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handler.go
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handler.go
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package handler
import (
"bytes"
gethTypes "github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/rlp"
"github.com/onflow/cadence/runtime/common"
"github.com/onflow/flow-go/fvm/environment"
"github.com/onflow/flow-go/fvm/errors"
"github.com/onflow/flow-go/fvm/evm/types"
)
// ContractHandler is responsible for triggering calls to emulator, metering,
// event emission and updating the block
//
// TODO and Warning: currently database keeps a copy of roothash, and if after
// commiting the changes by the evm we want to revert in this code we need to reset that
// or we should always do all the checks and return before calling the emulator,
// after that should be only event emissions and computation usage updates.
// thats another reason we first check the computation limit before using.
// in the future we might benefit from a view style of access to db passed as
// a param to the emulator.
type ContractHandler struct {
flowTokenAddress common.Address
blockstore types.BlockStore
addressAllocator types.AddressAllocator
backend types.Backend
emulator types.Emulator
}
func (h *ContractHandler) FlowTokenAddress() common.Address {
return h.flowTokenAddress
}
var _ types.ContractHandler = &ContractHandler{}
func NewContractHandler(
flowTokenAddress common.Address,
blockstore types.BlockStore,
addressAllocator types.AddressAllocator,
backend types.Backend,
emulator types.Emulator,
) *ContractHandler {
return &ContractHandler{
flowTokenAddress: flowTokenAddress,
blockstore: blockstore,
addressAllocator: addressAllocator,
backend: backend,
emulator: emulator,
}
}
// AllocateAddress allocates an address to be used by the bridged accounts
func (h *ContractHandler) AllocateAddress() types.Address {
target, err := h.addressAllocator.AllocateAddress()
handleError(err)
return target
}
// AccountByAddress returns the account for the given address,
// if isAuthorized is set, account is controlled by the FVM (bridged accounts)
func (h *ContractHandler) AccountByAddress(addr types.Address, isAuthorized bool) types.Account {
return newAccount(h, addr, isAuthorized)
}
// LastExecutedBlock returns the last executed block
func (h *ContractHandler) LastExecutedBlock() *types.Block {
block, err := h.blockstore.LatestBlock()
handleError(err)
return block
}
// Run runs an rlpencoded evm transaction and
// collects the gas fees and pay it to the coinbase address provided.
func (h *ContractHandler) Run(rlpEncodedTx []byte, coinbase types.Address) {
// step 1 - transaction decoding
encodedLen := uint(len(rlpEncodedTx))
err := h.backend.MeterComputation(environment.ComputationKindRLPDecoding, encodedLen)
handleError(err)
tx := gethTypes.Transaction{}
err = tx.DecodeRLP(
rlp.NewStream(
bytes.NewReader(rlpEncodedTx),
uint64(encodedLen)))
handleError(err)
// step 2 - run transaction
h.checkGasLimit(types.GasLimit(tx.Gas()))
ctx := h.getBlockContext()
ctx.GasFeeCollector = coinbase
blk, err := h.emulator.NewBlockView(ctx)
handleError(err)
res, err := blk.RunTransaction(&tx)
h.meterGasUsage(res)
handleError(err)
// step 3 - update block proposal
bp, err := h.blockstore.BlockProposal()
handleError(err)
txHash := tx.Hash()
bp.AppendTxHash(txHash)
// step 4 - emit events
h.emitEvent(types.NewTransactionExecutedEvent(
bp.Height,
rlpEncodedTx,
txHash,
res,
))
h.emitEvent(types.NewBlockExecutedEvent(bp))
// step 5 - commit block proposal
err = h.blockstore.CommitBlockProposal()
handleError(err)
}
func (h *ContractHandler) checkGasLimit(limit types.GasLimit) {
// check gas limit against what has been left on the transaction side
if !h.backend.ComputationAvailable(environment.ComputationKindEVMGasUsage, uint(limit)) {
handleError(types.ErrInsufficientComputation)
}
}
func (h *ContractHandler) meterGasUsage(res *types.Result) {
if res != nil {
err := h.backend.MeterComputation(environment.ComputationKindEVMGasUsage, uint(res.GasConsumed))
handleError(err)
}
}
func (h *ContractHandler) emitEvent(event *types.Event) {
ev, err := event.Payload.CadenceEvent()
handleError(err)
err = h.backend.EmitEvent(ev)
handleError(err)
}
func (h *ContractHandler) getBlockContext() types.BlockContext {
bp, err := h.blockstore.BlockProposal()
handleError(err)
return types.BlockContext{
BlockNumber: bp.Height,
DirectCallBaseGasUsage: types.DefaultDirectCallBaseGasUsage,
}
}
type Account struct {
isAuthorized bool
address types.Address
fch *ContractHandler
}
// newAccount creates a new evm account
func newAccount(fch *ContractHandler, addr types.Address, isAuthorized bool) *Account {
return &Account{
isAuthorized: isAuthorized,
fch: fch,
address: addr,
}
}
// Address returns the address associated with the bridged account
func (a *Account) Address() types.Address {
return a.address
}
// Balance returns the balance of this bridged account
//
// TODO: we might need to meter computation for read only operations as well
// currently the storage limits is enforced
func (a *Account) Balance() types.Balance {
ctx := a.fch.getBlockContext()
blk, err := a.fch.emulator.NewReadOnlyBlockView(ctx)
handleError(err)
bl, err := blk.BalanceOf(a.address)
handleError(err)
balance, err := types.NewBalanceFromAttoFlow(bl)
handleError(err)
return balance
}
// Deposit deposits the token from the given vault into the flow evm main vault
// and update the account balance with the new amount
func (a *Account) Deposit(v *types.FLOWTokenVault) {
cfg := a.fch.getBlockContext()
a.fch.checkGasLimit(types.GasLimit(cfg.DirectCallBaseGasUsage))
call := types.NewDepositCall(
a.address,
v.Balance().ToAttoFlow(),
)
a.executeAndHandleCall(a.fch.getBlockContext(), call, v.Balance().ToAttoFlow().Uint64(), false)
}
// Withdraw deducts the balance from the account and
// withdraw and return flow token from the Flex main vault.
