github.com/aigarnetwork/aigar@v0.0.0-20191115204914-d59a6eb70f8e/core/vm/gas.go (about)

     1  //  Copyright 2018 The go-ethereum Authors
     2  //  Copyright 2019 The go-aigar Authors
     3  //  This file is part of the go-aigar library.
     4  //
     5  //  The go-aigar 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-aigar 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-aigar library. If not, see <http://www.gnu.org/licenses/>.
    17  
    18  package vm
    19  
    20  import (
    21  	"math/big"
    22  )
    23  
    24  // Gas costs
    25  const (
    26  	GasQuickStep   uint64 = 2
    27  	GasFastestStep uint64 = 3
    28  	GasFastStep    uint64 = 5
    29  	GasMidStep     uint64 = 8
    30  	GasSlowStep    uint64 = 10
    31  	GasExtStep     uint64 = 20
    32  )
    33  
    34  // calcGas returns the actual gas cost of the call.
    35  //
    36  // The cost of gas was changed during the homestead price change HF.
    37  // As part of EIP 150 (TangerineWhistle), the returned gas is gas - base * 63 / 64.
    38  func callGas(isEip150 bool, availableGas, base uint64, callCost *big.Int) (uint64, error) {
    39  	if isEip150 {
    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. Therefor 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  	if !callCost.IsUint64() {
    50  		return 0, errGasUintOverflow
    51  	}
    52  
    53  	return callCost.Uint64(), nil
    54  }