/*
   * 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/radix-tree.h>
  #include <linux/gfp.h>

  #include <linux/percpu.h>

  
  struct idr {
  	struct radix_tree_root	idr_rt;
  	unsigned int		idr_next;
  };

  /*

   * The IDR API does not expose the tagging functionality of the radix tree
   * to users.  Use tag 0 to track whether a node has free space below it.

   */

  #define IDR_FREE	0

  /* Set the IDR flag and the IDR_FREE tag */
  #define IDR_RT_MARKER		((__force gfp_t)(3 << __GFP_BITS_SHIFT))

  #define IDR_INIT							\

  {									\

  	.idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER)			\

  }

  #define DEFINE_IDR(name)	struct idr name = IDR_INIT

  /**

   * idr_get_cursor - Return the current position of the cyclic allocator
   * @idr: idr handle
   *
   * The value returned is the value that will be next returned from
   * idr_alloc_cyclic() if it is free (otherwise the search will start from
   * this position).
   */

  static inline unsigned int idr_get_cursor(const struct idr *idr)

  {

  	return READ_ONCE(idr->idr_next);

  }
  
  /**
   * idr_set_cursor - Set the current position of the cyclic allocator
   * @idr: idr handle
   * @val: new position
   *
   * The next call to idr_alloc_cyclic() will return @val if it is free
   * (otherwise the search will start from this position).
   */
  static inline void idr_set_cursor(struct idr *idr, unsigned int val)
  {

  	WRITE_ONCE(idr->idr_next, val);

  }
  
  /**

   * 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).
   */

  void idr_preload(gfp_t gfp_mask);

  
  int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
  		  unsigned long start, unsigned long end, gfp_t gfp,
  		  bool ext);
  
  /**
   * idr_alloc - allocate an id
   * @idr: idr handle
   * @ptr: pointer to be associated with the new id
   * @start: the minimum id (inclusive)
   * @end: the maximum id (exclusive)
   * @gfp: memory allocation flags
   *
   * Allocates an unused ID in the range [start, end).  Returns -ENOSPC
   * if there are no unused IDs in that range.
   *
   * Note that @end is treated as max when <= 0.  This is to always allow
   * using @start + N as @end as long as N is inside integer range.
   *
   * Simultaneous modifications to the @idr are not allowed and should be
   * prevented by the user, usually with a lock.  idr_alloc() may be called
   * concurrently with read-only accesses to the @idr, such as idr_find() and
   * idr_for_each_entry().
   */
  static inline int idr_alloc(struct idr *idr, void *ptr,
  			    int start, int end, gfp_t gfp)
  {
  	unsigned long id;
  	int ret;
  
  	if (WARN_ON_ONCE(start < 0))
  		return -EINVAL;
  
  	ret = idr_alloc_cmn(idr, ptr, &id, start, end, gfp, false);
  
  	if (ret)
  		return ret;
  
  	return id;
  }
  
  static inline int idr_alloc_ext(struct idr *idr, void *ptr,
  				unsigned long *index,
  				unsigned long start,
  				unsigned long end,
  				gfp_t gfp)
  {
  	return idr_alloc_cmn(idr, ptr, index, start, end, gfp, true);
  }

  int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
  int idr_for_each(const struct idr *,

  		 int (*fn)(int id, void *p, void *data), void *data);

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

  void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);

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

  void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id);

  void idr_destroy(struct idr *);

  static inline void *idr_remove_ext(struct idr *idr, unsigned long id)

  {

  	return radix_tree_delete_item(&idr->idr_rt, id, NULL);

  }

  static inline void *idr_remove(struct idr *idr, int id)
  {
  	return idr_remove_ext(idr, id);
  }

  static inline void idr_init(struct idr *idr)
  {
  	INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
  	idr->idr_next = 0;
  }
  
  static inline bool idr_is_empty(const struct idr *idr)
  {
  	return radix_tree_empty(&idr->idr_rt) &&
  		radix_tree_tagged(&idr->idr_rt, IDR_FREE);
  }

  /**

   * 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_ext(const struct idr *idr, unsigned long id)

  {

  	return radix_tree_lookup(&idr->idr_rt, id);

  }

  static inline void *idr_find(const struct idr *idr, int id)
  {
  	return idr_find_ext(idr, id);
  }

  /**

   * idr_for_each_entry - iterate over an idr's elements of a given type

   * @idr:     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(idr, entry, id)			\
  	for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)

  #define idr_for_each_entry_ext(idr, entry, id)			\
  	for (id = 0; ((entry) = idr_get_next_ext(idr, &(id))) != NULL; ++id)

  /**

   * idr_for_each_entry_continue - continue iteration over an idr's elements of a given type
   * @idr:     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(idr, entry, id)			\
  	for ((entry) = idr_get_next((idr), &(id));			\

  	     entry;							\

  	     ++id, (entry) = idr_get_next((idr), &(id)))

  /*

   * IDA - IDR based id allocator, use when translation from id to
   * pointer isn't necessary.
   */
  #define IDA_CHUNK_SIZE		128	/* 128 bytes per chunk */

  #define IDA_BITMAP_LONGS	(IDA_CHUNK_SIZE / sizeof(long))

  #define IDA_BITMAP_BITS 	(IDA_BITMAP_LONGS * sizeof(long) * 8)

  
  struct ida_bitmap {

  	unsigned long		bitmap[IDA_BITMAP_LONGS];
  };

  DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);

  struct ida {

  	struct radix_tree_root	ida_rt;

  };

  #define IDA_INIT	{						\
  	.ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT),		\
  }
  #define DEFINE_IDA(name)	struct ida name = IDA_INIT

  
  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);

  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);

  static inline void ida_init(struct ida *ida)
  {
  	INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);

  }

  /**

   * 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);
  }

  static inline bool ida_is_empty(const struct ida *ida)

  {

  	return radix_tree_empty(&ida->ida_rt);

  }

  #endif /* __IDR_H__ */