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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169// SPDX-License-Identifier: GPL-2.0-or-later/* * lib/ts_kmp.c Knuth-Morris-Pratt text search implementation * * Authors: Thomas Graf <tgraf@suug.ch> * * ========================================================================== * * Implements a linear-time string-matching algorithm due to Knuth, * Morris, and Pratt [1]. Their algorithm avoids the explicit * computation of the transition function DELTA altogether. Its * matching time is O(n), for n being length(text), using just an * auxiliary function PI[1..m], for m being length(pattern), * precomputed from the pattern in time O(m). The array PI allows * the transition function DELTA to be computed efficiently * "on the fly" as needed. Roughly speaking, for any state * "q" = 0,1,...,m and any character "a" in SIGMA, the value * PI["q"] contains the information that is independent of "a" and * is needed to compute DELTA("q", "a") [2]. Since the array PI * has only m entries, whereas DELTA has O(m|SIGMA|) entries, we * save a factor of |SIGMA| in the preprocessing time by computing * PI rather than DELTA. * * [1] Cormen, Leiserson, Rivest, Stein * Introdcution to Algorithms, 2nd Edition, MIT Press * [2] See finite automaton theory */
#include <linux/module.h>#include <linux/types.h>#include <linux/string.h>#include <linux/ctype.h>#include <linux/textsearch.h>
struct ts_kmp{ u8 * pattern; unsigned int pattern_len; unsigned int prefix_tbl[];};
static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state){ struct ts_kmp *kmp = ts_config_priv(conf); unsigned int i, q = 0, text_len, consumed = state->offset; const u8 *text; const int icase = conf->flags & TS_IGNORECASE;
for (;;) { text_len = conf->get_next_block(consumed, &text, conf, state);
if (unlikely(text_len == 0)) break;
for (i = 0; i < text_len; i++) { while (q > 0 && kmp->pattern[q] != (icase ? toupper(text[i]) : text[i])) q = kmp->prefix_tbl[q - 1]; if (kmp->pattern[q] == (icase ? toupper(text[i]) : text[i])) q++; if (unlikely(q == kmp->pattern_len)) { state->offset = consumed + i + 1; return state->offset - kmp->pattern_len; } }
consumed += text_len; }
return UINT_MAX;}
static inline void compute_prefix_tbl(const u8 *pattern, unsigned int len, unsigned int *prefix_tbl, int flags){ unsigned int k, q; const u8 icase = flags & TS_IGNORECASE;
for (k = 0, q = 1; q < len; q++) { while (k > 0 && (icase ? toupper(pattern[k]) : pattern[k]) != (icase ? toupper(pattern[q]) : pattern[q])) k = prefix_tbl[k-1]; if ((icase ? toupper(pattern[k]) : pattern[k]) == (icase ? toupper(pattern[q]) : pattern[q])) k++; prefix_tbl[q] = k; }}
static struct ts_config *kmp_init(const void *pattern, unsigned int len, gfp_t gfp_mask, int flags){ struct ts_config *conf; struct ts_kmp *kmp; int i; unsigned int prefix_tbl_len; size_t priv_size;
/* Zero-length patterns would make kmp_find() read beyond kmp->pattern. */ if (unlikely(!len)) return ERR_PTR(-EINVAL);
/* * kmp->pattern is stored immediately after the prefix_tbl[] table. * Reject lengths that would wrap while sizing either region. */ if (unlikely(check_mul_overflow(len, sizeof(*kmp->prefix_tbl), &prefix_tbl_len) || check_add_overflow(sizeof(*kmp), (size_t)len, &priv_size) || check_add_overflow(priv_size, prefix_tbl_len, &priv_size))) return ERR_PTR(-EINVAL);
conf = alloc_ts_config(priv_size, gfp_mask); if (IS_ERR(conf)) return conf;
conf->flags = flags; kmp = ts_config_priv(conf); kmp->pattern_len = len; compute_prefix_tbl(pattern, len, kmp->prefix_tbl, flags); kmp->pattern = (u8 *) kmp->prefix_tbl + prefix_tbl_len; if (flags & TS_IGNORECASE) for (i = 0; i < len; i++) kmp->pattern[i] = toupper(((u8 *)pattern)[i]); else memcpy(kmp->pattern, pattern, len);
return conf;}
static void *kmp_get_pattern(struct ts_config *conf){ struct ts_kmp *kmp = ts_config_priv(conf); return kmp->pattern;}
static unsigned int kmp_get_pattern_len(struct ts_config *conf){ struct ts_kmp *kmp = ts_config_priv(conf); return kmp->pattern_len;}
static struct ts_ops kmp_ops = { .name = "kmp", .find = kmp_find, .init = kmp_init, .get_pattern = kmp_get_pattern, .get_pattern_len = kmp_get_pattern_len, .owner = THIS_MODULE, .list = LIST_HEAD_INIT(kmp_ops.list)};
static int __init init_kmp(void){ return textsearch_register(&kmp_ops);}
static void __exit exit_kmp(void){ textsearch_unregister(&kmp_ops);}
MODULE_DESCRIPTION("Knuth-Morris-Pratt text search implementation");MODULE_LICENSE("GPL");
module_init(init_kmp);module_exit(exit_kmp);