operator.c revision 1.2 1 1.1 cgd /*-
2 1.1 cgd * Copyright (c) 1990 The Regents of the University of California.
3 1.1 cgd * All rights reserved.
4 1.1 cgd *
5 1.1 cgd * This code is derived from software contributed to Berkeley by
6 1.1 cgd * Cimarron D. Taylor of the University of California, Berkeley.
7 1.1 cgd *
8 1.1 cgd * Redistribution and use in source and binary forms, with or without
9 1.1 cgd * modification, are permitted provided that the following conditions
10 1.1 cgd * are met:
11 1.1 cgd * 1. Redistributions of source code must retain the above copyright
12 1.1 cgd * notice, this list of conditions and the following disclaimer.
13 1.1 cgd * 2. Redistributions in binary form must reproduce the above copyright
14 1.1 cgd * notice, this list of conditions and the following disclaimer in the
15 1.1 cgd * documentation and/or other materials provided with the distribution.
16 1.1 cgd * 3. All advertising materials mentioning features or use of this software
17 1.1 cgd * must display the following acknowledgement:
18 1.1 cgd * This product includes software developed by the University of
19 1.1 cgd * California, Berkeley and its contributors.
20 1.1 cgd * 4. Neither the name of the University nor the names of its contributors
21 1.1 cgd * may be used to endorse or promote products derived from this software
22 1.1 cgd * without specific prior written permission.
23 1.1 cgd *
24 1.1 cgd * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 1.1 cgd * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 1.1 cgd * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 1.1 cgd * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 1.1 cgd * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 1.1 cgd * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 1.1 cgd * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 1.1 cgd * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 1.1 cgd * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 1.1 cgd * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 1.1 cgd * SUCH DAMAGE.
35 1.1 cgd */
36 1.1 cgd
37 1.1 cgd #ifndef lint
38 1.2 mycroft /*static char sccsid[] = "from: @(#)operator.c 5.4 (Berkeley) 5/24/91";*/
39 1.2 mycroft static char rcsid[] = "$Id: operator.c,v 1.2 1993/08/01 18:16:10 mycroft Exp $";
40 1.1 cgd #endif /* not lint */
41 1.1 cgd
42 1.1 cgd #include <sys/types.h>
43 1.1 cgd #include <stdio.h>
44 1.1 cgd #include "find.h"
45 1.1 cgd
46 1.1 cgd /*
47 1.1 cgd * yanknode --
48 1.1 cgd * destructively removes the top from the plan
49 1.1 cgd */
50 1.1 cgd static PLAN *
51 1.1 cgd yanknode(planp)
52 1.1 cgd PLAN **planp; /* pointer to top of plan (modified) */
53 1.1 cgd {
54 1.1 cgd PLAN *node; /* top node removed from the plan */
55 1.1 cgd
56 1.1 cgd if ((node = (*planp)) == NULL)
57 1.1 cgd return(NULL);
58 1.1 cgd (*planp) = (*planp)->next;
59 1.1 cgd node->next = NULL;
60 1.1 cgd return(node);
61 1.1 cgd }
62 1.1 cgd
63 1.1 cgd /*
64 1.1 cgd * yankexpr --
65 1.1 cgd * Removes one expression from the plan. This is used mainly by
66 1.1 cgd * paren_squish. In comments below, an expression is either a
67 1.1 cgd * simple node or a N_EXPR node containing a list of simple nodes.
68 1.1 cgd */
69 1.1 cgd static PLAN *
70 1.1 cgd yankexpr(planp)
71 1.1 cgd PLAN **planp; /* pointer to top of plan (modified) */
72 1.1 cgd {
73 1.1 cgd register PLAN *next; /* temp node holding subexpression results */
74 1.1 cgd PLAN *node; /* pointer to returned node or expression */
75 1.1 cgd PLAN *tail; /* pointer to tail of subplan */
76 1.1 cgd PLAN *subplan; /* pointer to head of ( ) expression */
77 1.1 cgd int f_expr();
78 1.1 cgd
79 1.1 cgd /* first pull the top node from the plan */
80 1.1 cgd if ((node = yanknode(planp)) == NULL)
81 1.1 cgd return(NULL);
82 1.1 cgd
83 1.1 cgd /*
84 1.1 cgd * If the node is an '(' then we recursively slurp up expressions
85 1.1 cgd * until we find its associated ')'. If it's a closing paren we
86 1.1 cgd * just return it and unwind our recursion; all other nodes are
87 1.1 cgd * complete expressions, so just return them.
