From eda385eb284e9992d463787b72cdbef4c9c3c82a Mon Sep 17 00:00:00 2001
From: Alex Sharov <AskAlexSharov@gmail.com>
Date: Thu, 28 Apr 2022 13:08:27 +0700
Subject: [PATCH] Handle system-txn in block_reader (#4012)

* reduce downloader deps

* reduce downloader deps

* save

* reduce downloader deps
---
 turbo/snapshotsync/block_reader.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/turbo/snapshotsync/block_reader.go b/turbo/snapshotsync/block_reader.go
index ed979e84c..c5f8bf1a0 100644
--- a/turbo/snapshotsync/block_reader.go
+++ b/turbo/snapshotsync/block_reader.go
@@ -565,6 +565,7 @@ func (back *BlockReaderWithSnapshots) txsFromSnapshot(baseTxnID uint64, txsAmoun
 }
 
 func (back *BlockReaderWithSnapshots) txnByHash(txnHash common.Hash, segments []*TxnSegment, buf []byte) (txn types.Transaction, blockNum, txnID uint64, err error) {
+
 	for i := len(segments) - 1; i >= 0; i-- {
 		sn := segments[i]
 		if sn.IdxTxnHash == nil || sn.IdxTxnHash2BlockNum == nil {
@@ -577,14 +578,19 @@ func (back *BlockReaderWithSnapshots) txnByHash(txnHash common.Hash, segments []
 		gg := sn.Seg.MakeGetter()
 		gg.Reset(offset)
 		buf, _ = gg.Next(buf[:0])
+		if len(buf) == 0 { // system-txn
+			continue
+		}
+
 		// first byte txnHash check - reducing false-positives 256 times. Allows don't store and don't calculate full hash of entity - when checking many snapshots.
 		if len(buf) > 1 && txnHash[0] != buf[0] {
 			continue
 		}
 
+		sender := buf[1 : 1+20]
+
 		reader2 := recsplit.NewIndexReader(sn.IdxTxnHash2BlockNum)
 		blockNum = reader2.Lookup(txnHash[:])
-		sender := buf[1 : 1+20]
 		txn, err = types.DecodeTransaction(rlp.NewStream(bytes.NewReader(buf[1+20:]), uint64(len(buf))))
 		if err != nil {
 			return