hermez-node/common/utils.go

package common

import (
	"math/big"

	ethCommon "github.com/ethereum/go-ethereum/common"
	"github.com/iden3/go-iden3-crypto/babyjub"
)

// SwapEndianness swaps the order of the bytes in the slice.
func SwapEndianness(b []byte) []byte {
	o := make([]byte, len(b))
	for i := range b {
		o[len(b)-1-i] = b[i]
	}
	return o
}

// EthAddrToBigInt returns a *big.Int from a given ethereum common.Address.
func EthAddrToBigInt(a ethCommon.Address) *big.Int {
	return new(big.Int).SetBytes(a.Bytes())
}

// BJJCompressedTo256BigInts returns a [256]*big.Int array with the bit
// representation of the babyjub.PublicKeyComp
func BJJCompressedTo256BigInts(pkComp babyjub.PublicKeyComp) [256]*big.Int {
	var r [256]*big.Int
	b := pkComp[:]

	for i := 0; i < 256; i++ {
		if b[i/8]&(1<<(i%8)) == 0 {
			r[i] = big.NewInt(0)
		} else {
			r[i] = big.NewInt(1)
		}
	}

	return r
}