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simulator.go
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simulator.go
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package sibyl
import (
"math/big"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/state"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/pkg/errors"
)
// Simulator is a transaction simulator, allowing you to run transactions against the current blockchain state
type Simulator struct {
mux sync.Mutex
db *state.StateDB
blockchain *core.BlockChain
vm *vm.EVM
}
// NewSimulator returns a bare simulator
func NewSimulator(blockchain *core.BlockChain) *Simulator {
return &Simulator{
blockchain: blockchain,
}
}
// Fork creates a new temporary context with the state for a given block number
func (s *Simulator) Fork(blockNumber uint64) error {
s.mux.Lock()
defer s.mux.Unlock()
header := s.blockchain.CurrentHeader()
block := s.blockchain.GetBlockByNumber(blockNumber)
db, err := s.blockchain.StateAt(block.Root())
if err != nil {
return errors.Wrap(err, "failed to read blockchain state for block")
}
s.db = db
blockCtx := core.NewEVMBlockContext(header, s.blockchain, nil)
txCtx := vm.TxContext{}
s.vm = vm.NewEVM(blockCtx, txCtx, db, s.blockchain.Config(), *s.blockchain.GetVMConfig())
return nil
}
// StaticCall executes an EVM static call on the current context
func (s *Simulator) StaticCall(sender, to common.Address, input []byte, gas uint64) ([]byte, error) {
s.mux.Lock()
defer s.mux.Unlock()
ret, _, err := s.vm.StaticCall(vm.AccountRef(sender), to, input, gas)
if err != nil {
return nil, err
}
return ret, nil
}
// Call executes an EVM call on the current context
func (s *Simulator) Call(sender, to common.Address, input []byte, gas uint64, value *big.Int) ([]byte, error) {
s.mux.Lock()
defer s.mux.Unlock()
ret, _, err := s.vm.Call(vm.AccountRef(sender), to, input, gas, value)
if err != nil {
return nil, err
}
return ret, nil
}
// Snapshot takes a snapshot of the current state
func (s *Simulator) Snapshot() int {
return s.db.Snapshot()
}
// Rollback rolls the state back to a specific snapshot
func (s *Simulator) Rollback(snapshot int) {
s.db.RevertToSnapshot(snapshot)
}