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// -*- C++ -*-
//=============================================================================
/**
* @file File_Lock.h
*
* $Id$
*
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
*/
//=============================================================================
#ifndef ACE_FILE_LOCK_H
#define ACE_FILE_LOCK_H
#include /**/ "ace/pre.h"
#include /**/ "ace/ACE_export.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#include "ace/OS_NS_stdio.h"
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
/**
* @class ACE_File_Lock
*
* @brief A wrapper around the UNIX file locking mechanism.
*
* Allows us to "adapt" the UNIX file locking mechanisms to work
* with all of our Guard stuff...
*/
class ACE_Export ACE_File_Lock
{
public:
/**
* Set the <handle_> of the File_Lock to <handle>. Note that this
* constructor assumes ownership of the <handle> and will close it
* down in <remove>. If you want the <handle> to stay open when
* <remove> is called make sure to call <dup> on the <handle>.
* If you don't want the file unlinked in the destructor pass a
* zero value for <unlink_in_destructor>.
*/
ACE_File_Lock (ACE_HANDLE handle = ACE_INVALID_HANDLE,
int unlink_in_destructor = 1);
/// Open the <filename> with <flags> and <mode> and set the result
/// to <handle_>. If you don't want the file unlinked in the
/// destructor pass a zero value for <unlink_in_destructor>.
ACE_File_Lock (const ACE_TCHAR *filename,
int flags,
mode_t mode = 0,
int unlink_in_destructor = 1);
/// Open the <filename> with <flags> and <mode> and set the result to
/// <handle_>.
int open (const ACE_TCHAR *filename,
int flags,
mode_t mode = 0);
/// Remove a File lock by releasing it and closing down the <handle_>.
~ACE_File_Lock (void);
/// Remove a File lock by releasing it and closing down the
/// <handle_>. If <unlink_file> is non-0 then we unlink the file.
int remove (int unlink_file = 1);
/**
* Note, for interface uniformity with other synchronization
* wrappers we include the <acquire> method. This is implemented as
* a write-lock to be on the safe-side...
*/
int acquire (short whence = 0, off_t start = 0, off_t len = 1);
/**
* Note, for interface uniformity with other synchronization
* wrappers we include the <tryacquire> method. This is implemented
* as a write-lock to be on the safe-side... Returns -1 on failure.
* If we "failed" because someone else already had the lock, <errno>
* is set to <EBUSY>.
*/
int tryacquire (short whence = 0, off_t start = 0, off_t len = 1);
/// Unlock a readers/writer lock.
int release (short whence = 0, off_t start = 0, off_t len = 1);
/// Acquire a write lock, but block if any readers or a
/// writer hold the lock.
int acquire_write (short whence = 0, off_t start = 0, off_t len = 1);
/**
* Conditionally acquire a write lock (i.e., won't block). Returns
* -1 on failure. If we "failed" because someone else already had
* the lock, <errno> is set to <EBUSY>.
*/
int tryacquire_write (short whence = 0, off_t start = 0, off_t len = 1);
/**
* Conditionally upgrade to a write lock (i.e., won't block). Returns
* -1 on failure. If we "failed" because someone else already had
* the lock, <errno> is set to <EBUSY>.
*/
int tryacquire_write_upgrade (short whence = 0,
off_t start = 0,
off_t len = 1);
/**
* Acquire a read lock, but block if a writer hold the lock.
* Returns -1 on failure. If we "failed" because someone else
* already had the lock, <errno> is set to <EBUSY>.
*/
int acquire_read (short whence = 0, off_t start = 0, off_t len = 1);
/**
* Conditionally acquire a read lock (i.e., won't block). Returns
* -1 on failure. If we "failed" because someone else already had
* the lock, <errno> is set to <EBUSY>.
*/
int tryacquire_read (short whence = 0, off_t start = 0, off_t len = 1);
/// Get underlying ACE_HANDLE for the file.
ACE_HANDLE get_handle (void) const;
/**
* Set underlying ACE_HANDLE. Note that this method assumes
* ownership of the <handle> and will close it down in <remove>. If
* you want the <handle> to stay open when <remove> is called make
* sure to call <dup> on the <handle> before closing it. You are
* responsible for the closing the existing <handle> before
* overwriting it.
*/
void set_handle (ACE_HANDLE);
/// Dump state of the object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
/// Locking structure for OS record locks.
ACE_OS::ace_flock_t lock_;
/// Keeps track of whether <remove> has been called yet to avoid
/// multiple <remove> calls, e.g., explicitly and implicitly in the
/// destructor. This flag isn't protected by a lock, so make sure
/// that you don't have multiple threads simultaneously calling
/// <remove> on the same object, which is a bad idea anyway...
int removed_;
/// Keeps track of whether to unlink the underlying file in the
/// destructor.
int unlink_in_destructor_;
private:
// = Prevent assignment and initialization.
void operator= (const ACE_File_Lock &);
ACE_File_Lock (const ACE_File_Lock &);
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/File_Lock.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* ACE_FILE_LOCK_H */
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