fixed size chunking for encrypted files (#410)

- Improvement: Use fixed size block chunking for know encrypted/compressed file types
- Improvement: Skip trying to compress chunks that are sourced from files that are known to be encrypted/compressed
- Improvement: Add global open file cache for written files increasing throughput during download by reducing overhead of open/close of file by 80%

1 files changed, 16 insertions, 7 deletions

diff --git a/src/zencore/filesystem.cpp b/src/zencore/filesystem.cpp
index 0a9b2a73a..c4264bc29 100644
--- a/src/zencore/filesystem.cpp
+++ b/src/zencore/filesystem.cpp
@@ -2275,23 +2275,32 @@ PrepareFileForScatteredWrite(void* FileHandle, uint64_t FinalSize)
 {
 	bool Result = true;
 #if ZEN_PLATFORM_WINDOWS
-	DWORD _	 = 0;
-	BOOL  Ok = DeviceIoControl(FileHandle, FSCTL_SET_SPARSE, nullptr, 0, nullptr, 0, &_, nullptr);
-	if (!Ok)
+
+	BY_HANDLE_FILE_INFORMATION Information;
+	if (GetFileInformationByHandle(FileHandle, &Information))
 	{
-		std::error_code DummyEc;
-		ZEN_DEBUG("Unable to set sparse mode for file '{}'", PathFromHandle(FileHandle, DummyEc));
-		Result = false;
+		if ((Information.dwFileAttributes & FILE_ATTRIBUTE_SPARSE_FILE) == 0)
+		{
+			DWORD _	 = 0;
+			BOOL  Ok = DeviceIoControl(FileHandle, FSCTL_SET_SPARSE, nullptr, 0, nullptr, 0, &_, nullptr);
+			if (!Ok)
+			{
+				std::error_code DummyEc;
+				ZEN_DEBUG("Unable to set sparse mode for file '{}'", PathFromHandle(FileHandle, DummyEc));
+				Result = false;
+			}
+		}
 	}
 
 	FILE_ALLOCATION_INFO AllocationInfo	   = {};
-	AllocationInfo.AllocationSize.QuadPart = FinalSize;
+	AllocationInfo.AllocationSize.QuadPart = LONGLONG(FinalSize);
 	if (!SetFileInformationByHandle(FileHandle, FileAllocationInfo, &AllocationInfo, DWORD(sizeof(AllocationInfo))))
 	{
 		std::error_code DummyEc;
 		ZEN_DEBUG("Unable to set file allocation size to {} for file '{}'", FinalSize, PathFromHandle(FileHandle, DummyEc));
 		Result = false;
 	}
+
 #else	// ZEN_PLATFORM_WINDOWS
 	ZEN_UNUSED(FileHandle, FinalSize);
 #endif	// ZEN_PLATFORM_WINDOWS