero() { stack.Push(Zero256) dbg.Printf(" %v %% %v = %v\n", x, y, 0) } else { xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) zb := new(big.Int).SetBytes(z[:]) mul := new(big.Int).Mul(xb, yb) mod := new(big.Int).Mod(mul, zb) res := LeftPadWord256(U256(mod).Bytes()) stack.Push(res) dbg.Printf(" %v * %v %% %v = %v (%X)\n", xb, yb, zb, mod, res) } case EXP: // 0x0A x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) pow := new(big.Int).Exp(xb, yb, big.NewInt(0)) res := LeftPadWord256(U256(pow).Bytes()) stack.Push(res) dbg.Printf(" %v ** %v = %v (%X)\n", xb, yb, pow, res) case SIGNEXTEND: // 0x0B back := stack.Pop() backb := new(big.Int).SetBytes(back[:]) if backb.Cmp(big.NewInt(31)) < 0 { bit := uint(backb.Uint64()*8 + 7) num := stack.Pop() numb := new(big.Int).SetBytes(num[:]) mask := new(big.Int).Lsh(big.NewInt(1), bit) mask.Sub(mask, big.NewInt(1)) if numb.Bit(int(bit)) == 1 { numb.Or(numb, mask.Not(mask)) } else { numb.Add(numb, mask) } res := LeftPadWord256(U256(numb).Bytes()) dbg.Printf(" = %v (%X)", numb, res) stack.Push(res) } case LT: // 0x10 x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) if xb.Cmp(yb) < 0 { stack.Push64(1) dbg.Printf(" %v < %v = %v\n", xb, yb, 1) } else { stack.Push(Zero256) dbg.Printf(" %v < %v = %v\n", xb, yb, 0) } case GT: // 0x11 x, y := stack.Pop(), stack.Pop() xb := new(big.Int).SetBytes(x[:]) yb := new(big.Int).SetBytes(y[:]) if xb.Cmp(yb) > 0 { stack.Push64(1) dbg.Printf(" %v > %v = %v\n", xb, yb, 1) } else { stack.Push(Zero256) dbg.Printf(" %v > %v = %v\n", xb, yb, 0) } case SLT: // 0x12 x, y := stack.Pop(), stack.Pop() xb := S256(new(big.Int).SetBytes(x[:])) yb := S256(new(big.Int).SetBytes(y[:])) if xb.Cmp(yb) < 0 { stack.Push64(1) dbg.Printf(" %v < %v = %v\n", xb, yb, 1) } else { stack.Push(Zero256) dbg.Printf(" %v < %v = %v\n", xb, yb, 0) } case SGT: // 0x13 x, y := stack.Pop(), stack.Pop() xb := S256(new(big.Int).SetBytes(x[:])) yb := S256(new(big.Int).SetBytes(y[:])) if xb.Cmp(yb) > 0 { stack.Push64(1) dbg.Printf(" %v > %v = %v\n", xb, yb, 1) } else { stack.Push(Zero256) dbg.Printf(" %v > %v = %v\n", xb, yb, 0) } case EQ: // 0x14 x, y := stack.Pop(), stack.Pop() if bytes.Equal(x[:], y[:]) { stack.Push64(1) dbg.Printf(" %X == %X = %v\n", x, y, 1) } else { stack.Push(Zero256) dbg.Printf(" %X == %X = %v\n", x, y, 0) } case ISZERO: // 0x15 x := stack.Pop() if x.IsZero() { stack.Push64(1) dbg.Printf(" %v == 0 = %v\n", x, 1) } else { stack.Push(Zero256) dbg.Printf(" %v == 0 = %v\n", x, 0) } case AND: // 0x16 x, y := stack.Pop(), stack.Pop() z := [32]byte{} for i := 0; i < 32; i++ { z[i] = x[i] & y[i] } stack.Push(z) dbg.Printf(" %X & %X = %X\n", x, y, z) case OR: // 0x17 x, y := stack.Pop(), stack.Pop() z := [32]byte{} for i := 0; i < 32; i++ { z[i] = x[i] | y[i] } stack.Push(z) dbg.Printf(" %X | %X = %X\n", x, y, z) case XOR: // 0x18 x, y := stack.Pop(), stack.Pop() z := [32]byte{} for i := 0; i < 32; i++ { z[i] = x[i] ^ y[i] } stack.Push(z) dbg.Printf(" %X ^ %X = %X\n", x, y, z) case NOT: // 0x19 x := stack.Pop() z := [32]byte{} for i := 0; i < 32; i++ { z[i] = ^x[i] } stack.Push(z) dbg.Printf(" !