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package common
import (
"bytes"
"encoding/binary"
"fmt"
"math"
"math/big"
eth "github.com/ethereum/go-ethereum/common"
cryptoUtils "github.com/iden3/go-iden3-crypto/utils"
)
// Leaf is the data structure stored in the Leaf of the MerkleTree
type Leaf struct {
TokenID TokenID
Nonce uint64 // max of 40 bits used
Balance *big.Int // max of 192 bits used
Ax *big.Int
Ay *big.Int
EthAddr eth.Address
}
// Bytes returns the bytes representing the Leaf, in a way that each BigInt is represented by 32 bytes, in spite of the BigInt could be represented in less bytes (due a small big.Int), so in this way each BigInt is always 32 bytes and can be automatically parsed from a byte array.
func (l *Leaf) Bytes() ([32 * 5]byte, error) {
var b [32 * 5]byte
if l.Nonce >= uint64(math.Pow(2, 40)) {
return b, fmt.Errorf("%s Nonce", ErrNumOverflow)
}
if len(l.Balance.Bytes()) > 24 {
return b, fmt.Errorf("%s Balance", ErrNumOverflow)
}
var tokenIDBytes [4]byte
binary.LittleEndian.PutUint32(tokenIDBytes[:], uint32(l.TokenID))
var nonceBytes [8]byte
binary.LittleEndian.PutUint64(nonceBytes[:], l.Nonce)
copy(b[0:4], tokenIDBytes[:])
copy(b[4:9], nonceBytes[:])
copy(b[32:64], SwapEndianness(l.Balance.Bytes())) // SwapEndianness, as big.Int uses BigEndian
copy(b[64:96], SwapEndianness(l.Ax.Bytes()))
copy(b[96:128], SwapEndianness(l.Ay.Bytes()))
copy(b[128:148], l.EthAddr.Bytes())
return b, nil
}
// BigInts returns the [5]*big.Int, where each *big.Int is inside the Finite Field
func (l *Leaf) BigInts() ([5]*big.Int, error) {
e := [5]*big.Int{}
b, err := l.Bytes()
if err != nil {
return e, err
}
e[0] = new(big.Int).SetBytes(SwapEndianness(b[0:32]))
e[1] = new(big.Int).SetBytes(SwapEndianness(b[32:64]))
e[2] = new(big.Int).SetBytes(SwapEndianness(b[64:96]))
e[3] = new(big.Int).SetBytes(SwapEndianness(b[96:128]))
e[4] = new(big.Int).SetBytes(SwapEndianness(b[128:160]))
return e, nil
}
// LeafFromBigInts returns a Leaf from a [5]*big.Int
func LeafFromBigInts(e [5]*big.Int) (*Leaf, error) {
if !cryptoUtils.CheckBigIntArrayInField(e[:]) {
return nil, ErrNotInFF
}
var b [32 * 5]byte
copy(b[0:32], SwapEndianness(e[0].Bytes())) // SwapEndianness, as big.Int uses BigEndian
copy(b[32:64], SwapEndianness(e[1].Bytes()))
copy(b[64:96], SwapEndianness(e[2].Bytes()))
copy(b[96:128], SwapEndianness(e[3].Bytes()))
copy(b[128:160], SwapEndianness(e[4].Bytes()))
return LeafFromBytes(b)
}
// LeafFromBytes returns a Leaf from a byte array
func LeafFromBytes(b [32 * 5]byte) (*Leaf, error) {
tokenID := binary.LittleEndian.Uint32(b[0:4])
nonce := binary.LittleEndian.Uint64(b[4:12])
if !bytes.Equal(b[9:12], []byte{0, 0, 0}) { // alternatively: if nonce >= uint64(math.Pow(2, 40)) {
return nil, fmt.Errorf("%s Nonce", ErrNumOverflow)
}
balance := new(big.Int).SetBytes(SwapEndianness(b[32:56])) // b[32:56], as Balance is 192 bits (24 bytes)
if !bytes.Equal(b[56:64], []byte{0, 0, 0, 0, 0, 0, 0, 0}) {
return nil, fmt.Errorf("%s Balance", ErrNumOverflow)
}
ax := new(big.Int).SetBytes(SwapEndianness(b[64:96])) // SwapEndianness, as big.Int uses BigEndian
ay := new(big.Int).SetBytes(SwapEndianness(b[96:128]))
ethAddr := eth.BytesToAddress(b[128:148])
if !cryptoUtils.CheckBigIntInField(balance) {
return nil, ErrNotInFF
}
if !cryptoUtils.CheckBigIntInField(ax) {
return nil, ErrNotInFF
}
if !cryptoUtils.CheckBigIntInField(ay) {
return nil, ErrNotInFF
}
l := Leaf{
TokenID: TokenID(tokenID),
Nonce: nonce,
Balance: balance,
Ax: ax,
Ay: ay,
EthAddr: ethAddr,
}
return &l, nil
}