quiz/rxp.c

   1 /*      $NetBSD: rxp.c,v 1.12 2004/01/27 20:30:30 jsm Exp $     */
   2
   3 /*-
   4  * Copyright (c) 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Jim R. Oldroyd at The Instruction Set and Keith Gabryelski at
   9  * Commodore Business Machines.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #ifndef lint
  38 #if 0
  39 static char sccsid[] = "@(#)rxp.c       8.1 (Berkeley) 5/31/93";
  40 #else
  41 __RCSID("$NetBSD: rxp.c,v 1.12 2004/01/27 20:30:30 jsm Exp $");
  42 #endif
  43 #endif /* not lint */
  44
  45 /*
  46  * regular expression parser
  47  *
  48  * external functions and return values are:
  49  * rxp_compile(s)
  50  *      TRUE    success
  51  *      FALSE   parse failure; error message will be in char rxperr[]
  52  * metas are:
  53  *      {...}   optional pattern, equialent to [...|]
  54  *      |       alternate pattern
  55  *      [...]   pattern delimiters
  56  *
  57  * rxp_match(s)
  58  *      TRUE    string s matches compiled pattern
  59  *      FALSE   match failure or regexp error
  60  *
  61  * rxp_expand()
  62  *      char *  reverse-engineered regular expression string
  63  *      NULL    regexp error
  64  */
  65
  66 #include <stdio.h>
  67 #include <stdlib.h>
  68 #include <ctype.h>
  69 #include "quiz.h"
  70                                         /* regexp tokens,       arg */
  71 #define LIT     (-1)                    /* literal character,   char */
  72 #define SOT     (-2)                    /* start text anchor,   - */
  73 #define EOT     (-3)                    /* end text anchor,     - */
  74 #define GRP_S   (-4)                    /* start alternate grp, ptr_to_end */
  75 #define GRP_E   (-5)                    /* end group,           - */
  76 #define ALT_S   (-6)                    /* alternate starts,    ptr_to_next */
  77 #define ALT_E   (-7)                    /* alternate ends,      - */
  78 #define END     (-8)                    /* end of regexp,       - */
  79
  80 typedef short Rxp_t;                    /* type for regexp tokens */
  81
  82 static Rxp_t rxpbuf[RXP_LINE_SZ];       /* compiled regular expression buffer */
  83 char rxperr[128];                       /* parser error message */
  84
  85 static int       rxp__compile(const char *, int);
  86 static char     *rxp__expand(int);
  87 static int       rxp__match(const char *, int, Rxp_t *, Rxp_t *, const char *);
  88
  89 int
  90 rxp_compile(s)
  91         const char *    s;
  92 {
  93         return (rxp__compile(s, TRUE));
  94 }
  95
  96 static int
  97 rxp__compile(s, first)
  98         const char *s;
  99         int first;
 100 {
 101         static Rxp_t *rp;
 102         static const char *sp;
 103         Rxp_t *grp_ptr;
 104         Rxp_t *alt_ptr;
 105         int esc, err;
 106
 107         esc = 0;
 108         if (first) {
 109                 rp = rxpbuf;
 110                 sp = s;
 111                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 112                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 113                 *rp++ = 0;
 114         }
 115         *rp++ = ALT_S;
 116         alt_ptr = rp;
 117         *rp++ = 0;
 118         for (; *sp; ++sp) {
 119                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 120                         (void)snprintf(rxperr, sizeof(rxperr),
 121                             "regular expression too long %s", s);
 122                         return (FALSE);
 123                 }
 124                 if (*sp == ':' && !esc)
 125                         break;
 126                 if (esc) {
 127                         *rp++ = LIT;
 128                         *rp++ = *sp;
 129                         esc = 0;
 130                 }
 131                 else switch (*sp) {
 132                 case '\\':
 133                         esc = 1;
 134                         break;
 135                 case '{':
 136                 case '[':
 137                         *rp++ = GRP_S;
 138                         grp_ptr = rp;
 139                         *rp++ = 0;
 140                         sp++;
 141                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 142                                 return (err);
 143                         *rp++ = GRP_E;
 144                         *grp_ptr = rp - rxpbuf;
 145                         break;
 146                 case '}':
 147                 case ']':
 148                 case '|':
 149                         *rp++ = ALT_E;
 150                         *alt_ptr = rp - rxpbuf;
 151                         if (*sp != ']') {
 152                                 *rp++ = ALT_S;
 153                                 alt_ptr = rp;
 154                                 *rp++ = 0;
 155                         }
 156                         if (*sp != '|') {
 157                                 if (*sp != ']') {
 158                                         *rp++ = ALT_E;
 159                                         *alt_ptr = rp - rxpbuf;
 160                                 }
 161                                 if (first) {
 162                                         (void)snprintf(rxperr, sizeof(rxperr),
 163                                             "unmatched alternator in regexp %s",