%X = %X\n", x, z) case BYTE: // 0x1A idx, val := stack.Pop64(), stack.Pop() res := byte(0) if idx < 32 { res = val[idx] } stack.Push64(uint64(res)) dbg.Printf(" => 0x%X\n", res) case SHA3: // 0x20 if ok = useGas(gas, GasSha3); !ok { return nil, firstErr(err, ErrInsufficientGas) } offset, size := stack.Pop64(), stack.Pop64() data, ok := subslice(memory, offset, size) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } data = sha3.Sha3(data) stack.PushBytes(data) dbg.Printf(" => (%v) %X\n", size, data) case ADDRESS: // 0x30 stack.Push(callee.Address) dbg.Printf(" => %X\n", callee.Address) case BALANCE: // 0x31 addr := stack.Pop() if ok = useGas(gas, GasGetAccount); !ok { return nil, firstErr(err, ErrInsufficientGas) } acc := vm.appState.GetAccount(addr) if acc == nil { return nil, firstErr(err, ErrUnknownAddress) } balance := acc.Balance stack.Push64(balance) dbg.Printf(" => %v (%X)\n", balance, addr) case ORIGIN: // 0x32 stack.Push(vm.origin) dbg.Printf(" => %X\n", vm.origin) case CALLER: // 0x33 stack.Push(caller.Address) dbg.Printf(" => %X\n", caller.Address) case CALLVALUE: // 0x34 stack.Push64(value) dbg.Printf(" => %v\n", value) case CALLDATALOAD: // 0x35 offset := stack.Pop64() data, ok := subslice(input, offset, 32) if !ok { return nil, firstErr(err, ErrInputOutOfBounds) } res := LeftPadWord256(data) stack.Push(res) dbg.Printf(" => 0x%X\n", res) case CALLDATASIZE: // 0x36 stack.Push64(uint64(len(input))) dbg.Printf(" => %d\n", len(input)) case CALLDATACOPY: // 0x37 memOff := stack.Pop64() inputOff := stack.Pop64() length := stack.Pop64() data, ok := subslice(input, inputOff, length) if !ok { return nil, firstErr(err, ErrInputOutOfBounds) } dest, ok := subslice(memory, memOff, length) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } copy(dest, data) dbg.Printf(" => [%v, %v, %v] %X\n", memOff, inputOff, length, data) case CODESIZE: // 0x38 l := uint64(len(code)) stack.Push64(l) dbg.Printf(" => %d\n", l) case CODECOPY: // 0x39 memOff := stack.Pop64() codeOff := stack.Pop64() length := stack.Pop64() data, ok := subslice(code, codeOff, length) if !ok { return nil, firstErr(err, ErrCodeOutOfBounds) } dest, ok := subslice(memory, memOff, length) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } copy(dest, data) dbg.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data) case GASPRICE_DEPRECATED: // 0x3A stack.Push(Zero256) dbg.Printf(" => %X (GASPRICE IS DEPRECATED)\n") case EXTCODESIZE: // 0x3B addr := stack.Pop() if ok = useGas(gas, GasGetAccount); !ok { return nil, firstErr(err, ErrInsufficientGas) } acc := vm.appState.GetAccount(addr) if acc == nil { return nil, firstErr(err, ErrUnknownAddress) } code := acc.Code l := uint64(len(code)) stack.Push64(l) dbg.Printf(" => %d\n", l) case EXTCODECOPY: // 0x3C addr := stack.Pop() if ok = useGas(gas, GasGetAccount); !ok { return nil, firstErr(err, ErrInsufficientGas) } acc := vm.appState.GetAccount(addr) if acc == nil { return nil, firstErr(err, ErrUnknownAddress) } code := acc.Code memOff := stack.Pop64() codeOff := stack.Pop64() length := stack.Pop64() data, ok := subslice(code, codeOff, length) if !ok { return nil, firstErr(err, ErrCodeOutOfBounds) } dest, ok := subslice(memory, memOff, length) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } copy(dest, data) dbg.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data) case BLOCKHASH: // 0x40 stack.Push(Zero256) dbg.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes()) case COINBASE: // 0x41 stack.Push(Zero256) dbg.