# README

Go-EVM

This repository is a module extracted from go-ethereum (geth) Ver. 1.14 and made available to EVM only.
This EVM doesn't test EOF(Ethereum Object Format)

Run on Example

Compile Contract

Whether you are using solc or Remix, you should have the *.abi and *.bin.

Run

$ cd example
$ go run main.go

Usage

Before using the EVM, you'll need to customize loadBin( ), loadAbi( ), and setDefaults( ) functions for your setup, see the example.

1. Create State

// If you use snapshot, this config must be used
snapconfig := snapshot.Config{
    CacheSize:  256,
    Recovery:   true,
    NoBuild:    false,
    AsyncBuild: false,
}

triedbConfig := &triedb.Config{
    Preimages: true,
    HashDB: &hashdb.Config{
        CleanCacheSize: 256 * 1024 * 1024,
    },
}

leveldb, _ := rawdb.NewLevelDBDatabase("../leveldb_path", 128, 1024, "", false)

// Create State
tdb := triedb.NewDatabase(leveldb, triedbConfig)
snaps, _ := snapshot.New(snapconfig, leveldb, tdb, types.EmptyRootHash)
statedb := state.NewDatabase(tdb, snaps) // If you don't use snapshot, snaps is null
globalstate, _ := state.New(types.EmptyRootHash, statedb)

You can use other database. Details

2. Create Account

testAddress := common.BytesToAddress([]byte("Random Value"))
globalstate.CreateAccount(testAddress)

3. Set Balance and Nonce

globalstate.SetBalance(testAddress, uint256.NewInt(balance), tracing.BalanceChangeUnspecified)
globalstate.SetNonce(testAddress, nonce)

4. Create EVM

cfg := SetDefaults(blockheight)
evm := runtime.NewEnv(cfg, globalstate)

5. Coin Transfer

evm.Context.Transfer(globalstate, testAddress, testAddress2, uint256.NewInt(transfer_amount))

6. Contract Deploy

data := loadBin("./bin_file_name")
sender := vm.AccountRef(testAddress)

returnValue, contractAddress, gasleftover, err := evm.Create(
    sender, // Deployer
    data, // Contract byte code
    globalstate.GetBalance(testAddress).Uint64(), // Gas
    uint256.NewInt(0), // msg.value
)
globalstate.SetBalance(testAddress, uint256.NewInt(gasleftover), tracing.BalanceChangeUnspecified) // Remaining balance after spending gas

7. Contract Execute

abiObj := loadAbi("./abi_file_name")
sender := vm.AccountRef(testAddress)
data, err := abiObj.Pack("contract function name", input1, input2)

returnValue, gasleftover, err = evm.Call(
    sender, // Executer address
    contractAddress, // Contract Address(CA)
    data, // Instruction
    globalstate.GetBalance(testAddress).Uint64(), // Gas
    uint256.NewInt(msg.value), // msg.value
)
globalstate.SetBalance(addrArray[i], uint256.NewInt(gasleftover-uint64(msg.value)), tracing.BalanceChangeUnspecified) // Remaining balance after spending gas

8. Get Balance and State Variable

globalstate.GetBalance(testAddress) // Get Balance

// Function to get the hash value of a variable in state storage owned by a contract, 
// depending on how state variables are stored in Ethereum.
func CalculateMappingSlotIndex(address common.Address, slot uint64) []byte {
    // left pad address with 0 to 32 bytes
    addressBytes := common.LeftPadBytes(address.Bytes(), 32)
    // left pad slot with 0 to 32 bytes
    slotBytes := make([]byte, 32)
    binary.BigEndian.PutUint64(slotBytes[24:], slot)
    return crypto.Keccak256(addressBytes, slotBytes)
}
deployinitstate.GetState(contractAddress, common.Hash(CalculateMappingSlotIndex(testAddress, slot_num))) // Get State

9. Commit State

rootHash, _ = globalstate.Commit(block_num, true, layer_num) // State Commit
if err := tdb.Commit(rootHash, false); err != nil { // Write committed state to disk
    panic(err)
}

Other

1. Database

You can use pebbledb and memory instead of leveldb.

Use PebbleDB

pebbledb, _ := rawdb.NewPebbleDBDatabase("../pebbledb_path", 128, 1024, "", false)

Use Memory

memdb := rawdb.NewMemoryDatabase()

If you want to use a different DB, you can create a new database in db/ethdb with the ethdb.KeyValueStore interface and create a NewOtherDB( ) in rawdb/database.go.

2. Trie

Ethereum uses MPT(Merkle Patricia trie).
If you want to modify this, you can modify the trie directory to match the Trie interface in state/database.go.

3. Snapshot

When commit state, if snapshot is not used, the value of layer_num can be any value.
Otherwise, you'll need to adjust the value of layer_num, which determines how many commits later a snapshot is taken.