func (a *Account) Withdraw(b types.Balance) *types.FLOWTokenVault {
a.checkAuthorized()
cfg := a.fch.getBlockContext()
a.fch.checkGasLimit(types.GasLimit(cfg.DirectCallBaseGasUsage))
// check balance of flex vault
bp, err := a.fch.blockstore.BlockProposal()
handleError(err)
if b.ToAttoFlow().Uint64() > bp.TotalSupply {
handleError(types.ErrInsufficientTotalSupply)
}
call := types.NewWithdrawCall(
a.address,
b.ToAttoFlow(),
)
a.executeAndHandleCall(a.fch.getBlockContext(), call, b.ToAttoFlow().Uint64(), true)
return types.NewFlowTokenVault(b)
}
// Transfer transfers tokens between accounts
func (a *Account) Transfer(to types.Address, balance types.Balance) {
a.checkAuthorized()
ctx := a.fch.getBlockContext()
a.fch.checkGasLimit(types.GasLimit(ctx.DirectCallBaseGasUsage))
call := types.NewTransferCall(
a.address,
to,
balance.ToAttoFlow(),
)
a.executeAndHandleCall(ctx, call, 0, false)
}
// Deploy deploys a contract to the EVM environment
// the new deployed contract would be at the returned address and
// the contract data is not controlled by the caller accounts
func (a *Account) Deploy(code types.Code, gaslimit types.GasLimit, balance types.Balance) types.Address {
a.checkAuthorized()
a.fch.checkGasLimit(gaslimit)
call := types.NewDeployCall(
a.address,
code,
uint64(gaslimit),
balance.ToAttoFlow(),
)
res := a.executeAndHandleCall(a.fch.getBlockContext(), call, 0, false)
return types.Address(res.DeployedContractAddress)
}
// Call calls a smart contract function with the given data
// it would limit the gas used according to the limit provided
// given it doesn't goes beyond what Flow transaction allows.
// the balance would be deducted from the OFA account and would be transferred to the target address
func (a *Account) Call(to types.Address, data types.Data, gaslimit types.GasLimit, balance types.Balance) types.Data {
a.checkAuthorized()
a.fch.checkGasLimit(gaslimit)
call := types.NewContractCall(
a.address,
to,
data,
uint64(gaslimit),
balance.ToAttoFlow(),
)
res := a.executeAndHandleCall(a.fch.getBlockContext(), call, 0, false)
return res.ReturnedValue
}
func (a *Account) executeAndHandleCall(
ctx types.BlockContext,
call *types.DirectCall,
totalSupplyDiff uint64,
deductSupplyDiff bool,
) *types.Result {
// execute the call
blk, err := a.fch.emulator.NewBlockView(ctx)
handleError(err)
res, err := blk.DirectCall(call)
a.fch.meterGasUsage(res)
handleError(err)
// update block proposal
callHash, err := call.Hash()
if err != nil {
err = types.NewFatalError(err)
handleError(err)
}
bp, err := a.fch.blockstore.BlockProposal()
handleError(err)
bp.AppendTxHash(callHash)
if deductSupplyDiff {
bp.TotalSupply -= totalSupplyDiff
} else {
// TODO: add overflow errors (even though we might never get there)
bp.TotalSupply += totalSupplyDiff
}
// emit events
encoded, err := call.Encode()
handleError(err)
a.fch.emitEvent(
types.NewTransactionExecutedEvent(
bp.Height,
encoded,
callHash,
res,
),
)
a.fch.emitEvent(types.NewBlockExecutedEvent(bp))
// commit block proposal
err = a.fch.blockstore.CommitBlockProposal()
handleError(err)
return res
}
func (a *Account) checkAuthorized() {
// check if account is authorized (i.e. is a bridged account)
if !a.isAuthorized {
handleError(types.ErrUnAuthroizedMethodCall)
}
}
func handleError(err error) {
if err == nil {
return
}
if types.IsAFatalError(err) {
// don't wrap it
panic(err)
}
panic(errors.NewEVMError(err))
}