Qore::Thread::AutoWriteLock Class Reference

A helper class for the RWLock class for exception-safe write lock handling. More...

#include <QC_AutoWriteLock.dox.h>

Public Member Methods
	constructor (RWLock rwl)
	Creates the AutoWriteLock object based on the RWLock argument passed and immediately calls RWLock::writeLock() More...
	copy ()
	Throws an exception; objects of this class cannot be copied. More...
	destructor ()
	Calls RWLock::writeUnlock() on the saved RWLock and destroys the AutoWriteLock object. More...

Detailed Description

A helper class for the RWLock class for exception-safe write lock handling.

Restrictions:

Qore::PO_NO_THREAD_CLASSES

AutoWriteLock objects, when used along with a RWLock object, allow Qore programmers to safely acquire and release a write lock, even if exceptions are thrown or return statements are executed in the block where the AutoWriteLock object is created.

AutoWriteLock objects are helper objects that acquire a write lock for the lifetime of the AutoWriteLock object. For this reason, it is normally only appropriate to assign an AutoWriteLock object to a local variable, so when the local variable goes out of scope, the AutoWriteLock object will be deleted and the write lock will be automatically released.

For example:

our RWLock rwl();
 
sub check_error(bool error) {
    # note that the write lock is acquired in the AutoWriteLock constructor, and
    # the write lock will be released as soon as the block is exited below.
    # (with either the throw statement or the return statement)
    AutoWriteLock awl(rwl);
    if (error) {
        throw "ERROR", "sorry, an error happened";
    }
 
    return "OK";
}

Note

This class is not available with the PO_NO_THREAD_CLASSES parse option

Member Function Documentation

constructor()

Qore::Thread::AutoWriteLock::constructor

(

RWLock

rwl

)

Creates the AutoWriteLock object based on the RWLock argument passed and immediately calls RWLock::writeLock()

The AutoWriteLock object immediately calls RWLock::writeLock() on the RWLock object passed, and saves it so it can be released when the AutoWriteLock object is destroyed.

Example:

AutoWriteLock awl(rwlock);

Exceptions

THREAD-DEADLOCK	A deadlock was detected while trying to acquire the lock
LOCK-ERROR	RWLock::writeLock() called while already holding the read lock, object deleted in another thread, etc.

copy()

Qore::Thread::AutoWriteLock::copy

(

)

Throws an exception; objects of this class cannot be copied.

Exceptions

AUTOWRITELOCK-COPY-ERROR

objects of this class cannot be copied

destructor()

Qore::Thread::AutoWriteLock::destructor

(

)

Calls RWLock::writeUnlock() on the saved RWLock and destroys the AutoWriteLock object.

Example:

delete awl;

Exceptions

LOCK-ERROR

RWLock::writeUnlock() called while not holding the write lock, RWLock object deleted in another thread, etc