[LIB]: Textsearch infrastructure.

#ifndef __LINUX_TEXTSEARCH_H

#define __LINUX_TEXTSEARCH_H

#ifdef __KERNEL__

#include <linux/types.h>

#include <linux/list.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/err.h>

struct ts_config;

/**

 * TS_AUTOLOAD - Automatically load textsearch modules when needed

 */

#define TS_AUTOLOAD	1

/**

 * struct ts_state - search state

 * @offset: offset for next match

 * @cb: control buffer, for persistant variables of get_next_block()

 */

struct ts_state

{

	unsigned int		offset;

	char			cb[40];

};

/**

 * struct ts_ops - search module operations

 * @name: name of search algorithm

 * @init: initialization function to prepare a search

 * @find: find the next occurrence of the pattern

 * @destroy: destroy algorithm specific parts of a search configuration

 * @get_pattern: return head of pattern

 * @get_pattern_len: return length of pattern

 * @owner: module reference to algorithm

 */

struct ts_ops

{

	const char		*name;

	struct ts_config *	(*init)(const void *, unsigned int, int);

	unsigned int		(*find)(struct ts_config *,

					struct ts_state *);

	void			(*destroy)(struct ts_config *);

	void *			(*get_pattern)(struct ts_config *);

	unsigned int		(*get_pattern_len)(struct ts_config *);

	struct module		*owner;

	struct list_head	list;

};

/**

 * struct ts_config - search configuration

 * @ops: operations of chosen algorithm

 * @get_next_block: callback to fetch the next block to search in

 * @finish: callback to finalize a search

 */

struct ts_config

{

	struct ts_ops		*ops;

	/**

	 * get_next_block - fetch next block of data

	 * @consumed: number of bytes consumed by the caller

	 * @dst: destination buffer

	 * @conf: search configuration

	 * @state: search state

	 *

	 * Called repeatedly until 0 is returned. Must assign the

	 * head of the next block of data to &*dst and return the length

	 * of the block or 0 if at the end. consumed == 0 indicates

	 * a new search. May store/read persistant values in state->cb.

	 */

	unsigned int		(*get_next_block)(unsigned int consumed,

						  const u8 **dst,

						  struct ts_config *conf,

						  struct ts_state *state);

	/**

	 * finish - finalize/clean a series of get_next_block() calls

	 * @conf: search configuration

	 * @state: search state

	 *

	 * Called after the last use of get_next_block(), may be used

	 * to cleanup any leftovers.

	 */

	void			(*finish)(struct ts_config *conf,

					  struct ts_state *state);

};

/**

 * textsearch_next - continue searching for a pattern

 * @conf: search configuration

 * @state: search state

 *

 * Continues a search looking for more occurrences of the pattern.

 * textsearch_find() must be called to find the first occurrence

 * in order to reset the state.

 *

 * Returns the position of the next occurrence of the pattern or

 * UINT_MAX if not match was found.

 */ 

static inline unsigned int textsearch_next(struct ts_config *conf,

					   struct ts_state *state)

{

	unsigned int ret = conf->ops->find(conf, state);

	if (conf->finish)

		conf->finish(conf, state);

	return ret;

}

/**

 * textsearch_find - start searching for a pattern

 * @conf: search configuration

 * @state: search state

 *

 * Returns the position of first occurrence of the pattern or

 * UINT_MAX if no match was found.

 */ 

static inline unsigned int textsearch_find(struct ts_config *conf,

					   struct ts_state *state)

{

	state->offset = 0;

	return textsearch_next(conf, state);

}

/**

 * textsearch_get_pattern - return head of the pattern

 * @conf: search configuration

 */

static inline void *textsearch_get_pattern(struct ts_config *conf)

{

	return conf->ops->get_pattern(conf);

}

/**

 * textsearch_get_pattern_len - return length of the pattern

 * @conf: search configuration

 */

static inline unsigned int textsearch_get_pattern_len(struct ts_config *conf)

{

	return conf->ops->get_pattern_len(conf);

}

extern int textsearch_register(struct ts_ops *);

extern int textsearch_unregister(struct ts_ops *);

extern struct ts_config *textsearch_prepare(const char *, const void *,

					    unsigned int, int, int);

extern void textsearch_destroy(struct ts_config *conf);

extern unsigned int textsearch_find_continuous(struct ts_config *,

					       struct ts_state *,

					       const void *, unsigned int);

#define TS_PRIV_ALIGNTO	8

#define TS_PRIV_ALIGN(len) (((len) + TS_PRIV_ALIGNTO-1) & ~(TS_PRIV_ALIGNTO-1))

static inline struct ts_config *alloc_ts_config(size_t payload, int gfp_mask)

{

	struct ts_config *conf;

	conf = kmalloc(TS_PRIV_ALIGN(sizeof(*conf)) + payload, gfp_mask);

	if (conf == NULL)

		return ERR_PTR(-ENOMEM);

	memset(conf, 0, TS_PRIV_ALIGN(sizeof(*conf)) + payload);

	return conf;

}

static inline void *ts_config_priv(struct ts_config *conf)

{

	return ((u8 *) conf + TS_PRIV_ALIGN(sizeof(struct ts_config)));

}

#endif /* __KERNEL__ */

#endif

config REED_SOLOMON_DEC16

	boolean

endmenu

config TEXTSEARCH

	boolean "Textsearch infrastructure"

	default y

	help

	  Say Y here if you want to provide a textsearch infrastructure

	  to other subsystems.

endmenu

obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/

obj-$(CONFIG_REED_SOLOMON) += reed_solomon/

lib-$(CONFIG_TEXTSEARCH) += textsearch.o

hostprogs-y	:= gen_crc32table

clean-files	:= crc32table.h

/*

 * lib/textsearch.c	Generic text search interface

 *

 *		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.

