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L1Tx Codec

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This commit is contained in:
ToniRamirezM
2020-09-09 10:00:22 +02:00
parent 230adfeb73
commit a8f6488eb1
2 changed files with 120 additions and 0 deletions
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77
common/l1tx.go
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@@ -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)
}