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/*
 * Copyright (C) 2013-2017 Tobias Brunner
 * Copyright (C) 2007 Martin Willi
 * HSR Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

/**
 * @defgroup enumerator enumerator
 * @{ @ingroup collections
 */

#ifndef ENUMERATOR_H_
#define ENUMERATOR_H_

typedef struct enumerator_t enumerator_t;

#include <utils/utils.h>

/**
 * Enumerator interface, allows enumeration over collections.
 */
struct enumerator_t {

	/**
	 * Enumerate collection.
	 *
	 * The enumerate() method takes a variable number of pointer arguments
	 * where the enumerated values get written to.
	 *
	 * @note Just assigning the generic enumerator_enumerate_default() function
	 * that calls the enumerator's venumerate() method is usually enough.
	 *
	 * @param ...	variable list of enumerated items, implementation dependent
	 * @return		TRUE if pointers returned
	 */
	bool (*enumerate)(enumerator_t *this, ...);

	/**
	 * Enumerate collection.
	 *
	 * The venumerate() method takes a variable argument list containing
	 * pointers where the enumerated values get written to.
	 *
	 * To simplify the implementation the VA_ARGS_VGET() macro may be used.
	 *
	 * @param args	variable list of enumerated items, implementation dependent
	 * @return		TRUE if pointers returned
	 */
	bool (*venumerate)(enumerator_t *this, va_list args);

	/**
	 * Destroy an enumerator_t instance.
	 */
	void (*destroy)(enumerator_t *this);
};

/**
 * Generic implementation of enumerator_t::enumerate() that simply calls
 * the enumerator's venumerate() method.
 *
 * @param enumerator	the enumerator
 * @param ...			arguments passed to enumerate()
 */
bool enumerator_enumerate_default(enumerator_t *enumerator, ...);

/**
 * Create an enumerator which enumerates over nothing
 *
 * @return			an enumerator over no values
 */
enumerator_t* enumerator_create_empty();

/**
 * Create an enumerator which enumerates over a single item
 *
 * @param item		item to enumerate
 * @param cleanup	cleanup function called on destroy with the item
 * @return			an enumerator over a single value
 */
enumerator_t *enumerator_create_single(void *item, void (*cleanup)(void *item));

/**
 * Create an enumerator over files/subdirectories in a directory.
 *
 * This enumerator_t.enumerate() function returns a (to the directory) relative
 * filename (as a char*), an absolute filename (as a char*) and a file status
 * (to a struct stat), which all may be NULL. "." and ".." entries are
 * skipped.
 *
 * Example:
 *
 * @code
	char *rel, *abs;
	struct stat st;
	enumerator_t *e;

	e = enumerator_create_directory("/tmp");
	if (e)
	{
		while (e->enumerate(e, &rel, &abs, &st))
		{
			if (S_ISDIR(st.st_mode) && *rel != '.')
			{
				printf("%s\n", abs);
			}
		}
		e->destroy(e);
	}
   @endcode
 *
 * @param path		path of the directory
 * @return 			the directory enumerator, NULL on failure
 */
enumerator_t* enumerator_create_directory(const char *path);

/**
 * Create an enumerator over files/directories matching a file pattern.
 *
 * This enumerator_t.enumerate() function returns the filename (as a char*),
 * and a file status (to a struct stat), which both may be NULL.
 *
 * Example:
 *
 * @code
	char *file;
	struct stat st;
	enumerator_t *e;

	e = enumerator_create_glob("/etc/ipsec.*.conf");
	if (e)
	{
		while (e->enumerate(e, &file, &st))
		{
			if (S_ISREG(st.st_mode))
			{
				printf("%s\n", file);
			}
		}
		e->destroy(e);
	}
   @endcode
 *
 * @param pattern	file pattern to match
 * @return 			the enumerator, NULL if not supported
 */
enumerator_t* enumerator_create_glob(const char *pattern);

/**
 * Create an enumerator over tokens of a string.
 *
 * Tokens are separated by one of the characters in sep and trimmed by the
 * characters in trim.
 *
 * @param string	string to parse
 * @param sep		separator characters
 * @param trim		characters to trim from tokens
 * @return			enumerator over char* tokens
 */
enumerator_t* enumerator_create_token(const char *string, const char *sep,
									  const char *trim);

/**
 * Creates an enumerator which enumerates over enumerated enumerators :-).
 *
 * The outer enumerator is expected to return objects that, when passed to
 * inner_constructor, will create a new enumerator that will be enumerated until
 * completion (to this enumerator will the pointer arguments that are passed to
 * this enumerator be forwarded) at which point a new element from the outer
 * enumerator is requested to create a new inner enumerator.
 *
 * @param outer					outer enumerator
 * @param inner_constructor		constructor to create inner enumerator
 * @param data					data to pass to each inner_constructor call
 * @param destructor			destructor function to clean up data after use
 * @return						the nested enumerator
 */
enumerator_t *enumerator_create_nested(enumerator_t *outer,
					enumerator_t *(*inner_constructor)(void *outer, void *data),
					void *data, void (*destructor)(void *data));

/**
 * Creates an enumerator which filters/maps output of another enumerator.
 *
 * The filter function receives the user supplied "data" followed by the
 * original enumerator, followed by the arguments passed to the outer
 * enumerator.  It returns TRUE to deliver the values assigned to these
 * arguments to the caller of enumerate() and FALSE to end the enumeration.
 * Filtering items is simple as the filter function may just skip enumerated
 * items from the original enumerator.
 *
 * @param orig					original enumerator to wrap, gets destroyed
 * @param filter				filter function
 * @param data					user data to supply to filter
 * @param destructor			destructor function to clean up data after use
 * @return						the filtered enumerator
 */
enumerator_t *enumerator_create_filter(enumerator_t *orig,
				bool (*filter)(void *data, enumerator_t *orig, va_list args),
				void *data, void (*destructor)(void *data));

/**
 * Create an enumerator wrapper which does a cleanup on destroy.
 *
 * @param wrapped				wrapped enumerator
 * @param cleanup				cleanup function called on destroy
 * @param data					user data to supply to cleanup
 * @return						the enumerator with cleanup
 */
enumerator_t *enumerator_create_cleaner(enumerator_t *wrapped,
					void (*cleanup)(void *data), void *data);

#endif /** ENUMERATOR_H_ @}*/