// Copyright 2015 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 evmcore

import (

"fmt"

"math"

)

// GasPool tracks the amount of gas available during execution of the transactions

// in a block. The zero value is a pool with zero gas available.

type GasPool uint64

// AddGas makes gas available for execution.

func (gp *GasPool) AddGas(amount uint64) *GasPool {

if uint64(*gp) > math.MaxUint64-amount {

panic("gas pool pushed above uint64")

}

*(*uint64)(gp) += amount

return gp

}

// SubGas deducts the given amount from the pool if enough gas is

// available and returns an error otherwise.

func (gp *GasPool) SubGas(amount uint64) error {

if uint64(*gp) < amount {

return ErrGasLimitReached

}

*(*uint64)(gp) -= amount

return nil

}

// Gas returns the amount of gas remaining in the pool.

func (gp *GasPool) Gas() uint64 {

return uint64(*gp)

}

func (gp *GasPool) String() string {

return fmt.Sprintf("%d", *gp)

}