/*******************************************************************************

    Copyright(C) Jonas 'Sortie' Termansen 2012, 2013.

    This file is part of Sortix.

    Sortix is free software: you can redistribute it and/or modify it under the
    terms of the GNU General Public License as published by the Free Software
    Foundation, either version 3 of the License, or (at your option) any later
    version.

    Sortix 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 General Public License for more
    details.

    You should have received a copy of the GNU General Public License along with
    Sortix. If not, see <http://www.gnu.org/licenses/>.

    interlock.cpp
    Functions that perform non-atomic operations in an atomic manner.

*******************************************************************************/

#include <sortix/kernel/interlock.h>
#include <sortix/kernel/kernel.h>

namespace Sortix {

// TODO: This is likely not the most optimal way to perform these operations.

ilret_t InterlockedModify(unsigned long* ptr,
                          ilockfunc f,
                          unsigned long user)
{
	unsigned long old_value, new_value;
	do
	{
		old_value = *((volatile unsigned long*) ptr); /* TODO: Need volatile? */
		new_value = f(old_value, user);
	} while ( !__sync_bool_compare_and_swap(ptr, old_value, new_value) );
	ilret_t ret;
	ret.o = old_value;
	ret.n = new_value;
	return ret;
}

static unsigned long AddFunction(unsigned long val, unsigned long arg)
{
	return val + arg;
}

static unsigned long SubFunction(unsigned long val, unsigned long arg)
{
	return val - arg;
}

ilret_t InterlockedIncrement(unsigned long* ptr)
{
	return InterlockedModify(ptr, AddFunction, 1);
}

ilret_t InterlockedDecrement(unsigned long* ptr)
{
	return InterlockedModify(ptr, SubFunction, 1);
}

ilret_t InterlockedAdd(unsigned long* ptr, unsigned long arg)
{
	return InterlockedModify(ptr, AddFunction, arg);
}

ilret_t InterlockedSub(unsigned long* ptr, unsigned long arg)
{
	return InterlockedModify(ptr, SubFunction, arg);
}

} // namespace Sortix