src/dict.h

/**
 * @file dict.h
 * @author Radek Krejci <rkrejci@cesnet.cz>
 * @brief libyang dictionary
 *
 * Copyright (c) 2015 CESNET, z.s.p.o.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the Company nor the names of its contributors
 *    may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 */

#ifndef LY_DICT_H_
#define LY_DICT_H_

#include <stdint.h>

/*
 * structure definition from context.h
 */
struct ly_ctx;

/**
 * size of the dictionary for each context
 */
#define DICT_SIZE 1024

/**
 * record of the dictionary
 * TODO: save the next pointer by different collision strategy, will need to
 * make dictionary size dynamic
 */
struct dict_rec {
	char *value;
	uint32_t refcount;
	struct dict_rec *next;
};

/**
 * dictionary to store repeating strings
 * TODO: make it variable size
 */
struct dict_table {
	struct dict_rec recs[DICT_SIZE];
	int hash_mask;
	uint32_t used;
};

/**
 * @brief Initiate content (non-zero values) of the dictionary
 *
 * @param[in] dict Dictionary table to initiate
 */
void lydict_init(struct dict_table *dict);

/**
 * @brief Cleanup the dictionary content
 *
 * @param[in] dict Dictionary table to cleanup
 */
void lydict_clean(struct dict_table *dict);

/**
 * @brief Insert string into dictionary. If the string is already present,
 * only a reference counter is incremented and no memory allocation is
 * performed.
 *
 * @param[in] ctx libyang context handler
 * @param[in] value String to be stored in the dictionary.
 * @param[in] len Number of bytes to store. The value is not required to be
 * NULL terminated string, the len parameter says number of bytes stored in
 * dictionary. The specified number of bytes is duplicated and terminating NULL
 * byte is added automatically.
 * @return pointer to the string stored in the dictionary
 */
const char *lydict_insert(struct ly_ctx *ctx, const char *value, size_t len);

/**
 * @brief Insert string into dictionary - zerocopy version. If the string is
 * already present, only a reference counter is incremented and no memory
 * allocation is performed. This insert function variant avoids duplication of
 * specified value - it is inserted into the dictionary directly.
 *
 * @param[in] ctx libyang context handler
 * @param[in] value NULL-terminated string to be stored in the dictionary. If
 * the string is not present in dictionary, the pointer is directly used by the
 * dictionary. Otherwise, the reference counter is incremented and the value is
 * freed. So, after calling the function, caller is supposed to not use the
 * value address anymore.
 * @return pointer to the string stored in the dictionary
 */
const char *lydict_insert_zc(struct ly_ctx *ctx, char *value);


/**
 * @brief Remove specified string from the dictionary. It decrement reference
 * counter for the string and if it is zero, the string itself is freed.
 *
 * @param[in] ctx libyang context handler
 * @param[in] value String to be freed. Note, that not only the string itself
 * must match the stored value, but also the address is being compared and the
 * counter is decremented only if it matches.
 */
void lydict_remove(struct ly_ctx *ctx, const char *value);

#endif /* LY_DICT_H_ */