 *

 * Authors:	Thomas Graf <tgraf@suug.ch>

 * 		Pablo Neira Ayuso <pablo@eurodev.net>

 *

 * ==========================================================================

 *

 * INTRODUCTION

 *

 *   The textsearch infrastructure provides text searching facitilies for

 *   both linear and non-linear data. Individual search algorithms are

 *   implemented in modules and chosen by the user.

 *

 * ARCHITECTURE

 *

 *      User

 *     +----------------+

 *     |        finish()|<--------------(6)-----------------+

 *     |get_next_block()|<--------------(5)---------------+ |

 *     |                |                     Algorithm   | |

 *     |                |                    +------------------------------+

 *     |                |                    |  init()   find()   destroy() |

 *     |                |                    +------------------------------+

 *     |                |       Core API           ^       ^          ^

 *     |                |      +---------------+  (2)     (4)        (8)

 *     |             (1)|----->| prepare()     |---+       |          |

 *     |             (3)|----->| find()/next() |-----------+          |

 *     |             (7)|----->| destroy()     |----------------------+

 *     +----------------+      +---------------+

 *  

 *   (1) User configures a search by calling _prepare() specifying the

 *       search parameters such as the pattern and algorithm name.

 *   (2) Core requests the algorithm to allocate and initialize a search

 *       configuration according to the specified parameters.

 *   (3) User starts the search(es) by calling _find() or _next() to

 *       fetch subsequent occurrences. A state variable is provided

 *       to the algorihtm to store persistant variables.

 *   (4) Core eventually resets the search offset and forwards the find()

 *       request to the algorithm.

 *   (5) Algorithm calls get_next_block() provided by the user continously

 *       to fetch the data to be searched in block by block.

 *   (6) Algorithm invokes finish() after the last call to get_next_block

 *       to clean up any leftovers from get_next_block. (Optional)

 *   (7) User destroys the configuration by calling _destroy().

 *   (8) Core notifies the algorithm to destroy algorithm specific

 *       allocations. (Optional)

 *

 * USAGE

 *

 *   Before a search can be performed, a configuration must be created

 *   by calling textsearch_prepare() specyfing the searching algorithm and

 *   the pattern to look for. The returned configuration may then be used

 *   for an arbitary amount of times and even in parallel as long as a

 *   separate struct ts_state variable is provided to every instance.

 *

 *   The actual search is performed by either calling textsearch_find_-

 *   continuous() for linear data or by providing an own get_next_block()

 *   implementation and calling textsearch_find(). Both functions return

 *   the position of the first occurrence of the patern or UINT_MAX if

 *   no match was found. Subsequent occurences can be found by calling

 *   textsearch_next() regardless of the linearity of the data.

 *

 *   Once you're done using a configuration it must be given back via

 *   textsearch_destroy.

 *

 * EXAMPLE

 *

 *   int pos;

 *   struct ts_config *conf;

 *   struct ts_state state;

 *   const char *pattern = "chicken";

 *   const char *example = "We dance the funky chicken";

 *

 *   conf = textsearch_prepare("kmp", pattern, strlen(pattern),

 *                             GFP_KERNEL, TS_AUTOLOAD);

 *   if (IS_ERR(conf)) {

 *       err = PTR_ERR(conf);

 *       goto errout;

 *   }

 *

 *   pos = textsearch_find_continuous(conf, &state, example, strlen(example));

 *   if (pos != UINT_MAX)

 *       panic("Oh my god, dancing chickens at %d\n", pos);

 *

 *   textsearch_destroy(conf);

 *

 * ==========================================================================

 */

#include <linux/config.h>

#include <linux/module.h>

#include <linux/types.h>

#include <linux/string.h>

#include <linux/init.h>

#include <linux/rcupdate.h>

#include <linux/err.h>

#include <linux/textsearch.h>

static LIST_HEAD(ts_ops);

static DEFINE_SPINLOCK(ts_mod_lock);

static inline struct ts_ops *lookup_ts_algo(const char *name)

{

	struct ts_ops *o;

	rcu_read_lock();

	list_for_each_entry_rcu(o, &ts_ops, list) {

		if (!strcmp(name, o->name)) {

			if (!try_module_get(o->owner))

				o = NULL;

			rcu_read_unlock();

			return o;

		}

	}

	rcu_read_unlock();

	return NULL;

}

/**

 * textsearch_register - register a textsearch module

 * @ops: operations lookup table

 *

 * This function must be called by textsearch modules to announce

 * their presence. The specified &@ops must have %name set to a

 * unique identifier and the callbacks find(), init(), get_pattern(),

 * and get_pattern_len() must be implemented.

