cidstore: made all updates log using LogMapping()

also fixed issue with FindChunkByCid() which would assert when it should not

1 files changed, 23 insertions, 7 deletions

diff --git a/zenstore/cidstore.cpp b/zenstore/cidstore.cpp
index 08a3192ff..d76058bd1 100644
--- a/zenstore/cidstore.cpp
+++ b/zenstore/cidstore.cpp
@@ -45,11 +45,23 @@ struct CidStore::Impl
 		ZEN_ASSERT(Compressed != IoHash::Zero);
 
 		RwLock::ExclusiveLockScope _(m_Lock);
-		m_CidMap.insert_or_assign(DecompressedId, Compressed);
-		// TODO: it's pretty wasteful to log even idempotent updates
-		// however we can't simply use the boolean returned by insert_or_assign
-		// since there's not a 1:1 mapping between compressed and uncompressed
-		// so if we want a last-write-wins policy then we have to log each update
+
+        auto It = m_CidMap.try_emplace(DecompressedId, Compressed);
+		if (!It.second)
+		{
+			if (It.first.value() != Compressed)
+			{
+				It.first.value() = Compressed;
+			}
+			else
+			{
+				// No point logging an update that won't change anything
+				return;
+			}
+		}
+
+		// It's not ideal to do this while holding the lock in case
+		// we end up in blocking I/O but that's for later
 		LogMapping(DecompressedId, Compressed);
 	}
 
@@ -68,6 +80,10 @@ struct CidStore::Impl
 			{
 				CompressedHash = It->second;
 			}
+			else
+			{
+				return {};
+			}
 		}
 
 		ZEN_ASSERT(CompressedHash != IoHash::Zero);
@@ -84,7 +100,7 @@ struct CidStore::Impl
 
 		if (It == m_CidMap.end())
 		{
-			// Not in map, or tombstone
+			// Not in map
 			return false;
 		}
 
@@ -171,7 +187,7 @@ struct CidStore::Impl
 					const IoHash& BadHash = It->first;
 
 					// Log a tombstone record
-					m_LogFile.Append({.Uncompressed = BadHash, .Compressed = IoHash::Zero});
+					LogMapping(BadHash, IoHash::Zero);
 
 					BadChunks.push_back(BadHash);