Add header to cas index file

1 files changed, 40 insertions, 8 deletions

diff --git a/zenstore/compactcas.cpp b/zenstore/compactcas.cpp
index 684a91233..2dcc9aa7c 100644
--- a/zenstore/compactcas.cpp
+++ b/zenstore/compactcas.cpp
@@ -23,6 +23,20 @@
 
 namespace zen {
 
+struct CasDiskIndexHeader
+{
+	static constexpr uint32_t ExpectedMagic		= 0x75696478;  // 'uidx';
+	static constexpr uint32_t CurrentVersion	= 1;
+	uint32_t				  Magic				= ExpectedMagic;
+	uint32_t				  Version			= CurrentVersion;
+	uint32_t				  PayloadAlignement;
+	uint32_t				  Reserved0 = 0;
+	uint64_t				  MaxBlockSize;
+	uint64_t				  EntryCount;
+};
+
+static_assert(sizeof(CasDiskIndexHeader) == 32);
+
 namespace {
 	uint64_t AlignPositon(uint64_t Offset, uint64_t Alignment) { return (Offset + Alignment - 1) & ~(Alignment - 1); }
 
@@ -742,7 +756,11 @@ CasContainerStrategy::MakeIndexSnapshot()
 
 		BasicFile SmallObjectIndex;
 		SmallObjectIndex.Open(SidxPath, true);
-		SmallObjectIndex.Write(Entries.data(), Entries.size() * sizeof(CasDiskIndexEntry), 0);
+		CasDiskIndexHeader Header = {.PayloadAlignement = gsl::narrow<uint32_t>(m_PayloadAlignment),
+									 .MaxBlockSize		= m_MaxBlockSize,
+									 .EntryCount		= Entries.size()};
+		SmallObjectIndex.Write(&Header, sizeof(CasDiskIndexEntry), 0);
+		SmallObjectIndex.Write(Entries.data(), Entries.size() * sizeof(CasDiskIndexEntry), sizeof(CasDiskIndexEntry));
 		SmallObjectIndex.Close();
 	}
 	catch (std::exception& Err)
@@ -980,15 +998,29 @@ CasContainerStrategy::OpenContainer(bool IsNewStore)
 		{
 			BasicFile SmallObjectIndex;
 			SmallObjectIndex.Open(SidxPath, false);
-			uint64_t					   Size		  = SmallObjectIndex.FileSize();
-			uint64_t					   EntryCount = Size / sizeof(CasDiskIndexEntry);
-			std::vector<CasDiskIndexEntry> Entries{EntryCount};
-			SmallObjectIndex.Read(Entries.data(), Size, 0);
-			for (const auto& Entry : Entries)
+			uint64_t Size = SmallObjectIndex.FileSize();
+			if (SmallObjectIndex.FileSize() >= sizeof(CasDiskIndexHeader))
 			{
-				m_LocationMap[Entry.Key] = Entry.Location;
+				uint64_t		   ExpectedEntryCount = (Size - sizeof(sizeof(CasDiskIndexHeader))) / sizeof(CasDiskIndexEntry);
+				CasDiskIndexHeader Header;
+				SmallObjectIndex.Read(&Header, sizeof(Header), 0);
+				if (Header.Magic == CasDiskIndexHeader::ExpectedMagic &&
+					Header.Version == CasDiskIndexHeader::CurrentVersion &&
+					Header.MaxBlockSize > 0 &&
+					Header.PayloadAlignement > 0 &&
+					Header.EntryCount == ExpectedEntryCount)
+				{
+					std::vector<CasDiskIndexEntry> Entries{Header.EntryCount};
+					SmallObjectIndex.Read(Entries.data(), Header.EntryCount * sizeof(CasDiskIndexEntry), sizeof(CasDiskIndexHeader));
+					SmallObjectIndex.Close();
+					for (const auto& Entry : Entries)
+					{
+						m_LocationMap[Entry.Key] = Entry.Location;
+					}
+					m_MaxBlockSize = Header.MaxBlockSize;
+					m_PayloadAlignment = Header.PayloadAlignement;
+				}
 			}
-			SmallObjectIndex.Close();
 		}
 
 		m_CasLog.Open(SlogPath, false);