/*-
 * Copyright 2003 John-Mark Gurney.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	$Id: util.c,v 1.4 2003/09/15 23:37:19 jmg Exp $
 *
 */

#include <string.h>

#if 0
char *
memmemory(const char *big, int blen, const char *lit, int llen)
{
	const char *pos;

	for (pos = big; pos - big <= blen - llen; pos++) {
		if (*pos == *lit && memcmp(pos, lit, llen) == 0)
			return (char *)pos;
	}

	return NULL;
}
#else

static int cols = 0;

static unsigned int
powmod(int x, int y, int q)
{
	unsigned int ret = 1;

	while (y) {
		if (y & 1)
			ret = ((unsigned long long)ret * x) % q;
		x = (unsigned long long) x * x % q;
		y = y / 2;
	}
	return ret;
}

const char *
memmemory(const char *T, size_t n, const char *P, size_t m)
{
	static unsigned int q = 4294967291u;
	static unsigned int d = 256;

	unsigned int h;
	unsigned int p;
	unsigned int t;

	int i;
	int s;

	h = powmod(d, m - 1, q);
	p = 0;
	t = 0;

	for (i = 0; i < m; i++) {
		p = (d * p + P[i]) % q;
		t = (d * t + T[i]) % q;
	}
	for (s = 0; s <= n - m; s++) {
		if (p == t) {
			if (memcmp(P, T + s, m) == 0)
				return T + s;
			cols++;
		}
		if (s < n - m)
			t = (d * (t - T[s] * h) + T[s + m]) % q;
	}
	return NULL;
}
#endif