txorphanage: comment improvements

Author: ajtowns

src/txorphanage.h

@@ -13,7 +13,10 @@
 /** Guards orphan transactions and extra txs for compact blocks */
 extern RecursiveMutex g_cs_orphans;
 
-/** Data structure to keep track of orphan transactions
+/** A class to track orphan transactions (failed on TX_MISSING_INPUTS)
+ * Since we cannot distinguish orphans from bad transactions with
+ * non-existent inputs, we heavily limit the number of orphans
+ * we keep and the duration we keep them for.
  */
 class TxOrphanage {
 public:
@@ -23,7 +26,9 @@ class TxOrphanage {
     /** Check if we already have an orphan transaction (by txid or wtxid) */
     bool HaveTx(const GenTxid& gtxid) const EXCLUSIVE_LOCKS_REQUIRED(!g_cs_orphans);
 
-    /** Get the details of an orphan transaction (returns nullptr if not found) */
+    /** Get an orphan transaction and its orginating peer
+     * (Transaction ref will be nullptr if not found)
+     */
     std::pair<CTransactionRef, NodeId> GetTx(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans);
 
     /** Erase an orphan by txid */
@@ -32,7 +37,7 @@ class TxOrphanage {
     /** Erase all orphans announced by a peer (eg, after that peer disconnects) */
     void EraseForPeer(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans);
 
-    /** Erase all orphans included in / invalidated by a new block */
+    /** Erase all orphans included in or invalidated by a new block */
     void EraseForBlock(const CBlock& block) EXCLUSIVE_LOCKS_REQUIRED(!g_cs_orphans);
 
     /** Limit the orphanage to the given maximum */