file: Add LOCK subcommand to do file and directory locking

Provide options to fail without blocking or to block up to a timeout.
Provide options to specify the scope containing the lock so it can be
released automatically at the end of a function, file, or process.

Extend the RunCMake.file test with cases covering the file(LOCK) command
usage and error cases.

1 files changed, 74 insertions, 0 deletions

diff --git a/Source/cmFileLock.h b/Source/cmFileLock.h
new file mode 100644
index 0000000..4d922a0
--- /dev/null
+++ b/Source/cmFileLock.h
@@ -0,0 +1,74 @@
+/*============================================================================
+  CMake - Cross Platform Makefile Generator
+  Copyright 2014 Ruslan Baratov
+
+  Distributed under the OSI-approved BSD License (the "License");
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+============================================================================*/
+
+#ifndef cmFileLock_h
+#define cmFileLock_h
+
+#include "cmStandardIncludes.h"
+
+#if defined(_WIN32)
+# include <windows.h> // HANDLE
+#endif
+
+class cmFileLockResult;
+
+/**
+  * @brief Cross-platform file locking.
+  * @details Under the hood this class use 'fcntl' for Unix-like platforms and
+  * 'LockFileEx'/'UnlockFileEx' for Win32 platform. Locks are exclusive and
+  * advisory.
+  */
+class cmFileLock
+{
+ public:
+  cmFileLock();
+  ~cmFileLock();
+
+  /**
+    * @brief Lock the file.
+    * @param timeoutSec Lock timeout. If -1 try until success or fatal error.
+    */
+  cmFileLockResult Lock(const std::string& filename, unsigned timeoutSec);
+
+  /**
+    * @brief Unlock the file.
+    */
+  cmFileLockResult Release();
+
+  /**
+    * @brief Check file is locked by this class.
+    * @details This function helps to find double locks (deadlocks) and to do
+    * explicit unlocks.
+    */
+  bool IsLocked(const std::string& filename) const;
+
+ private:
+  cmFileLock(const cmFileLock&);
+  cmFileLock& operator=(const cmFileLock&);
+
+  cmFileLockResult OpenFile();
+  cmFileLockResult LockWithoutTimeout();
+  cmFileLockResult LockWithTimeout(unsigned timeoutSec);
+
+#if defined(_WIN32)
+  typedef HANDLE FileId;
+  BOOL LockFile(DWORD flags);
+#else
+  typedef int FileId;
+  int LockFile(int cmd, int type);
+#endif
+
+  FileId File;
+  std::string Filename;
+};
+
+#endif // cmFileLock_h