games/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(const char *s)
  91 {
  92         return (rxp__compile(s, TRUE));
  93 }
  94
  95 static int
  96 rxp__compile(const char *s, int first)
  97 {
  98         static Rxp_t *rp;
  99         static const char *sp;
 100         Rxp_t *grp_ptr;
 101         Rxp_t *alt_ptr;
 102         int esc, err;
 103
 104         esc = 0;
 105         if (first) {
 106                 rp = rxpbuf;
 107                 sp = s;
 108                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 109                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 110                 *rp++ = 0;
 111         }
 112         *rp++ = ALT_S;
 113         alt_ptr = rp;
 114         *rp++ = 0;
 115         for (; *sp; ++sp) {
 116                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 117                         (void)snprintf(rxperr, sizeof(rxperr),
 118                             "regular expression too long %s", s);
 119                         return (FALSE);
 120                 }
 121                 if (*sp == ':' && !esc)
 122                         break;
 123                 if (esc) {
 124                         *rp++ = LIT;
 125                         *rp++ = *sp;
 126                         esc = 0;
 127                 }
 128                 else switch (*sp) {
 129                 case '\\':
 130                         esc = 1;
 131                         break;
 132                 case '{':
 133                 case '[':
 134                         *rp++ = GRP_S;
 135                         grp_ptr = rp;
 136                         *rp++ = 0;
 137                         sp++;
 138                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 139                                 return (err);
 140                         *rp++ = GRP_E;
 141                         *grp_ptr = rp - rxpbuf;
 142                         break;
 143                 case '}':
 144                 case ']':
 145                 case '|':
 146                         *rp++ = ALT_E;
 147                         *alt_ptr = rp - rxpbuf;
 148                         if (*sp != ']') {
 149                                 *rp++ = ALT_S;
 150                                 alt_ptr = rp;
 151                                 *rp++ = 0;
 152                         }
 153                         if (*sp != '|') {
 154                                 if (*sp != ']') {
 155                                         *rp++ = ALT_E;
 156                                         *alt_ptr = rp - rxpbuf;
 157                                 }
 158                                 if (first) {
 159                                         (void)snprintf(rxperr, sizeof(rxperr),
 160                                             "unmatched alternator in regexp %s",
 161                                              s);
 162                                         return (FALSE);
 163                                 }
 164                                 return (TRUE);
 165                         }
 166                         break;
 167                 default:
 168                         *rp++ = LIT;
 169                         *rp++ = *sp;
 170                         esc = 0;
 171                         break;
 172                 }
 173         }
 174         if (!first) {
 175                 (void)snprintf(rxperr, sizeof(rxperr),
 176                     "unmatched alternator in regexp %s", s);
 177                 return (FALSE);
 178         }
 179         *rp++ = ALT_E;
 180         *alt_ptr = rp - rxpbuf;
 181         *rp++ = GRP_E;
 182         *(rxpbuf + 2) = rp - rxpbuf;
 183         *rp++ = EOT;
 184         *rp = END;
 185         return (TRUE);
 186 }
 187
 188 /*
 189  * match string against compiled regular expression
 190  */
 191 int
 192 rxp_match(const char *s)
 193 {
 194         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 195 }
 196
 197 static int
 198 rxp__match(const char *s,
 199            int first,
 200            Rxp_t *j_succ,               /* jump here on successful alt match */
 201            Rxp_t *j_fail,               /* jump here on failed match */
 202            const char *sp_fail)         /* reset sp to here on failed match */
 203 {
 204         static Rxp_t *rp;
 205         static const char *sp;
 206         int ch;
 207         Rxp_t *grp_end = NULL;
 208
 209         if (first) {
 210                 rp = rxpbuf;
 211                 sp = s;
 212         }
 213         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 214                 switch(*rp) {
 215                 case LIT:
 216                         rp++;
 217                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 218                         if (ch != *sp++) {
 219                                 rp = j_fail;
 220                                 sp = sp_fail;
 221                                 return (FALSE);
 222                         }
 223                         rp++;
 224                         break;
 225                 case SOT:
 226                         if (sp != s)
 227                                 return (FALSE);
 228                         rp++;
 229                         break;
 230                 case EOT:
 231                         if (*sp != 0)
 232                                 return (FALSE);
 233                         rp++;
 234                         break;
 235                 case GRP_S:
 236                         rp++;
 237                         grp_end = rxpbuf + *rp++;
 238                         break;
 239                 case ALT_S:
 240                         rp++;
 241                         rxp__match(sp, FALSE, grp_end, rxpbuf + *rp++, sp);
 242                         break;
 243                 case ALT_E:
 244                         rp = j_succ;
 245                         return (TRUE);
 246                 case GRP_E:
 247                         rp = j_fail;
 248                         sp = sp_fail;
 249                         return (FALSE);
 250                 default:
 251                         abort();
 252                 }
 253         return (*rp != END ? FALSE : TRUE);
 254 }
 255
 256 /*
 257  * Reverse engineer the regular expression, by picking first of all alternates.
 258  */
 259 char *
 260 rxp_expand(void)
 261 {
 262         return (rxp__expand(TRUE));
 263 }
 264
 265 static char *
 266 rxp__expand(int first)
 267 {
 268         static char buf[RXP_LINE_SZ/2];
 269         static Rxp_t *rp;
 270         static char *bp;
 271         Rxp_t *grp_ptr;
 272         char *err;
 273
 274         if (first) {
 275                 rp = rxpbuf;
 276                 bp = buf;
 277         }
 278         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 279                 switch(*rp) {
 280                 case LIT:
 281                         rp++;
 282                         *bp++ = *rp++;
 283                         break;
 284                 case GRP_S:
 285                         rp++;
 286                         grp_ptr = rxpbuf + *rp;
 287                         rp++;
 288                         if ((err = rxp__expand(FALSE)) == NULL)
 289                                 return (err);
 290                         rp = grp_ptr;
 291                         break;
 292                 case ALT_E:
 293                         return (buf);
 294                 case ALT_S:
 295                         rp++;
 296                         /* FALLTHROUGH */
 297                 case SOT:
 298                 case EOT:
 299                 case GRP_E:
 300                         rp++;
 301                         break;
 302                 default:
 303                         return (NULL);
 304                 }
 305         if (first) {
 306                 if (*rp != END)
 307                         return (NULL);
 308                 *bp = '\0';
 309         }
 310         return (buf);
 311 }