88 1.1 cgd */
89 1.1 cgd if (node->type == N_OPENPAREN)
90 1.1 cgd for (tail = subplan = NULL;;) {
91 1.1 cgd if ((next = yankexpr(planp)) == NULL)
92 1.1 cgd err("%s: %s", "(", "missing closing ')'");
93 1.1 cgd /*
94 1.1 cgd * If we find a closing ')' we store the collected
95 1.1 cgd * subplan in our '(' node and convert the node to
96 1.1 cgd * a N_EXPR. The ')' we found is ignored. Otherwise,
97 1.1 cgd * we just continue to add whatever we get to our
98 1.1 cgd * subplan.
99 1.1 cgd */
100 1.1 cgd if (next->type == N_CLOSEPAREN) {
101 1.1 cgd if (subplan == NULL)
102 1.1 cgd err("%s: %s",
103 1.1 cgd "()", "empty inner expression");
104 1.1 cgd node->p_data[0] = subplan;
105 1.1 cgd node->type = N_EXPR;
106 1.1 cgd node->eval = f_expr;
107 1.1 cgd break;
108 1.1 cgd } else {
109 1.1 cgd if (subplan == NULL)
110 1.1 cgd tail = subplan = next;
111 1.1 cgd else {
112 1.1 cgd tail->next = next;
113 1.1 cgd tail = next;
114 1.1 cgd }
115 1.1 cgd tail->next = NULL;
116 1.1 cgd }
117 1.1 cgd }
118 1.1 cgd return(node);
119 1.1 cgd }
120 1.1 cgd
121 1.1 cgd /*
122 1.1 cgd * paren_squish --
123 1.1 cgd * replaces "parentheisized" plans in our search plan with "expr" nodes.
124 1.1 cgd */
125 1.1 cgd PLAN *
126 1.1 cgd paren_squish(plan)
127 1.1 cgd PLAN *plan; /* plan with ( ) nodes */
128 1.1 cgd {
129 1.1 cgd register PLAN *expr; /* pointer to next expression */
130 1.1 cgd register PLAN *tail; /* pointer to tail of result plan */
131 1.1 cgd PLAN *result; /* pointer to head of result plan */
132 1.1 cgd
133 1.1 cgd result = tail = NULL;
134 1.1 cgd
135 1.1 cgd /*
136 1.1 cgd * the basic idea is to have yankexpr do all our work and just
137 1.1 cgd * collect it's results together.
138 1.1 cgd */
139 1.1 cgd while ((expr = yankexpr(&plan)) != NULL) {
140 1.1 cgd /*
141 1.1 cgd * if we find an unclaimed ')' it means there is a missing
142 1.1 cgd * '(' someplace.
143 1.1 cgd */
144 1.1 cgd if (expr->type == N_CLOSEPAREN)
145 1.1 cgd err("%s: %s", ")", "no beginning '('");
146 1.1 cgd
147 1.1 cgd /* add the expression to our result plan */
148 1.1 cgd if (result == NULL)
149 1.1 cgd tail = result = expr;
150 1.1 cgd else {
151 1.1 cgd tail->next = expr;
152 1.1 cgd tail = expr;
153 1.1 cgd }
154 1.1 cgd tail->next = NULL;
155 1.1 cgd }
156 1.1 cgd return(result);
157 1.1 cgd }
158 1.1 cgd
159 1.1 cgd /*
160 1.1 cgd * not_squish --
161 1.1 cgd * compresses "!" expressions in our search plan.
162 1.1 cgd */
163 1.1 cgd PLAN *
164 1.1 cgd not_squish(plan)
165 1.1 cgd PLAN *plan; /* plan to process */
166 1.1 cgd {
167 1.1 cgd register PLAN *next; /* next node being processed */
168 1.1 cgd register PLAN *node; /* temporary node used in N_NOT processing */
169 1.1 cgd register PLAN *tail; /* pointer to tail of result plan */
170 1.1 cgd PLAN *result; /* pointer to head of result plan */
171 1.1 cgd
172 1.1 cgd tail = result = next = NULL;
173 1.1 cgd
174 1.1 cgd while ((next = yanknode(&plan)) != NULL) {
175 1.1 cgd /*
176 1.1 cgd * if we encounter a ( expression ) then look for nots in
177 1.1 cgd * the expr subplan.
