github.com/SmartMeshFoundation/Spectrum@v0.0.0-20220621030607-452a266fee1e/core/vm/gas.go (about)

     1  // Copyright 2015 The Spectrum Authors
     2  // This file is part of the Spectrum library.
     3  //
     4  // The Spectrum 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 Spectrum 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 Spectrum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"github.com/holiman/uint256"
    21  )
    22  
    23  const (
    24  	GasQuickStep   uint64 = 2
    25  	GasFastestStep uint64 = 3
    26  	GasFastStep    uint64 = 5
    27  	GasMidStep     uint64 = 8
    28  	GasSlowStep    uint64 = 10
    29  	GasExtStep     uint64 = 20
    30  )
    31  
    32  // calcGas returns the actual gas cost of the call.
    33  //
    34  // The cost of gas was changed during the homestead price change HF. To allow for EIP150
    35  // to be implemented. The returned gas is gas - base * 63 / 64.
    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 *uint256.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. 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  	if !callCost.IsUint64() {
    50  		return 0, ErrGasUintOverflow
    51  	}
    52  	return callCost.Uint64(), nil
    53  }