/* 
 * Copyright 2010 Steffen Vogel, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM. 
 */

#include <metalsvm/malloc.h>
#include <metalsvm/spinlock.h>
#include <metalsvm/stdio.h>
#include <metalsvm/mmu.h>

/// A linked list for each binary size exponent
static buddy_t* buddy_lists[BUDDY_LISTS] = { NULL };
/// Lock for the buddy lists
static spinlock_t buddy_lock = SPINLOCK_INIT;

/** @brief Check if larger free buddies are available */
static inline int buddy_large_avail(uint8_t exp)
{
	while (exp<BUDDY_MAX && !buddy_lists[exp-BUDDY_MIN]) exp++;
	return exp != BUDDY_MAX;
}

/** @brief Calculate the required buddy size */
static inline int buddy_exp(size_t sz)
{
	int exp;
	for (exp=0; (1<<exp)<sz; exp++);

	if (exp > BUDDY_MAX)
		return 0;
	else if (exp < BUDDY_MIN)
		return BUDDY_MIN;
	else
		return exp;
}

/** @brief Get a free buddy by potentially splitting a larger one */
static buddy_t* buddy_get(int exp)
{
	spinlock_lock(&buddy_lock);
	buddy_t** list = &buddy_lists[exp-BUDDY_MIN];
	buddy_t* buddy = *list;
	buddy_t* split;

	if (buddy)
		// there is already a free buddy =>
		// we remove it from the list
		*list = buddy->next;
	else if (exp >= BUDDY_ALLOC && !buddy_large_avail(exp))
		// theres no free buddy larger than exp =>
		// we can allocate new memory
		buddy = (buddy_t*) palloc(1<<exp, MAP_KERNEL_SPACE);
	else {
		// we recursivly request a larger buddy...
		buddy = buddy_get(exp+1);
		if (BUILTIN_EXPECT(!buddy, 0))
			goto out;

		// ... and split it, by putting the second half back to the list
		split = (buddy_t*) ((size_t) buddy + (1<<exp));
		split->next = *list;
		*list = split;
	}

out:
	spinlock_unlock(&buddy_lock);

	return buddy;
}

/** @brief Put a buddy back to its free list
 *
 * TODO: merge adjacent buddies (memory compaction)
 */
static void buddy_put(buddy_t* buddy)
{
	spinlock_lock(&buddy_lock);
	buddy_t** list = &buddy_lists[buddy->prefix.exponent-BUDDY_MIN];
	buddy->next = *list;
	*list = buddy;
	spinlock_unlock(&buddy_lock);
}

void buddy_dump()
{
	size_t free = 0;
	int i;
	for (i=0; i<BUDDY_LISTS; i++) {
		buddy_t* buddy;
		int exp = i+BUDDY_MIN;

		if (buddy_lists[i])
			kprintf("buddy_list[%u] (exp=%u, size=%lu bytes):\n", i, exp, 1<<exp);

		for (buddy=buddy_lists[i]; buddy; buddy=buddy->next) {
			kprintf("  %p -> %p \n", buddy, buddy->next);
			free += 1<<exp;
		}
	}
	kprintf("free buddies: %lu bytes\n", free);
}

void* palloc(size_t sz, uint32_t flags)
{
	size_t phyaddr, viraddr;
	uint32_t npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;

	kprintf("palloc(%lu) (%lu pages)\n", sz, npages); // TODO: remove

	// get free virtual address space
	viraddr = vma_alloc(npages*PAGE_SIZE, VMA_HEAP);
	if (BUILTIN_EXPECT(!viraddr, 0))
		return NULL;

	// get continous physical pages
	phyaddr = get_pages(npages);
	if (BUILTIN_EXPECT(!phyaddr, 0)) {
		vma_free(viraddr, viraddr+npages*PAGE_SIZE);
		return NULL;
	}

	// map physical pages to VMA
	viraddr = map_region(viraddr, phyaddr, npages, flags);
	if (BUILTIN_EXPECT(!viraddr, 0)) {
		vma_free(viraddr, viraddr+npages*PAGE_SIZE);
		put_pages(phyaddr, npages);
		return NULL;
	}

	return (void*) viraddr;
}

void pfree(void* addr, size_t sz)
{
	if (BUILTIN_EXPECT(!addr || !sz, 0))
		return;

	size_t i;
	size_t phyaddr;
	size_t viraddr = (size_t) addr & PAGE_MASK;
	uint32_t npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;

	// memory is propably not continously mapped!
	for (i=0; i<npages; i++) {
		phyaddr = virt_to_phys(viraddr+i*PAGE_SHIFT);
		put_page(phyaddr);
	}

	unmap_region(viraddr, npages);
	vma_free(viraddr, viraddr+npages*PAGE_SIZE);
}

void* kmalloc(size_t sz)
{
	if (BUILTIN_EXPECT(!sz, 0))
		return NULL;

	// add space for the prefix
	sz += sizeof(buddy_t);

	int exp = buddy_exp(sz);
	if (BUILTIN_EXPECT(!exp, 0))
		return NULL;

	buddy_t* buddy = buddy_get(exp);
	if (BUILTIN_EXPECT(!buddy, 0))
		return NULL;

	// setup buddy prefix
	buddy->prefix.magic = BUDDY_MAGIC;
	buddy->prefix.exponent = exp;

	// pointer arithmetic: we hide the prefix
	return buddy+1;
}

void kfree(void *addr)
{
	if (BUILTIN_EXPECT(!addr, 0))
		return;

	buddy_t* buddy = (buddy_t*) addr - 1; // get prefix

	// check magic
	if (BUILTIN_EXPECT(buddy->prefix.magic != BUDDY_MAGIC, 0))
		return;

	buddy_put(buddy);
}