Move Clang's file-level locking facility over to LLVM's support

library, since it doesn't really have anything to do with Clang.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149203 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 74 insertions, 0 deletions

diff --git a/include/llvm/Support/LockFileManager.h b/include/llvm/Support/LockFileManager.h
new file mode 100644
index 0000000000..e2fa8ebc56
--- /dev/null
+++ b/include/llvm/Support/LockFileManager.h
@@ -0,0 +1,74 @@
+//===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H
+#define LLVM_SUPPORT_LOCKFILEMANAGER_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/system_error.h"
+#include <utility> // for std::pair
+
+namespace llvm {
+
+/// \brief Class that manages the creation of a lock file to aid
+/// implicit coordination between different processes.
+///
+/// The implicit coordination works by creating a ".lock" file alongside
+/// the file that we're coordinating for, using the atomicity of the file
+/// system to ensure that only a single process can create that ".lock" file.
+/// When the lock file is removed, the owning process has finished the
+/// operation.
+class LockFileManager {
+public:
+  /// \brief Describes the state of a lock file.
+  enum LockFileState {
+    /// \brief The lock file has been created and is owned by this instance
+    /// of the object.
+    LFS_Owned,
+    /// \brief The lock file already exists and is owned by some other
+    /// instance.
+    LFS_Shared,
+    /// \brief An error occurred while trying to create or find the lock
+    /// file.
+    LFS_Error
+  };
+
+private:
+  SmallString<128> LockFileName;
+  SmallString<128> UniqueLockFileName;
+
+  Optional<std::pair<std::string, int> > Owner;
+  Optional<error_code> Error;
+
+  LockFileManager(const LockFileManager &);
+  LockFileManager &operator=(const LockFileManager &);
+
+  static Optional<std::pair<std::string, int> >
+  readLockFile(StringRef LockFileName);
+
+  static bool processStillExecuting(StringRef Hostname, int PID);
+
+public:
+
+  LockFileManager(StringRef FileName);
+  ~LockFileManager();
+
+  /// \brief Determine the state of the lock file.
+  LockFileState getState() const;
+
+  operator LockFileState() const { return getState(); }
+
+  /// \brief For a shared lock, wait until the owner releases the lock.
+  void waitForUnlock();
+};
+
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_LOCKFILEMANAGER_H