mempool: add notification for added/removed entries

Add notification signals to make it possible to subscribe to mempool
changes:

- NotifyEntryAdded(CTransactionRef)>
- NotifyEntryRemoved(CTransactionRef, MemPoolRemovalReason)>

Also add a mempool removal reason enumeration, which is passed to the
removed notification based on why the transaction was removed from
the mempool.

1 files changed, 13 insertions, 10 deletions

diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 5b085f492d..54400caccc 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -393,6 +393,7 @@ void CTxMemPool::AddTransactionsUpdated(unsigned int n)
 
 bool CTxMemPool::addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, setEntries &setAncestors, bool validFeeEstimate)
 {
+    NotifyEntryAdded(entry.GetSharedTx());
     // Add to memory pool without checking anything.
     // Used by main.cpp AcceptToMemoryPool(), which DOES do
     // all the appropriate checks.
@@ -449,8 +450,9 @@ bool CTxMemPool::addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry,
     return true;
 }
 
-void CTxMemPool::removeUnchecked(txiter it)
+void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason)
 {
+    NotifyEntryRemoved(it->GetSharedTx(), reason);
     const uint256 hash = it->GetTx().GetHash();
     BOOST_FOREACH(const CTxIn& txin, it->GetTx().vin)
         mapNextTx.erase(txin.prevout);
@@ -502,7 +504,7 @@ void CTxMemPool::CalculateDescendants(txiter entryit, setEntries &setDescendants
     }
 }
 
-void CTxMemPool::removeRecursive(const CTransaction &origTx)
+void CTxMemPool::removeRecursive(const CTransaction &origTx, MemPoolRemovalReason reason)
 {
     // Remove transaction from memory pool
     {
@@ -529,7 +531,8 @@ void CTxMemPool::removeRecursive(const CTransaction &origTx)
         BOOST_FOREACH(txiter it, txToRemove) {
             CalculateDescendants(it, setAllRemoves);
         }
-        RemoveStaged(setAllRemoves, false);
+
+        RemoveStaged(setAllRemoves, false, reason);
     }
 }
 
@@ -567,7 +570,7 @@ void CTxMemPool::removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMem
     for (txiter it : txToRemove) {
         CalculateDescendants(it, setAllRemoves);
     }
-    RemoveStaged(setAllRemoves, false);
+    RemoveStaged(setAllRemoves, false, MemPoolRemovalReason::REORG);
 }
 
 void CTxMemPool::removeConflicts(const CTransaction &tx)
@@ -581,7 +584,7 @@ void CTxMemPool::removeConflicts(const CTransaction &tx)
             if (txConflict != tx)
             {
                 ClearPrioritisation(txConflict.GetHash());
-                removeRecursive(txConflict);
+                removeRecursive(txConflict, MemPoolRemovalReason::CONFLICT);
             }
         }
     }
@@ -610,7 +613,7 @@ void CTxMemPool::removeForBlock(const std::vector<CTransactionRef>& vtx, unsigne
         if (it != mapTx.end()) {
             setEntries stage;
             stage.insert(it);
-            RemoveStaged(stage, true);
+            RemoveStaged(stage, true, MemPoolRemovalReason::BLOCK);
         }
         removeConflicts(*tx);
         ClearPrioritisation(tx->GetHash());
@@ -989,11 +992,11 @@ size_t CTxMemPool::DynamicMemoryUsage() const {
     return memusage::MallocUsage(sizeof(CTxMemPoolEntry) + 15 * sizeof(void*)) * mapTx.size() + memusage::DynamicUsage(mapNextTx) + memusage::DynamicUsage(mapDeltas) + memusage::DynamicUsage(mapLinks) + memusage::DynamicUsage(vTxHashes) + cachedInnerUsage;
 }
 
-void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants) {
+void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants, MemPoolRemovalReason reason) {
     AssertLockHeld(cs);
     UpdateForRemoveFromMempool(stage, updateDescendants);
     BOOST_FOREACH(const txiter& it, stage) {
-        removeUnchecked(it);
+        removeUnchecked(it, reason);
     }
 }
 
@@ -1009,7 +1012,7 @@ int CTxMemPool::Expire(int64_t time) {
     BOOST_FOREACH(txiter removeit, toremove) {
         CalculateDescendants(removeit, stage);
     }
-    RemoveStaged(stage, false);
+    RemoveStaged(stage, false, MemPoolRemovalReason::EXPIRY);
     return stage.size();
 }
 
@@ -1118,7 +1121,7 @@ void CTxMemPool::TrimToSize(size_t sizelimit, std::vector<uint256>* pvNoSpendsRe
             BOOST_FOREACH(txiter iter, stage)
                 txn.push_back(iter->GetTx());
         }
-        RemoveStaged(stage, false);
+        RemoveStaged(stage, false, MemPoolRemovalReason::SIZELIMIT);
         if (pvNoSpendsRemaining) {
             BOOST_FOREACH(const CTransaction& tx, txn) {
                 BOOST_FOREACH(const CTxIn& txin, tx.vin) {