#include <stdlib.h> //malloc

extern //apc.c
long sys_pagesize;

#define SYS_PAGESIZE     (sys_pagesize)
#define NAME_PAGESIZE    (APC_NAME_MAX * 1024)
#define PL_HEADERSIZE    (sizeof(struct pagenode_header_t))
#define PL_HEADSIZE(_PL) (_PL.head->header.head - _PL.head->root)
#define PL_HEADMEM(_PL)  (_PL.pagesize - PL_HEADERSIZE - PL_HEADSIZE(_PL))
#define  struct_clear(_S) (memset((_S), 0, sizeof(*(_S))))
/* Memory allocation structures */
struct pagenode_t;
struct pagenode_header_t {
  struct pagenode_t* next;
  char*              head;
};
struct pagenode_t {
  struct pagenode_header_t header;
  char                     root[];
};
struct pagelist_t {
  struct pagenode_t* root, * head;
  size_t             pagesize;
};

static
void*    stack_alloc(struct pagelist_t*, size_t);
static inline
void*    pagelist_pop(struct pagelist_t*,size_t);
#define $($)#$
#define  pagelist_alloc(pagelist) do {					\
    pagelist.head->header.next = (struct pagenode_t*) malloc(pagelist.pagesize); \
    if (pagelist.head->header.next == NULL)				\
      eprintf("Memory allocation error\n");				\
    struct_clear(pagelist.head->header.next);				\
    pagelist.head = pagelist.head->header.next;				\
    pagelist.head->header.head = pagelist.head->root;			\
  } while (0)
#define  pagelist_init(pagelist,size) do {			\
    pagelist.pagesize = size;					\
    pagelist.root = (struct pagenode_t*) malloc(size);		\
    if (pagelist.root == NULL)					\
      eprintf("Memory allocation error\n");			\
    struct_clear(pagelist.root);				\
    pagelist.head = pagelist.root;				\
    pagelist.head->header.head = pagelist.head->root;		\
  } while (0)
static
void     pagenode_free(struct pagenode_t*);

static inline
void* pagelist_pop
( struct pagelist_t* pagelist,
  size_t             size
)
{ size_t headsize = PL_HEADSIZE((*pagelist));
  if (!headsize)
    { free(pagelist->head);
      pagelist->head = pagelist->root;
      while (pagelist->head->header.next != NULL)
	pagelist->head = pagelist->head->header.next;
    }
  if (headsize < size)
    eprintf("Attempted to pop unaligned value from pagelist\n");
  pagelist->head->header.head -= size;
  return pagelist->head->header.head;
}

/* Recursively clean pagenode linked list, freeing last first */
static
void pagenode_free
( struct pagenode_t* pagenode )
{ if (pagenode->header.next != NULL)
    pagenode_free(pagenode->header.next);
  free(pagenode);
}
static
void* stack_alloc
( struct pagelist_t* pagelist,
  size_t bytes )
{ void* p;
  if (PL_HEADMEM((*pagelist)) < bytes) 
    pagelist_alloc((*pagelist));
  p = pagelist->head->header.head;
  pagelist->head->header.head += bytes;
  return p;
}