/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Cimarron D. Taylor of the University of California, Berkeley.
*
* 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.
* 3. Neither the name of the University 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 REGENTS 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 REGENTS 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.
*/
static PLAN *yanknode(PLAN **);
static PLAN *yankexpr(PLAN **);
/*
* yanknode --
* destructively removes the top from the plan
*/
static PLAN *
yanknode(PLAN **planp) /* pointer to top of plan (modified) */
{
PLAN *node; /* top node removed from the plan */
/*
* yankexpr --
* Removes one expression from the plan. This is used mainly by
* paren_squish. In comments below, an expression is either a
* simple node or a N_EXPR node containing a list of simple nodes.
*/
static PLAN *
yankexpr(PLAN **planp) /* pointer to top of plan (modified) */
{
PLAN *next; /* temp node holding subexpression results */
PLAN *node; /* pointer to returned node or expression */
PLAN *tail; /* pointer to tail of subplan */
PLAN *subplan; /* pointer to head of ( ) expression */
/* first pull the top node from the plan */
if ((node = yanknode(planp)) == NULL)
return (NULL);
/*
* If the node is an '(' then we recursively slurp up expressions
* until we find its associated ')'. If it's a closing paren we
* just return it and unwind our recursion; all other nodes are
* complete expressions, so just return them.
*/
if (node->type == N_OPENPAREN)
for (tail = subplan = NULL;;) {
if ((next = yankexpr(planp)) == NULL)
err(1, "(: missing closing ')'");
/*
* If we find a closing ')' we store the collected
* subplan in our '(' node and convert the node to
* a N_EXPR. The ')' we found is ignored. Otherwise,
* we just continue to add whatever we get to our
* subplan.
*/
if (next->type == N_CLOSEPAREN) {
if (subplan == NULL)
errx(1, "(): empty inner expression");
node->p_data[0] = subplan;
node->type = N_EXPR;
node->eval = f_expr;
break;
} else {
if (subplan == NULL)
tail = subplan = next;
else {
tail->next = next;
tail = next;
}
tail->next = NULL;
}
}
return (node);
}
/*
* paren_squish --
* replaces "parentheisized" plans in our search plan with "expr" nodes.
*/
PLAN *
paren_squish(PLAN *plan) /* plan with ( ) nodes */
{
PLAN *expr; /* pointer to next expression */
PLAN *tail; /* pointer to tail of result plan */
PLAN *result; /* pointer to head of result plan */
result = tail = NULL;
/*
* the basic idea is to have yankexpr do all our work and just
* collect its results together.
*/
while ((expr = yankexpr(&plan)) != NULL) {
/*
* if we find an unclaimed ')' it means there is a missing
* '(' someplace.
*/
if (expr->type == N_CLOSEPAREN)
errx(1, "): no beginning '('");
/* add the expression to our result plan */
if (result == NULL)
tail = result = expr;
else {
tail->next = expr;
tail = expr;
}
tail->next = NULL;
}
return (result);
}
/*
* not_squish --
* compresses "!" expressions in our search plan.
*/
PLAN *
not_squish(PLAN *plan) /* plan to process */
{
PLAN *next; /* next node being processed */
PLAN *node; /* temporary node used in N_NOT processing */
PLAN *tail; /* pointer to tail of result plan */
PLAN *result; /* pointer to head of result plan */
tail = result = next = NULL;
while ((next = yanknode(&plan)) != NULL) {
/*
* if we encounter a ( expression ) then look for nots in
* the expr subplan.
*/
if (next->type == N_EXPR)
next->p_data[0] = not_squish(next->p_data[0]);
/*
* if we encounter a not, then snag the next node and place
* it in the not's subplan. As an optimization we compress
* several not's to zero or one not.
*/
if (next->type == N_NOT) {
int notlevel = 1;
node = yanknode(&plan);
while (node != NULL && node->type == N_NOT) {
++notlevel;
node = yanknode(&plan);
}
if (node == NULL)
errx(1, "!: no following expression");
if (node->type == N_OR)
errx(1, "!: nothing between ! and -o");
if (node->type == N_EXPR)
node = not_squish(node);
if (notlevel % 2 != 1)
next = node;
else
next->p_data[0] = node;
}
/* add the node to our result plan */
if (result == NULL)
tail = result = next;
else {
tail->next = next;
tail = next;
}
tail->next = NULL;
}
return (result);
}
/*
* or_squish --
* compresses -o expressions in our search plan.
*/
PLAN *
or_squish(PLAN *plan) /* plan with ors to be squished */
{
PLAN *next; /* next node being processed */
PLAN *tail; /* pointer to tail of result plan */
PLAN *result; /* pointer to head of result plan */
tail = result = next = NULL;
while ((next = yanknode(&plan)) != NULL) {
/*
* if we encounter a ( expression ) then look for or's in
* the expr subplan.
*/
if (next->type == N_EXPR)
next->p_data[0] = or_squish(next->p_data[0]);
/* if we encounter a not then look for not's in the subplan */
if (next->type == N_NOT)
next->p_data[0] = or_squish(next->p_data[0]);
/*
* if we encounter an or, then place our collected plan in the
* or's first subplan and then recursively collect the
* remaining stuff into the second subplan and return the or.
*/
if (next->type == N_OR) {
if (result == NULL)
errx(1, "-o: no expression before -o");
next->p_data[0] = result;
next->p_data[1] = or_squish(plan);
if (next->p_data[1] == NULL)
errx(1, "-o: no expression after -o");
return (next);
}
/* add the node to our result plan */
if (result == NULL)
tail = result = next;
else {
tail->next = next;
tail = next;
}
tail->next = NULL;
}
return (result);
}