 *

 * Returns 0 or -EEXISTS if another module has already registered

 * with same name.

 */

int textsearch_register(struct ts_ops *ops)

{

	int err = -EEXIST;

	struct ts_ops *o;

	if (ops->name == NULL || ops->find == NULL || ops->init == NULL ||

	    ops->get_pattern == NULL || ops->get_pattern_len == NULL)

		return -EINVAL;

	spin_lock(&ts_mod_lock);

	list_for_each_entry(o, &ts_ops, list) {

		if (!strcmp(ops->name, o->name))

			goto errout;

	}

	list_add_tail_rcu(&ops->list, &ts_ops);

	err = 0;

errout:

	spin_unlock(&ts_mod_lock);

	return err;

}

/**

 * textsearch_unregister - unregister a textsearch module

 * @ops: operations lookup table

 *

 * This function must be called by textsearch modules to announce

 * their disappearance for examples when the module gets unloaded.

 * The &ops parameter must be the same as the one during the

 * registration.

 *

 * Returns 0 on success or -ENOENT if no matching textsearch

 * registration was found.

 */

int textsearch_unregister(struct ts_ops *ops)

{

	int err = 0;

	struct ts_ops *o;

	spin_lock(&ts_mod_lock);

	list_for_each_entry(o, &ts_ops, list) {

		if (o == ops) {

			list_del_rcu(&o->list);

			goto out;

		}

	}

	err = -ENOENT;

out:

	spin_unlock(&ts_mod_lock);

	return err;

}

struct ts_linear_state

{

	unsigned int	len;

	const void	*data;

};

static unsigned int get_linear_data(unsigned int consumed, const u8 **dst,

				    struct ts_config *conf,

				    struct ts_state *state)

{

	struct ts_linear_state *st = (struct ts_linear_state *) state->cb;

	if (likely(consumed < st->len)) {

		*dst = st->data + consumed;

		return st->len - consumed;

	}

	return 0;

}

/**

 * textsearch_find_continuous - search a pattern in continuous/linear data

 * @conf: search configuration

 * @state: search state

 * @data: data to search in

 * @len: length of data

 *

 * A simplified version of textsearch_find() for continuous/linear data.

 * Call textsearch_next() to retrieve subsequent matches.

 *

 * Returns the position of first occurrence of the pattern or

 * UINT_MAX if no occurrence was found.

 */ 

unsigned int textsearch_find_continuous(struct ts_config *conf,

					struct ts_state *state,

					const void *data, unsigned int len)

{

	struct ts_linear_state *st = (struct ts_linear_state *) state->cb;

	conf->get_next_block = get_linear_data;

	st->data = data;

	st->len = len;

	return textsearch_find(conf, state);

}

/**

 * textsearch_prepare - Prepare a search

 * @algo: name of search algorithm

 * @pattern: pattern data

 * @len: length of pattern

 * @gfp_mask: allocation mask

 * @flags: search flags

 *

 * Looks up the search algorithm module and creates a new textsearch

 * configuration for the specified pattern. Upon completion all

 * necessary refcnts are held and the configuration must be put back

 * using textsearch_put() after usage.

 *

 * Note: The format of the pattern may not be compatible between

 *       the various search algorithms.

 *

 * Returns a new textsearch configuration according to the specified

 *         parameters or a ERR_PTR().

 */

struct ts_config *textsearch_prepare(const char *algo, const void *pattern,

				     unsigned int len, int gfp_mask, int flags)

{

	int err = -ENOENT;

	struct ts_config *conf;

	struct ts_ops *ops;

	ops = lookup_ts_algo(algo);

#ifdef CONFIG_KMOD

	/*

	 * Why not always autoload you may ask. Some users are

	 * in a situation where requesting a module may deadlock,

	 * especially when the module is located on a NFS mount.

	 */

	if (ops == NULL && flags & TS_AUTOLOAD) {

		request_module("ts_%s", algo);

		ops = lookup_ts_algo(algo);

	}

#endif

	if (ops == NULL)

		goto errout;

	conf = ops->init(pattern, len, gfp_mask);

	if (IS_ERR(conf)) {

		err = PTR_ERR(conf);

		goto errout;

	}

	conf->ops = ops;

	return conf;

errout:

	if (ops)

		module_put(ops->owner);

	return ERR_PTR(err);

}

/**

 * textsearch_destroy - destroy a search configuration

 * @conf: search configuration

 *

 * Releases all references of the configuration and frees

 * up the memory.

 */

void textsearch_destroy(struct ts_config *conf)

{

	if (conf->ops) {

		if (conf->ops->destroy)

			conf->ops->destroy(conf);

		module_put(conf->ops->owner);

	}

	kfree(conf);

}

EXPORT_SYMBOL(textsearch_register);

EXPORT_SYMBOL(textsearch_unregister);

EXPORT_SYMBOL(textsearch_prepare);

EXPORT_SYMBOL(textsearch_find_continuous);

EXPORT_SYMBOL(textsearch_destroy);