#include "kernel.h"
#include "kmalloc.h"
#include "spinlock.h"
#include "log.h"

#define BLOCKS KMALLOC_MEM_SIZE/KMALLOC_BLOCK_SIZE

// this is in .bss so we can assume it was zeroed!
static uint8_t    data[KMALLOC_MEM_SIZE] __attribute__((aligned (4096))); // bytes
static uint8_t    map[BLOCKS];
//
static uint32_t   data_addr;

static uint32_t   next;
static uint32_t   first;
static uint8_t    init=0;

static uint32_t next_free(uint32_t start)
{
    for(int i=start;i<BLOCKS;i++)
    {
	if(!map[i])return i;
	return next_free(i+map[i]); 
    }
    return BLOCKS; // out of mem
}

static uint32_t next_used(uint32_t start,uint32_t max)
{
    for(int i=start;i<BLOCKS;i++)
    {
	if(map[i])return i; 
	//means i is free
	if(i-start>=max)return i;
    }
    return BLOCKS; // all free
}

static uint32_t free_cont(uint32_t blocks)
{
    uint32_t pos=0;

    while(1)
    {
	pos=next_free(pos);
//	klog("next_free:%d",pos);
	if(pos==BLOCKS)return BLOCKS; // out of mem
	uint32_t end=next_used(pos,blocks);
//	klog("next_used:%d",end);
	if(end-pos>=blocks)return pos;
//	klog("here we have only %d blocks but we need at least %d",end-pos+1,blocks);
	pos=end;
    }
}

static void mark_used(uint32_t start,uint32_t blocks)
{
    uint32_t b=blocks;
    for(int i=start;i<start+blocks;i++)
    {
	if(map[i]!=0)kpanic("memory map corrupted?");
	map[i]=b;
	b--;
    }
}

static void mark_free(uint32_t start,uint32_t blocks)
{
    if(map[start]!=blocks)
    {
	kpanic("mark_free(%d,%d),mem map corrupted at %d (value=%d)?",start,blocks,start,map[start]);
    }

    if(start!=0&&(map[start-1]!=1&&map[start-1]!=0))
    {
	kpanic("mem map corrupted one before %d (value=%d)?",start,map[start-1]);
    }

    map[start]=0;
    if(blocks>1)mark_free(start+1,blocks-1);
}

// will be initialized on first call to kballoc() //
static void kmallocinit()
{
    next=&(data[0]);
    data_addr=next;
    first=next;
    if(next%4096)kpanic("kmalloc data not aligned properly.");

    klog("In-Kernel Block Memory Allocation Initialized at: 0x%08X (free: %d x 4096KB BLOCKS)",next,BLOCKS);
    init=1;
}

// kernel block memory allocation //
uint32_t kballoc(uint32_t size)
{
    if(size>255)kpanic("max supported size 255 blocks");
    
    spinlock_spin(SPINLOCK_ALLOC);
    if(!init)kmallocinit();

    uint32_t blk=free_cont(size);
    if(blk==BLOCKS)kpanic("out of mem");
    mark_used(blk,size);
    spinlock_release(SPINLOCK_ALLOC);

    return data_addr+blk*4096;
}

void kbfree(uint32_t pos)
{
    uint32_t blk=(pos-data_addr)/4096;
    spinlock_spin(SPINLOCK_ALLOC);
    klog("freeing %d blocks ad 0x%08X",map[blk],pos);
    mark_free(blk,map[blk]);
    spinlock_release(SPINLOCK_ALLOC);
}

void kmalloc_sysfs(ringbuffer *r,void (*f)(ringbuffer *r,char *fmt, ...))
{
    uint32_t free=0;
    uint32_t used=0;
    for(int i=0;i<BLOCKS;i++)
    {
	if(map[i]) used++;
	else free++;
    }

    f(r,"kernel blocks allocation/deallocation");
    f(r,"total 4096kb blocks: %d (%d bytes)",BLOCKS,BLOCKS*4096);
    f(r,"used 4096kb blocks: %d (%d bytes)",used,used*4096);
    f(r,"free 4096kb blocks: %d (%d bytes)",free,free*4096);
}