# ACE_RW_Process_Mutex Class Reference

Wrapper for readers/writer locks that exist across processes. More...

`#include <RW_Process_Mutex.h>`

Collaboration diagram for ACE_RW_Process_Mutex:

[legend]
List of all members.

## Public Member Functions

| ACE_RW_Process_Mutex (const ACE_TCHAR *name=0, int flags=O_CREAT|O_RDWR, mode_t mode=ACE_DEFAULT_OPEN_PERMS)
| ~ACE_RW_Process_Mutex (void)
int | remove (void)
int | acquire (void)
| Acquire lock ownership (wait on queue if necessary).
int | tryacquire (void)
int | release (void)
| Release lock and unblock a thread at head of queue.
int | acquire_read (void)
| Acquire lock ownership (wait on queue if necessary).
int | acquire_write (void)
| Acquire lock ownership (wait on queue if necessary).
int | tryacquire_read (void)
int | tryacquire_write (void)
int | tryacquire_write_upgrade (void)
const ACE_File_Lock & | lock (void) const
| Return the underlying lock.
void | dump (void) const
| Dump the state of an object.

## Public Attributes

| ACE_ALLOC_HOOK_DECLARE
| Declare the dynamic allocation hooks.

## Private Member Functions

const ACE_TCHAR * | unique_name (void)
| Create and return the unique name.

## Private Attributes

ACE_TCHAR | name_ [ACE_UNIQUE_NAME_LEN]
ACE_File_Lock | lock_
| We need this to get the readers/writer semantics...

## Detailed Description

Wrapper for readers/writer locks that exist across processes.

Note that because this class uses the <ace_file_lock> as its implementation it only can be reliably used between separate processes, rather than threads in the same process. This isn't a limitation of ACE, it's simply the file lock semantics on UNIX and Win32.

Todo:
  For systems with pthread_rwlockattr_setpshared one may consider using them to make the mutex faster.

## Constructor & Destructor Documentation

ACE_RW_Process_Mutex::ACE_RW_Process_Mutex | ( | const ACE_TCHAR * | name = `0`,
|  | int | flags = `O_CREAT|O_RDWR`,
|  | mode_t | mode = `ACE_DEFAULT_OPEN_PERMS`
| ) |

Create a readers/writer <process_mutex>, passing in the optional <name>, <flags> and <mode>

See also:
  ACE_File_Lock. If not specified, a name is generated and flags and mode are set to default platform values.

ACE_RW_Process_Mutex::~ACE_RW_Process_Mutex | ( | void |  | ) |

## Member Function Documentation

ACE_INLINE int ACE_RW_Process_Mutex::acquire | ( | void |  | ) |

| Acquire lock ownership (wait on queue if necessary).

ACE_INLINE int ACE_RW_Process_Mutex::acquire_read | ( | void |  | ) |

| Acquire lock ownership (wait on queue if necessary).

ACE_INLINE int ACE_RW_Process_Mutex::acquire_write | ( | void |  | ) |

| Acquire lock ownership (wait on queue if necessary).

void ACE_RW_Process_Mutex::dump | ( | void |  | ) | const

| Dump the state of an object.

ACE_INLINE const ACE_File_Lock & ACE_RW_Process_Mutex::lock | ( | void |  | ) | const

| Return the underlying lock.

ACE_INLINE int ACE_RW_Process_Mutex::release | ( | void |  | ) |

| Release lock and unblock a thread at head of queue.

ACE_BEGIN_VERSIONED_NAMESPACE_DECL ACE_INLINE int ACE_RW_Process_Mutex::remove | ( | void |  | ) |

| Explicitly destroy the mutex. Note that only one thread should call this method since it doesn't protect against race conditions.

ACE_INLINE int ACE_RW_Process_Mutex::tryacquire | ( | void |  | ) |

| Conditionally acquire lock (i.e., don't wait on queue). Returns -1 on failure. If we "failed" because someone else already had the lock, <errno> is set to <ebusy>.

ACE_INLINE int ACE_RW_Process_Mutex::tryacquire_read | ( | void |  | ) |

| Conditionally acquire a 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_RW_Process_Mutex::tryacquire_write | ( | void |  | ) |

| Conditionally acquire a 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_RW_Process_Mutex::tryacquire_write_upgrade | ( | void |  | ) |

| Attempt to upgrade a read lock to a write lock. Returns 0 on success, -1 on failure.

ACE_BEGIN_VERSIONED_NAMESPACE_DECL const ACE_TCHAR * ACE_RW_Process_Mutex::unique_name | ( | void |  | ) | `[private]`

| Create and return the unique name.

## Member Data Documentation

ACE_RW_Process_Mutex::ACE_ALLOC_HOOK_DECLARE

| Declare the dynamic allocation hooks.

ACE_File_Lock ACE_RW_Process_Mutex::lock_ `[private]`

| We need this to get the readers/writer semantics...

ACE_TCHAR ACE_RW_Process_Mutex::name_[ACE_UNIQUE_NAME_LEN]`[private]`

| If the user does not provide a name we generate a unique name in this buffer.

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

- RW_Process_Mutex.h
- RW_Process_Mutex.cpp
- RW_Process_Mutex.inl