/*
   * include/linux/idr.h
   * 
   * 2002-10-18  written by Jim Houston jim.houston@ccur.com
   *	Copyright (C) 2002 by Concurrent Computer Corporation
   *	Distributed under the GNU GPL license version 2.
   *
   * Small id to pointer translation service avoiding fixed sized
   * tables.
   */

  
  #ifndef __IDR_H__
  #define __IDR_H__

  #include <linux/types.h>
  #include <linux/bitops.h>

  #include <linux/init.h>

  #include <linux/rcupdate.h>

  /*
   * We want shallower trees and thus more bits covered at each layer.  8
   * bits gives us large enough first layer for most use cases and maximum
   * tree depth of 4.  Each idr_layer is slightly larger than 2k on 64bit and
   * 1k on 32bit.
   */
  #define IDR_BITS 8

  #define IDR_SIZE (1 << IDR_BITS)
  #define IDR_MASK ((1 << IDR_BITS)-1)

  struct idr_layer {

  	int			prefix;	/* the ID prefix of this idr_layer */

  	int			layer;	/* distance from leaf */

  	struct idr_layer __rcu	*ary[1<<IDR_BITS];

  	int			count;	/* When zero, we can release it */

  	union {
  		/* A zero bit means "space here" */
  		DECLARE_BITMAP(bitmap, IDR_SIZE);
  		struct rcu_head		rcu_head;
  	};

  };
  
  struct idr {

  	struct idr_layer __rcu	*hint;	/* the last layer allocated from */

  	struct idr_layer __rcu	*top;

  	int			layers;	/* only valid w/o concurrent changes */

  	int			cur;	/* current pos for cyclic allocation */

  	spinlock_t		lock;

  	int			id_free_cnt;
  	struct idr_layer	*id_free;

  };

  #define IDR_INIT(name)							\
  {									\
  	.lock			= __SPIN_LOCK_UNLOCKED(name.lock),	\

  }
  #define DEFINE_IDR(name)	struct idr name = IDR_INIT(name)

  /**

   * DOC: idr sync

   * idr synchronization (stolen from radix-tree.h)
   *
   * idr_find() is able to be called locklessly, using RCU. The caller must
   * ensure calls to this function are made within rcu_read_lock() regions.
   * Other readers (lock-free or otherwise) and modifications may be running
   * concurrently.
   *
   * It is still required that the caller manage the synchronization and
   * lifetimes of the items. So if RCU lock-free lookups are used, typically
   * this would mean that the items have their own locks, or are amenable to
   * lock-free access; and that the items are freed by RCU (or only freed after
   * having been deleted from the idr tree *and* a synchronize_rcu() grace
   * period).
   */

  /*
   * This is what we export.
   */

  void *idr_find_slowpath(struct idr *idp, int id);

  void idr_preload(gfp_t gfp_mask);
  int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);

  int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);

  int idr_for_each(struct idr *idp,
  		 int (*fn)(int id, void *p, void *data), void *data);

  void *idr_get_next(struct idr *idp, int *nextid);

  void *idr_replace(struct idr *idp, void *ptr, int id);

  void idr_remove(struct idr *idp, int id);

  void idr_destroy(struct idr *idp);

  void idr_init(struct idr *idp);

  bool idr_is_empty(struct idr *idp);

  /**

   * idr_preload_end - end preload section started with idr_preload()
   *
   * Each idr_preload() should be matched with an invocation of this
   * function.  See idr_preload() for details.
   */
  static inline void idr_preload_end(void)
  {
  	preempt_enable();
  }
  
  /**

   * idr_find - return pointer for given id

   * @idr: idr handle

   * @id: lookup key
   *
   * Return the pointer given the id it has been registered with.  A %NULL
   * return indicates that @id is not valid or you passed %NULL in
   * idr_get_new().
   *
   * This function can be called under rcu_read_lock(), given that the leaf
   * pointers lifetimes are correctly managed.
   */
  static inline void *idr_find(struct idr *idr, int id)
  {
  	struct idr_layer *hint = rcu_dereference_raw(idr->hint);
  
  	if (hint && (id & ~IDR_MASK) == hint->prefix)
  		return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
  
  	return idr_find_slowpath(idr, id);
  }
  
  /**

   * idr_for_each_entry - iterate over an idr's elements of a given type
   * @idp:     idr handle
   * @entry:   the type * to use as cursor
   * @id:      id entry's key

   *
   * @entry and @id do not need to be initialized before the loop, and
   * after normal terminatinon @entry is left with the value NULL.  This
   * is convenient for a "not found" value.

   */

  #define idr_for_each_entry(idp, entry, id)			\
  	for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)

  /**
   * idr_for_each_entry - continue iteration over an idr's elements of a given type
   * @idp:     idr handle
   * @entry:   the type * to use as cursor
   * @id:      id entry's key
   *
   * Continue to iterate over list of given type, continuing after
   * the current position.
   */
  #define idr_for_each_entry_continue(idp, entry, id)			\
  	for ((entry) = idr_get_next((idp), &(id));			\
  	     entry;							\
  	     ++id, (entry) = idr_get_next((idp), &(id)))

  /*

   * IDA - IDR based id allocator, use when translation from id to
   * pointer isn't necessary.

   *
   * IDA_BITMAP_LONGS is calculated to be one less to accommodate
   * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.

   */
  #define IDA_CHUNK_SIZE		128	/* 128 bytes per chunk */

  #define IDA_BITMAP_LONGS	(IDA_CHUNK_SIZE / sizeof(long) - 1)
  #define IDA_BITMAP_BITS 	(IDA_BITMAP_LONGS * sizeof(long) * 8)

  
  struct ida_bitmap {
  	long			nr_busy;
  	unsigned long		bitmap[IDA_BITMAP_LONGS];
  };
  
  struct ida {
  	struct idr		idr;
  	struct ida_bitmap	*free_bitmap;
  };

  #define IDA_INIT(name)		{ .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }

  #define DEFINE_IDA(name)	struct ida name = IDA_INIT(name)
  
  int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
  int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);

  void ida_remove(struct ida *ida, int id);
  void ida_destroy(struct ida *ida);
  void ida_init(struct ida *ida);

  int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
  		   gfp_t gfp_mask);
  void ida_simple_remove(struct ida *ida, unsigned int id);

  /**

   * ida_get_new - allocate new ID
   * @ida:	idr handle
   * @p_id:	pointer to the allocated handle
   *
   * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.

   */

  static inline int ida_get_new(struct ida *ida, int *p_id)
  {
  	return ida_get_new_above(ida, 0, p_id);
  }
  
  void __init idr_init_cache(void);

  #endif /* __IDR_H__ */