1 files changed, 42 insertions, 0 deletions
diff --git a/src/test/blockmanager_tests.cpp b/src/test/blockmanager_tests.cpp
new file mode 100644
index 0000000000..dd7c32cc46
--- /dev/null
+++ b/src/test/blockmanager_tests.cpp
@@ -0,0 +1,42 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <chainparams.h>
+#include <node/blockstorage.h>
+#include <node/context.h>
+#include <validation.h>
+
+#include <boost/test/unit_test.hpp>
+#include <test/util/setup_common.h>
+
+using node::BlockManager;
+using node::BLOCK_SERIALIZATION_HEADER_SIZE;
+
+// use BasicTestingSetup here for the data directory configuration, setup, and cleanup
+BOOST_FIXTURE_TEST_SUITE(blockmanager_tests, BasicTestingSetup)
+
+BOOST_AUTO_TEST_CASE(blockmanager_find_block_pos)
+{
+    const auto params {CreateChainParams(ArgsManager{}, CBaseChainParams::MAIN)};
+    BlockManager blockman {};
+    CChain chain {};
+    // simulate adding a genesis block normally
+    BOOST_CHECK_EQUAL(blockman.SaveBlockToDisk(params->GenesisBlock(), 0, chain, *params, nullptr).nPos, BLOCK_SERIALIZATION_HEADER_SIZE);
+    // simulate what happens during reindex
+    // simulate a well-formed genesis block being found at offset 8 in the blk00000.dat file
+    // the block is found at offset 8 because there is an 8 byte serialization header
+    // consisting of 4 magic bytes + 4 length bytes before each block in a well-formed blk file.
+    FlatFilePos pos{0, BLOCK_SERIALIZATION_HEADER_SIZE};
+    BOOST_CHECK_EQUAL(blockman.SaveBlockToDisk(params->GenesisBlock(), 0, chain, *params, &pos).nPos, BLOCK_SERIALIZATION_HEADER_SIZE);
+    // now simulate what happens after reindex for the first new block processed
+    // the actual block contents don't matter, just that it's a block.
+    // verify that the write position is at offset 0x12d.
+    // this is a check to make sure that https://github.com/bitcoin/bitcoin/issues/21379 does not recur
+    // 8 bytes (for serialization header) + 285 (for serialized genesis block) = 293
+    // add another 8 bytes for the second block's serialization header and we get 293 + 8 = 301
+    FlatFilePos actual{blockman.SaveBlockToDisk(params->GenesisBlock(), 1, chain, *params, nullptr)};
+    BOOST_CHECK_EQUAL(actual.nPos, BLOCK_SERIALIZATION_HEADER_SIZE + ::GetSerializeSize(params->GenesisBlock(), CLIENT_VERSION) + BLOCK_SERIALIZATION_HEADER_SIZE);
+}
+
+BOOST_AUTO_TEST_SUITE_END()