 164                                              s);
 165                                         return (FALSE);
 166                                 }
 167                                 return (TRUE);
 168                         }
 169                         break;
 170                 default:
 171                         *rp++ = LIT;
 172                         *rp++ = *sp;
 173                         esc = 0;
 174                         break;
 175                 }
 176         }
 177         if (!first) {
 178                 (void)snprintf(rxperr, sizeof(rxperr),
 179                     "unmatched alternator in regexp %s", s);
 180                 return (FALSE);
 181         }
 182         *rp++ = ALT_E;
 183         *alt_ptr = rp - rxpbuf;
 184         *rp++ = GRP_E;
 185         *(rxpbuf + 2) = rp - rxpbuf;
 186         *rp++ = EOT;
 187         *rp = END;
 188         return (TRUE);
 189 }
 190
 191 /*
 192  * match string against compiled regular expression
 193  */
 194 int
 195 rxp_match(s)
 196         const char *    s;
 197 {
 198         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 199 }
 200
 201 static int
 202 rxp__match(s, first, j_succ, j_fail, sp_fail)
 203         const char *s;
 204         int first;
 205         Rxp_t *j_succ;          /* jump here on successful alt match */
 206         Rxp_t *j_fail;          /* jump here on failed match */
 207         const char *sp_fail;            /* reset sp to here on failed match */
 208 {
 209         static Rxp_t *rp;
 210         static const char *sp;
 211         int ch;
 212         Rxp_t *grp_end = NULL;
 213
 214         if (first) {
 215                 rp = rxpbuf;
 216                 sp = s;
 217         }
 218         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 219                 switch(*rp) {
 220                 case LIT:
 221                         rp++;
 222                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 223                         if (ch != *sp++) {
 224                                 rp = j_fail;
 225                                 sp = sp_fail;
 226                                 return (FALSE);
 227                         }
 228                         rp++;
 229                         break;
 230                 case SOT:
 231                         if (sp != s)
 232                                 return (FALSE);
 233                         rp++;
 234                         break;
 235                 case EOT:
 236                         if (*sp != 0)
 237                                 return (FALSE);
 238                         rp++;
 239                         break;
 240                 case GRP_S:
 241                         rp++;
 242                         grp_end = rxpbuf + *rp++;
 243                         break;
 244                 case ALT_S:
 245                         rp++;
 246                         rxp__match(sp, FALSE, grp_end, rxpbuf + *rp++, sp);
 247                         break;
 248                 case ALT_E:
 249                         rp = j_succ;
 250                         return (TRUE);
 251                 case GRP_E:
 252                         rp = j_fail;
 253                         sp = sp_fail;
 254                         return (FALSE);
 255                 default:
 256                         abort();
 257                 }
 258         return (*rp != END ? FALSE : TRUE);
 259 }
 260
 261 /*
 262  * Reverse engineer the regular expression, by picking first of all alternates.
 263  */
 264 char *
 265 rxp_expand()
 266 {
 267         return (rxp__expand(TRUE));
 268 }
 269
 270 static char *
 271 rxp__expand(first)
 272         int first;
 273 {
 274         static char buf[RXP_LINE_SZ/2];
 275         static Rxp_t *rp;
 276         static char *bp;
 277         Rxp_t *grp_ptr;
 278         char *err;
 279
 280         if (first) {
 281                 rp = rxpbuf;
 282                 bp = buf;
 283         }
 284         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 285                 switch(*rp) {
 286                 case LIT:
 287                         rp++;
 288                         *bp++ = *rp++;
 289                         break;
 290                 case GRP_S:
 291                         rp++;
 292                         grp_ptr = rxpbuf + *rp;
 293                         rp++;
 294                         if ((err = rxp__expand(FALSE)) == NULL)
 295                                 return (err);
 296                         rp = grp_ptr;
 297                         break;
 298                 case ALT_E:
 299                         return (buf);
 300                 case ALT_S:
 301                         rp++;
 302                         /* FALLTHROUGH */
 303                 case SOT:
 304                 case EOT:
 305                 case GRP_E:
 306                         rp++;
 307                         break;
 308                 default:
 309                         return (NULL);
 310                 }
 311         if (first) {
 312                 if (*rp != END)
 313                         return (NULL);
 314                 *bp = '\0';
 315         }
 316         return (buf);
 317 }