+/* Knuth-Morris-Pratt algorithm.
+ See http://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm
+ Return a boolean indicating success. */
+
+static bool
+knuth_morris_pratt_unibyte (const char *haystack, const char *needle,
+ const char **resultp)
+{
+ size_t m = strlen (needle);
+
+ /* Allocate the table. */
+ size_t *table = (size_t *) allocsa (m * sizeof (size_t));
+ if (table == NULL)
+ return false;
+ /* Fill the table.
+ For 0 < i < m:
+ 0 < table[i] <= i is defined such that
+ rhaystack[0..i-1] == needle[0..i-1] and rhaystack[i] != needle[i]
+ implies
+ forall 0 <= x < table[i]: rhaystack[x..x+m-1] != needle[0..m-1],
+ and table[i] is as large as possible with this property.
+ table[0] remains uninitialized. */
+ {
+ size_t i, j;
+
+ table[1] = 1;
+ j = 0;
+ for (i = 2; i < m; i++)
+ {
+ unsigned char b = TOLOWER ((unsigned char) needle[i - 1]);
+
+ for (;;)
+ {
+ if (b == TOLOWER ((unsigned char) needle[j]))
+ {
+ table[i] = i - ++j;
+ break;
+ }
+ if (j == 0)
+ {
+ table[i] = i;
+ break;
+ }
+ j = j - table[j];
+ }
+ }
+ }
+
+ /* Search, using the table to accelerate the processing. */
+ {
+ size_t j;
+ const char *rhaystack;
+ const char *phaystack;
+
+ *resultp = NULL;
+ j = 0;
+ rhaystack = haystack;
+ phaystack = haystack;
+ /* Invariant: phaystack = rhaystack + j. */
+ while (*phaystack != '\0')
+ if (TOLOWER ((unsigned char) needle[j])
+ == TOLOWER ((unsigned char) *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++;
+ }
+ }
+
+ freesa (table);
+ return true;
+}
+
+#if HAVE_MBRTOWC
+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 *) allocsa (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
+ rhaystack[0..i-1] == needle[0..i-1] and rhaystack[i] != needle[i]
+ implies
+ forall 0 <= x < table[i]: rhaystack[x..x+m-1] != needle[0..m-1],
+ and table[i] is as large as possible with this property.
+ table[0] remains uninitialized. */
+ {
+ size_t i, j;
+
+ table[1] = 1;
+ j = 0;
+ for (i = 2; i < m; i++)
+ {
+ mbchar_t *b = &needle_mbchars[i - 1];
+
+ for (;;)
+ {
+ if (mb_equal (*b, needle_mbchars[j]))
+ {
+ table[i] = i - ++j;
+ break;
+ }
+ if (j == 0)
+ {
+ table[i] = i;
+ break;
+ }
+ j = j - table[j];
+ }
+ }
+ }
+
+ /* 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);
+ }
+ }
+ }
+
+ freesa (memory);
+ return true;
+}
+#endif
+