path: root/core/execution.go

// 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 (
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/vm"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/params"
)

// Call executes within the given contract
func Call(env vm.Environment, caller vm.ContractRef, addr common.Address, input []byte, gas, gasPrice, value *big.Int) (ret []byte, err error) {
    ret, _, err = exec(env, caller, &addr, &addr, input, env.Db().GetCode(addr), gas, gasPrice, value)
    return ret, err
}

// CallCode executes the given address' code as the given contract address
func CallCode(env vm.Environment, caller vm.ContractRef, addr common.Address, input []byte, gas, gasPrice, value *big.Int) (ret []byte, err error) {
    callerAddr := caller.Address()
    ret, _, err = exec(env, caller, &callerAddr, &addr, input, env.Db().GetCode(addr), gas, gasPrice, value)
    return ret, err
}

// DelegateCall is equivalent to CallCode except that sender and value propagates from parent scope to child scope
func DelegateCall(env vm.Environment, caller vm.ContractRef, addr common.Address, input []byte, gas, gasPrice *big.Int) (ret []byte, err error) {
    callerAddr := caller.Address()
    originAddr := env.Origin()
    callerValue := caller.Value()
    ret, _, err = execDelegateCall(env, caller, &originAddr, &callerAddr, &addr, input, env.Db().GetCode(addr), gas, gasPrice, callerValue)
    return ret, err
}

// Create creates a new contract with the given code
func Create(env vm.Environment, caller vm.ContractRef, code []byte, gas, gasPrice, value *big.Int) (ret []byte, address common.Address, err error) {
    ret, address, err = exec(env, caller, nil, nil, nil, code, gas, gasPrice, value)
    // Here we get an error if we run into maximum stack depth,
    // See: https://github.com/ethereum/yellowpaper/pull/131
    // and YP definitions for CREATE instruction
    if err != nil {
        return nil, address, err
    }
    return ret, address, err
}

func exec(env vm.Environment, caller vm.ContractRef, address, codeAddr *common.Address, input, code []byte, gas, gasPrice, value *big.Int) (ret []byte, addr common.Address, err error) {
    evm := env.Vm()
    // Depth check execution. Fail if we're trying to execute above the
    // limit.
    if env.Depth() > int(params.CallCreateDepth.Int64()) {
        caller.ReturnGas(gas, gasPrice)

        return nil, common.Address{}, vm.DepthError
    }

    if !env.CanTransfer(caller.Address(), value) {
        caller.ReturnGas(gas, gasPrice)

        return nil, common.Address{}, ValueTransferErr("insufficient funds to transfer value. Req %v, has %v", value, env.Db().GetBalance(caller.Address()))
    }

    var createAccount bool
    if address == nil {
        // Create a new account on the state
        nonce := env.Db().GetNonce(caller.Address())
        env.Db().SetNonce(caller.Address(), nonce+1)
        addr = crypto.CreateAddress(caller.Address(), nonce)
        address = &addr
        createAccount = true
    }

    snapshotPreTransfer := env.MakeSnapshot()
    var (
        from = env.Db().GetAccount(caller.Address())
        to   vm.Account
    )
    if createAccount {
        to = env.Db().CreateAccount(*address)
    } else {
        if !env.Db().Exist(*address) {
            to = env.Db().CreateAccount(*address)
        } else {
            to = env.Db().GetAccount(*address)
        }
    }
    env.Transfer(from, to, value)

    // initialise a new contract and set the code that is to be used by the
    // EVM. The contract is a scoped environment for this execution context
    // only.
    contract := vm.NewContract(caller, to, value, gas, gasPrice)
    contract.SetCallCode(codeAddr, code)
    defer contract.Finalise()

    ret, err = evm.Run(contract, input)
    // if the contract creation ran successfully and no errors were returned
    // calculate the gas required to store the code. If the code could not
    // be stored due to not enough gas set an error and let it be handled
    // by the error checking condition below.
    if err == nil && createAccount {
        dataGas := big.NewInt(int64(len(ret)))
        dataGas.Mul(dataGas, params.CreateDataGas)
        if contract.UseGas(dataGas) {
            env.Db().SetCode(*address, ret)
        } else {
            err = vm.CodeStoreOutOfGasError
        }
    }

    // When an error was returned by the EVM or when setting the creation code
    // above we revert to the snapshot and consume any gas remaining. Additionally
    // when we're in homestead this also counts for code storage gas errors.
    if err != nil && (env.RuleSet().IsHomestead(env.BlockNumber()) || err != vm.CodeStoreOutOfGasError) {
        contract.UseGas(contract.Gas)

        env.SetSnapshot(snapshotPreTransfer)
    }

    return ret, addr, err
}

func execDelegateCall(env vm.Environment, caller vm.ContractRef, originAddr, toAddr, codeAddr *common.Address, input, code []byte, gas, gasPrice, value *big.Int) (ret []byte, addr common.Address, err error) {
    evm := env.Vm()
    // Depth check execution. Fail if we're trying to execute above the
    // limit.
    if env.Depth() > int(params.CallCreateDepth.Int64()) {
        caller.ReturnGas(gas, gasPrice)
        return nil, common.Address{}, vm.DepthError
    }

    snapshot := env.MakeSnapshot()

    var to vm.Account
    if !env.Db().Exist(*toAddr) {
        to = env.Db().CreateAccount(*toAddr)
    } else {
        to = env.Db().GetAccount(*toAddr)
    }

    // Iinitialise a new contract and make initialise the delegate values
    contract := vm.NewContract(caller, to, value, gas, gasPrice).AsDelegate()
    contract.SetCallCode(codeAddr, code)
    defer contract.Finalise()

    ret, err = evm.Run(contract, input)
    if err != nil {
        contract.UseGas(contract.Gas)

        env.SetSnapshot(snapshot)
    }

    return ret, addr, err
}

// generic transfer method
func Transfer(from, to vm.Account, amount *big.Int) {
    from.SubBalance(amount)
    to.AddBalance(amount)
}