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Diffstat (limited to 'lib/str-kmp.h')
| -rw-r--r-- | lib/str-kmp.h | 161 |
1 files changed, 0 insertions, 161 deletions
diff --git a/lib/str-kmp.h b/lib/str-kmp.h deleted file mode 100644 index 959ff65a..00000000 --- a/lib/str-kmp.h +++ /dev/null @@ -1,161 +0,0 @@ -/* Substring search in a NUL terminated string of UNIT elements, - using the Knuth-Morris-Pratt algorithm. - Copyright (C) 2005-2022 Free Software Foundation, Inc. - Written by Bruno Haible <bruno@clisp.org>, 2005. - - This file is free software. - It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+". - You can redistribute it and/or modify it under either - - the terms of the GNU Lesser General Public License as published - by the Free Software Foundation, either version 3, or (at your - option) any later version, or - - the terms of the GNU General Public License as published by the - Free Software Foundation; either version 2, or (at your option) - any later version, or - - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+". - - This file 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 - Lesser General Public License and the GNU General Public License - for more details. - - You should have received a copy of the GNU Lesser General Public - License and of the GNU General Public License along with this - program. If not, see <https://www.gnu.org/licenses/>. */ - -/* Before including this file, you need to define: - UNIT The element type of the needle and haystack. - CANON_ELEMENT(c) A macro that canonicalizes an element right after - it has been fetched from needle or haystack. - The argument is of type UNIT; the result must be - of type UNIT as well. */ - -/* Knuth-Morris-Pratt algorithm. - See https://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm - HAYSTACK is the NUL terminated string in which to search for. - NEEDLE is the string to search for in HAYSTACK, consisting of NEEDLE_LEN - units. - Return a boolean indicating success: - Return true and set *RESULTP if the search was completed. - Return false if it was aborted because not enough memory was available. */ -static bool -knuth_morris_pratt (const UNIT *haystack, - const UNIT *needle, size_t needle_len, - const UNIT **resultp) -{ - size_t m = needle_len; - - /* Allocate the table. */ - size_t *table = (size_t *) nmalloca (m, sizeof (size_t)); - if (table == NULL) - return false; - /* Fill the table. - For 0 < i < m: - 0 < table[i] <= i is defined such that - forall 0 < x < table[i]: needle[x..i-1] != needle[0..i-1-x], - and table[i] is as large as possible with this property. - This implies: - 1) For 0 < i < m: - If table[i] < i, - needle[table[i]..i-1] = needle[0..i-1-table[i]]. - 2) For 0 < i < m: - rhaystack[0..i-1] == needle[0..i-1] - and exists h, i <= h < m: rhaystack[h] != needle[h] - implies - forall 0 <= x < table[i]: rhaystack[x..x+m-1] != needle[0..m-1]. - table[0] remains uninitialized. */ - { - size_t i, j; - - /* i = 1: Nothing to verify for x = 0. */ - table[1] = 1; - j = 0; - - for (i = 2; i < m; i++) - { - /* Here: j = i-1 - table[i-1]. - The inequality needle[x..i-1] != needle[0..i-1-x] is known to hold - for x < table[i-1], by induction. - Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1]. */ - UNIT b = CANON_ELEMENT (needle[i - 1]); - - for (;;) - { - /* Invariants: The inequality needle[x..i-1] != needle[0..i-1-x] - is known to hold for x < i-1-j. - Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1]. */ - if (b == CANON_ELEMENT (needle[j])) - { - /* Set table[i] := i-1-j. */ - table[i] = i - ++j; - break; - } - /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds - for x = i-1-j, because - needle[i-1] != needle[j] = needle[i-1-x]. */ - if (j == 0) - { - /* The inequality holds for all possible x. */ - table[i] = i; - break; - } - /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds - for i-1-j < x < i-1-j+table[j], because for these x: - needle[x..i-2] - = needle[x-(i-1-j)..j-1] - != needle[0..j-1-(x-(i-1-j))] (by definition of table[j]) - = needle[0..i-2-x], - hence needle[x..i-1] != needle[0..i-1-x]. - Furthermore - needle[i-1-j+table[j]..i-2] - = needle[table[j]..j-1] - = needle[0..j-1-table[j]] (by definition of table[j]). */ - j = j - table[j]; - } - /* Here: j = i - table[i]. */ - } - } - - /* Search, using the table to accelerate the processing. */ - { - size_t j; - const UNIT *rhaystack; - const UNIT *phaystack; - - *resultp = NULL; - j = 0; - rhaystack = haystack; - phaystack = haystack; - /* Invariant: phaystack = rhaystack + j. */ - while (*phaystack != 0) - if (CANON_ELEMENT (needle[j]) == CANON_ELEMENT (*phaystack)) - { - j++; - phaystack++; - if (j == m) - { - /* The entire needle has been found. */ - *resultp = rhaystack; - break; - } - } - else if (j > 0) - { - /* Found a match of needle[0..j-1], mismatch at needle[j]. */ - rhaystack += table[j]; - j -= table[j]; - } - else - { - /* Found a mismatch at needle[0] already. */ - rhaystack++; - phaystack++; - } - } - - freea (table); - return true; -} - -#undef CANON_ELEMENT |