/* Case-insensitive searching in a string.
- Copyright (C) 2005-2007 Free Software Foundation, Inc.
+ Copyright (C) 2005-2008 Free Software Foundation, Inc.
Written by Bruno Haible <bruno@clisp.org>, 2005.
- This program is free software; you can redistribute it and/or modify
+ 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 2, or (at your option)
- any later version.
+ the Free Software Foundation; either version 3 of the License, 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
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. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include <string.h>
#include <ctype.h>
+#include <stdbool.h>
#include <stddef.h> /* for NULL, in case a nonstandard string.h lacks it */
-#if HAVE_MBRTOWC
-# include "mbuiter.h"
-#endif
+#include "malloca.h"
+#include "mbuiter.h"
#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
-/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
- comparison.
+/* Knuth-Morris-Pratt algorithm. */
+#define CANON_ELEMENT(c) TOLOWER (c)
+#include "str-kmp.h"
+
+/* Knuth-Morris-Pratt algorithm.
+ See http://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm
+ 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_multibyte (const char *haystack, const char *needle,
+ const char **resultp)
+{
+ size_t m = mbslen (needle);
+ mbchar_t *needle_mbchars;
+ size_t *table;
+
+ /* Allocate room for needle_mbchars and the table. */
+ char *memory = (char *) nmalloca (m, sizeof (mbchar_t) + sizeof (size_t));
+ if (memory == NULL)
+ return false;
+ needle_mbchars = (mbchar_t *) memory;
+ table = (size_t *) (memory + m * sizeof (mbchar_t));
+
+ /* Fill needle_mbchars. */
+ {
+ mbui_iterator_t iter;
+ size_t j;
+
+ j = 0;
+ for (mbui_init (iter, needle); mbui_avail (iter); mbui_advance (iter), j++)
+ {
+ mb_copy (&needle_mbchars[j], &mbui_cur (iter));
+ if (needle_mbchars[j].wc_valid)
+ needle_mbchars[j].wc = towlower (needle_mbchars[j].wc);
+ }
+ }
+
+ /* 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]. */
+ mbchar_t *b = &needle_mbchars[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 (mb_equal (*b, needle_mbchars[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;
+ mbui_iterator_t rhaystack;
+ mbui_iterator_t phaystack;
+
+ *resultp = NULL;
+ j = 0;
+ mbui_init (rhaystack, haystack);
+ mbui_init (phaystack, haystack);
+ /* Invariant: phaystack = rhaystack + j. */
+ while (mbui_avail (phaystack))
+ {
+ mbchar_t c;
+
+ mb_copy (&c, &mbui_cur (phaystack));
+ if (c.wc_valid)
+ c.wc = towlower (c.wc);
+ if (mb_equal (needle_mbchars[j], c))
+ {
+ j++;
+ mbui_advance (phaystack);
+ if (j == m)
+ {
+ /* The entire needle has been found. */
+ *resultp = mbui_cur_ptr (rhaystack);
+ break;
+ }
+ }
+ else if (j > 0)
+ {
+ /* Found a match of needle[0..j-1], mismatch at needle[j]. */
+ size_t count = table[j];
+ j -= count;
+ for (; count > 0; count--)
+ {
+ if (!mbui_avail (rhaystack))
+ abort ();
+ mbui_advance (rhaystack);
+ }
+ }
+ else
+ {
+ /* Found a mismatch at needle[0] already. */
+ if (!mbui_avail (rhaystack))
+ abort ();
+ mbui_advance (rhaystack);
+ mbui_advance (phaystack);
+ }
+ }
+ }
+
+ freea (memory);
+ return true;
+}
+
+/* Find the first occurrence of the character string NEEDLE in the character
+ string HAYSTACK, using case-insensitive comparison.
Note: This function may, in multibyte locales, return success even if
strlen (haystack) < strlen (needle) ! */
char *
-strcasestr (const char *haystack, const char *needle)
+mbscasestr (const char *haystack, const char *needle)
{
/* Be careful not to look at the entire extent of haystack or needle
until needed. This is useful because of these two cases:
- haystack may be very long, and a match of needle found early,
- needle may be very long, and not even a short initial segment of
needle may be found in haystack. */
-#if HAVE_MBRTOWC
if (MB_CUR_MAX > 1)
{
mbui_iterator_t iter_needle;
mbui_init (iter_needle, needle);
if (mbui_avail (iter_needle))
{
+ /* Minimizing the worst-case complexity:
+ Let n = mbslen(haystack), m = mbslen(needle).
+ The naïve algorithm is O(n*m) worst-case.
+ The Knuth-Morris-Pratt algorithm is O(n) worst-case but it needs a
+ memory allocation.
