plugeth/core/state_transition.go

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// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
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//
// The go-ethereum library is free software: you can redistribute it and/or modify
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// 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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// 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/>.
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package core
import (
"errors"
"math/big"
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"github.com/ethereum/go-ethereum/common"
common: move big integer math to common/math (#3699) * common: remove CurrencyToString Move denomination values to params instead. * common: delete dead code * common: move big integer operations to common/math This commit consolidates all big integer operations into common/math and adds tests and documentation. There should be no change in semantics for BigPow, BigMin, BigMax, S256, U256, Exp and their behaviour is now locked in by tests. The BigD, BytesToBig and Bytes2Big functions don't provide additional value, all uses are replaced by new(big.Int).SetBytes(). BigToBytes is now called PaddedBigBytes, its minimum output size parameter is now specified as the number of bytes instead of bits. The single use of this function is in the EVM's MSTORE instruction. Big and String2Big are replaced by ParseBig, which is slightly stricter. It previously accepted leading zeros for hexadecimal inputs but treated decimal inputs as octal if a leading zero digit was present. ParseUint64 is used in places where String2Big was used to decode a uint64. The new functions MustParseBig and MustParseUint64 are now used in many places where parsing errors were previously ignored. * common: delete unused big integer variables * accounts/abi: replace uses of BytesToBig with use of encoding/binary * common: remove BytesToBig * common: remove Bytes2Big * common: remove BigTrue * cmd/utils: add BigFlag and use it for error-checked integer flags While here, remove environment variable processing for DirectoryFlag because we don't use it. * core: add missing error checks in genesis block parser * common: remove String2Big * cmd/evm: use utils.BigFlag * common/math: check for 256 bit overflow in ParseBig This is supposed to prevent silent overflow/truncation of values in the genesis block JSON. Without this check, a genesis block that set a balance larger than 256 bits would lead to weird behaviour in the VM. * cmd/utils: fixup import
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"github.com/ethereum/go-ethereum/common/math"
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"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")
)
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/*
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 {
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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
}
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// IntrinsicGas computes the 'intrinsic gas' for a message
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// 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)
}
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if len(data) > 0 {
var nz int64
for _, byt := range data {
if byt != 0 {
nz++
}
}
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m := big.NewInt(nz)
m.Mul(m, new(big.Int).SetUint64(params.TxDataNonZeroGas))
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igas.Add(igas, m)
m.SetInt64(int64(len(data)) - nz)
m.Mul(m, new(big.Int).SetUint64(params.TxDataZeroGas))
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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{
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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()
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// Make sure this transaction's nonce is correct
if msg.CheckNonce() {
nonce := st.state.GetNonce(sender.Address())
if nonce < msg.Nonce() {
return ErrNonceTooHigh
} else if nonce > msg.Nonce() {
return ErrNonceTooLow
}
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}
return st.buyGas()
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}
// 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 {
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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)
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} else {
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// 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))
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return ret, requiredGas, st.gasUsed(), vmerr != nil, err
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}
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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))
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// 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))
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}
func (st *StateTransition) gasUsed() *big.Int {
return new(big.Int).Sub(st.initialGas, new(big.Int).SetUint64(st.gas))
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}