# ACE_File_Lock Class Reference

A wrapper around the UNIX file locking mechanism. More...

`#include <File_Lock.h>`

Collaboration diagram for ACE_File_Lock:

[legend]
List of all members.

## Public Member Functions

| ACE_File_Lock (ACE_HANDLE handle=ACE_INVALID_HANDLE, int unlink_in_destructor=1)
| ACE_File_Lock (const ACE_TCHAR *filename, int flags, mode_t mode=0, int unlink_in_destructor=1)
int | open (const ACE_TCHAR *filename, int flags, mode_t mode=0)
| ~ACE_File_Lock (void)
| Remove a File lock by releasing it and closing down the <handle_>.
int | remove (int unlink_file=1)
int | acquire (short whence=0, off_t start=0, off_t len=1)
int | tryacquire (short whence=0, off_t start=0, off_t len=1)
int | release (short whence=0, off_t start=0, off_t len=1)
| Unlock a readers/writer lock.
int | acquire_write (short whence=0, off_t start=0, off_t len=1)
int | tryacquire_write (short whence=0, off_t start=0, off_t len=1)
int | tryacquire_write_upgrade (short whence=0, off_t start=0, off_t len=1)
int | acquire_read (short whence=0, off_t start=0, off_t len=1)
int | tryacquire_read (short whence=0, off_t start=0, off_t len=1)
ACE_HANDLE | get_handle (void) const
| Get underlying ACE_HANDLE for the file.
void | set_handle (ACE_HANDLE)
void | dump (void) const
| Dump state of the object.

## Public Attributes

| ACE_ALLOC_HOOK_DECLARE
| Declare the dynamic allocation hooks.

## Protected Attributes

ACE_OS::ace_flock_t | lock_
| Locking structure for OS record locks.
int | removed_
int | unlink_in_destructor_

## Private Member Functions

void | operator= (const ACE_File_Lock &)
| ACE_File_Lock (const ACE_File_Lock &)

## Detailed Description

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...

## Constructor & Destructor Documentation

ACE_File_Lock::ACE_File_Lock | ( | ACE_HANDLE | handle = `ACE_INVALID_HANDLE`,
|  | int | unlink_in_destructor = `1`
| ) |

| 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_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_>. If you don't want the file unlinked in the destructor pass a zero value for <unlink_in_destructor>.

ACE_File_Lock::~ACE_File_Lock | ( | void |  | ) |

| Remove a File lock by releasing it and closing down the <handle_>.

ACE_File_Lock::ACE_File_Lock | ( | const ACE_File_Lock & |  | ) | `[private]`

## Member Function Documentation

ACE_INLINE int ACE_File_Lock::acquire | ( | short | whence = `0`,
|  | off_t | start = `0`,
|  | off_t | len = `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...

ACE_BEGIN_VERSIONED_NAMESPACE_DECL ACE_INLINE int ACE_File_Lock::acquire_read | ( | 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>.

ACE_INLINE int ACE_File_Lock::acquire_write | ( | 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.

ACE_BEGIN_VERSIONED_NAMESPACE_DECL void ACE_File_Lock::dump | ( | void |  | ) | const

| Dump state of the object.

ACE_INLINE ACE_HANDLE ACE_File_Lock::get_handle | ( | void |  | ) | const

| Get underlying ACE_HANDLE for the file.

int ACE_File_Lock::open | ( | const ACE_TCHAR * | filename,
|  | int | flags,
|  | mode_t | mode = `0`
| ) |

| Open the <filename> with <flags> and <mode> and set the result to <handle_>.

void ACE_File_Lock::operator= | ( | const ACE_File_Lock & |  | ) | `[private]`

ACE_INLINE int ACE_File_Lock::release | ( | short | whence = `0`,
|  | off_t | start = `0`,
|  | off_t | len = `1`
| ) |

| Unlock a readers/writer lock.

ACE_INLINE int ACE_File_Lock::remove | ( | int | unlink_file = `1` | ) |

| Remove a File lock by releasing it and closing down the <handle_>. If <unlink_file> is non-0 then we unlink the file.

ACE_INLINE void ACE_File_Lock::set_handle | ( | ACE_HANDLE |  | ) |

| 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.

ACE_INLINE int ACE_File_Lock::tryacquire | ( | 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>.

ACE_INLINE int ACE_File_Lock::tryacquire_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>.

ACE_INLINE int ACE_File_Lock::tryacquire_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>.

ACE_INLINE int ACE_File_Lock::tryacquire_write_upgrade | ( | 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>.

## Member Data Documentation

ACE_File_Lock::ACE_ALLOC_HOOK_DECLARE

| Declare the dynamic allocation hooks.

ACE_OS::ace_flock_t ACE_File_Lock::lock_`[protected]`

| Locking structure for OS record locks.

int ACE_File_Lock::removed_`[protected]`

| 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 ACE_File_Lock::unlink_in_destructor_`[protected]`

| Keeps track of whether to unlink the underlying file in the destructor.

The documentation for this class was generated from the following files:

- File_Lock.h
- File_Lock.cpp
- File_Lock.inl