use direct file access for large file hash (#63)

- Improvement: Refactor `IoHash::HashBuffer` and `BLAKE3::HashBuffer` to not use memory mapped files. Performs better and saves ~10% of oplog export time on CI

1 files changed, 20 insertions, 4 deletions

diff --git a/src/zenserver/projectstore/remoteprojectstore.cpp b/src/zenserver/projectstore/remoteprojectstore.cpp
index 0aa8df362..42c93f7cd 100644
--- a/src/zenserver/projectstore/remoteprojectstore.cpp
+++ b/src/zenserver/projectstore/remoteprojectstore.cpp
@@ -296,12 +296,28 @@ WriteToTempFile(CompressedBuffer&& CompressedBuffer, std::filesystem::path Path)
 	uint64_t Offset = 0;
 	{
 		CompositeBuffer Compressed = std::move(CompressedBuffer).GetCompressed();
-		BasicFileWriter BlockWriter(BlockFile, 64u * 1024u);
 		for (const SharedBuffer& Segment : Compressed.GetSegments())
 		{
-			size_t SegmentSize = Segment.GetSize();
-			BlockWriter.Write(Segment.GetData(), SegmentSize, Offset);
-			Offset += SegmentSize;
+			size_t				  SegmentSize	= Segment.GetSize();
+			static const uint64_t BufferingSize = 256u * 1024u;
+
+			IoBufferFileReference FileRef;
+			if (SegmentSize >= (BufferingSize + BufferingSize / 2) && Segment.GetFileReference(FileRef))
+			{
+				ScanFile(FileRef.FileHandle,
+						 FileRef.FileChunkOffset,
+						 FileRef.FileChunkSize,
+						 BufferingSize,
+						 [&BlockFile, &Offset](const void* Data, size_t Size) {
+							 BlockFile.Write(Data, Size, Offset);
+							 Offset += Size;
+						 });
+			}
+			else
+			{
+				BlockFile.Write(Segment.GetData(), SegmentSize, Offset);
+				Offset += SegmentSize;
+			}
 		}
 	}
 	void* FileHandle = BlockFile.Detach();