#include <stdint.h>
#include <stdio.h>

#define SWAP_FREE_LIST 8192

typedef struct sw_free_block
  {
  int32_t size,seek;
  }SW_FREE_BLOCK;

SW_FREE_BLOCK swp_list[SWAP_FREE_LIST];
int swp_ptr;
int swp_fnot_used=-1;
int swp_unuseds=0;
int swpl_overruns=0;

void swap_init(void)
  {
  swp_ptr=0;
  swp_list[swp_ptr].seek=0;
  swp_list[swp_ptr].size=-1;
  swp_ptr=1;
  }

int swap_find_block(int32_t size)
  {
  int i;
  SW_FREE_BLOCK *p;

  p=swp_list;
  for(i=0;i<swp_ptr;i++,p++)
      if (p->size>=size) return i;
      else if (p->seek==-1) swp_fnot_used=i;
  return 0;
  }

int swap_add_block(int32_t size)
  {
  int i;
  int32_t sp;
  SW_FREE_BLOCK *p;

  size+=255;
  size&=~255;
  i=swap_find_block(size);
  p=&swp_list[i];
  sp=p->seek;
  if (p->size==-1) p->seek+=size;
  else if (p->size==size)
     {
     p->seek=-1;
     p->size=-1;
     swp_unuseds++;
     swp_fnot_used=i;
     }
  else
     {
     p->seek+=size;
     p->size-=size;
     }
  return sp;
  }

void swap_find_seek(int32_t seek1,int32_t seek2,int *pos1,int *pos2)
  {
  int i;
  SW_FREE_BLOCK *p;

  p=swp_list;*pos1=-1;*pos2=-1;
  for(i=0;i<swp_ptr;i++,p++)
      {
      if (p->seek==seek2)
        {
        *pos2=i;
        if (*pos1>=0) return;
        }
      if (p->seek+p->size==seek1)
        {
        *pos1=i;
        if (*pos2>=0) return;
        }
      }
  }


void alloc_swp_block(int32_t seek,int32_t size)
  {

  if (swp_fnot_used<0 && swp_unuseds) swap_find_block(0x7fffffff);
  if (swp_fnot_used<0)
     {
     swp_list[swp_ptr].seek=seek;
     swp_list[swp_ptr].size=size;
     swp_unuseds=0;
     swp_ptr++;if (swp_ptr>=SWAP_FREE_LIST)
        {
        swpl_overruns++;
        return;
        }
     }
  else
     {
     swp_list[swp_fnot_used].seek=seek;
     swp_list[swp_fnot_used].size=size;
     swp_fnot_used=-1;
     swp_unuseds--;
     }
  }

void swap_free_block(int32_t seek,int32_t size)
  {
  int i1,i2;

  seek&=~255;
  size+=255;
  size&=~255;
  swap_find_seek(seek,seek+size,&i1,&i2);
    if (i2>=0 && i1>=0)
     {
     if (swp_list[i2].size!=-1) swp_list[i2].size+=swp_list[i1].size+size;
     swp_list[i2].seek=swp_list[i1].seek;
     swp_list[i1].seek=-1;
     swp_list[i1].size=-1;
     swp_unuseds++;swp_fnot_used=i1;
     }
  else if (i1>=0) swp_list[i1].size+=size;
  else if (i2>=0)
     {
     if (swp_list[i2].size!=-1) swp_list[i2].size+=size;
     swp_list[i2].seek=seek;
     }
  if (i1<0 && i2<0)
     {
     alloc_swp_block(seek,size);
     }
  }

/*main()
  {
  int i1,i2,i3,i4;
  swap_init();
  i1=swap_add_block(1024);
  i2=swap_add_block(250);
  i3=swap_add_block(1024);
  i4=swap_add_block(1024);
  swap_free_block(i1,1024);
  swap_free_block(i3,1024);
  swap_free_block(i2,250);
  swap_free_block(i4,1024);
  }
 */