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