/*
- caltdissect - dissect match for alternation node
^ static int caltdissect(struct vars *, struct subre *, chr *, chr *);
*/
static int /* regexec return code */
caltdissect(
struct vars *v,
struct subre *t,
chr *begin, /* beginning of relevant substring */
chr *end) /* end of same */
{
struct dfa *d;
int er;
/* We loop, rather than tail-recurse, to handle a chain of alternatives */
while (t != NULL) {
assert(t->op == '|');
assert(t->left != NULL && t->left->cnfa.nstates > 0);
MDEBUG(("calt n%d\n", t->id));
d = getsubdfa(v, t->left);
NOERR();
if (longest(v, d, begin, end, (int *) NULL) == end) {
MDEBUG(("calt matched\n"));
er = cdissect(v, t->left, begin, end);
if (er != REG_NOMATCH) {
return er;
}
}
t = t->right;
}
return REG_NOMATCH;
}
/*
- citerdissect - dissect match for iteration node
^ static int citerdissect(struct vars *, struct subre *, chr *, chr *);
*/
static int /* regexec return code */
citerdissect(struct vars * v,
struct subre * t,
chr *begin, /* beginning of relevant substring */
chr *end) /* end of same */
{
struct dfa *d;
chr **endpts;
chr *limit;
int min_matches;
size_t max_matches;
int nverified;
int k;
int i;
int er;
assert(t->op == '*');
assert(t->left != NULL && t->left->cnfa.nstates > 0);
assert(!(t->left->flags & SHORTER));
assert(begin <= end);
/*
* If zero matches are allowed, and target string is empty, just declare
* victory. OTOH, if target string isn't empty, zero matches can't work
* so we pretend the min is 1.
*/
min_matches = t->min;
if (min_matches <= 0) {
if (begin == end)
return REG_OKAY;
min_matches = 1;
}
/*
* We need workspace to track the endpoints of each sub-match. Normally
* we consider only nonzero-length sub-matches, so there can be at most
* end-begin of them. However, if min is larger than that, we will also
* consider zero-length sub-matches in order to find enough matches.
*
* For convenience, endpts[0] contains the "begin" pointer and we store
* sub-match endpoints in endpts[1..max_matches].
*/
max_matches = end - begin;
if (max_matches > (size_t)t->max && t->max != DUPINF)
max_matches = t->max;
if (max_matches < (size_t)min_matches)
max_matches = min_matches;
endpts = (chr **) MALLOC((max_matches + 1) * sizeof(chr *));
if (endpts == NULL)
return REG_ESPACE;
endpts[0] = begin;
d = getsubdfa(v, t->left);
if (ISERR()) {
FREE(endpts);
return v->err;
}
MDEBUG(("citer %d\n", t->id));
/*
* Our strategy is to first find a set of sub-match endpoints that are
* valid according to the child node's DFA, and then recursively dissect
* each sub-match to confirm validity. If any validity check fails,
* backtrack the last sub-match and try again. And, when we next try for
* a validity check, we need not recheck any successfully verified
* sub-matches that we didn't move the endpoints of. nverified remembers
* how many sub-matches are currently known okay.
*/
/* initialize to consider first sub-match */
nverified = 0;
k = 1;
limit = end;
/* iterate until satisfaction or failure */
while (k > 0) {
/* try to find an endpoint for the k'th sub-match */
endpts[k] = longest(v, d, endpts[k - 1], limit, (int *) NULL);
if (endpts[k] == NULL) {
/* no match possible, so see if we can shorten previous one */
k--;
goto backtrack;
}
MDEBUG(("%d: working endpoint %d: %ld\n",
t->id, k, LOFF(endpts[k])));
/* k'th sub-match can no longer be considered verified */
if (nverified >= k)
nverified = k - 1;
if (endpts[k] != end) {
/* haven't reached end yet, try another iteration if allowed */
if ((size_t)k >= max_matches) {
/* must try to shorten some previous match */
k--;
goto backtrack;
}
/* reject zero-length match unless necessary to achieve min */
if (endpts[k] == endpts[k - 1] &&
(k >= min_matches || min_matches - k < end - endpts[k]))
goto backtrack;
k++;
limit = end;
continue;
}
/*
* We've identified a way to divide the string into k sub-matches
* that works so far as the child DFA can tell. If k is an allowed
* number of matches, start the slow part: recurse to verify each
* sub-match. We always have k <= max_matches, needn't check that.
*/
if (k < min_matches)
goto backtrack;
MDEBUG(("%d: verifying %d..%d\n", t->id, nverified + 1, k));
for (i = nverified + 1; i <= k; i++) {
zaptreesubs(v, t->left);
er = cdissect(v, t->left, endpts[i - 1], endpts[i]);
if (er == REG_OKAY) {
nverified = i;
continue;
}
if (er == REG_NOMATCH)
break;
/* oops, something failed */
FREE(endpts);
return er;
}
if (i > k) {
/* satisfaction */
MDEBUG(("%d successful\n", t->id));
FREE(endpts);
return REG_OKAY;
}
/* match failed to verify, so backtrack */
backtrack:
/*
* Must consider shorter versions of the current sub-match. However,
* we'll only ask for a zero-length match if necessary.
