github.com/oskarth/go-ethereum@v1.6.8-0.20191013093314-dac24a9d3494/core/vm/gas.go (about)

     1  // Copyright 2015 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"math/big"
    21  
    22  	"github.com/ethereum/go-ethereum/params"
    23  )
    24  
    25  // Gas costs
    26  const (
    27  	GasQuickStep   uint64 = 2
    28  	GasFastestStep uint64 = 3
    29  	GasFastStep    uint64 = 5
    30  	GasMidStep     uint64 = 8
    31  	GasSlowStep    uint64 = 10
    32  	GasExtStep     uint64 = 20
    33  
    34  	GasReturn       uint64 = 0
    35  	GasStop         uint64 = 0
    36  	GasContractByte uint64 = 200
    37  )
    38  
    39  // calcGas returns the actual gas cost of the call.
    40  //
    41  // The cost of gas was changed during the homestead price change HF. To allow for EIP150
    42  // to be implemented. The returned gas is gas - base * 63 / 64.
    43  func callGas(gasTable params.GasTable, availableGas, base uint64, callCost *big.Int) (uint64, error) {
    44  	if gasTable.CreateBySuicide > 0 {
    45  		availableGas = availableGas - base
    46  		gas := availableGas - availableGas/64
    47  		// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    48  		// is smaller than the requested amount. Therefor we return the new gas instead
    49  		// of returning an error.
    50  		if callCost.BitLen() > 64 || gas < callCost.Uint64() {
    51  			return gas, nil
    52  		}
    53  	}
    54  	if callCost.BitLen() > 64 {
    55  		return 0, errGasUintOverflow
    56  	}
    57  
    58  	return callCost.Uint64(), nil
    59  }