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kernel
os
linux
[LIB]: Textsearch infrastructure.
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.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
authored by Thomas Graf and committed by David S. Miller 2de4ff7b 5f8ef48d
+180
include/linux/textsearch.h
+180
include/linux/textsearch.h
···
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#ifndef __LINUX_TEXTSEARCH_H
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#define __LINUX_TEXTSEARCH_H
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#ifdef __KERNEL__
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#include <linux/types.h>
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#include <linux/list.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/err.h>
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struct ts_config;
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+
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/**
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* TS_AUTOLOAD - Automatically load textsearch modules when needed
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*/
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#define TS_AUTOLOAD 1
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/**
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* struct ts_state - search state
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* @offset: offset for next match
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* @cb: control buffer, for persistant variables of get_next_block()
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*/
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struct ts_state
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{
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unsigned int offset;
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char cb[40];
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};
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/**
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* struct ts_ops - search module operations
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* @name: name of search algorithm
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* @init: initialization function to prepare a search
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* @find: find the next occurrence of the pattern
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* @destroy: destroy algorithm specific parts of a search configuration
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* @get_pattern: return head of pattern
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* @get_pattern_len: return length of pattern
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* @owner: module reference to algorithm
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*/
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struct ts_ops
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{
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const char *name;
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struct ts_config * (*init)(const void *, unsigned int, int);
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unsigned int (*find)(struct ts_config *,
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struct ts_state *);
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void (*destroy)(struct ts_config *);
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void * (*get_pattern)(struct ts_config *);
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unsigned int (*get_pattern_len)(struct ts_config *);
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struct module *owner;
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struct list_head list;
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};
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/**
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* struct ts_config - search configuration
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* @ops: operations of chosen algorithm
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* @get_next_block: callback to fetch the next block to search in
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* @finish: callback to finalize a search
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*/
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struct ts_config
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{
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struct ts_ops *ops;
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/**
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* get_next_block - fetch next block of data
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* @consumed: number of bytes consumed by the caller
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* @dst: destination buffer
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* @conf: search configuration
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* @state: search state
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*
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* Called repeatedly until 0 is returned. Must assign the
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* head of the next block of data to &*dst and return the length
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* of the block or 0 if at the end. consumed == 0 indicates
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* a new search. May store/read persistant values in state->cb.
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*/
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unsigned int (*get_next_block)(unsigned int consumed,
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const u8 **dst,
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struct ts_config *conf,
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struct ts_state *state);
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/**
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* finish - finalize/clean a series of get_next_block() calls
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* @conf: search configuration
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* @state: search state
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*
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* Called after the last use of get_next_block(), may be used
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* to cleanup any leftovers.
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*/
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void (*finish)(struct ts_config *conf,
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struct ts_state *state);
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};
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/**
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* textsearch_next - continue searching for a pattern
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* @conf: search configuration
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* @state: search state
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*
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* Continues a search looking for more occurrences of the pattern.
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* textsearch_find() must be called to find the first occurrence
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* in order to reset the state.
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*
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* Returns the position of the next occurrence of the pattern or
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* UINT_MAX if not match was found.
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*/
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static inline unsigned int textsearch_next(struct ts_config *conf,
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struct ts_state *state)
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{
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unsigned int ret = conf->ops->find(conf, state);
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if (conf->finish)
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conf->finish(conf, state);
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return ret;
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}
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/**
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* textsearch_find - start searching for a pattern
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* @conf: search configuration
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* @state: search state
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*
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* Returns the position of first occurrence of the pattern or
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* UINT_MAX if no match was found.
