/*
 *	BIRD Internet Routing Daemon -- Network prefix storage
 *
 *	(c) 1998--2000 Martin Mares <mj@ucw.cz>
 *	(c) 2022 Maria Matejka <mq@jmq.cz>
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

#ifndef _BIRD_LIB_FIB_H_
#define _BIRD_LIB_FIB_H_

/*
 *	BIRD FIBs are generic data structure for storing network prefixes.
 *	Also used for the master routing table. Currently implemented as
 *	a hash table.
 *
 *	Available operations:
 *		- insertion of new entry
 *		- deletion of entry
 *		- searching for entry by network prefix
 *		- asynchronous retrieval of fib contents
 */

struct fib;

struct fib_node {
  struct fib_node *next;		/* Next in hash chain */
  struct fib_iterator *readers;		/* List of readers of this node */
  net_addr addr[0];
};

struct fib_iterator {			/* See lib/slists.h for an explanation */
  struct fib_iterator *prev, *next;	/* Must be synced with struct fib_node! */
  byte efef;				/* 0xff to distinguish between iterator and node */
  byte pad[3];
  struct fib_node *node;		/* Or NULL if freshly merged */
  uint hash;
};

typedef void (*fib_init_fn)(struct fib *, void *);

struct fib {
  pool *fib_pool;			/* Pool holding all our data */
  slab *fib_slab;			/* Slab holding all fib nodes */
  struct fib_node **hash_table;		/* Node hash table */
  uint hash_size;			/* Number of hash table entries (a power of two) */
  uint hash_order;			/* Binary logarithm of hash_size */
  uint hash_shift;			/* 32 - hash_order */
  uint addr_type;			/* Type of address data stored in fib (NET_*) */
  uint node_size;			/* FIB node size, 0 for nonuniform */
  uint node_offset;			/* Offset of fib_node struct inside of user data */
  uint entries;				/* Number of entries */
  uint entries_min, entries_max;	/* Entry count limits (else start rehashing) */
  fib_init_fn init;			/* Constructor */
};

static inline void * fib_node_to_user(struct fib *f, struct fib_node *e)
{ return e ? (void *) ((char *) e - f->node_offset) : NULL; }

static inline struct fib_node * fib_user_to_node(struct fib *f, void *e)
{ return e ? (void *) ((char *) e + f->node_offset) : NULL; }

void fib_init(struct fib *f, pool *p, uint addr_type, uint node_size, uint node_offset, uint hash_order, fib_init_fn init);
void *fib_find(struct fib *, const net_addr *);	/* Find or return NULL if doesn't exist */
void *fib_get_chain(struct fib *f, const net_addr *a); /* Find first node in linked list from hash table */
void *fib_get(struct fib *, const net_addr *);	/* Find or create new if nonexistent */
void *fib_route(struct fib *, const net_addr *); /* Longest-match routing lookup */
void fib_delete(struct fib *, void *);	/* Remove fib entry */
void fib_free(struct fib *);		/* Destroy the fib */
void fib_check(struct fib *);		/* Consistency check for debugging */

void fit_init(struct fib_iterator *, struct fib *); /* Internal functions, don't call */
struct fib_node *fit_get(struct fib *, struct fib_iterator *);
void fit_put(struct fib_iterator *, struct fib_node *);
void fit_put_next(struct fib *f, struct fib_iterator *i, struct fib_node *n, uint hpos);
void fit_put_end(struct fib_iterator *i);
void fit_copy(struct fib *f, struct fib_iterator *dst, struct fib_iterator *src);


#define FIB_WALK(fib, type, z) do {				\
	struct fib_node *fn_, **ff_ = (fib)->hash_table;	\
	uint count_ = (fib)->hash_size;				\
	type *z;						\
	while (count_--)					\
	  for (fn_ = *ff_++; z = fib_node_to_user(fib, fn_); fn_=fn_->next)

#define FIB_WALK_END } while (0)

#define FIB_ITERATE_INIT(it, fib) fit_init(it, fib)

#define FIB_ITERATE_START(fib, it, type, z) do {		\
	struct fib_node *fn_ = fit_get(fib, it);		\
	uint count_ = (fib)->hash_size;				\
	uint hpos_ = (it)->hash;				\
	type *z;						\
	for(;;fn_ = fn_->next) {				\
	  while (!fn_ && ++hpos_ < count_)			\
	    {							\
	       fn_ = (fib)->hash_table[hpos_];			\
	    }							\
	  if (hpos_ >= count_)					\
	    break;						\
	  z = fib_node_to_user(fib, fn_);

#define FIB_ITERATE_END } } while(0)

#define FIB_ITERATE_PUT(it) fit_put(it, fn_)

#define FIB_ITERATE_PUT_NEXT(it, fib) fit_put_next(fib, it, fn_, hpos_)

#define FIB_ITERATE_PUT_END(it) fit_put_end(it)

#define FIB_ITERATE_UNLINK(it, fib) fit_get(fib, it)

#define FIB_ITERATE_COPY(dst, src, fib) fit_copy(fib, dst, src)

#endif