*/
while (k > 0) {
chr *prev_end = endpts[k - 1];
if (endpts[k] > prev_end) {
limit = endpts[k] - 1;
if (limit > prev_end ||
(k < min_matches && min_matches - k >= end - prev_end)) {
/* break out of backtrack loop, continue the outer one */
break;
}
}
/* can't shorten k'th sub-match any more, consider previous one */
k--;
}
}
/* all possibilities exhausted */
MDEBUG(("%d failed\n", t->id));
FREE(endpts);
return REG_NOMATCH;
}
/*
- crevcondissect - dissect match for concatenation node, shortest-first
^ static int crevcondissect(struct vars *, struct subre *, chr *, chr *);
*/
static int /* regexec return code */
crevcondissect(
struct vars *v,
struct subre *t,
chr *begin, /* beginning of relevant substring */
chr *end) /* end of same */
{
struct dfa *d, *d2;
chr *mid;
assert(t->op == '.');
assert(t->left != NULL && t->left->cnfa.nstates > 0);
assert(t->right != NULL && t->right->cnfa.nstates > 0);
assert(t->left->flags&SHORTER);
d = getsubdfa(v, t->left);
NOERR();
d2 = getsubdfa(v, t->right);
NOERR();
MDEBUG(("crevcon %d\n", t->id));
/*
* Pick a tentative midpoint.
*/
mid = shortest(v, d, begin, begin, end, (chr **) NULL, (int *) NULL);
if (mid == NULL) {
return REG_NOMATCH;
}
MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
/*
* Iterate until satisfaction or failure.
*/
for (;;) {
/*
* Try this midpoint on for size.
*/
if (longest(v, d2, mid, end, NULL) == end) {
int er = cdissect(v, t->left, begin, mid);
if (er == REG_OKAY) {
er = cdissect(v, t->right, mid, end);
if (er == REG_OKAY) {
/*
* Satisfaction.
*/
MDEBUG(("successful\n"));
return REG_OKAY;
}
}
if (er != REG_NOMATCH) {
return er;
}
}
/*
* That midpoint didn't work, find a new one.
*/
if (mid == end) {
/*
* All possibilities exhausted.
*/
MDEBUG(("%d no midpoint\n", t->id));
return REG_NOMATCH;
}
mid = shortest(v, d, begin, mid+1, end, NULL, NULL);
if (mid == NULL) {
/*
* Failed to find a new one.
*/
MDEBUG(("%d failed midpoint\n", t->id));
return REG_NOMATCH;
}
MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
zaptreesubs(v, t->left);
zaptreesubs(v, t->right);
}
}
/*
* ccondissect - dissect match for concatenation node
*/
static int /* regexec return code */
ccondissect(struct vars * v,
struct subre * t,
chr *begin, /* beginning of relevant substring */
chr *end) /* end of same */
{
struct dfa *d;
struct dfa *d2;
chr *mid;
int er;
assert(t->op == '.');
assert(t->left != NULL && t->left->cnfa.nstates > 0);
assert(t->right != NULL && t->right->cnfa.nstates > 0);
assert(!(t->left->flags & SHORTER));
d = getsubdfa(v, t->left);
NOERR();
d2 = getsubdfa(v, t->right);
NOERR();
MDEBUG(("cconcat %d\n", t->id));
/* pick a tentative midpoint */
mid = longest(v, d, begin, end, (int *) NULL);
if (mid == NULL)
return REG_NOMATCH;
MDEBUG(("tentative midpoint %ld\n", LOFF(mid)));
/* iterate until satisfaction or failure */
for (;;)
{
/* try this midpoint on for size */
if (longest(v, d2, mid, end, (int *) NULL) == end)
{
er = cdissect(v, t->left, begin, mid);
if (er == REG_OKAY)
{
er = cdissect(v, t->right, mid, end);
if (er == REG_OKAY)
{
/* satisfaction */
MDEBUG(("successful\n"));
return REG_OKAY;
}
}
if (er != REG_NOMATCH)
return er;
}
/* that midpoint didn't work, find a new one */
if (mid == begin)
{
/* all possibilities exhausted */
MDEBUG(("%d no midpoint\n", t->id));
return REG_NOMATCH;
}
mid = longest(v, d, begin, mid - 1, (int *) NULL);
if (mid == NULL)
{
/* failed to find a new one */
MDEBUG(("%d failed midpoint\n", t->id));
return REG_NOMATCH;
}
MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
zaptreesubs(v, t->left);
zaptreesubs(v, t->right);
}
/* can't get here */
return REG_ASSERT;
}
