refactor: Simplify `extra_txn` to be a vec of CTransactionRef instead of a vec of pair<Wtxid, CTransactionRef>

All `CTransactionRef` have `.GetWitnessHash()` that returns a cached `const Wtxid` (since fac1223a56),
so we don't need to pass transaction refs around with their IDs as they're easy to get from a ref.

src/blockencodings.cpp

@@ -47,7 +47,7 @@ uint64_t CBlockHeaderAndShortTxIDs::GetShortID(const Wtxid& wtxid) const {
 
 
 
-ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<std::pair<Wtxid, CTransactionRef>>& extra_txn) {
+ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<CTransactionRef>& extra_txn) {
     if (cmpctblock.header.IsNull() || (cmpctblock.shorttxids.empty() && cmpctblock.prefilledtxn.empty()))
         return READ_STATUS_INVALID;
     if (cmpctblock.shorttxids.size() + cmpctblock.prefilledtxn.size() > MAX_BLOCK_WEIGHT / MIN_SERIALIZABLE_TRANSACTION_WEIGHT)
@@ -134,11 +134,14 @@ ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& c
     }
 
     for (size_t i = 0; i < extra_txn.size(); i++) {
-        uint64_t shortid = cmpctblock.GetShortID(extra_txn[i].first);
+        if (extra_txn[i] == nullptr) {
+            continue;
+        }
+        uint64_t shortid = cmpctblock.GetShortID(extra_txn[i]->GetWitnessHash());
         std::unordered_map<uint64_t, uint16_t>::iterator idit = shorttxids.find(shortid);
         if (idit != shorttxids.end()) {
             if (!have_txn[idit->second]) {
-                txn_available[idit->second] = extra_txn[i].second;
+                txn_available[idit->second] = extra_txn[i];
                 have_txn[idit->second]  = true;
                 mempool_count++;
                 extra_count++;
@@ -150,7 +153,7 @@ ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& c
                 // Note that we don't want duplication between extra_txn and mempool to
                 // trigger this case, so we compare witness hashes first
                 if (txn_available[idit->second] &&
-                        txn_available[idit->second]->GetWitnessHash() != extra_txn[i].second->GetWitnessHash()) {
+                        txn_available[idit->second]->GetWitnessHash() != extra_txn[i]->GetWitnessHash()) {
                     txn_available[idit->second].reset();
                     mempool_count--;
                     extra_count--;

src/blockencodings.h

@@ -142,7 +142,7 @@ public:
     explicit PartiallyDownloadedBlock(CTxMemPool* poolIn) : pool(poolIn) {}
 
     // extra_txn is a list of extra transactions to look at, in <witness hash, reference> form
-    ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<std::pair<Wtxid, CTransactionRef>>& extra_txn);
+    ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<CTransactionRef>& extra_txn);
     bool IsTxAvailable(size_t index) const;
     ReadStatus FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing);
 };

src/net_processing.cpp

@@ -1006,7 +1006,7 @@ private:
     /** Orphan/conflicted/etc transactions that are kept for compact block reconstruction.
      *  The last -blockreconstructionextratxn/DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN of
      *  these are kept in a ring buffer */
-    std::vector<std::pair<Wtxid, CTransactionRef>> vExtraTxnForCompact GUARDED_BY(g_msgproc_mutex);
+    std::vector<CTransactionRef> vExtraTxnForCompact GUARDED_BY(g_msgproc_mutex);
     /** Offset into vExtraTxnForCompact to insert the next tx */
     size_t vExtraTxnForCompactIt GUARDED_BY(g_msgproc_mutex) = 0;
 
@@ -1802,7 +1802,7 @@ void PeerManagerImpl::AddToCompactExtraTransactions(const CTransactionRef& tx)
         return;
     if (!vExtraTxnForCompact.size())
         vExtraTxnForCompact.resize(m_opts.max_extra_txs);
-    vExtraTxnForCompact[vExtraTxnForCompactIt] = std::make_pair(tx->GetWitnessHash(), tx);
+    vExtraTxnForCompact[vExtraTxnForCompactIt] = tx;
     vExtraTxnForCompactIt = (vExtraTxnForCompactIt + 1) % m_opts.max_extra_txs;
 }
 

src/test/blockencodings_tests.cpp

@@ -14,7 +14,7 @@
 
 #include <boost/test/unit_test.hpp>
 
-std::vector<std::pair<Wtxid, CTransactionRef>> extra_txn;
+std::vector<CTransactionRef> extra_txn;
 
 BOOST_FIXTURE_TEST_SUITE(blockencodings_tests, RegTestingSetup)
 

src/test/fuzz/partially_downloaded_block.cpp

@@ -60,7 +60,7 @@ FUZZ_TARGET(partially_downloaded_block, .init = initialize_pdb)
     // The coinbase is always available
     available.insert(0);
 
-    std::vector<std::pair<Wtxid, CTransactionRef>> extra_txn;
+    std::vector<CTransactionRef> extra_txn;
     for (size_t i = 1; i < block->vtx.size(); ++i) {
         auto tx{block->vtx[i]};
 
@@ -68,7 +68,7 @@ FUZZ_TARGET(partially_downloaded_block, .init = initialize_pdb)
         bool add_to_mempool{fuzzed_data_provider.ConsumeBool()};
 
         if (add_to_extra_txn) {
-            extra_txn.emplace_back(tx->GetWitnessHash(), tx);
+            extra_txn.emplace_back(tx);
             available.insert(i);
         }