pjs/xpcom/threads/nsAutoLock.h

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2.9 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* The contents of this file are subject to the Netscape Public License
* Version 1.0 (the "NPL"); you may not use this file except in
* compliance with the NPL. You may obtain a copy of the NPL at
* http://www.mozilla.org/NPL/
*
* Software distributed under the NPL is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
* for the specific language governing rights and limitations under the
* NPL.
*
* The Initial Developer of this code under the NPL is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All Rights
* Reserved.
*/
/*
A stack-based lock object that makes using PRLock a bit more
convenient. It acquires the monitor when constructed, and releases
it when it goes out of scope.
For example,
class Foo {
private:
PRLock* mLock;
public:
Foo(void) {
mLock = PR_NewLock();
}
virtual ~Foo(void) {
PR_DestroyLock(mLock);
}
void ThreadSafeMethod(void) {
// we're don't hold the lock yet...
nsAutoLock lock(mLock);
// ...but now we do.
// we even can do wacky stuff like return from arbitrary places w/o
// worrying about forgetting to release the lock
if (some_weird_condition)
return;
// otherwise do some other stuff
}
void ThreadSafeBlockScope(void) {
// we're not in the lock here...
{
nsAutoLock lock(mLock);
// but we are now, at least until the block scope closes
}
// ...now we're not in the lock anymore
}
};
*/
#ifndef nsAutoLock_h__
#define nsAutoLock_h__
#include "nscore.h"
#include "prlock.h"
#include "prlog.h"
// If you ever decide that you need to add a non-inline method to this
// class, be sure to change the class declaration to "class NS_BASE
// nsAutoLock".
class nsAutoLock {
private:
PRLock* mLock;
// Not meant to be implemented. This makes it a compiler error to
// construct or assign an nsAutoLock object incorrectly.
nsAutoLock(void) {}
nsAutoLock(nsAutoLock& aLock) {}
nsAutoLock& operator =(nsAutoLock& aLock) {
return *this;
}
// Not meant to be implemented. This makes it a compiler error to
// attempt to create an nsAutoLock object on the heap.
static void* operator new(size_t size) {
return nsnull;
}
static void operator delete(void* memory) {}
public:
nsAutoLock(PRLock* aLock) : mLock(aLock) {
PR_ASSERT(mLock);
// This will assert deep in the bowels of NSPR if you attempt
// to re-enter the lock.
PR_Lock(mLock);
}
~nsAutoLock(void) {
PR_Unlock(mLock);
}
};
#endif // nsAutoLock_h__