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323 lines
9.3 KiB
323 lines
9.3 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* lib/textsearch.c Generic text search interface |
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* |
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* Authors: Thomas Graf <[email protected]> |
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* Pablo Neira Ayuso <[email protected]> |
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* |
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* ========================================================================== |
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*/ |
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/** |
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* DOC: ts_intro |
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* INTRODUCTION |
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* |
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* The textsearch infrastructure provides text searching facilities 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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* .. code-block:: none |
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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 textsearch_prepare() specifying |
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* the 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 textsearch_find() or |
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* textsearch_next() to fetch subsequent occurrences. A state variable |
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* is provided to the algorithm to store persistent 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 continuously |
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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 textsearch_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() specifying the searching algorithm, |
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* the pattern to look for and flags. As a flag, you can set TS_IGNORECASE |
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* to perform case insensitive matching. But it might slow down |
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* performance of algorithm, so you should use it at own your risk. |
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* The returned configuration may then be used for an arbitrary |
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* amount of times and even in parallel as long as a separate struct |
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* ts_state variable is provided to every instance. |
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* |
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* The actual search is performed by either calling |
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* textsearch_find_continuous() for linear data or by providing |
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* an own get_next_block() implementation and |
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* calling textsearch_find(). Both functions return |
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* the position of the first occurrence of the pattern or UINT_MAX if |
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* no match was found. Subsequent occurrences 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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#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/rculist.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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#include <linux/slab.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; |
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rcu_read_lock(); |
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list_for_each_entry_rcu(o, &ts_ops, list) { |
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if (!strcmp(name, o->name)) { |
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if (!try_module_get(o->owner)) |
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o = NULL; |
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rcu_read_unlock(); |
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return o; |
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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 |
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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 |
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* with same name. |
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*/ |
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int textsearch_register(struct ts_ops *ops) |
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{ |
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int err = -EEXIST; |
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struct ts_ops *o; |
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if (ops->name == NULL || ops->find == NULL || ops->init == NULL || |
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ops->get_pattern == NULL || ops->get_pattern_len == NULL) |
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return -EINVAL; |
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spin_lock(&ts_mod_lock); |
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list_for_each_entry(o, &ts_ops, list) { |
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if (!strcmp(ops->name, o->name)) |
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goto errout; |
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} |
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list_add_tail_rcu(&ops->list, &ts_ops); |
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err = 0; |
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errout: |
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spin_unlock(&ts_mod_lock); |
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return err; |
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} |
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EXPORT_SYMBOL(textsearch_register); |
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/** |
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* textsearch_unregister - unregister 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 disappearance for examples when the module gets unloaded. |
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* The &ops parameter must be the same as the one during the |
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* registration. |
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* |
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* Returns 0 on success or -ENOENT if no matching textsearch |
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* registration was found. |
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*/ |
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int textsearch_unregister(struct ts_ops *ops) |
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{ |
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int err = 0; |
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struct ts_ops *o; |
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spin_lock(&ts_mod_lock); |
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list_for_each_entry(o, &ts_ops, list) { |
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if (o == ops) { |
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list_del_rcu(&o->list); |
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goto out; |
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} |
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} |
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err = -ENOENT; |
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out: |
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spin_unlock(&ts_mod_lock); |
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return err; |
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} |
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EXPORT_SYMBOL(textsearch_unregister); |
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struct ts_linear_state |
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{ |
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unsigned int len; |
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const void *data; |
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}; |
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static unsigned int get_linear_data(unsigned int consumed, 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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struct ts_linear_state *st = (struct ts_linear_state *) state->cb; |
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if (likely(consumed < st->len)) { |
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*dst = st->data + consumed; |
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return st->len - consumed; |
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} |
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return 0; |
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} |
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/** |
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* textsearch_find_continuous - search a pattern in continuous/linear data |
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* @conf: search configuration |
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* @state: search state |
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* @data: data to search in |
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* @len: length of data |
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* |
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* A simplified version of textsearch_find() for continuous/linear data. |
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* Call textsearch_next() to retrieve subsequent matches. |
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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 occurrence was found. |
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*/ |
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unsigned int textsearch_find_continuous(struct ts_config *conf, |
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struct ts_state *state, |
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const void *data, unsigned int len) |
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{ |
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struct ts_linear_state *st = (struct ts_linear_state *) state->cb; |
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conf->get_next_block = get_linear_data; |
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st->data = data; |
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st->len = len; |
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return textsearch_find(conf, state); |
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} |
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EXPORT_SYMBOL(textsearch_find_continuous); |
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/** |
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* textsearch_prepare - Prepare a search |
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* @algo: name of search algorithm |
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* @pattern: pattern data |
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* @len: length of pattern |
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* @gfp_mask: allocation mask |
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* @flags: search flags |
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* |
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* Looks up the search algorithm module and creates a new textsearch |
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* configuration for the specified pattern. |
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* |
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* Note: The format of the pattern may not be compatible between |
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* the various search algorithms. |
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* |
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* Returns a new textsearch configuration according to the specified |
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* parameters or a ERR_PTR(). If a zero length pattern is passed, this |
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* function returns EINVAL. |
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*/ |
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struct ts_config *textsearch_prepare(const char *algo, const void *pattern, |
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unsigned int len, gfp_t gfp_mask, int flags) |
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{ |
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int err = -ENOENT; |
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struct ts_config *conf; |
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struct ts_ops *ops; |
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if (len == 0) |
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return ERR_PTR(-EINVAL); |
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ops = lookup_ts_algo(algo); |
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#ifdef CONFIG_MODULES |
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/* |
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* Why not always autoload you may ask. Some users are |
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* in a situation where requesting a module may deadlock, |
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* especially when the module is located on a NFS mount. |
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*/ |
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if (ops == NULL && flags & TS_AUTOLOAD) { |
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request_module("ts_%s", algo); |
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ops = lookup_ts_algo(algo); |
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} |
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#endif |
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if (ops == NULL) |
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goto errout; |
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conf = ops->init(pattern, len, gfp_mask, flags); |
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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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conf->ops = ops; |
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return conf; |
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errout: |
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if (ops) |
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module_put(ops->owner); |
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return ERR_PTR(err); |
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} |
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EXPORT_SYMBOL(textsearch_prepare); |
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/** |
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* textsearch_destroy - destroy a search configuration |
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* @conf: search configuration |
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* |
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* Releases all references of the configuration and frees |
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* up the memory. |
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*/ |
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void textsearch_destroy(struct ts_config *conf) |
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{ |
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if (conf->ops) { |
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if (conf->ops->destroy) |
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conf->ops->destroy(conf); |
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module_put(conf->ops->owner); |
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} |
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kfree(conf); |
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} |
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EXPORT_SYMBOL(textsearch_destroy);
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