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*/
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static inline unsigned int textsearch_find(struct ts_config *conf,
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struct ts_state *state)
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{
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state->offset = 0;
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return textsearch_next(conf, state);
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}
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/**
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* textsearch_get_pattern - return head of the pattern
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* @conf: search configuration
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*/
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static inline void *textsearch_get_pattern(struct ts_config *conf)
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{
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return conf->ops->get_pattern(conf);
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}
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/**
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* textsearch_get_pattern_len - return length of the pattern
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* @conf: search configuration
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*/
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static inline unsigned int textsearch_get_pattern_len(struct ts_config *conf)
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{
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return conf->ops->get_pattern_len(conf);
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}
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extern int textsearch_register(struct ts_ops *);
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extern int textsearch_unregister(struct ts_ops *);
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extern struct ts_config *textsearch_prepare(const char *, const void *,
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unsigned int, int, int);
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extern void textsearch_destroy(struct ts_config *conf);
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extern unsigned int textsearch_find_continuous(struct ts_config *,
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struct ts_state *,
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const void *, unsigned int);
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#define TS_PRIV_ALIGNTO 8
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#define TS_PRIV_ALIGN(len) (((len) + TS_PRIV_ALIGNTO-1) & ~(TS_PRIV_ALIGNTO-1))
160
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static inline struct ts_config *alloc_ts_config(size_t payload, int gfp_mask)
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{
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struct ts_config *conf;
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conf = kmalloc(TS_PRIV_ALIGN(sizeof(*conf)) + payload, gfp_mask);
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if (conf == NULL)
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return ERR_PTR(-ENOMEM);
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memset(conf, 0, TS_PRIV_ALIGN(sizeof(*conf)) + payload);
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return conf;
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}
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static inline void *ts_config_priv(struct ts_config *conf)
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{
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return ((u8 *) conf + TS_PRIV_ALIGN(sizeof(struct ts_config)));
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}
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#endif /* __KERNEL__ */
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#endif
+7
-1
lib/Kconfig
+7
-1
lib/Kconfig
+2
lib/Makefile
+2
lib/Makefile
+317
lib/textsearch.c
+317
lib/textsearch.c
···
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/*
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* lib/textsearch.c Generic text search interface
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Thomas Graf <tgraf@suug.ch>
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* Pablo Neira Ayuso <pablo@eurodev.net>
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*
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* ==========================================================================
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*
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* INTRODUCTION
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*
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* The textsearch infrastructure provides text searching facitilies for
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* both linear and non-linear data. Individual search algorithms are
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* implemented in modules and chosen by the user.
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*
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* ARCHITECTURE
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*
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* User
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* +----------------+
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* | finish()|<--------------(6)-----------------+
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* |get_next_block()|<--------------(5)---------------+ |
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* | | Algorithm | |
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* | | +------------------------------+
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* | | | init() find() destroy() |
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* | | +------------------------------+
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* | | Core API ^ ^ ^
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* | | +---------------+ (2) (4) (8)
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* | (1)|----->| prepare() |---+ | |
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* | (3)|----->| find()/next() |-----------+ |
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* | (7)|----->| destroy() |----------------------+
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* +----------------+ +---------------+
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*
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* (1) User configures a search by calling _prepare() specifying the
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* search parameters such as the pattern and algorithm name.
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* (2) Core requests the algorithm to allocate and initialize a search
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* configuration according to the specified parameters.
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* (3) User starts the search(es) by calling _find() or _next() to
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* fetch subsequent occurrences. A state variable is provided
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* to the algorihtm to store persistant variables.
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* (4) Core eventually resets the search offset and forwards the find()
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* request to the algorithm.
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* (5) Algorithm calls get_next_block() provided by the user continously
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* to fetch the data to be searched in block by block.
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* (6) Algorithm invokes finish() after the last call to get_next_block
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* to clean up any leftovers from get_next_block. (Optional)
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* (7) User destroys the configuration by calling _destroy().
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* (8) Core notifies the algorithm to destroy algorithm specific
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* allocations. (Optional)
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*
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* USAGE
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*
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* Before a search can be performed, a configuration must be created
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* by calling textsearch_prepare() specyfing the searching algorithm and
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* the pattern to look for. The returned configuration may then be used
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* for an arbitary amount of times and even in parallel as long as a
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* separate struct ts_state variable is provided to every instance.
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*
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* The actual search is performed by either calling textsearch_find_-
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* continuous() for linear data or by providing an own get_next_block()
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* implementation and calling textsearch_find(). Both functions return
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* the position of the first occurrence of the patern or UINT_MAX if
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* no match was found. Subsequent occurences can be found by calling
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* textsearch_next() regardless of the linearity of the data.
