gecko-dev/xpcom/threads/nsAutoLock.h

298 lines
8.0 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 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/NPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*/
/*
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"
class NS_COM nsAutoLockBase {
protected:
nsAutoLockBase() {}
enum nsAutoLockType {eAutoLock, eAutoMonitor, eAutoCMonitor};
#ifdef DEBUG
nsAutoLockBase(void* addr, nsAutoLockType type);
~nsAutoLockBase();
void* mAddr;
nsAutoLockBase* mDown;
nsAutoLockType mType;
#else
nsAutoLockBase(void* addr, nsAutoLockType type) {}
~nsAutoLockBase() {}
#endif
};
// 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_COM
// nsAutoLock".
class NS_COM nsAutoLock : public nsAutoLockBase {
private:
PRLock* mLock;
PRBool mLocked;
// 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.
#if (__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95))
static void* operator new(size_t /*size*/) throw () {
#else
static void* operator new(size_t /*size*/) {
#endif
return nsnull;
}
static void operator delete(void* /*memory*/) {}
public:
nsAutoLock(PRLock* aLock)
: nsAutoLockBase(aLock, eAutoLock),
mLock(aLock),
mLocked(PR_TRUE) {
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) {
if (mLocked)
PR_Unlock(mLock);
}
void lock() {
PR_ASSERT(!mLocked);
PR_Lock(mLock);
mLocked = PR_TRUE;
}
void unlock() {
PR_ASSERT(mLocked);
PR_Unlock(mLock);
mLocked = PR_FALSE;
}
};
////////////////////////////////////////////////////////////////////////////////
// Same sort of shit here. Imagine if you will:
//
// nsresult MyClass::MyMethod(...) {
// nsAutoMonitor mon(this); // or some random object as a monitor
// ...
// // go ahead and do deeply nested returns...
// return NS_ERROR_FAILURE;
// ...
// // or call Wait or Notify...
// mon.Wait();
// ...
// // cleanup is automatic
// }
#include "prcmon.h"
#include "nsError.h"
class NS_COM nsAutoMonitor : public nsAutoLockBase {
public:
static PRMonitor* NewMonitor(const char* name);
static void DestroyMonitor(PRMonitor* mon);
nsAutoMonitor(PRMonitor* mon)
: nsAutoLockBase((void*)mon, eAutoMonitor),
mMonitor(mon)
{
NS_ASSERTION(mMonitor, "null monitor");
PR_EnterMonitor(mMonitor);
}
~nsAutoMonitor() {
PRStatus status = PR_ExitMonitor(mMonitor);
NS_ASSERTION(status == PR_SUCCESS, "PR_ExitMonitor failed");
}
void Enter();
void Exit();
nsresult Wait(PRIntervalTime interval = PR_INTERVAL_NO_TIMEOUT) {
return PR_Wait(mMonitor, interval) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
nsresult Notify() {
return PR_Notify(mMonitor) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
nsresult NotifyAll() {
return PR_NotifyAll(mMonitor) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
private:
PRMonitor* mMonitor;
// Not meant to be implemented. This makes it a compiler error to
// construct or assign an nsAutoLock object incorrectly.
nsAutoMonitor(void) {}
nsAutoMonitor(nsAutoMonitor& /*aMon*/) {}
nsAutoMonitor& operator =(nsAutoMonitor& /*aMon*/) {
return *this;
}
// Not meant to be implemented. This makes it a compiler error to
// attempt to create an nsAutoLock object on the heap.
#if (__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95))
static void* operator new(size_t /*size*/) throw () {
#else
static void* operator new(size_t /*size*/) {
#endif
return nsnull;
}
static void operator delete(void* /*memory*/) {}
};
////////////////////////////////////////////////////////////////////////////////
// Once again, this time with a cache...
// (Using this avoids the need to allocate a PRMonitor, which may be useful when
// a large number of objects of the same class need associated monitors.)
#include "prcmon.h"
#include "nsError.h"
class NS_COM nsAutoCMonitor : public nsAutoLockBase {
public:
nsAutoCMonitor(void* lockObject)
: nsAutoLockBase(lockObject, eAutoCMonitor),
mLockObject(lockObject)
{
NS_ASSERTION(lockObject, "null lock object");
PR_CEnterMonitor(mLockObject);
}
~nsAutoCMonitor() {
PRStatus status = PR_CExitMonitor(mLockObject);
NS_ASSERTION(status == PR_SUCCESS, "PR_CExitMonitor failed");
}
void Enter();
void Exit();
nsresult Wait(PRIntervalTime interval = PR_INTERVAL_NO_TIMEOUT) {
return PR_CWait(mLockObject, interval) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
nsresult Notify() {
return PR_CNotify(mLockObject) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
nsresult NotifyAll() {
return PR_CNotifyAll(mLockObject) == PR_SUCCESS
? NS_OK : NS_ERROR_FAILURE;
}
private:
void* mLockObject;
// Not meant to be implemented. This makes it a compiler error to
// construct or assign an nsAutoLock object incorrectly.
nsAutoCMonitor(void) {}
nsAutoCMonitor(nsAutoCMonitor& /*aMon*/) {}
nsAutoCMonitor& operator =(nsAutoCMonitor& /*aMon*/) {
return *this;
}
// Not meant to be implemented. This makes it a compiler error to
// attempt to create an nsAutoLock object on the heap.
#if (__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95))
static void* operator new(size_t /*size*/) throw() {
#else
static void* operator new(size_t /*size*/) {
#endif
return nsnull;
}
static void operator delete(void* /*memory*/) {}
};
#endif // nsAutoLock_h__