1 files changed, 117 insertions, 0 deletions
diff --git a/src/zencore/basicfile.cpp b/src/zencore/basicfile.cpp
index 9dcf7663a..fdf742261 100644
--- a/src/zencore/basicfile.cpp
+++ b/src/zencore/basicfile.cpp
@@ -3,6 +3,7 @@
 #include <zencore/basicfile.h>
 
 #include <zencore/compactbinary.h>
+#include <zencore/compactbinarybuilder.h>
 #include <zencore/except.h>
 #include <zencore/filesystem.h>
 #include <zencore/fmtutils.h>
@@ -608,6 +609,67 @@ LockFile::Update(CbObject Payload, std::error_code& Ec)
 	BasicFile::Write(Payload.GetBuffer(), 0, Ec);
 }
 
+bool
+LockFile::IsHeldLive(const std::filesystem::path& FileName, bool AttemptCleanup)
+{
+#if ZEN_PLATFORM_WINDOWS
+	if (AttemptCleanup)
+	{
+		if (DeleteFileW(FileName.c_str()))
+		{
+			return false;
+		}
+		const DWORD Err = ::GetLastError();
+		if (Err == ERROR_FILE_NOT_FOUND || Err == ERROR_PATH_NOT_FOUND)
+		{
+			return false;
+		}
+		return true;
+	}
+
+	HANDLE Handle = CreateFileW(FileName.c_str(),
+								DELETE,
+								FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+								nullptr,
+								OPEN_EXISTING,
+								FILE_ATTRIBUTE_NORMAL,
+								nullptr);
+	if (Handle != INVALID_HANDLE_VALUE)
+	{
+		CloseHandle(Handle);
+		return false;
+	}
+	const DWORD Err = ::GetLastError();
+	if (Err == ERROR_FILE_NOT_FOUND || Err == ERROR_PATH_NOT_FOUND)
+	{
+		return false;
+	}
+	return true;
+#else
+	int	  Fd		 = open(FileName.c_str(), O_RDONLY | O_CLOEXEC);
+	if (Fd < 0)
+	{
+		if (errno == ENOENT)
+		{
+			return false;
+		}
+		return true;
+	}
+	if (flock(Fd, LOCK_EX | LOCK_NB) == 0)
+	{
+		if (AttemptCleanup)
+		{
+			unlink(FileName.c_str());
+		}
+		flock(Fd, LOCK_UN);
+		close(Fd);
+		return false;
+	}
+	close(Fd);
+	return true;
+#endif
+}
+
 //////////////////////////////////////////////////////////////////////////
 
 BasicFileBuffer::BasicFileBuffer(BasicFile& Base, uint64_t BufferSize)
@@ -947,6 +1009,61 @@ TEST_CASE("TemporaryFile")
 	}
 }
 
+TEST_CASE("LockFile.IsHeldLive")
+{
+	ScopedCurrentDirectoryChange _;
+	const std::filesystem::path	 Path = std::filesystem::current_path() / "heldlive.lock";
+
+	SUBCASE("Nonexistent")
+	{
+		std::error_code Ec;
+		RemoveFile(Path, Ec);
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ true) == false);
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ false) == false);
+		CHECK(IsFile(Path) == false);
+	}
+
+	SUBCASE("Live holder")
+	{
+		LockFile		Lock;
+		std::error_code Ec;
+		Lock.Create(Path, CbObjectWriter().Save(), Ec);
+		CHECK(!Ec);
+		CHECK(IsFile(Path));
+
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ false) == true);
+		CHECK(IsFile(Path));
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ true) == true);
+		CHECK(IsFile(Path));
+	}
+
+	SUBCASE("Stale file, cleanup")
+	{
+		{
+			BasicFile File;
+			File.Open(Path, BasicFile::Mode::kTruncate);
+			File.Write("x", 1, 0);
+		}
+		CHECK(IsFile(Path));
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ true) == false);
+		CHECK(IsFile(Path) == false);
+	}
+
+	SUBCASE("Stale file, no cleanup")
+	{
+		{
+			BasicFile File;
+			File.Open(Path, BasicFile::Mode::kTruncate);
+			File.Write("x", 1, 0);
+		}
+		CHECK(IsFile(Path));
+		CHECK(LockFile::IsHeldLive(Path, /*AttemptCleanup*/ false) == false);
+		CHECK(IsFile(Path));
+		std::error_code Ec;
+		RemoveFile(Path, Ec);
+	}
+}
+
 TEST_CASE("BasicFileBuffer")
 {
 	ScopedCurrentDirectoryChange _;