libs-base/Source/NSLock.m

/* 
   NSLock.m

   Mutual exclusion locking classes

   Copyright (C) 1996 Free Software Foundation, Inc.

   Author:  Scott Christley <scottc@net-community.com>
   Date: 1996
   
   This file is part of the GNUstep Objective-C Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   If you are interested in a warranty or support for this source code,
   contact Scott Christley <scottc@net-community.com> for more information.
   
   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/ 

#include <Foundation/NSLock.h>

//
// NSLock class
// Simplest lock for protecting critical sections of code
//
@implementation NSLock

// Class initialization
+ (void)initialize
{
	if (self == [NSLock class])
	{
		// Initial version
		[self setVersion:1];
	}
}

// Default initializer
- init
{
	[super init];

	// Allocate the mutex from the runtime
	mutex = objc_mutex_allocate();
	if (!mutex)
		return nil;
	else
		return self;
}

- (void)dealloc
{
	// Ask the runtime to deallocate the mutex
	// If there are outstanding locks then it will block
	objc_mutex_deallocate(mutex);

	[super dealloc];
}

// Try to acquire the lock
// Does not block
- (BOOL)tryLock
{
	// Ask the runtime to acquire a lock on the mutex
	if (objc_mutex_trylock(mutex) == -1)
		return NO;
	else
		return YES;
}

// NSLocking protocol
- (void)lock
{
	// Ask the runtime to acquire a lock on the mutex
	// This will block
	objc_mutex_lock(mutex);
}

- (void)unlock
{
	// Ask the runtime to release a lock on the mutex
	objc_mutex_unlock(mutex);
}

@end

//
// NSConditionLock
// Allows locking and unlocking to be based upon a condition
//
@implementation NSConditionLock

// Class initialization
+ (void)initialize
{
	if (self == [NSConditionLock class])
	{
		// Initial version
		[self setVersion:1];
	}
}

- init
{
	return [self initWithCondition:0];
}

// Default initializer
// Initialize lock with condition
- (id)initWithCondition:(int)value
{
	[super init];

	condition = value;

	// Allocate the mutex from the runtime
	mutex = objc_mutex_allocate();
	if (!mutex)
		return nil;
	else
		return self;
}

- (void)dealloc
{
	// Ask the runtime to deallocate the mutex
	// If there are outstanding locks then it will block
	objc_mutex_deallocate(mutex);

	[super dealloc];
}

// Return the current condition of the lock
- (int)condition
{
	return condition;
}

// Acquiring and release the lock
- (void)lockWhenCondition:(int)value
{
	BOOL done;

	done = NO;
	while (!done)
	{
		// Try to get the lock
		[self lock];

		// Is it in the condition we are looking for?
		if (condition == value)
			done = YES;
		else
			// Release the lock and keep waiting
			[self unlock];
	}
}

- (void)unlockWithCondition:(int)value
{
	int depth;

	// First check to make sure we have the lock
	depth= objc_mutex_trylock(mutex);

	// Another thread has the lock so abort
	if (depth == -1)
		return;

	// If the depth is only 1 then we just acquired
	// the lock above, bogus unlock so abort
	if (depth == 1)
		return;

	// This is a valid unlock so set the condition
	// and unlock twice
	condition = value;
	objc_mutex_unlock(mutex);
	objc_mutex_unlock(mutex);
}

- (BOOL)tryLock
{
	// Ask the runtime to acquire a lock on the mutex
	if (objc_mutex_trylock(mutex) == -1)
		return NO;
	else
		return YES;
}

- (BOOL)tryLockWhenCondition:(int)value
{
	// First can we even get the lock?
	if (![self tryLock])
		return NO;

	// If we got the lock is it the right condition?
	if (condition == value)
		return YES;
	else
	{
		// Wrong condition so release the lock
		[self unlock];
		return NO;
	}
}

// NSLocking protocol
// These methods ignore the condition
- (void)lock
{
	// Ask the runtime to acquire a lock on the mutex
	// This will block
	objc_mutex_lock(mutex);
}

- (void)unlock
{
	// Ask the runtime to release a lock on the mutex
	objc_mutex_unlock(mutex);
}

@end

//
// NSRecursiveLock
// Allows the lock to be recursively acquired by the same thread
//
// If the same thread locks the mutex (n) times then that same 
// thread must also unlock it (n) times before another thread 
// can acquire the lock.
//
@implementation NSRecursiveLock

// Class initialization
+ (void)initialize
{
	if (self == [NSRecursiveLock class])
	{
		// Initial version
		[self setVersion:1];
	}
}

// Default initializer
- init
{
	[super init];

	// Allocate the mutex from the runtime
	mutex = objc_mutex_allocate();
	if (!mutex)
		return nil;
	else
		return self;
}

- (void)dealloc
{
	// Ask the runtime to deallocate the mutex
	// If there are outstanding locks then it will block.
	objc_mutex_deallocate(mutex);

	[super dealloc];
}

// Try to acquire the lock
// Does not block
- (BOOL)tryLock
{
	// Ask the runtime to acquire a lock on the mutex
	if (objc_mutex_trylock(mutex) == -1)
		return NO;
	else
		return YES;
}

// NSLocking protocol
- (void)lock
{
	// Ask the runtime to acquire a lock on the mutex
	// This will block
	objc_mutex_lock(mutex);
}

- (void)unlock
{
	// Ask the runtime to release a lock onthe mutex
	objc_mutex_unlock(mutex);
}

@end