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*
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* Once you're done using a configuration it must be given back via
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* textsearch_destroy.
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*
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* EXAMPLE
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*
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* int pos;
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* struct ts_config *conf;
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* struct ts_state state;
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* const char *pattern = "chicken";
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* const char *example = "We dance the funky chicken";
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*
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* conf = textsearch_prepare("kmp", pattern, strlen(pattern),
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* GFP_KERNEL, TS_AUTOLOAD);
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* if (IS_ERR(conf)) {
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* err = PTR_ERR(conf);
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* goto errout;
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* }
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*
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* pos = textsearch_find_continuous(conf, &state, example, strlen(example));
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* if (pos != UINT_MAX)
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* panic("Oh my god, dancing chickens at %d\n", pos);
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*
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* textsearch_destroy(conf);
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*
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* ==========================================================================
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*/
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#include <linux/config.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/init.h>
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#include <linux/rcupdate.h>
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#include <linux/err.h>
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#include <linux/textsearch.h>
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static LIST_HEAD(ts_ops);
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static DEFINE_SPINLOCK(ts_mod_lock);
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static inline struct ts_ops *lookup_ts_algo(const char *name)
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{
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struct ts_ops *o;
111
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112
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rcu_read_lock();
113
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list_for_each_entry_rcu(o, &ts_ops, list) {
114
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if (!strcmp(name, o->name)) {
115
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if (!try_module_get(o->owner))
116
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o = NULL;
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rcu_read_unlock();
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return o;
119
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}
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}
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rcu_read_unlock();
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return NULL;
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}
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/**
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* textsearch_register - register a textsearch module
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* @ops: operations lookup table
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*
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* This function must be called by textsearch modules to announce
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* their presence. The specified &@ops must have %name set to a
132
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* unique identifier and the callbacks find(), init(), get_pattern(),
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* and get_pattern_len() must be implemented.
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*
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* Returns 0 or -EEXISTS if another module has already registered
136
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* with same name.
137
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*/
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int textsearch_register(struct ts_ops *ops)
139
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{
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int err = -EEXIST;
141
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struct ts_ops *o;
142
+
143
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if (ops->name == NULL || ops->find == NULL || ops->init == NULL ||
144
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ops->get_pattern == NULL || ops->get_pattern_len == NULL)
145
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return -EINVAL;
146
+
147
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spin_lock(&ts_mod_lock);
148
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list_for_each_entry(o, &ts_ops, list) {
149
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if (!strcmp(ops->name, o->name))
150
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goto errout;
151
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}
152
+
153
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list_add_tail_rcu(&ops->list, &ts_ops);
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err = 0;
155
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errout:
156
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spin_unlock(&ts_mod_lock);
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return err;
158
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}
159
+
160
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/**
161
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* textsearch_unregister - unregister a textsearch module
162
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* @ops: operations lookup table
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*
164
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* This function must be called by textsearch modules to announce
165
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* their disappearance for examples when the module gets unloaded.
166
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* The &ops parameter must be the same as the one during the
167
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* registration.
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*
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* Returns 0 on success or -ENOENT if no matching textsearch
170
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* registration was found.
171
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*/
172
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int textsearch_unregister(struct ts_ops *ops)
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{
174
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int err = 0;
175
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struct ts_ops *o;
176
+
177
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spin_lock(&ts_mod_lock);
178
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list_for_each_entry(o, &ts_ops, list) {
179
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if (o == ops) {
180
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list_del_rcu(&o->list);
181
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goto out;
182
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}
183
+
}
184
+
185
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err = -ENOENT;
186
+
out:
187
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spin_unlock(&ts_mod_lock);
188
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return err;
189
+
}
190
+
191
+
struct ts_linear_state
192
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{
193
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unsigned int len;
194
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const void *data;
195
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};
196
+
197
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static unsigned int get_linear_data(unsigned int consumed, const u8 **dst,
198
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struct ts_config *conf,
199
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struct ts_state *state)
200
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{
201
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struct ts_linear_state *st = (struct ts_linear_state *) state->cb;
202
+
203
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if (likely(consumed < st->len)) {
204
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*dst = st->data + consumed;
205
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return st->len - consumed;
206
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}
207
+
208
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return 0;
209
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}
210
+
211
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/**
212
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* textsearch_find_continuous - search a pattern in continuous/linear data
213
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* @conf: search configuration
214
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* @state: search state
215
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* @data: data to search in
216
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* @len: length of data
217
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*
218
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* A simplified version of textsearch_find() for continuous/linear data.
