gitlab.com/flarenetwork/coreth@v0.1.1/core/vm/gas.go (about)

     1  // (c) 2019-2020, Ava Labs, Inc.
     2  //
     3  // This file is a derived work, based on the go-ethereum library whose original
     4  // notices appear below.
     5  //
     6  // It is distributed under a license compatible with the licensing terms of the
     7  // original code from which it is derived.
     8  //
     9  // Much love to the original authors for their work.
    10  // **********
    11  // Copyright 2015 The go-ethereum Authors
    12  // This file is part of the go-ethereum library.
    13  //
    14  // The go-ethereum library is free software: you can redistribute it and/or modify
    15  // it under the terms of the GNU Lesser General Public License as published by
    16  // the Free Software Foundation, either version 3 of the License, or
    17  // (at your option) any later version.
    18  //
    19  // The go-ethereum library is distributed in the hope that it will be useful,
    20  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    21  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    22  // GNU Lesser General Public License for more details.
    23  //
    24  // You should have received a copy of the GNU Lesser General Public License
    25  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    26  
    27  package vm
    28  
    29  import (
    30  	"github.com/holiman/uint256"
    31  )
    32  
    33  // Gas costs
    34  const (
    35  	GasQuickStep   uint64 = 2
    36  	GasFastestStep uint64 = 3
    37  	GasFastStep    uint64 = 5
    38  	GasMidStep     uint64 = 8
    39  	GasSlowStep    uint64 = 10
    40  	GasExtStep     uint64 = 20
    41  )
    42  
    43  // callGas returns the actual gas cost of the call.
    44  //
    45  // The cost of gas was changed during the homestead price change HF.
    46  // As part of EIP 150 (TangerineWhistle), the returned gas is gas - base * 63 / 64.
    47  func callGas(isEip150 bool, availableGas, base uint64, callCost *uint256.Int) (uint64, error) {
    48  	if isEip150 {
    49  		availableGas = availableGas - base
    50  		gas := availableGas - availableGas/64
    51  		// If the bit length exceeds 64 bit we know that the newly calculated "gas" for EIP150
    52  		// is smaller than the requested amount. Therefore we return the new gas instead
    53  		// of returning an error.
    54  		if !callCost.IsUint64() || gas < callCost.Uint64() {
    55  			return gas, nil
    56  		}
    57  	}
    58  	if !callCost.IsUint64() {
    59  		return 0, ErrGasUintOverflow
    60  	}
    61  
    62  	return callCost.Uint64(), nil
    63  }