games/quiz/rxp.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Jim R. Oldroyd at The Instruction Set and Keith Gabryelski at
   7  * Commodore Business Machines.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  *
  37  * @(#)rxp.c    8.1 (Berkeley) 5/31/93
  38  * $FreeBSD: src/games/quiz/rxp.c,v 1.5 1999/12/12 02:29:54 billf Exp $
  39  * $DragonFly: src/games/quiz/rxp.c,v 1.4 2005/04/25 16:10:24 liamfoy Exp $
  40  */
  41
  42 /*
  43  * regular expression parser
  44  *
  45  * external functions and return values are:
  46  * rxp_compile(s)
  47  *      TRUE    success
  48  *      FALSE   parse failure; error message will be in char rxperr[]
  49  * metas are:
  50  *      {...}   optional pattern, equialent to [...|]
  51  *      |       alternate pattern
  52  *      [...]   pattern delimiters
  53  *
  54  * rxp_match(s)
  55  *      TRUE    string s matches compiled pattern
  56  *      FALSE   match failure or regexp error
  57  *
  58  * rxp_expand()
  59  *      char *  reverse-engineered regular expression string
  60  *      NULL    regexp error
  61  */
  62
  63 #include <stdio.h>
  64 #include <ctype.h>
  65 #include "quiz.h"
  66                                         /* regexp tokens,       arg */
  67 #define LIT     (-1)                    /* literal character,   char */
  68 #define SOT     (-2)                    /* start text anchor,   - */
  69 #define EOT     (-3)                    /* end text anchor,     - */
  70 #define GRP_S   (-4)                    /* start alternate grp, ptr_to_end */
  71 #define GRP_E   (-5)                    /* end group,           - */
  72 #define ALT_S   (-6)                    /* alternate starts,    ptr_to_next */
  73 #define ALT_E   (-7)                    /* alternate ends,      - */
  74 #define END     (-8)                    /* end of regexp,       - */
  75
  76 typedef short Rxp_t;                    /* type for regexp tokens */
  77
  78 static Rxp_t rxpbuf[RXP_LINE_SZ];       /* compiled regular expression buffer */
  79 char rxperr[128];                       /* parser error message */
  80
  81 static int       rxp__compile (char *, int);
  82 static char     *rxp__expand (int);
  83 static int       rxp__match (char *, int, Rxp_t *, Rxp_t *, char *);
  84
  85 int
  86 rxp_compile(char *s)
  87 {
  88         return (rxp__compile(s, TRUE));
  89 }
  90
  91 static int
  92 rxp__compile(char *s, int first)
  93 {
  94         static Rxp_t *rp;
  95         static char *sp;
  96         Rxp_t *grp_ptr;
  97         Rxp_t *alt_ptr;
  98         int esc, err;
  99
 100         esc = 0;
 101         if (first) {
 102                 rp = rxpbuf;
 103                 sp = s;
 104                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 105                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 106                 *rp++ = 0;
 107         }
 108         *rp++ = ALT_S;
 109         alt_ptr = rp;
 110         *rp++ = 0;
 111         for (; *sp; ++sp) {
 112                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 113                         (void)snprintf(rxperr, sizeof(rxperr),
 114                             "regular expression too long %s", s);
 115                         return (FALSE);
 116                 }
 117                 if (*sp == ':' && !esc)
 118                         break;
 119                 if (esc) {
 120                         *rp++ = LIT;
 121                         *rp++ = *sp;
 122                         esc = 0;
 123                 }
 124                 else switch (*sp) {
 125                 case '\\':
 126                         esc = 1;
 127                         break;
 128                 case '{':
 129                 case '[':
 130                         *rp++ = GRP_S;
 131                         grp_ptr = rp;
 132                         *rp++ = 0;
 133                         sp++;
 134                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 135                                 return (err);
 136                         *rp++ = GRP_E;
 137                         *grp_ptr = rp - rxpbuf;
 138                         break;
 139                 case '}':
 140                 case ']':
 141                 case '|':
 142                         *rp++ = ALT_E;
 143                         *alt_ptr = rp - rxpbuf;
 144                         if (*sp != ']') {
 145                                 *rp++ = ALT_S;
 146                                 alt_ptr = rp;
 147                                 *rp++ = 0;
 148                         }
 149                         if (*sp != '|') {
 150                                 if (*sp != ']') {
 151                                         *rp++ = ALT_E;
 152                                         *alt_ptr = rp - rxpbuf;
 153                                 }
 154                                 if (first) {
 155                                         (void)snprintf(rxperr, sizeof(rxperr),
 156                                             "unmatched alternator in regexp %s",
