-/* 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;
-}