github.com/klaytn/klaytn@v1.10.2/blockchain/vm/gas.go (about)

     1  // Modifications Copyright 2018 The klaytn Authors
     2  // Copyright 2015 The go-ethereum Authors
     3  // This file is part of the go-ethereum library.
     4  //
     5  // The go-ethereum library is free software: you can redistribute it and/or modify
     6  // it under the terms of the GNU Lesser General Public License as published by
     7  // the Free Software Foundation, either version 3 of the License, or
     8  // (at your option) any later version.
     9  //
    10  // The go-ethereum library is distributed in the hope that it will be useful,
    11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    13  // GNU Lesser General Public License for more details.
    14  //
    15  // You should have received a copy of the GNU Lesser General Public License
    16  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    17  //
    18  // This file is derived from core/vm/gas.go (2018/06/04).
    19  // Modified and improved for the klaytn development.
    20  
    21  package vm
    22  
    23  import (
    24  	"math/big"
    25  )
    26  
    27  // Gas costs
    28  const (
    29  	GasZero        uint64 = 0  // G_zero
    30  	GasQuickStep   uint64 = 2  // G_base
    31  	GasFastestStep uint64 = 3  // G_verylow
    32  	GasFastStep    uint64 = 5  // G_low
    33  	GasMidStep     uint64 = 8  // G_mid
    34  	GasSlowStep    uint64 = 10 // G_high or G_exp
    35  	GasExtStep     uint64 = 20 // G_blockhash
    36  )
    37  
    38  // calcGas returns the actual gas cost of the call.
    39  //
    40  // The returned gas is gas - base * 63 / 64.
    41  func callGas(availableGas, base uint64, callCost *big.Int) (uint64, error) {
    42  	availableGas = availableGas - base
    43  	gas := availableGas - availableGas/64
    44  	// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    45  	// is smaller than the requested amount. Therefore we return the new gas instead
    46  	// of returning an error.
    47  	if !callCost.IsUint64() || gas < callCost.Uint64() {
    48  		return gas, nil
    49  	}
    50  
    51  	return callCost.Uint64(), nil
    52  }