Expose EVM Object

[AusIV]

Rationale

The EVM object would be useful for simulating EVM functions, for use cases similar to Cardinal's Estimate Gas List

Implementation

Start with a plugeth-utils interface:

type EVM interface {
  func Reset(txCtx TxContext, statedb StateDB)
  func Cancel()
  func Cancelled() bool
  func Call(caller *core.Address, addr core.Address, input []byte, gas uint64, value *big.Int) (ret []byte, leftOverGas uint64, err error)
  func CallCode(caller *core.Address, addr core.Address, input []byte, gas uint64, value *big.Int) (ret []byte, leftOverGas uint64, err error)
  func DelegateCall(caller *core.Address, addr core.Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error)
  func StaticCall(caller *core.Address, addr core.Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error)
  func Create(caller *core.Address, code []byte, gas uint64, value *big.Int) (ret []byte, contractAddr core.Address, leftOverGas uint64, err error)
  func Create2(caller *core.Address, code []byte, gas uint64, endowment *big.Int, salt *uint256.Int) (ret []byte, contractAddr core.Address, leftOverGas uint64, err error)
  func ChainConfig() *params.ChainConfig { return evm.chainConfig
}

Then in plugeth's plugins/wrappers, implement a wrapper object that takes a core.EVM object and translates calls to comply with the Plugeth-utils interface.

This could then be exposed through the PluGeth backend by proxying the internal/ethapi backend's GetEVM() call. Note that this will require the implmentation of #52 so that the StateDB can be passed through.