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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"
)
var (
U256 = common.U256 // Shortcut to common.U256
S256 = common.S256 // Shortcut to common.S256
)
// 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)
}
// 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()))
}
// bigUint64 returns the integer casted to a uint64 and returns whether it
// overflowed in the process.
func bigUint64(v *big.Int) (uint64, bool) {
return v.Uint64(), v.BitLen() > 64
}
// toWordSize returns the ceiled word size required for memory expansion.
func toWordSize(size uint64) uint64 {
if size > math.MaxUint64-31 {
return math.MaxUint64/32 + 1
}
return (size + 31) / 32
}
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