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//===--- 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 <system_error>
#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
};
/// \brief Describes the result of waiting for the owner to release the lock.
enum WaitForUnlockResult {
/// \brief The lock was released successfully.
Res_Success,
/// \brief Owner died while holding the lock.
Res_OwnerDied,
/// \brief Reached timeout while waiting for the owner to release the lock.
Res_Timeout
};
private:
SmallString<128> FileName;
SmallString<128> LockFileName;
SmallString<128> UniqueLockFileName;
Optional<std::pair<std::string, int> > Owner;
Optional<std::error_code> Error;
LockFileManager(const LockFileManager &) = delete;
LockFileManager &operator=(const LockFileManager &) = delete;
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.
WaitForUnlockResult waitForUnlock();
/// \brief Remove the lock file. This may delete a different lock file than
/// the one previously read if there is a race.
std::error_code unsafeRemoveLockFile();
};
} // end namespace llvm
#endif // LLVM_SUPPORT_LOCKFILEMANAGER_H
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