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