optimize block store CompactBlocks (#384)

- Improvement: Optimize block compact reducing memcpy operations
- Improvement: Handle padding of block store blocks when compacting to avoid excessive flusing of write buffer
- Improvement: Handle padding when writing oplog index snapshot to avoid unnecessary flushing of write buffer

2 files changed, 34 insertions, 3 deletions

diff --git a/src/zencore/basicfile.cpp b/src/zencore/basicfile.cpp
index ea526399c..12ee26155 100644
--- a/src/zencore/basicfile.cpp
+++ b/src/zencore/basicfile.cpp
@@ -792,6 +792,35 @@ BasicFileWriter::~BasicFileWriter()
 }
 
 void
+BasicFileWriter::AddPadding(uint64_t Padding)
+{
+	while (Padding)
+	{
+		const uint64_t BufferOffset			   = m_BufferEnd - m_BufferStart;
+		const uint64_t RemainingBufferCapacity = m_BufferSize - BufferOffset;
+		const uint64_t BlockPadBytes		   = Min(RemainingBufferCapacity, Padding);
+
+		memset(m_Buffer + BufferOffset, 0, BlockPadBytes);
+		m_BufferEnd += BlockPadBytes;
+		Padding -= BlockPadBytes;
+
+		if ((BufferOffset + BlockPadBytes) == m_BufferSize)
+		{
+			Flush();
+		}
+	}
+}
+
+uint64_t
+BasicFileWriter::AlignTo(uint64_t Alignment)
+{
+	uint64_t AlignedPos = RoundUp(m_BufferEnd, Alignment);
+	uint64_t Padding	= AlignedPos - m_BufferEnd;
+	AddPadding(Padding);
+	return AlignedPos;
+}
+
+void
 BasicFileWriter::Write(const void* Data, uint64_t Size, uint64_t FileOffset)
 {
 	if (m_Buffer == nullptr || (Size >= m_BufferSize))
diff --git a/src/zencore/include/zencore/basicfile.h b/src/zencore/include/zencore/basicfile.h
index 57798b6f4..465499d2b 100644
--- a/src/zencore/include/zencore/basicfile.h
+++ b/src/zencore/include/zencore/basicfile.h
@@ -174,9 +174,11 @@ public:
 	BasicFileWriter(BasicFile& Base, uint64_t BufferSize);
 	~BasicFileWriter();
 
-	void Write(const void* Data, uint64_t Size, uint64_t FileOffset);
-	void Write(const CompositeBuffer& Data, uint64_t FileOffset);
-	void Flush();
+	void	 Write(const void* Data, uint64_t Size, uint64_t FileOffset);
+	void	 Write(const CompositeBuffer& Data, uint64_t FileOffset);
+	void	 AddPadding(uint64_t Padding);
+	uint64_t AlignTo(uint64_t Alignment);
+	void	 Flush();
 
 private:
 	BasicFile&	   m_Base;