 157                                              s);
 158                                         return (FALSE);
 159                                 }
 160                                 return (TRUE);
 161                         }
 162                         break;
 163                 default:
 164                         *rp++ = LIT;
 165                         *rp++ = *sp;
 166                         esc = 0;
 167                         break;
 168                 }
 169         }
 170         if (!first) {
 171                 (void)snprintf(rxperr, sizeof(rxperr),
 172                     "unmatched alternator in regexp %s", s);
 173                 return (FALSE);
 174         }
 175         *rp++ = ALT_E;
 176         *alt_ptr = rp - rxpbuf;
 177         *rp++ = GRP_E;
 178         *(rxpbuf + 2) = rp - rxpbuf;
 179         *rp++ = EOT;
 180         *rp = END;
 181         return (TRUE);
 182 }
 183
 184 /*
 185  * match string against compiled regular expression
 186  */
 187 int
 188 rxp_match(char *s)
 189 {
 190         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 191 }
 192
 193 /*
 194  * jump to j_succ on successful alt match
 195  * jump to j_fail on failed match
 196  * reset sp to sp_fail on failed match
 197  */
 198 static int
 199 rxp__match(char *s, int first, Rxp_t *j_succ, Rxp_t *j_fail, char *sp_fail)
 200 {
 201         static Rxp_t *rp;
 202         static char *sp;
 203         int ch;
 204         Rxp_t *grp_end;
 205         int err;
 206
 207         grp_end = NULL;
 208         if (first) {
 209                 rp = rxpbuf;
 210                 sp = s;
 211         }
 212         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 213                 switch(*rp) {
 214                 case LIT:
 215                         rp++;
 216                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 217                         if (ch != *sp++) {
 218                                 rp = j_fail;
 219                                 sp = sp_fail;
 220                                 return (TRUE);
 221                         }
 222                         rp++;
 223                         break;
 224                 case SOT:
 225                         if (sp != s)
 226                                 return (FALSE);
 227                         rp++;
 228                         break;
 229                 case EOT:
 230                         if (*sp != 0)
 231                                 return (FALSE);
 232                         rp++;
 233                         break;
 234                 case GRP_S:
 235                         rp++;
 236                         grp_end = rxpbuf + *rp++;
 237                         break;
 238                 case ALT_S:
 239                         rp++;
 240                         if ((err = rxp__match(sp,
 241                             FALSE, grp_end, rxpbuf + *rp++, sp)) != TRUE)
 242                                 return (err);
 243                         break;
 244                 case ALT_E:
 245                         rp = j_succ;
 246                         return (TRUE);
 247                 case GRP_E:
 248                 default:
 249                         return (FALSE);
 250                 }
 251         return (*rp != END ? FALSE : TRUE);
 252 }
 253
 254 /*
 255  * Reverse engineer the regular expression, by picking first of all alternates.
 256  */
 257 char *
 258 rxp_expand(void)
 259 {
 260         return (rxp__expand(TRUE));
 261 }
 262
 263 static char *
 264 rxp__expand(int first)
 265 {
 266         static char buf[RXP_LINE_SZ/2];
 267         static Rxp_t *rp;
 268         static char *bp;
 269         Rxp_t *grp_ptr;
 270         char *err;
 271
 272         if (first) {
 273                 rp = rxpbuf;
 274                 bp = buf;
 275         }
 276         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 277                 switch(*rp) {
 278                 case LIT:
 279                         rp++;
 280                         *bp++ = *rp++;
 281                         break;
 282                 case GRP_S:
 283                         rp++;
 284                         grp_ptr = rxpbuf + *rp;
 285                         rp++;
 286                         if ((err = rxp__expand(FALSE)) == NULL)
 287                                 return (err);
 288                         rp = grp_ptr;
 289                         break;
 290                 case ALT_E:
 291                         return (buf);
 292                 case ALT_S:
 293                         rp++;
 294                         /* FALLTHROUGH */
 295                 case SOT:
 296                 case EOT:
 297                 case GRP_E:
 298                         rp++;
 299                         break;
 300                 default:
 301                         return (NULL);
 302                 }
 303         if (first) {
 304                 if (*rp != END)
 305                         return (NULL);
 306                 *bp = '\0';
 307         }
 308         return (buf);
 309 }