path: root/core/vm/common.go

// 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/big"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/common/math"
)

// calculates the memory size required for a step
func CalcMemSize(off, l *big.Int) *big.Int {
    if l.Sign() == 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 uint64, size uint64) []byte {
    length := uint64(len(data))
    if start > length {
        start = length
    }
    end := start + size
    if end > length {
        end = length
    }
    return common.RightPadBytes(data[start:end], int(size))
}

// getDataBig 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 GetDataBig(data []byte, start *big.Int, size *big.Int) []byte {
    dlen := big.NewInt(int64(len(data)))

    s := math.BigMin(start, dlen)
    e := math.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
}

func AllZero(b []byte) bool {
    for _, byte := range b {
        if byte != 0 {
            return false
        }
    }
    return true
}