+/*-
+ * Copyright (c) 1990 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. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. 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.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)operator.c 5.4 (Berkeley) 5/24/91";
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <stdio.h>
+#include "find.h"
+
+/*
+ * yanknode --
+ * destructively removes the top from the plan
+ */
+static PLAN *
+yanknode(planp)
+ PLAN **planp; /* pointer to top of plan (modified) */
+{
+ PLAN *node; /* top node removed from the plan */
+
+ if ((node = (*planp)) == NULL)
+ return(NULL);
+ (*planp) = (*planp)->next;
+ node->next = NULL;
+ return(node);
+}
+
+/*
+ * 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(planp)
+ PLAN **planp; /* pointer to top of plan (modified) */
+{
+ register 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 */
+ int f_expr();
+
+ /* 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("%s: %s", "(", "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)
+ err("%s: %s",
+ "()", "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; /* plan with ( ) nodes */
+{
+ register PLAN *expr; /* pointer to next expression */
+ register 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 it's results together.
+ */
+ while ((expr = yankexpr(&plan)) != NULL) {
+ /*
+ * if we find an unclaimed ')' it means there is a missing
+ * '(' someplace.
+ */
+ if (expr->type == N_CLOSEPAREN)
+ err("%s: %s", ")", "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; /* plan to process */
+{
+ register PLAN *next; /* next node being processed */
+ register PLAN *node; /* temporary node used in N_NOT processing */
+ register 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->type == N_NOT) {
+ ++notlevel;
+ node = yanknode(&plan);
+ }
+ if (node == NULL)
+ err("%s: %s", "!", "no following expression");
+ if (node->type == N_OR)
+ err("%s: %s", "!", "nothing between ! and -o");
+ 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; /* plan with ors to be squished */
+{
+ register PLAN *next; /* next node being processed */
+ register 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)
+ err("%s: %s", "-o", "no expression before -o");
+ next->p_data[0] = result;
+ next->p_data[1] = or_squish(plan);
+ if (next->p_data[1] == NULL)
+ err("%s: %s", "-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);
+}
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