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// Copyright 2014 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 (
"math"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/params"
)
// Global Debug flag indicating Debug VM (full logging)
var Debug bool
// Type is the VM type accepted by **NewVm**
type Type byte
const (
StdVmTy Type = iota // Default standard VM
JitVmTy // LLVM JIT VM
MaxVmTy
)
var (
Pow256 = common.BigPow(2, 256) // Pow256 is 2**256
U256 = common.U256 // Shortcut to common.U256
S256 = common.S256 // Shortcut to common.S256
Zero = common.Big0 // Shortcut to common.Big0
One = common.Big1 // Shortcut to common.Big1
max = big.NewInt(math.MaxInt64) // Maximum 64 bit integer
)
// NewVm returns a new VM based on the Environment
func NewVm(env Environment) VirtualMachine {
switch env.VmType() {
case JitVmTy:
return NewJitVm(env)
default:
glog.V(0).Infoln("unsupported vm type %d", env.VmType())
fallthrough
case StdVmTy:
return New(env)
}
}
// calculates the memory size required for a step
func calcMemSize(off, l *big.Int) *big.Int {
if l.Cmp(common.Big0) == 0 {
return common.Big0
}
return new(big.Int).Add(off, l)
}
// calculates the quadratic gas
func quadMemGas(mem *Memory, newMemSize, gas *big.Int) {
if newMemSize.Cmp(common.Big0) > 0 {
newMemSizeWords := toWordSize(newMemSize)
newMemSize.Mul(newMemSizeWords, u256(32))
if newMemSize.Cmp(u256(int64(mem.Len()))) > 0 {
// be careful reusing variables here when changing.
// The order has been optimised to reduce allocation
oldSize := toWordSize(big.NewInt(int64(mem.Len())))
pow := new(big.Int).Exp(oldSize, common.Big2, Zero)
linCoef := oldSize.Mul(oldSize, params.MemoryGas)
quadCoef := new(big.Int).Div(pow, params.QuadCoeffDiv)
oldTotalFee := new(big.Int).Add(linCoef, quadCoef)
pow.Exp(newMemSizeWords, common.Big2, Zero)
linCoef = linCoef.Mul(newMemSizeWords, params.MemoryGas)
quadCoef = quadCoef.Div(pow, params.QuadCoeffDiv)
newTotalFee := linCoef.Add(linCoef, quadCoef)
fee := newTotalFee.Sub(newTotalFee, oldTotalFee)
gas.Add(gas, fee)
}
}
}
// Simple helper
func u256(n int64) *big.Int {
return big.NewInt(n)
}
// Mainly used for print variables and passing to Print*
func toValue(val *big.Int) interface{} {
// Let's assume a string on right padded zero's
b := val.Bytes()
if b[0] != 0 && b[len(b)-1] == 0x0 && b[len(b)-2] == 0x0 {
return string(b)
}
return val
}
// getData returns a slice from the data based on the start and size and pads
// up to size with zero's. This function is overflow safe.
func getData(data []byte, start, size *big.Int) []byte {
dlen := big.NewInt(int64(len(data)))
s := common.BigMin(start, dlen)
e := common.BigMin(new(big.Int).Add(s, size), dlen)
return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
}
// useGas attempts to subtract the amount of gas and returns whether it was
// successful
func useGas(gas, amount *big.Int) bool {
if gas.Cmp(amount) < 0 {
return false
}
// Sub the amount of gas from the remaining
gas.Sub(gas, amount)
return true
}
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