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes()) case TIMESTAMP: // 0x42 time := vm.params.BlockTime stack.Push64(uint64(time)) dbg.Printf(" => 0x%X\n", time) case BLOCKHEIGHT: // 0x43 number := uint64(vm.params.BlockHeight) stack.Push64(number) dbg.Printf(" => 0x%X\n", number) case GASLIMIT: // 0x45 stack.Push64(vm.params.GasLimit) dbg.Printf(" => %v\n", vm.params.GasLimit) case POP: // 0x50 stack.Pop() dbg.Printf(" => %v\n", vm.params.GasLimit) case MLOAD: // 0x51 offset := stack.Pop64() data, ok := subslice(memory, offset, 32) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } stack.Push(LeftPadWord256(data)) dbg.Printf(" => 0x%X\n", data) case MSTORE: // 0x52 offset, data := stack.Pop64(), stack.Pop() dest, ok := subslice(memory, offset, 32) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } copy(dest, data[:]) dbg.Printf(" => 0x%X\n", data) case MSTORE8: // 0x53 offset, val := stack.Pop64(), byte(stack.Pop64()&0xFF) if len(memory) <= int(offset) { return nil, firstErr(err, ErrMemoryOutOfBounds) } memory[offset] = val dbg.Printf(" => [%v] 0x%X\n", offset, val) case SLOAD: // 0x54 loc := stack.Pop() data := vm.appState.GetStorage(callee.Address, loc) stack.Push(data) dbg.Printf(" {0x%X : 0x%X}\n", loc, data) case SSTORE: // 0x55 loc, data := stack.Pop(), stack.Pop() vm.appState.SetStorage(callee.Address, loc, data) useGas(gas, GasStorageUpdate) dbg.Printf(" {0x%X : 0x%X}\n", loc, data) case JUMP: // 0x56 err = jump(code, stack.Pop64(), &pc) continue case JUMPI: // 0x57 pos, cond := stack.Pop64(), stack.Pop() if !cond.IsZero() { err = jump(code, pos, &pc) continue } dbg.Printf(" ~> false\n") case PC: // 0x58 stack.Push64(pc) case MSIZE: // 0x59 stack.Push64(uint64(len(memory))) case GAS: // 0x5A stack.Push64(*gas) dbg.Printf(" => %X\n", *gas) case JUMPDEST: // 0x5B dbg.Printf("\n") // Do nothing case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32: a := uint64(op - PUSH1 + 1) codeSegment, ok := subslice(code, pc+1, a) if !ok { return nil, firstErr(err, ErrCodeOutOfBounds) } res := LeftPadWord256(codeSegment) stack.Push(res) pc += a dbg.Printf(" => 0x%X\n", res) stack.Print(10) case DUP1, DUP2, DUP3, DUP4, DUP5, DUP6, DUP7, DUP8, DUP9, DUP10, DUP11, DUP12, DUP13, DUP14, DUP15, DUP16: n := int(op - DUP1 + 1) stack.Dup(n) dbg.Printf(" => [%d] 0x%X\n", n, stack.Peek().Bytes()) case SWAP1, SWAP2, SWAP3, SWAP4, SWAP5, SWAP6, SWAP7, SWAP8, SWAP9, SWAP10, SWAP11, SWAP12, SWAP13, SWAP14, SWAP15, SWAP16: n := int(op - SWAP1 + 2) stack.Swap(n) dbg.Printf(" => [%d] %X\n", n, stack.Peek()) stack.Print(10) case LOG0, LOG1, LOG2, LOG3, LOG4: n := int(op - LOG0) topics := make([]Word256, n) offset, size := stack.Pop64(), stack.Pop64() for i := 0; i < n; i++ { topics[i] = stack.Pop() } data, ok := subslice(memory, offset, size) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } log := &Log{ callee.Address, topics, data, vm.params.BlockHeight, } vm.appState.AddLog(log) dbg.Printf(" => %v\n", log) case CREATE: // 0xF0 contractValue := stack.Pop64() offset, size := stack.Pop64(), stack.Pop64() input, ok := subslice(memory, offset, size) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } // Check balance if callee.Balance < contractValue { return nil, firstErr(err, ErrInsufficientBalance) } // TODO charge for gas to create account _ the code length * GasCreateByte newAccount := vm.appState.CreateAccount(callee) // Run the input to get the contract code. ret, err_ := vm.Call(callee, newAccount, input, input, contractValue, gas) if err_ != nil { stack.Push(Zero256) } else { newAccount.Code = ret // Set the code stack.Push(newAccount.Address) } case CALL, CALLCODE: // 0xF1, 