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/*
* Copyright (c) 2015-2016, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
*/
#ifndef INFIX_H
#define INFIX_H
#include "ue2common.h"
#include "nfa/nfa_api.h"
#include "nfa/nfa_api_queue.h"
#include "nfa/nfa_internal.h"
static really_inline
int infixTooOld(struct mq *q, s64a curr_loc) {
u32 maxAge = q->nfa->maxWidth;
if (!maxAge) {
return 0;
}
return q_last_loc(q) + maxAge < curr_loc;
}
static really_inline
int canReduceQueue(const struct mq *q, s64a curr_loc, u32 maxTops, u32 maxAge) {
u32 qlen = q->end - q->cur; /* includes MQE_START */
if (maxAge && q->items[q->cur].location + maxAge < curr_loc) {
return 1;
}
if (qlen - 1 > maxTops) {
return 1;
}
if (qlen - 1 == maxTops
&& q->items[q->cur].location != q->items[q->cur + 1].location) {
/* we can advance start to the first top location */
return 1;
}
return 0;
}
/**
* Removes tops which are known not to affect the final state from the queue.
* May also reinitialise the engine state if it is unneeded.
*
* maxAge is the maximum width of the infix. Any tops/state before this can be
* ignored. 0 is used to indicate that there is no upper bound on the width of
* the pattern.
*
* maxTops is the maximum number of locations of tops that can affect the top.
* It is only possible for the last maxTops tops to affect the final state -
* earlier ones can be safely removed. Also, any state before the max tops may
* be ignored.
*
* This code assumes/requires that there are not multiple tops at the same
* location in the queue. This code also assumes that it is not a multitop
* engine.
*/
static really_inline
void reduceInfixQueue(struct mq *q, s64a curr_loc, u32 maxTops, u32 maxAge) {
assert(q->end > q->cur);
assert(maxTops);
u32 qlen = q->end - q->cur; /* includes MQE_START */
DEBUG_PRINTF("q=%p, len=%u, maxTops=%u maxAge=%u\n", q, qlen, maxTops,
maxAge);
if (!canReduceQueue(q, curr_loc, maxTops, maxAge)) {
DEBUG_PRINTF("nothing to do\n");
return;
}
#ifdef DEBUG
debugQueue(q);
#endif
char drop_state = qlen - 1 >= maxTops
|| (maxAge && q->items[q->cur].location + maxAge < curr_loc);
LIMIT_TO_AT_MOST(&maxTops, qlen - 1);
// We leave our START where it is, at the front of the queue.
assert(q->items[q->cur].type == MQE_START);
// We want to shuffle maxQueueLen items from the end of the queue to just
// after the start, effectively dequeuing old items. We could use memmove
// for this, but it's probably not a good idea to take the cost of the
// function call.
const struct mq_item *src = &q->items[q->cur + qlen - maxTops];
q->items[0] = q->items[q->cur]; /* shift start event to 0 slot */
q->cur = 0;
q->end = 1;
struct mq_item *dst = &q->items[1];
u32 i = 0;
if (maxAge) {
/* any event which is older than maxAge can be dropped */
for (; i < maxTops; i++, src++) {
if (src->location >= curr_loc - maxAge) {
break;
}
}
}
for (; i < maxTops; i++) {
*dst = *src;
src++;
dst++;
q->end++;
}
if (drop_state) {
/* clear state and shift start up to first top */
s64a new_loc;
if (q->end > 1) {
new_loc = q->items[1].location;
} else {
DEBUG_PRINTF("no tops\n");
new_loc = curr_loc;
}
DEBUG_PRINTF("advancing start from %lld to %lld\n",
q->items[0].location, new_loc);
assert(new_loc > q->items[0].location);
q->items[0].location = new_loc;
nfaQueueInitState(q->nfa, q);
}
DEBUG_PRINTF("reduced queue to len=%u\n", q->end - q->cur);
#ifdef DEBUG
debugQueue(q);
#endif
}
#endif
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