/*
   * Statically sized hash table implementation
   * (C) 2012  Sasha Levin <levinsasha928@gmail.com>
   */
  
  #ifndef _LINUX_HASHTABLE_H
  #define _LINUX_HASHTABLE_H
  
  #include <linux/list.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/hash.h>
  #include <linux/rculist.h>
  
  #define DEFINE_HASHTABLE(name, bits)						\
  	struct hlist_head name[1 << (bits)] =					\
  			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
  
  #define DECLARE_HASHTABLE(name, bits)                                   	\
  	struct hlist_head name[1 << (bits)]
  
  #define HASH_SIZE(name) (ARRAY_SIZE(name))
  #define HASH_BITS(name) ilog2(HASH_SIZE(name))
  
  /* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
  #define hash_min(val, bits)							\
  	(sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))
  
  static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
  {
  	unsigned int i;
  
  	for (i = 0; i < sz; i++)
  		INIT_HLIST_HEAD(&ht[i]);
  }
  
  /**
   * hash_init - initialize a hash table
   * @hashtable: hashtable to be initialized
   *
   * Calculates the size of the hashtable from the given parameter, otherwise
   * same as hash_init_size.
   *
   * This has to be a macro since HASH_BITS() will not work on pointers since
   * it calculates the size during preprocessing.
   */
  #define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))
  
  /**
   * hash_add - add an object to a hashtable
   * @hashtable: hashtable to add to
   * @node: the &struct hlist_node of the object to be added
   * @key: the key of the object to be added
   */
  #define hash_add(hashtable, node, key)						\
  	hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
  
  /**
   * hash_add_rcu - add an object to a rcu enabled hashtable
   * @hashtable: hashtable to add to
   * @node: the &struct hlist_node of the object to be added
   * @key: the key of the object to be added
   */
  #define hash_add_rcu(hashtable, node, key)					\
  	hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
  
  /**
   * hash_hashed - check whether an object is in any hashtable
   * @node: the &struct hlist_node of the object to be checked
   */
  static inline bool hash_hashed(struct hlist_node *node)
  {
  	return !hlist_unhashed(node);
  }
  
  static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
  {
  	unsigned int i;
  
  	for (i = 0; i < sz; i++)
  		if (!hlist_empty(&ht[i]))
  			return false;
  
  	return true;
  }
  
  /**
   * hash_empty - check whether a hashtable is empty
   * @hashtable: hashtable to check
   *
   * This has to be a macro since HASH_BITS() will not work on pointers since
   * it calculates the size during preprocessing.
   */
  #define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))
  
  /**
   * hash_del - remove an object from a hashtable
   * @node: &struct hlist_node of the object to remove
   */
  static inline void hash_del(struct hlist_node *node)
  {
  	hlist_del_init(node);
  }
  
  /**
   * hash_del_rcu - remove an object from a rcu enabled hashtable
   * @node: &struct hlist_node of the object to remove
   */
  static inline void hash_del_rcu(struct hlist_node *node)
  {
  	hlist_del_init_rcu(node);
  }
  
  /**
   * hash_for_each - iterate over a hashtable
   * @name: hashtable to iterate
   * @bkt: integer to use as bucket loop cursor
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   */
  #define hash_for_each(name, bkt, obj, member)				\
  	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
  			(bkt)++)\
  		hlist_for_each_entry(obj, &name[bkt], member)
  
  /**
   * hash_for_each_rcu - iterate over a rcu enabled hashtable
   * @name: hashtable to iterate
   * @bkt: integer to use as bucket loop cursor
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   */
  #define hash_for_each_rcu(name, bkt, obj, member)			\
  	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
  			(bkt)++)\
  		hlist_for_each_entry_rcu(obj, &name[bkt], member)
  
  /**
   * hash_for_each_safe - iterate over a hashtable safe against removal of
   * hash entry
   * @name: hashtable to iterate
   * @bkt: integer to use as bucket loop cursor
   * @tmp: a &struct used for temporary storage
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   */
  #define hash_for_each_safe(name, bkt, tmp, obj, member)			\
  	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
  			(bkt)++)\
  		hlist_for_each_entry_safe(obj, tmp, &name[bkt], member)
  
  /**
   * hash_for_each_possible - iterate over all possible objects hashing to the
   * same bucket
   * @name: hashtable to iterate
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   * @key: the key of the objects to iterate over
   */
  #define hash_for_each_possible(name, obj, member, key)			\
  	hlist_for_each_entry(obj, &name[hash_min(key, HASH_BITS(name))], member)
  
  /**
   * hash_for_each_possible_rcu - iterate over all possible objects hashing to the
   * same bucket in an rcu enabled hashtable
   * in a rcu enabled hashtable
   * @name: hashtable to iterate
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   * @key: the key of the objects to iterate over
   */
  #define hash_for_each_possible_rcu(name, obj, member, key)		\
  	hlist_for_each_entry_rcu(obj, &name[hash_min(key, HASH_BITS(name))],\
  		member)
  
  /**
   * hash_for_each_possible_rcu_notrace - iterate over all possible objects hashing
   * to the same bucket in an rcu enabled hashtable in a rcu enabled hashtable
   * @name: hashtable to iterate
   * @obj: the type * to use as a loop cursor for each entry
   * @member: the name of the hlist_node within the struct
   * @key: the key of the objects to iterate over
   *
   * This is the same as hash_for_each_possible_rcu() except that it does
   * not do any RCU debugging or tracing.
   */
  #define hash_for_each_possible_rcu_notrace(name, obj, member, key) \
  	hlist_for_each_entry_rcu_notrace(obj, \
  		&name[hash_min(key, HASH_BITS(name))], member)
  
  /**
   * hash_for_each_possible_safe - iterate over all possible objects hashing to the
   * same bucket safe against removals
   * @name: hashtable to iterate
   * @obj: the type * to use as a loop cursor for each entry
   * @tmp: a &struct used for temporary storage
   * @member: the name of the hlist_node within the struct
   * @key: the key of the objects to iterate over
   */
  #define hash_for_each_possible_safe(name, obj, tmp, member, key)	\
  	hlist_for_each_entry_safe(obj, tmp,\
  		&name[hash_min(key, HASH_BITS(name))], member)
  
  
  #endif