0xF2 gasLimit := stack.Pop64() addr, value := stack.Pop(), stack.Pop64() inOffset, inSize := stack.Pop64(), stack.Pop64() // inputs retOffset, retSize := stack.Pop64(), stack.Pop64() // outputs dbg.Printf(" => %X\n", addr) // Get the arguments from the memory args, ok := subslice(memory, inOffset, inSize) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } // Ensure that gasLimit is reasonable if *gas < gasLimit { return nil, firstErr(err, ErrInsufficientGas) } else { *gas -= gasLimit // NOTE: we will return any used gas later. } // Begin execution var ret []byte var err error if nativeContract := nativeContracts[addr]; nativeContract != nil { // Native contract ret, err = nativeContract(args, &gasLimit) } else { // EVM contract if ok = useGas(gas, GasGetAccount); !ok { return nil, firstErr(err, ErrInsufficientGas) } acc := vm.appState.GetAccount(addr) if acc == nil { return nil, firstErr(err, ErrUnknownAddress) } if op == CALLCODE { ret, err = vm.Call(callee, callee, acc.Code, args, value, gas) } else { ret, err = vm.Call(callee, acc, acc.Code, args, value, gas) } } // Push result if err != nil { stack.Push(Zero256) } else { stack.Push(One256) dest, ok := subslice(memory, retOffset, retSize) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } copy(dest, ret) } // Handle remaining gas. *gas += gasLimit dbg.Printf("resume %X (%v)\n", callee.Address, gas) case RETURN: // 0xF3 offset, size := stack.Pop64(), stack.Pop64() ret, ok := subslice(memory, offset, size) if !ok { return nil, firstErr(err, ErrMemoryOutOfBounds) } dbg.Printf(" => [%v, %v] (%d) 0x%X\n", offset, size, len(ret), ret) return ret, nil case SUICIDE: // 0xFF addr := stack.Pop() if ok = useGas(gas, GasGetAccount); !ok { return nil, firstErr(err, ErrInsufficientGas) } // TODO if the receiver is , then make it the fee. receiver := vm.appState.GetAccount(addr) if receiver == nil { return nil, firstErr(err, ErrUnknownAddress) } balance := callee.Balance receiver.Balance += balance vm.appState.UpdateAccount(receiver) vm.appState.RemoveAccount(callee) dbg.Printf(" => (%X) %v\n", addr[:4], balance) fallthrough default: dbg.Printf("(pc) %-3v Invalid opcode %X\n", pc, op) panic(fmt.Errorf("Invalid opcode %X", op)) } pc++ } } func subslice(data []byte, offset, length uint64) (ret []byte, ok bool) { size := uint64(len(data)) if size < offset { return nil, false } else if size < offset+length { ret, ok = data[offset:], true ret = RightPadBytes(ret, 32) } else { ret, ok = data[offset:offset+length], true } return } func rightMostBytes(data []byte, n int) []byte { size := MinInt(len(data), n) offset := len(data) - size return data[offset:] } func codeGetOp(code []byte, n uint64) OpCode { if uint64(len(code)) <= n { return OpCode(0) // stop } else { return OpCode(code[n]) } } func jump(code []byte, to uint64, pc *uint64) (err error) { dest := codeGetOp(code, to) if dest != JUMPDEST { dbg.Printf(" ~> %v invalid jump dest %v\n", to, dest) return ErrInvalidJumpDest } dbg.Printf(" ~> %v\n", to) *pc = to return nil } func firstErr(errA, errB error) error { if errA != nil { return errA } else { return errB } } func useGas(gas *uint64, gasToUse uint64) bool { if *gas > gasToUse { *gas -= gasToUse return true } else { return false } } func transfer(from, to *Account, amount uint64) error { if from.Balance < amount { return ErrInsufficientBalance } else { from.Balance -= amount to.Balance += amount return nil } }