178 1.1 cgd */
179 1.1 cgd if (next->type == N_EXPR)
180 1.1 cgd next->p_data[0] = not_squish(next->p_data[0]);
181 1.1 cgd
182 1.1 cgd /*
183 1.1 cgd * if we encounter a not, then snag the next node and place
184 1.1 cgd * it in the not's subplan. As an optimization we compress
185 1.1 cgd * several not's to zero or one not.
186 1.1 cgd */
187 1.1 cgd if (next->type == N_NOT) {
188 1.1 cgd int notlevel = 1;
189 1.1 cgd
190 1.1 cgd node = yanknode(&plan);
191 1.1 cgd while (node->type == N_NOT) {
192 1.1 cgd ++notlevel;
193 1.1 cgd node = yanknode(&plan);
194 1.1 cgd }
195 1.1 cgd if (node == NULL)
196 1.1 cgd err("%s: %s", "!", "no following expression");
197 1.1 cgd if (node->type == N_OR)
198 1.1 cgd err("%s: %s", "!", "nothing between ! and -o");
199 1.1 cgd if (notlevel % 2 != 1)
200 1.1 cgd next = node;
201 1.1 cgd else
202 1.1 cgd next->p_data[0] = node;
203 1.1 cgd }
204 1.1 cgd
205 1.1 cgd /* add the node to our result plan */
206 1.1 cgd if (result == NULL)
207 1.1 cgd tail = result = next;
208 1.1 cgd else {
209 1.1 cgd tail->next = next;
210 1.1 cgd tail = next;
211 1.1 cgd }
212 1.1 cgd tail->next = NULL;
213 1.1 cgd }
214 1.1 cgd return(result);
215 1.1 cgd }
216 1.1 cgd
217 1.1 cgd /*
218 1.1 cgd * or_squish --
219 1.1 cgd * compresses -o expressions in our search plan.
220 1.1 cgd */
221 1.1 cgd PLAN *
222 1.1 cgd or_squish(plan)
223 1.1 cgd PLAN *plan; /* plan with ors to be squished */
224 1.1 cgd {
225 1.1 cgd register PLAN *next; /* next node being processed */
226 1.1 cgd register PLAN *tail; /* pointer to tail of result plan */
227 1.1 cgd PLAN *result; /* pointer to head of result plan */
228 1.1 cgd
229 1.1 cgd tail = result = next = NULL;
230 1.1 cgd
231 1.1 cgd while ((next = yanknode(&plan)) != NULL) {
232 1.1 cgd /*
233 1.1 cgd * if we encounter a ( expression ) then look for or's in
234 1.1 cgd * the expr subplan.
235 1.1 cgd */
236 1.1 cgd if (next->type == N_EXPR)
237 1.1 cgd next->p_data[0] = or_squish(next->p_data[0]);
238 1.1 cgd
239 1.1 cgd /* if we encounter a not then look for not's in the subplan */
240 1.1 cgd if (next->type == N_NOT)
241 1.1 cgd next->p_data[0] = or_squish(next->p_data[0]);
242 1.1 cgd
243 1.1 cgd /*
244 1.1 cgd * if we encounter an or, then place our collected plan in the
245 1.1 cgd * or's first subplan and then recursively collect the
246 1.1 cgd * remaining stuff into the second subplan and return the or.
247 1.1 cgd */
248 1.1 cgd if (next->type == N_OR) {
249 1.1 cgd if (result == NULL)
250 1.1 cgd err("%s: %s", "-o", "no expression before -o");
251 1.1 cgd next->p_data[0] = result;
252 1.1 cgd next->p_data[1] = or_squish(plan);
253 1.1 cgd if (next->p_data[1] == NULL)
254 1.1 cgd err("%s: %s", "-o", "no expression after -o");
255 1.1 cgd return(next);
256 1.1 cgd }
257 1.1 cgd
258 1.1 cgd /* add the node to our result plan */
259 1.1 cgd if (result == NULL)
260 1.1 cgd tail = result = next;
261 1.1 cgd else {
262 1.1 cgd tail->next = next;
263 1.1 cgd tail = next;
264 1.1 cgd }
265 1.1 cgd tail->next = NULL;
266 1.1 cgd }
267 1.1 cgd return(result);
268 1.1 cgd }
269