+ To achieve linear complexity and yet amortize the cost of the
+ memory allocation, we activate the Knuth-Morris-Pratt algorithm
+ only once the naïve algorithm has already run for some time; more
+ precisely, when
+ - the outer loop count is >= 10,
+ - the average number of comparisons per outer loop is >= 5,
+ - the total number of comparisons is >= m.
+ But we try it only once. If the memory allocation attempt failed,
+ we don't retry it. */
+ bool try_kmp = true;
+ size_t outer_loop_count = 0;
+ size_t comparison_count = 0;
+ size_t last_ccount = 0; /* last comparison count */
+ mbui_iterator_t iter_needle_last_ccount; /* = needle + last_ccount */
+
mbchar_t b;
mbui_iterator_t iter_haystack;
+ mbui_init (iter_needle_last_ccount, needle);
+
mb_copy (&b, &mbui_cur (iter_needle));
if (b.wc_valid)
b.wc = towlower (b.wc);
/* No match. */
return NULL;
+ /* See whether it's advisable to use an asymptotically faster
+ algorithm. */
+ if (try_kmp
+ && outer_loop_count >= 10
+ && comparison_count >= 5 * outer_loop_count)
+ {
+ /* See if needle + comparison_count now reaches the end of
+ needle. */
+ size_t count = comparison_count - last_ccount;
+ for (;
+ count > 0 && mbui_avail (iter_needle_last_ccount);
+ count--)
+ mbui_advance (iter_needle_last_ccount);
+ last_ccount = comparison_count;
+ if (!mbui_avail (iter_needle_last_ccount))
+ {
+ /* Try the Knuth-Morris-Pratt algorithm. */
+ const char *result;
+ bool success =
+ knuth_morris_pratt_multibyte (haystack, needle,
+ &result);
+ if (success)
+ return (char *) result;
+ try_kmp = false;
+ }
+ }
+
+ outer_loop_count++;
+ comparison_count++;
mb_copy (&c, &mbui_cur (iter_haystack));
if (c.wc_valid)
c.wc = towlower (c.wc);
if (!mbui_avail (rhaystack))
/* No match. */
return NULL;
+ comparison_count++;
if (!mb_caseequal (mbui_cur (rhaystack),
mbui_cur (rneedle)))
/* Nothing in this round. */
return (char *) haystack;
}
else
-#endif
{
if (*needle != '\0')
{
+ /* Minimizing the worst-case complexity:
+ Let n = strlen(haystack), m = strlen(needle).
+ The naïve algorithm is O(n*m) worst-case.
+ The Knuth-Morris-Pratt algorithm is O(n) worst-case but it needs a
+ memory allocation.
+ To achieve linear complexity and yet amortize the cost of the
+ memory allocation, we activate the Knuth-Morris-Pratt algorithm
+ only once the naïve algorithm has already run for some time; more
+ precisely, when
+ - the outer loop count is >= 10,
+ - the average number of comparisons per outer loop is >= 5,
+ - the total number of comparisons is >= m.
+ But we try it only once. If the memory allocation attempt failed,
+ we don't retry it. */
+ bool try_kmp = true;
+ size_t outer_loop_count = 0;
+ size_t comparison_count = 0;
+ size_t last_ccount = 0; /* last comparison count */
+ const char *needle_last_ccount = needle; /* = needle + last_ccount */
+
/* Speed up the following searches of needle by caching its first
character. */
unsigned char b = TOLOWER ((unsigned char) *needle);
if (*haystack == '\0')
/* No match. */
return NULL;
+
+ /* See whether it's advisable to use an asymptotically faster
+ algorithm. */
+ if (try_kmp
+ && outer_loop_count >= 10
+ && comparison_count >= 5 * outer_loop_count)
+ {
+ /* See if needle + comparison_count now reaches the end of
+ needle. */
+ if (needle_last_ccount != NULL)
+ {
+ needle_last_ccount +=
+ strnlen (needle_last_ccount,
+ comparison_count - last_ccount);
+ if (*needle_last_ccount == '\0')
+ needle_last_ccount = NULL;
+ last_ccount = comparison_count;
+ }
+ if (needle_last_ccount == NULL)
+ {
+ /* Try the Knuth-Morris-Pratt algorithm. */
+ const char *result;
+ bool success =
+ knuth_morris_pratt_unibyte (haystack, needle - 1,
+ &result);
+ if (success)
+ return (char *) result;
+ try_kmp = false;
+ }
+ }
+
+ outer_loop_count++;
+ comparison_count++;
if (TOLOWER ((unsigned char) *haystack) == b)
/* The first character matches. */
{
if (*rhaystack == '\0')
/* No match. */
return NULL;
+ comparison_count++;
if (TOLOWER ((unsigned char) *rhaystack)
!= TOLOWER ((unsigned char) *rneedle))
/* Nothing in this round. */
projects / gnulib.git / blobdiff