219
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* Call textsearch_next() to retrieve subsequent matches.
220
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*
221
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* Returns the position of first occurrence of the pattern or
222
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* UINT_MAX if no occurrence was found.
223
+
*/
224
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unsigned int textsearch_find_continuous(struct ts_config *conf,
225
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struct ts_state *state,
226
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const void *data, unsigned int len)
227
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{
228
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struct ts_linear_state *st = (struct ts_linear_state *) state->cb;
229
+
230
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conf->get_next_block = get_linear_data;
231
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st->data = data;
232
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st->len = len;
233
+
234
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return textsearch_find(conf, state);
235
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}
236
+
237
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/**
238
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* textsearch_prepare - Prepare a search
239
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* @algo: name of search algorithm
240
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* @pattern: pattern data
241
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* @len: length of pattern
242
+
* @gfp_mask: allocation mask
243
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* @flags: search flags
244
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*
245
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* Looks up the search algorithm module and creates a new textsearch
246
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* configuration for the specified pattern. Upon completion all
247
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* necessary refcnts are held and the configuration must be put back
248
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* using textsearch_put() after usage.
249
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*
250
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* Note: The format of the pattern may not be compatible between
251
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* the various search algorithms.
252
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*
253
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* Returns a new textsearch configuration according to the specified
254
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* parameters or a ERR_PTR().
255
+
*/
256
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struct ts_config *textsearch_prepare(const char *algo, const void *pattern,
257
+
unsigned int len, int gfp_mask, int flags)
258
+
{
259
+
int err = -ENOENT;
260
+
struct ts_config *conf;
261
+
struct ts_ops *ops;
262
+
263
+
ops = lookup_ts_algo(algo);
264
+
#ifdef CONFIG_KMOD
265
+
/*
266
+
* Why not always autoload you may ask. Some users are
267
+
* in a situation where requesting a module may deadlock,
268
+
* especially when the module is located on a NFS mount.
269
+
*/
270
+
if (ops == NULL && flags & TS_AUTOLOAD) {
271
+
request_module("ts_%s", algo);
272
+
ops = lookup_ts_algo(algo);
273
+
}
274
+
#endif
275
+
276
+
if (ops == NULL)
277
+
goto errout;
278
+
279
+
conf = ops->init(pattern, len, gfp_mask);
280
+
if (IS_ERR(conf)) {
281
+
err = PTR_ERR(conf);
282
+
goto errout;
283
+
}
284
+
285
+
conf->ops = ops;
286
+
return conf;
287
+
288
+
errout:
289
+
if (ops)
290
+
module_put(ops->owner);
291
+
292
+
return ERR_PTR(err);
293
+
}
294
+
295
+
/**
296
+
* textsearch_destroy - destroy a search configuration
297
+
* @conf: search configuration
298
+
*
299
+
* Releases all references of the configuration and frees
300
+
* up the memory.
301
+
*/
302
+
void textsearch_destroy(struct ts_config *conf)
303
+
{
304
+
if (conf->ops) {
305
+
if (conf->ops->destroy)
306
+
conf->ops->destroy(conf);
307
+
module_put(conf->ops->owner);
308
+
}
309
+
310
+
kfree(conf);
311
+
}
312
+
313
+
EXPORT_SYMBOL(textsearch_register);
314
+
EXPORT_SYMBOL(textsearch_unregister);
315
+
EXPORT_SYMBOL(textsearch_prepare);
316
+
EXPORT_SYMBOL(textsearch_find_continuous);
317
+
EXPORT_SYMBOL(textsearch_destroy);