1package common
  2
  3import (
  4	"bytes"
  5	"encoding/binary"
  6	"fmt"
  7	"math"
  8	"math/big"
  9
 10	eth "github.com/ethereum/go-ethereum/common"
 11	"github.com/iden3/go-iden3-crypto/poseidon"
 12	cryptoUtils "github.com/iden3/go-iden3-crypto/utils"
 13)
 14
 15const NLEAFELEMS = 4
 16
 17// Leaf is the data structure stored in the Leaf of the MerkleTree
 18type Leaf struct {
 19	TokenID TokenID
 20	Nonce   uint64   // max of 40 bits used
 21	Balance *big.Int // max of 192 bits used
 22	Sign    bool
 23	Ay      *big.Int
 24	EthAddr eth.Address
 25}
 26
 27// 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.
 28func (l *Leaf) Bytes() ([32 * NLEAFELEMS]byte, error) {
 29	var b [32 * NLEAFELEMS]byte
 30
 31	if l.Nonce >= uint64(math.Pow(2, 40)) {
 32		return b, fmt.Errorf("%s Nonce", ErrNumOverflow)
 33	}
 34	if len(l.Balance.Bytes()) > 24 {
 35		return b, fmt.Errorf("%s Balance", ErrNumOverflow)
 36	}
 37
 38	var tokenIDBytes [4]byte
 39	binary.LittleEndian.PutUint32(tokenIDBytes[:], uint32(l.TokenID))
 40	var nonceBytes [8]byte
 41	binary.LittleEndian.PutUint64(nonceBytes[:], l.Nonce)
 42
 43	copy(b[0:4], tokenIDBytes[:])
 44	copy(b[4:9], nonceBytes[:])
 45	if l.Sign {
 46		b[10] = 1
 47	}
 48	copy(b[32:64], SwapEndianness(l.Balance.Bytes())) // SwapEndianness, as big.Int uses BigEndian
 49	copy(b[64:96], SwapEndianness(l.Ay.Bytes()))
 50	copy(b[96:116], l.EthAddr.Bytes())
 51
 52	return b, nil
 53}
 54
 55// BigInts returns the [5]*big.Int, where each *big.Int is inside the Finite Field
 56func (l *Leaf) BigInts() ([NLEAFELEMS]*big.Int, error) {
 57	e := [NLEAFELEMS]*big.Int{}
 58
 59	b, err := l.Bytes()
 60	if err != nil {
 61		return e, err
 62	}
 63
 64	e[0] = new(big.Int).SetBytes(SwapEndianness(b[0:32]))
 65	e[1] = new(big.Int).SetBytes(SwapEndianness(b[32:64]))
 66	e[2] = new(big.Int).SetBytes(SwapEndianness(b[64:96]))
 67	e[3] = new(big.Int).SetBytes(SwapEndianness(b[96:128]))
 68
 69	return e, nil
 70}
 71
 72// HashValue returns the value of the Leaf, which is the Poseidon hash of its *big.Int representation
 73func (l *Leaf) HashValue() (*big.Int, error) {
 74	toHash := [poseidon.T]*big.Int{}
 75	lBI, err := l.BigInts()
 76	if err != nil {
 77		return nil, err
 78	}
 79	copy(toHash[:], lBI[:])
 80
 81	v, err := poseidon.Hash(toHash)
 82	return v, err
 83}
 84
 85// LeafFromBigInts returns a Leaf from a [5]*big.Int
 86func LeafFromBigInts(e [NLEAFELEMS]*big.Int) (*Leaf, error) {
 87	if !cryptoUtils.CheckBigIntArrayInField(e[:]) {
 88		return nil, ErrNotInFF
 89	}
 90	var b [32 * NLEAFELEMS]byte
 91	copy(b[0:32], SwapEndianness(e[0].Bytes())) // SwapEndianness, as big.Int uses BigEndian
 92	copy(b[32:64], SwapEndianness(e[1].Bytes()))
 93	copy(b[64:96], SwapEndianness(e[2].Bytes()))
 94	copy(b[96:128], SwapEndianness(e[3].Bytes()))
 95
 96	return LeafFromBytes(b)
 97}
 98
 99// LeafFromBytes returns a Leaf from a byte array
100func LeafFromBytes(b [32 * NLEAFELEMS]byte) (*Leaf, error) {
101	tokenID := binary.LittleEndian.Uint32(b[0:4])
102	var nonceBytes [8]byte
103	copy(nonceBytes[:], b[4:9])
104	nonce := binary.LittleEndian.Uint64(nonceBytes[:])
105	if nonce >= uint64(math.Pow(2, 40)) {
106		return nil, fmt.Errorf("%s Nonce", ErrNumOverflow)
107	}
108	sign := b[10] == 1
109	balance := new(big.Int).SetBytes(SwapEndianness(b[32:56])) // b[32:56], as Balance is 192 bits (24 bytes)
110	if !bytes.Equal(b[56:64], []byte{0, 0, 0, 0, 0, 0, 0, 0}) {
111		return nil, fmt.Errorf("%s Balance", ErrNumOverflow)
112	}
113	ay := new(big.Int).SetBytes(SwapEndianness(b[64:96]))
114	ethAddr := eth.BytesToAddress(b[96:116])
115
116	if !cryptoUtils.CheckBigIntInField(balance) {
117		return nil, ErrNotInFF
118	}
119	if !cryptoUtils.CheckBigIntInField(ay) {
120		return nil, ErrNotInFF
121	}
122
123	l := Leaf{
124		TokenID: TokenID(tokenID),
125		Nonce:   nonce,
126		Balance: balance,
127		Sign:    sign,
128		Ay:      ay,
129		EthAddr: ethAddr,
130	}
131	return &l, nil
132}