//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       Early and very dumb heap managment                            //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K 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         //
//  any later version.                                                        //
//                                                                            //
//  OS/K 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 OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <kernel/heap.h>

// Least address out of the heap
static void *_heap_end;

// Maximal value of the heap
static size_t _heap_max;

// Lock NOT used internally, but used by KalAllocMemory() & co.
static Lock_t _heap_lock = ExINITLOCK(KLOCK_SPINLOCK);

// Debugging stub
size_t MmGetAvailZoneSize(void *x) { (void)x; return 8 * MB; }

//
// Initializes heap managment
//
void MmInitHeap(void)
{
    assert(_heap_end == NULL);
    _heap_end = (void *)_HEAP_START;
    _heap_max = lmin(8 * MB, MmGetAvailZoneSize((void *)_HEAP_START));
}

//
// Acquires control of the heap's lock
//
void MmLockHeap(void)
{
    ExAcquireLock(&_heap_lock);
}

//
// Releases control of the heap's lock
//
void MmUnlockHeap(void)
{
    ExReleaseLock(&_heap_lock);
}

//
// Returns the heap's current size
//
size_t MmGetHeapSize(void)
{
    return (size_t)_heap_end - _HEAP_START;
}

//
// Returns the heap's maximum size
//
size_t MmGetMaxHeapSize(void)
{
    return _heap_max;
}

//
// Changes the heap's maximal size
//
error_t MmSetMaxHeapSize(size_t new)
{
    if (new > MmGetAvailZoneSize((void *)_HEAP_START)) {
        return ENOMEM;
    }

    if (new < (size_t)_heap_end - _HEAP_START) {
        return EADDRINUSE;
    }

    _heap_max = new;

    return EOK;
}

//
// Extends the heap's size
//
error_t MmGrowHeap(size_t req)
{
    assert(req % alignof(QWORD));

    if ((size_t)_heap_end + req > _HEAP_START + _heap_max) {
        return ENOMEM;
    }

    _heap_end += req;

    return EOK;
}

//
// Reduces the heap's size
//
error_t MmShrinkHeap(size_t req)
{
    assert(req % alignof(QWORD));

    if (req > (size_t)_heap_end - _HEAP_START) {
        return EADDRINUSE;
    }

    _heap_end -= req;

    return EOK;
}