/* -*- buffer-read-only: t -*- vi: set ro: */ /* DO NOT EDIT! GENERATED AUTOMATICALLY! */ /* Substring search in a NUL terminated string of UNIT elements, using the Knuth-Morris-Pratt algorithm. Copyright (C) 2005-2011 Free Software Foundation, Inc. Written by Bruno Haible <bruno@clisp.org>, 2005. 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 3, or (at your option) any later version. This program 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ /* 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 http://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

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