-/* Substring search in a NUL terminated string of 'char' elements,
+/* Substring search in a NUL terminated string of UNIT elements,
using the Knuth-Morris-Pratt algorithm.
- Copyright (C) 2005-2007 Free Software Foundation, Inc.
+ Copyright (C) 2005-2013 Free Software Foundation, Inc.
Written by Bruno Haible <bruno@clisp.org>, 2005.
This program is free software; you can redistribute it and/or modify
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/>. */
/* 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 one of the two strings.
- The argument is an 'unsigned char'; the result
- must be an 'unsigned char' as well. */
+ 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
- Return a boolean indicating success. */
+ 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_unibyte (const char *haystack, const char *needle,
- const char **resultp)
+knuth_morris_pratt (const UNIT *haystack,
+ const UNIT *needle, size_t needle_len,
+ const UNIT **resultp)
{
- size_t m = strlen (needle);
+ size_t m = needle_len;
/* Allocate the table. */
size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
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]. */
- unsigned char b = CANON_ELEMENT ((unsigned char) needle[i - 1]);
+ /* 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 ((unsigned char) 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]. */
+ 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 char *rhaystack;
- const char *phaystack;
+ const UNIT *rhaystack;
+ const UNIT *phaystack;
*resultp = NULL;
j = 0;
rhaystack = haystack;
phaystack = haystack;
/* Invariant: phaystack = rhaystack + j. */
- while (*phaystack != '\0')
- if (CANON_ELEMENT ((unsigned char) needle[j])
- == CANON_ELEMENT ((unsigned char) *phaystack))
- {
- j++;
- phaystack++;
- if (j == m)
- {
- /* The entire needle has been found. */
- *resultp = rhaystack;
- break;
- }
- }
+ 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];
- }
+ {
+ /* 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++;
- }
+ {
+ /* Found a mismatch at needle[0] already. */
+ rhaystack++;
+ phaystack++;
+ }
}
freea (table);
projects / gnulib.git / blobdiff