[net processing] Add doxygen comments for orphan data and function

Author: jnewbery

src/net_processing.cpp

@@ -153,8 +153,14 @@ struct COrphanTx {
     int64_t nTimeExpire;
     size_t list_pos;
 };
+
+/** Guards orphan transactions and extra txs for compact blocks */
 RecursiveMutex g_cs_orphans;
+/** Map from txid to orphan transaction record. Limited by
+ *  -maxorphantx/DEFAULT_MAX_ORPHAN_TRANSACTIONS */
 std::map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(g_cs_orphans);
+/** Index from wtxid into the mapOrphanTransactions to lookup orphan
+ *  transactions using their witness ids. */
 std::map<uint256, std::map<uint256, COrphanTx>::iterator> g_orphans_by_wtxid GUARDED_BY(g_cs_orphans);
 
 void EraseOrphansFor(NodeId peer);
@@ -258,12 +264,19 @@ namespace {
             return &(*a) < &(*b);
         }
     };
-    std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);
 
-    std::vector<std::map<uint256, COrphanTx>::iterator> g_orphan_list GUARDED_BY(g_cs_orphans); //! For random eviction
+    /** Index from the parents' COutPoint into the mapOrphanTransactions. Used
+     *  to remove orphan transactions from the mapOrphanTransactions */
+    std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);
+    /** Orphan transactions in vector for quick random eviction */
+    std::vector<std::map<uint256, COrphanTx>::iterator> g_orphan_list GUARDED_BY(g_cs_orphans);
 
-    static size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
+    /** 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 */
     static std::vector<std::pair<uint256, CTransactionRef>> vExtraTxnForCompact GUARDED_BY(g_cs_orphans);
+    /** Offset into vExtraTxnForCompact to insert the next tx */
+    static size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
 } // namespace
 
 namespace {
@@ -2021,6 +2034,16 @@ void PeerManager::ProcessHeadersMessage(CNode& pfrom, const std::vector<CBlockHe
     return;
 }
 
+/**
+ * Reconsider orphan transactions after a parent has been accepted to the mempool.
+ *
+ * @param[in/out]  orphan_work_set  The set of orphan transactions to reconsider. Generally only one
+ *                                  orphan will be reconsidered on each call of this function. This set
+ *                                  may be added to if accepting an orphan causes its children to be
+ *                                  reconsidered.
+ * @param[out]     removed_txn      Transactions that were removed from the mempool as a result of an
+ *                                  orphan transaction being added.
+ */
 void PeerManager::ProcessOrphanTx(std::set<uint256>& orphan_work_set, std::list<CTransactionRef>& removed_txn)
 {
     AssertLockHeld(cs_main);