github.com/theQRL/go-zond@v0.1.1/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  	"github.com/holiman/uint256"
    21  )
    22  
    23  // Gas costs
    24  const (
    25  	GasQuickStep   uint64 = 2
    26  	GasFastestStep uint64 = 3
    27  	GasFastStep    uint64 = 5
    28  	GasMidStep     uint64 = 8
    29  	GasSlowStep    uint64 = 10
    30  	GasExtStep     uint64 = 20
    31  )
    32  
    33  // callGas returns the actual gas cost of the call.
    34  //
    35  // The cost of gas was changed during the homestead price change HF.
    36  // As part of EIP 150 (TangerineWhistle), the returned gas is gas - base * 63 / 64.
    37  func callGas(isEip150 bool, availableGas, base uint64, callCost *uint256.Int) (uint64, error) {
    38  	if isEip150 {
    39  		availableGas = availableGas - base
    40  		gas := availableGas - availableGas/64
    41  		// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    42  		// is smaller than the requested amount. Therefore we return the new gas instead
    43  		// of returning an error.
    44  		if !callCost.IsUint64() || gas < callCost.Uint64() {
    45  			return gas, nil
    46  		}
    47  	}
    48  	if !callCost.IsUint64() {
    49  		return 0, ErrGasUintOverflow
    50  	}
    51  
    52  	return callCost.Uint64(), nil
    53  }