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 * $Id: linkhash.h,v 1.6 2006/01/30 23:07:57 mclark Exp $
 *
 * Copyright (c) 2004, 2005 Metaparadigm Pte. Ltd.
 * Michael Clark <michael@metaparadigm.com>
 * Copyright (c) 2009 Hewlett-Packard Development Company, L.P.
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the MIT license. See COPYING for details.
 *
 */

/**
 * @file
 * @brief Internal methods for working with json_type_object objects.  Although
 *        this is exposed by the json_object_get_object() function and within the
 *        json_object_iter type, it is not recommended for direct use.
 */
#ifndef _linkhash_h_
#define _linkhash_h_

#include "json_object.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * golden prime used in hash functions
 */
#define LH_PRIME 0x9e370001UL

/**
 * The fraction of filled hash buckets until an insert will cause the table
 * to be resized.
 * This can range from just above 0 up to 1.0.
 */
#define LH_LOAD_FACTOR 0.66

/**
 * sentinel pointer value for empty slots
 */
#define LH_EMPTY (void *)-1

/**
 * sentinel pointer value for freed slots
 */
#define LH_FREED (void *)-2

/**
 * default string hash function
 */
#define JSON_C_STR_HASH_DFLT 0

/**
 * perl-like string hash function
 */
#define JSON_C_STR_HASH_PERLLIKE 1

/**
 * This function sets the hash function to be used for strings.
 * Must be one of the JSON_C_STR_HASH_* values.
 * @returns 0 - ok, -1 if parameter was invalid
 */
int json_global_set_string_hash(const int h);

struct lh_entry;

/**
 * callback function prototypes
 */
typedef void(lh_entry_free_fn)(struct lh_entry *e);
/**
 * callback function prototypes
 */
typedef unsigned long(lh_hash_fn)(const void *k);
/**
 * callback function prototypes
 */
typedef int(lh_equal_fn)(const void *k1, const void *k2);

/**
 * An entry in the hash table
 */
struct lh_entry
{
	/**
	 * The key.  Use lh_entry_k() instead of accessing this directly.
	 */
	const void *k;
	/**
	 * A flag for users of linkhash to know whether or not they
	 * need to free k.
	 */
	int k_is_constant;
	/**
	 * The value.  Use lh_entry_v() instead of accessing this directly.
	 */
	const void *v;
	/**
	 * The next entry
	 */
	struct lh_entry *next;
	/**
	 * The previous entry.
	 */
	struct lh_entry *prev;
};

/**
 * The hash table structure.
 */
struct lh_table
{
	/**
	 * Size of our hash.
	 */
	int size;
	/**
	 * Numbers of entries.
	 */
	int count;

	/**
	 * The first entry.
	 */
	struct lh_entry *head;

	/**
	 * The last entry.
	 */
	struct lh_entry *tail;

	struct lh_entry *table;

	/**
	 * A pointer onto the function responsible for freeing an entry.
	 */
	lh_entry_free_fn *free_fn;
	lh_hash_fn *hash_fn;
	lh_equal_fn *equal_fn;
};
typedef struct lh_table lh_table;

/**
 * Convenience list iterator.
 */
#define lh_foreach(table, entry) for (entry = table->head; entry; entry = entry->next)

/**
 * lh_foreach_safe allows calling of deletion routine while iterating.
 *
 * @param table a struct lh_table * to iterate over
 * @param entry a struct lh_entry * variable to hold each element
 * @param tmp a struct lh_entry * variable to hold a temporary pointer to the next element
 */
#define lh_foreach_safe(table, entry, tmp) \
	for (entry = table->head; entry && ((tmp = entry->next) || 1); entry = tmp)

/**
 * Create a new linkhash table.
 *
 * @param size initial table size. The table is automatically resized
 * although this incurs a performance penalty.
 * @param free_fn callback function used to free memory for entries
 * when lh_table_free or lh_table_delete is called.
 * If NULL is provided, then memory for keys and values
 * must be freed by the caller.
 * @param hash_fn  function used to hash keys. 2 standard ones are defined:
 * lh_ptr_hash and lh_char_hash for hashing pointer values
 * and C strings respectively.
 * @param equal_fn comparison function to compare keys. 2 standard ones defined:
 * lh_ptr_hash and lh_char_hash for comparing pointer values
 * and C strings respectively.
 * @return On success, a pointer to t