L1Tx Codec

common/l1tx.go

@@ -7,6 +7,14 @@ import (
 	"github.com/iden3/go-iden3-crypto/babyjub"
 )
 
+const (
+	fromBJJCompressedB = 256
+	fromEthAddrB       = 160
+	f16B               = 16
+	tokenIDB           = 32
+	cidXB              = 32
+)
+
 // L1Tx is a struct that represents a L1 tx
 type L1Tx struct {
 	// Stored in DB: mandatory fileds
@@ -23,6 +31,7 @@ type L1Tx struct {
 	LoadAmount      *big.Int           `meddler:"load_amount,bigint"`
 	EthBlockNum     uint64             `meddler:"eth_block_num"` // Ethereum Block Number in which this L1Tx was added to the queue
 	Type            TxType             `meddler:"tx_type"`
+	BatchNum        BatchNum           `meddler:"-"`
 }
 
 // Tx returns a *Tx from the L1Tx
@@ -35,3 +44,71 @@ func (tx *L1Tx) Tx() *Tx {
 		Type:    tx.Type,
 	}
 }
+
+// Bytes encodes a L1Tx into []byte
+func (tx *L1Tx) Bytes(nLevels int) []byte {
+	res := big.NewInt(0)
+	res = res.Add(res, big.NewInt(0).Or(big.NewInt(0), tx.ToIdx.BigInt()))
+	res = res.Add(res, big.NewInt(0).Lsh(big.NewInt(0).Or(big.NewInt(0), big.NewInt(int64(tx.TokenID))), uint(nLevels)))
+	res = res.Add(res, big.NewInt(0).Lsh(big.NewInt(0).Or(big.NewInt(0), tx.Amount), uint(nLevels+tokenIDB)))
+	res = res.Add(res, big.NewInt(0).Lsh(big.NewInt(0).Or(big.NewInt(0), tx.LoadAmount), uint(nLevels+tokenIDB+f16B)))
+	res = res.Add(res, big.NewInt(0).Lsh(big.NewInt(0).Or(big.NewInt(0), tx.FromIdx.BigInt()), uint(nLevels+tokenIDB+2*f16B)))
+
+	fromBJJ := big.NewInt(0)
+	fromBJJ.SetString(tx.FromBJJ.String(), 16)
+	fromBJJCompressed := big.NewInt(0).Or(big.NewInt(0), fromBJJ)
+	res = res.Add(res, big.NewInt(0).Lsh(fromBJJCompressed, uint(2*nLevels+tokenIDB+2*f16B)))
+
+	fromEthAddr := big.NewInt(0).Or(big.NewInt(0), tx.FromEthAddr.Hash().Big())
+	res = res.Add(res, big.NewInt(0).Lsh(fromEthAddr, uint(fromBJJCompressedB+2*nLevels+tokenIDB+2*f16B)))
+
+	return res.Bytes()
+}
+
+// L1TxFromBytes decodes a L1Tx from []byte
+func L1TxFromBytes(l1TxEncoded []byte) (*L1Tx, error) {
+	l1Tx := &L1Tx{}
+	var idxB uint = cidXB
+
+	l1TxEncodedBI := big.NewInt(0)
+	l1TxEncodedBI.SetBytes(l1TxEncoded)
+
+	toIdx, err := IdxFromBigInt(extract(l1TxEncodedBI, 0, idxB))
+
+	if err != nil {
+		return nil, err
+	}
+
+	l1Tx.ToIdx = toIdx
+
+	l1Tx.TokenID = TokenID(extract(l1TxEncodedBI, idxB, tokenIDB).Uint64())
+	l1Tx.Amount = extract(l1TxEncodedBI, idxB+tokenIDB, f16B)
+	l1Tx.LoadAmount = extract(l1TxEncodedBI, idxB+tokenIDB+f16B, f16B)
+	fromIdx, err := IdxFromBigInt(extract(l1TxEncodedBI, idxB+tokenIDB+2*f16B, f16B))
+
+	if err != nil {
+		return nil, err
+	}
+
+	l1Tx.FromIdx = fromIdx
+
+	var pkComp babyjub.PublicKeyComp
+	copy(pkComp[:], extract(l1TxEncodedBI, 2*idxB+tokenIDB+2*f16B, fromBJJCompressedB).Bytes())
+	pk, err := pkComp.Decompress()
+
+	if err != nil {
+		return nil, err
+	}
+
+	l1Tx.FromBJJ = pk
+
+	l1Tx.FromEthAddr = ethCommon.BigToAddress(extract(l1TxEncodedBI, fromBJJCompressedB+2*idxB+tokenIDB+2*f16B, fromEthAddrB))
+
+	return l1Tx, nil
+}
+
+// extract masks and shifts a bigInt
+func extract(num *big.Int, origin uint, len uint) *big.Int {
+	mask := big.NewInt(0).Sub(big.NewInt(0).Lsh(big.NewInt(1), len), big.NewInt(1))
+	return big.NewInt(0).And(big.NewInt(0).Rsh(num, origin), mask)
+}

common/l1tx_test.go

@@ -0,0 +1,43 @@
+package common
+
+import (
+	"math/big"
+	"testing"
+
+	ethCommon "github.com/ethereum/go-ethereum/common"
+	"github.com/iden3/go-iden3-crypto/babyjub"
+	"github.com/iden3/go-iden3-crypto/utils"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestL1TxCodec(t *testing.T) {
+	var pkComp babyjub.PublicKeyComp
+	err := pkComp.UnmarshalText([]byte("0x56ca90f80d7c374ae7485e9bcc47d4ac399460948da6aeeb899311097925a72c"))
+	require.Nil(t, err)
+
+	pk, err := pkComp.Decompress()
+	require.Nil(t, err)
+
+	l1Tx := L1Tx{
+		ToIdx:       3,
+		TokenID:     5,
+		Amount:      big.NewInt(1),
+		LoadAmount:  big.NewInt(2),
+		FromIdx:     2,
+		FromBJJ:     pk,
+		FromEthAddr: ethCommon.HexToAddress("0xc58d29fA6e86E4FAe04DDcEd660d45BCf3Cb2370"),
+	}
+
+	expected, err := utils.HexDecode("c58d29fa6e86e4fae04ddced660d45bcf3cb237056ca90f80d7c374ae7485e9bcc47d4ac399460948da6aeeb899311097925a72c00000002000200010000000500000003")
+	require.Nil(t, err)
+
+	encodedData := l1Tx.Bytes(32)
+	assert.Equal(t, expected, encodedData)
+
+	decodedData, err := L1TxFromBytes(encodedData)
+	require.Nil(t, err)
+
+	encodedData2 := decodedData.Bytes(32)
+	assert.Equal(t, encodedData, encodedData2)
+}