/*
 * Copyright (c) 2012 Adam Hraska
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup genericadt
 * @{
 */
/** @file
 */

#ifndef KERN_CONC_HASH_TABLE_H_
#define KERN_CONC_HASH_TABLE_H_

#include <stdint.h>
#include <adt/list.h>
#include <synch/rcu_types.h>
#include <macros.h>
#include <synch/workqueue.h>

typedef uintptr_t cht_ptr_t;

/** Concurrent hash table node link. */
typedef struct cht_link {
	/* Must be placed first.
	 *
	 * The function pointer (rcu_link.func) is used to store the item's
	 * mixed memoized hash. If in use by RCU (ie waiting for deferred
	 * destruction) the hash will contain the value of
	 * cht_t.op->remove_callback.
	 */
	union {
		rcu_item_t rcu_link;
		size_t hash;
	};
	/** Link to the next item in the bucket including any marks. */
	cht_ptr_t link;
} cht_link_t;

/** Set of operations for a concurrent hash table. */
typedef struct cht_ops {
	/** Returns the hash of the item.
	 *
	 * Applicable also to items that were logically deleted from the table
	 * but have yet to be physically removed by means of remove_callback().
	 */
	size_t (*hash)(const cht_link_t *item);
	/** Returns the hash value of the key used to search for entries. */
	size_t (*key_hash)(void *key);
	/** Returns true if the two items store equal search keys. */
	bool (*equal)(const cht_link_t *item1, const cht_link_t *item2);
	/** Returns true if the item contains an equal search key. */
	bool (*key_equal)(void *key, const cht_link_t *item);
	/** Invoked to free a removed item once all references to it are dropped. */
	void (*remove_callback)(cht_link_t *item);
} cht_ops_t;

/** Groups hash table buckets with their count.
 *
 * It allows both the number of buckets as well as the bucket array
 * to be swapped atomically when resing the table.
 */
typedef struct cht_buckets {
	/** The number of buckets is 2^order. */
	size_t order;
	/** Array of single linked list bucket heads along with any marks. */
	cht_ptr_t head[1];
} cht_buckets_t;

/** Concurrent hash table structure. */
typedef struct {
	/** Item specific operations. */
	cht_ops_t *op;
	
	/** Buckets currently in use. */
	cht_buckets_t *b;
	/** Resized table buckets that will replace b once resize is complete. */
	cht_buckets_t *new_b;
	/** Invalid memoized hash value.
	 *
	 * If cht_link.hash contains this value the item had been logically
	 * removed and is waiting to be freed. Such hashes (and the associated
	 * items) are disregarded and skipped or the actual hash must be
	 * determined via op->hash().
	 */
	size_t invalid_hash;

	/** Minimum number of buckets is 2^min_order. */
	size_t min_order;
	/** Maximum number of items per bucket before the table grows. */
	size_t max_load;
	/** Table is resized in the background in a work queue. */
	work_t resize_work;
	/** If positive the table should grow or shrink.
	 *
	 * If not 0 resize work had already been posted to the system work queue.
	 */
	atomic_t resize_reqs;
	
	/** Number of items in the table that have not been logically deleted. */
	atomic_t item_cnt;
} cht_t;

#define cht_get_inst(item, type, member) \
	member_to_inst((item), type, member)


#define cht_read_lock()     rcu_read_lock()
#define cht_read_unlock()   rcu_read_unlock()

extern bool cht_create_simple(cht_t *h, cht_ops_t *op);
extern bool cht_create(cht_t *h, size_t init_size, size_t min_size,
	size_t max_load, bool can_block, cht_ops_t *op);
extern void cht_destroy(cht_t *h);
extern void cht_destroy_unsafe(cht_t *h);

extern cht_link_t *cht_find(cht_t *h, void *key);
extern cht_link_t *cht_find_lazy(cht_t *h, void *key);
extern cht_link_t *cht_find_next(cht_t *h, const cht_link_t *item);
extern cht_link_t *cht_find_next_lazy(cht_t *h, const cht_link_t *item);

extern void cht_insert(cht_t *h, cht_link_t *item);
extern bool cht_insert_unique(cht_t *h, cht_link_t *item, cht_link_t **dup_item);
extern size_t cht_remove_key(cht_t *h, void *key);
extern bool cht_remove_item(cht_t *h, cht_link_t *item);

#endif

/** @}
 */