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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package vm
import (
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/params"
)
var (
GasQuickStep = big.NewInt(2)
GasFastestStep = big.NewInt(3)
GasFastStep = big.NewInt(5)
GasMidStep = big.NewInt(8)
GasSlowStep = big.NewInt(10)
GasExtStep = big.NewInt(20)
GasReturn = big.NewInt(0)
GasStop = big.NewInt(0)
GasContractByte = big.NewInt(200)
n64 = big.NewInt(64)
)
// calcGas returns the actual gas cost of the call.
//
// The cost of gas was changed during the homestead price change HF. To allow for EIP150
// to be implemented. The returned gas is gas - base * 63 / 64.
func callGas(gasTable params.GasTable, availableGas, base, callCost *big.Int) *big.Int {
if gasTable.CreateBySuicide != nil {
availableGas = new(big.Int).Sub(availableGas, base)
g := new(big.Int).Div(availableGas, n64)
g.Sub(availableGas, g)
if g.Cmp(callCost) < 0 {
return g
}
}
return callCost
}
// baseCheck checks for any stack error underflows
func baseCheck(op OpCode, stack *Stack, gas *big.Int) error {
// PUSH and DUP are a bit special. They all cost the same but we do want to have checking on stack push limit
// PUSH is also allowed to calculate the same price for all PUSHes
// DUP requirements are handled elsewhere (except for the stack limit check)
if op >= PUSH1 && op <= PUSH32 {
op = PUSH1
}
if op >= DUP1 && op <= DUP16 {
op = DUP1
}
if r, ok := _baseCheck[op]; ok {
err := stack.require(r.stackPop)
if err != nil {
return err
}
if r.stackPush > 0 && stack.len()-r.stackPop+r.stackPush > int(params.StackLimit.Int64()) {
return fmt.Errorf("stack limit reached %d (%d)", stack.len(), params.StackLimit.Int64())
}
gas.Add(gas, r.gas)
}
return nil
}
// casts a arbitrary number to the amount of words (sets of 32 bytes)
func toWordSize(size *big.Int) *big.Int {
tmp := new(big.Int)
tmp.Add(size, u256(31))
tmp.Div(tmp, u256(32))
return tmp
}
type req struct {
stackPop int
gas *big.Int
stackPush int
}
var _baseCheck = map[OpCode]req{
// opcode | stack pop | gas price | stack push
ADD: {2, GasFastestStep, 1},
LT: {2, GasFastestStep, 1},
GT: {2, GasFastestStep, 1},
SLT: {2, GasFastestStep, 1},
SGT: {2, GasFastestStep, 1},
EQ: {2, GasFastestStep, 1},
ISZERO: {1, GasFastestStep, 1},
SUB: {2, GasFastestStep, 1},
AND: {2, GasFastestStep, 1},
OR: {2, GasFastestStep, 1},
XOR: {2, GasFastestStep, 1},
NOT: {1, GasFastestStep, 1},
BYTE: {2, GasFastestStep, 1},
CALLDATALOAD: {1, GasFastestStep, 1},
CALLDATACOPY: {3, GasFastestStep, 1},
MLOAD: {1, GasFastestStep, 1},
MSTORE: {2, GasFastestStep, 0},
MSTORE8: {2, GasFastestStep, 0},
CODECOPY: {3, GasFastestStep, 0},
MUL: {2, GasFastStep, 1},
DIV: {2, GasFastStep, 1},
SDIV: {2, GasFastStep, 1},
MOD: {2, GasFastStep, 1},
SMOD: {2, GasFastStep, 1},
SIGNEXTEND: {2, GasFastStep, 1},
ADDMOD: {3, GasMidStep, 1},
MULMOD: {3, GasMidStep, 1},
JUMP: {1, GasMidStep, 0},
JUMPI: {2, GasSlowStep, 0},
EXP: {2, GasSlowStep, 1},
ADDRESS: {0, GasQuickStep, 1},
ORIGIN: {0, GasQuickStep, 1},
CALLER: {0, GasQuickStep, 1},
CALLVALUE: {0, GasQuickStep, 1},
CODESIZE: {0, GasQuickStep, 1},
GASPRICE: {0, GasQuickStep, 1},
COINBASE: {0, GasQuickStep, 1},
TIMESTAMP: {0, GasQuickStep, 1},
NUMBER: {0, GasQuickStep, 1},
CALLDATASIZE: {0, GasQuickStep, 1},
DIFFICULTY: {0, GasQuickStep, 1},
GASLIMIT: {0, GasQuickStep, 1},
POP: {1, GasQuickStep, 0},
PC: {0, GasQuickStep, 1},
MSIZE: {0, GasQuickStep, 1},
GAS: {0, GasQuickStep, 1},
BLOCKHASH: {1, GasExtStep, 1},
BALANCE: {1, Zero, 1},
EXTCODESIZE: {1, Zero, 1},
EXTCODECOPY: {4, Zero, 0},
SLOAD: {1, params.SloadGas, 1},
SSTORE: {2, Zero, 0},
SHA3: {2, params.Sha3Gas, 1},
CREATE: {3, params.CreateGas, 1},
// Zero is calculated in the gasSwitch
CALL: {7, Zero, 1},
CALLCODE: {7, Zero, 1},
DELEGATECALL: {6, Zero, 1},
SUICIDE: {1, Zero, 0},
JUMPDEST: {0, params.JumpdestGas, 0},
RETURN: {2, Zero, 0},
PUSH1: {0, GasFastestStep, 1},
DUP1: {0, Zero, 1},
}