From de6057de814a4dc16654bdda84f697476b2ebef5 Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Sat, 30 Apr 2022 01:29:24 +0200
Subject: first pass at generic block store with gc

---
 zenstore/include/zenstore/blockstore.h | 41 ++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

(limited to 'zenstore/include')

diff --git a/zenstore/include/zenstore/blockstore.h b/zenstore/include/zenstore/blockstore.h
index 424db461a..4dd6e5289 100644
--- a/zenstore/include/zenstore/blockstore.h
+++ b/zenstore/include/zenstore/blockstore.h
@@ -15,8 +15,14 @@ struct BlockStoreLocation
 	uint32_t BlockIndex;
 	uint64_t Offset;
 	uint64_t Size;
+
+	inline auto operator<=>(const BlockStoreLocation& Rhs) const = default;
 };
 
+constexpr BlockStoreLocation InvalidBlockStoreLocation{.BlockIndex = 0xfffffffful,
+													   .Offset	   = 0xffffffffffffffffull,
+													   .Size	   = 0xffffffffffffffffull};
+
 #pragma pack(push)
 #pragma pack(1)
 
@@ -99,6 +105,41 @@ private:
 	BasicFile					m_File;
 };
 
+class BlockStore
+{
+public:
+	void				Initialize(const std::filesystem::path&			  BlocksBasePath,
+								   uint64_t								  MaxBlockSize,
+								   uint64_t								  MaxBlockCount,
+								   const std::vector<BlockStoreLocation>& KnownLocations);
+	BlockStoreLocation	WriteChunk(const void* Data, uint64_t Size, uint64_t Alignment);
+	Ref<BlockStoreFile> GetChunkBlock(const BlockStoreLocation& Location);
+	void				Flush();
+
+	typedef std::function<void(const std::unordered_map<size_t, BlockStoreLocation>& MovedChunks, const std::vector<size_t> RemovedChunks)>
+		ReclaimCallback;
+
+	void ReclaimSpace(
+		const std::vector<BlockStoreLocation>& ChunkLocations,
+		const std::vector<size_t>&			   KeepChunkIndexes,
+		uint64_t							   PayloadAlignment,
+		bool								   DryRun,
+		const ReclaimCallback& Callback = [](const std::unordered_map<size_t, BlockStoreLocation>&, const std::vector<size_t>&) {});
+
+private:
+	std::unordered_map<uint32_t, Ref<BlockStoreFile>> m_ChunkBlocks;
+
+	RwLock				 m_InsertLock;	// used to serialize inserts
+	Ref<BlockStoreFile>	 m_WriteBlock;
+	std::uint64_t		 m_CurrentInsertOffset = 0;
+	std::atomic_uint32_t m_WriteBlockIndex{};
+
+	uint64_t			  m_MaxBlockSize  = 1u << 28;
+	uint64_t			  m_MaxBlockCount = BlockStoreDiskLocation::MaxBlockIndex + 1;
+	std::filesystem::path m_BlocksBasePath;
+	std::atomic_uint64_t  m_TotalSize{};
+};
+
 void blockstore_forcelink();
 
 }  // namespace zen
-- 
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