github.com/fly8eros/go-ethereum@v1.9.1/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  	"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  
    35  // calcGas returns the actual gas cost of the call.
    36  //
    37  // The cost of gas was changed during the homestead price change HF. To allow for EIP150
    38  // to be implemented. The returned gas is gas - base * 63 / 64.
    39  func callGas(gasTable params.GasTable, availableGas, base uint64, callCost *big.Int) (uint64, error) {
    40  	if gasTable.CreateBySuicide > 0 {
    41  		availableGas = availableGas - base
    42  		gas := availableGas - availableGas/64
    43  		// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    44  		// is smaller than the requested amount. Therefor we return the new gas instead
    45  		// of returning an error.
    46  		if !callCost.IsUint64() || gas < callCost.Uint64() {
    47  			return gas, nil
    48  		}
    49  	}
    50  	if !callCost.IsUint64() {
    51  		return 0, errGasUintOverflow
    52  	}
    53  
    54  	return callCost.Uint64(), nil
    55  }