core: delete dao.go (#15113)

- dao.go is already present in consensus/misc
- core/dao.go is not used anywhere in the codebase

core/dao.go

-// Copyright 2016 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 (
-	"bytes"
-	"fmt"
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/core/state"
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/params"
-)
-
-// ValidateDAOHeaderExtraData validates the extra-data field of a block header to
-// ensure it conforms to DAO hard-fork rules.
-//
-// DAO hard-fork extension to the header validity:
-//   a) if the node is no-fork, do not accept blocks in the [fork, fork+10) range
-//      with the fork specific extra-data set
-//   b) if the node is pro-fork, require blocks in the specific range to have the
-//      unique extra-data set.
-func ValidateDAOHeaderExtraData(config *params.ChainConfig, header *types.Header) error {
-	// Short circuit validation if the node doesn't care about the DAO fork
-	if config.DAOForkBlock == nil {
-		return nil
-	}
-	// Make sure the block is within the fork's modified extra-data range
-	limit := new(big.Int).Add(config.DAOForkBlock, params.DAOForkExtraRange)
-	if header.Number.Cmp(config.DAOForkBlock) < 0 || header.Number.Cmp(limit) >= 0 {
-		return nil
-	}
-	// Depending whether we support or oppose the fork, validate the extra-data contents
-	if config.DAOForkSupport {
-		if !bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
-			return fmt.Errorf("DAO pro-fork bad block extra-data: 0x%x", header.Extra)
-		}
-	} else {
-		if bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
-			return fmt.Errorf("DAO no-fork bad block extra-data: 0x%x", header.Extra)
-		}
-	}
-	// All ok, header has the same extra-data we expect
-	return nil
-}
-
-// ApplyDAOHardFork modifies the state database according to the DAO hard-fork
-// rules, transferring all balances of a set of DAO accounts to a single refund
-// contract.
-func ApplyDAOHardFork(statedb *state.StateDB) {
-	// Retrieve the contract to refund balances into
-	if !statedb.Exist(params.DAORefundContract) {
-		statedb.CreateAccount(params.DAORefundContract)
-	}
-
-	// Move every DAO account and extra-balance account funds into the refund contract
-	for _, addr := range params.DAODrainList() {
-		statedb.AddBalance(params.DAORefundContract, statedb.GetBalance(addr))
-		statedb.SetBalance(addr, new(big.Int))
-	}
-}