// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package core
import (
"errors"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/params"
)
var (
Big0 = big.NewInt(0)
errInsufficientBalanceForGas = errors.New("insufficient balance to pay for gas")
)
/*
The State Transitioning Model
A state transition is a change made when a transaction is applied to the current world state
The state transitioning model does all all the necessary work to work out a valid new state root.
1) Nonce handling
2) Pre pay gas
3) Create a new state object if the recipient is \0*32
4) Value transfer
== If contract creation ==
4a) Attempt to run transaction data
4b) If valid, use result as code for the new state object
== end ==
5) Run Script section
6) Derive new state root
*/
type StateTransition struct {
gp *GasPool
msg Message
gas uint64
gasPrice *big.Int
initialGas *big.Int
value *big.Int
data []byte
state vm.StateDB
evm *vm.EVM
}
// Message represents a message sent to a contract.
type Message interface {
From() common.Address
//FromFrontier() (common.Address, error)
To() *common.Address
GasPrice() *big.Int
Gas() *big.Int
Value() *big.Int
Nonce() uint64
CheckNonce() bool
Data() []byte
}
// IntrinsicGas computes the 'intrinsic gas' for a message
// with the given data.
//
// TODO convert to uint64
func IntrinsicGas(data []byte, contractCreation, homestead bool) *big.Int {
igas := new(big.Int)
if contractCreation && homestead {
igas.SetUint64(params.TxGasContractCreation)
} else {
igas.SetUint64(params.TxGas)
}
if len(data) > 0 {
var nz int64
for _, byt := range data {
if byt != 0 {
nz++
}
}
m := big.NewInt(nz)
m.Mul(m, new(big.Int).SetUint64(params.TxDataNonZeroGas))
igas.Add(igas, m)
m.SetInt64(int64(len(data)) - nz)
m.Mul(m, new(big.Int).SetUint64(params.TxDataZeroGas))
igas.Add(igas, m)
}
return igas
}
// NewStateTransition initialises and returns a new state transition object.
func NewStateTransition(evm *vm.EVM, msg Message, gp *GasPool) *StateTransition {
return &StateTransition{
gp: gp,
evm: evm,
msg: msg,
gasPrice: msg.GasPrice(),
initialGas: new(big.Int),
value: msg.Value(),
data: msg.Data(),
state: evm.StateDB,
}
}
// ApplyMessage computes the new state by applying the given message
// against the old state within the environment.
//
// ApplyMessage returns the bytes returned by any EVM execution (if it took place),
// the gas used (which includes gas refunds) and an error if it failed. An error always
// indicates a core error meaning that the message would always fail for that particular
// state and would never be accepted within a block.
func ApplyMessage(evm *vm.EVM, msg Message, gp *GasPool) ([]byte, *big.Int, bool, error) {
st := NewStateTransition(evm, msg, gp)
ret, _, gasUsed, failed, err := st.TransitionDb()
return ret, gasUsed, failed, err
}
func (st *StateTransition) from() vm.AccountRef {
f := st.msg.From()
if !st.state.Exist(f) {
st.state.CreateAccount(f)
}
return vm.AccountRef(f)
}
func (st *StateTransition) to() vm.AccountRef {
if st.msg == nil {
return vm.AccountRef{}
}
to := st.msg.To()
if to == nil {
return vm.AccountRef{} // contract creation
}
reference := vm.AccountRef(*to)
if !st.state.Exist(*to) {
st.state.CreateAccount(*to)
}
return reference
}
func (st *StateTransition) useGas(amount uint64) error {
if st.gas < amount {
return vm.ErrOutOfGas
}
st.gas -= amount
return nil
}
func (st *StateTransition) buyGas() error {
mgas := st.msg.Gas()
if mgas.BitLen() > 64 {
return vm.ErrOutOfGas
}
mgval := new(big.Int).Mul(mgas, st.gasPrice)
var (
state = st.state
sender = st.from()
)
if state.GetBalance(sender.Address()).Cmp(mgval) < 0 {
return errInsufficientBalanceForGas
}
if err := st.gp.SubGas(mgas); err != nil {
return err
}
st.gas += mgas.Uint64()
st.initialGas.Set(mgas)
state.SubBalance(sender.Address(), mgval)
return nil
}
func (st *StateTransition) preCheck() error {
msg := st.msg
sender := st.from()
// Make sure this transaction's nonce is correct
if msg.CheckNonce() {
if n := st.state.GetNonce(sender.Address()); n != msg.Nonce() {
return fmt.Errorf("invalid nonce: have %d, expected %d", msg.Nonce(), n)
}
}
return st.buyGas()
}
// TransitionDb will transition the state by applying the current message and returning the result
// including the required gas for the operation as well as the used gas. It returns an error if it
// failed. An error indicates a consensus issue.
func (st *StateTransition) TransitionDb() (ret []byte, requiredGas, usedGas *big.Int, failed bool, err error) {
if err = st.preCheck(); err != nil {
return
}
msg := st.msg
sender := st.from() // err checked in preCheck
homestead := st.evm.ChainConfig().IsHomestead(st.evm.BlockNumber)
contractCreation := msg.To() == nil
// Pay intrinsic gas
// TODO convert to uint64
intrinsicGas := IntrinsicGas(st.data, contractCreation, homestead)
if intrinsicGas.BitLen() > 64 {
return nil, nil, nil, false, vm.ErrOutOfGas
}
if err = st.useGas(intrinsicGas.Uint64()); err != nil {
return nil, nil, nil, false, err
}
var (
evm = st.evm
// vm errors do not effect consensus and are therefor
// not assigned to err, except for insufficient balance
// error.
vmerr error
)
if contractCreation {
ret, _, st.gas, vmerr = evm.Create(sender, st.data, st.gas, st.value)
} else {
// Increment the nonce for the next transaction
st.state.SetNonce(sender.Address(), st.state.GetNonce(sender.Address())+1)
ret, st.gas, vmerr = evm.Call(sender, st.to().Address(), st.data, st.gas, st.value)
}
if vmerr != nil {
log.Debug("VM returned with error", "err", vmerr)
// The only possible consensus-error would be if there wasn't
// sufficient balance to make the transfer happen. The first
// balance transfer may never fail.
if vmerr == vm.ErrInsufficientBalance {
return nil, nil, nil, false, vmerr
}
}
requiredGas = new(big.Int).Set(st.gasUsed())
st.refundGas()
st.state.AddBalance(st.evm.Coinbase, new(big.Int).Mul(st.gasUsed(), st.gasPrice))
return ret, requiredGas, st.gasUsed(), vmerr != nil, err
}
func (st *StateTransition) refundGas() {
// Return eth for remaining gas to the sender account,
// exchanged at the original rate.
sender := st.from() // err already checked
remaining := new(big.Int).Mul(new(big.Int).SetUint64(st.gas), st.gasPrice)
st.state.AddBalance(sender.Address(), remaining)
// Apply refund counter, capped to half of the used gas.
uhalf := remaining.Div(st.gasUsed(), common.Big2)
refund := math.BigMin(uhalf, st.state.GetRefund())
st.gas += refund.Uint64()
st.state.AddBalance(sender.Address(), refund.Mul(refund, st.gasPrice))
// Also return remaining gas to the block gas counter so it is
// available for the next transaction.
st.gp.AddGas(new(big.Int).SetUint64(st.gas))
}
func (st *StateTransition) gasUsed() *big.Int {
return new(big.Int).Sub(st.initialGas, new(big.Int).SetUint64(st.gas))
}