Enable FILE_SHARE_DELETE on standalone files in disk buckets

This allows us to delete the file even if it is open for read.
We do a delete, the rename since we are not allowed to do a rename-overwrite, only delete.
As we have the shard lock for the file we want to replace we can safely do a delete+rename.
In the rare case that we fail to rename the file into place the old data is lost.
As this is a *cache* and it should be very rare this is OK.

1 files changed, 45 insertions, 0 deletions

diff --git a/zencore/iobuffer.cpp b/zencore/iobuffer.cpp
index c4b7f7bdf..61db25d0f 100644
--- a/zencore/iobuffer.cpp
+++ b/zencore/iobuffer.cpp
@@ -470,6 +470,51 @@ IoBufferBuilder::MakeFromFileHandle(void* FileHandle, uint64_t Offset, uint64_t
 }
 
 IoBuffer
+IoBufferBuilder::MakeFromFileWithSharedDelete(const std::filesystem::path& FileName)
+{
+	uint64_t Size;
+
+#if ZEN_PLATFORM_WINDOWS
+	CAtlFile DataFile;
+
+	HRESULT hRes = DataFile.Create(FileName.c_str(), GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_DELETE, OPEN_EXISTING);
+
+	if (FAILED(hRes))
+	{
+		return {};
+	}
+
+	DataFile.GetSize((ULONGLONG&)Size);
+#else
+	int Fd = open(FileName.c_str(), O_RDONLY | O_CLOEXEC);
+	if (Fd < 0)
+	{
+		return {};
+	}
+
+	static_assert(sizeof(decltype(stat::st_size)) == sizeof(uint64_t), "fstat() doesn't support large files");
+	struct stat Stat;
+	fstat(Fd, &Stat);
+	Size   = Stat.st_size;
+#endif	// ZEN_PLATFORM_WINDOWS
+
+	if (Size)
+	{
+#if ZEN_PLATFORM_WINDOWS
+		void* Fd = DataFile.Detach();
+#endif
+		return IoBuffer(IoBuffer::File, (void*)uintptr_t(Fd), 0, Size);
+	}
+
+#if !ZEN_PLATFORM_WINDOWS
+	close(Fd);
+#endif
+
+	// For an empty file, we may as well just return an empty memory IoBuffer
+	return IoBuffer(IoBuffer::Wrap, "", 0);
+}
+
+IoBuffer
 IoBufferBuilder::MakeFromFile(const std::filesystem::path& FileName, uint64_t Offset, uint64_t Size)
 {
 	uint64_t FileSize;