github.com/klaytn/klaytn@v1.12.1/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 "github.com/holiman/uint256"
    24  
    25  // Gas costs
    26  const (
    27  	GasZero        uint64 = 0  // G_zero
    28  	GasQuickStep   uint64 = 2  // G_base
    29  	GasFastestStep uint64 = 3  // G_verylow
    30  	GasFastStep    uint64 = 5  // G_low
    31  	GasMidStep     uint64 = 8  // G_mid
    32  	GasSlowStep    uint64 = 10 // G_high or G_exp
    33  	GasExtStep     uint64 = 20 // G_blockhash
    34  )
    35  
    36  // calcGas returns the actual gas cost of the call.
    37  //
    38  // The returned gas is gas - base * 63 / 64.
    39  func callGas(availableGas, base uint64, callCost *uint256.Int) (uint64, error) {
    40  	availableGas = availableGas - base
    41  	gas := availableGas - availableGas/64
    42  	// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    43  	// is smaller than the requested amount. Therefore we return the new gas instead
    44  	// of returning an error.
    45  	if !callCost.IsUint64() || gas < callCost.Uint64() {
    46  		return gas, nil
    47  	}
    48  
    49  	return callCost.Uint64(), nil
    50  }