quiz/rxp.c

   1 /*      $NetBSD: rxp.c,v 1.5 1995/04/22 10:17:00 cgd 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. All advertising materials mentioning features or use of this software
  20  *    must display the following acknowledgement:
  21  *      This product includes software developed by the University of
  22  *      California, Berkeley and its contributors.
  23  * 4. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  */
  39
  40 #ifndef lint
  41 #if 0
  42 static char sccsid[] = "@(#)rxp.c       8.1 (Berkeley) 5/31/93";
  43 #else
  44 static char rcsid[] = "$NetBSD: rxp.c,v 1.5 1995/04/22 10:17:00 cgd Exp $";
  45 #endif
  46 #endif /* not lint */
  47
  48 /*
  49  * regular expression parser
  50  *
  51  * external functions and return values are:
  52  * rxp_compile(s)
  53  *      TRUE    success
  54  *      FALSE   parse failure; error message will be in char rxperr[]
  55  * metas are:
  56  *      {...}   optional pattern, equialent to [...|]
  57  *      |       alternate pattern
  58  *      [...]   pattern delimiters
  59  *
  60  * rxp_match(s)
  61  *      TRUE    string s matches compiled pattern
  62  *      FALSE   match failure or regexp error
  63  *
  64  * rxp_expand()
  65  *      char *  reverse-engineered regular expression string
  66  *      NULL    regexp error
  67  */
  68
  69 #include <stdio.h>
  70 #include <ctype.h>
  71 #include "quiz.h"
  72                                         /* regexp tokens,       arg */
  73 #define LIT     (-1)                    /* literal character,   char */
  74 #define SOT     (-2)                    /* start text anchor,   - */
  75 #define EOT     (-3)                    /* end text anchor,     - */
  76 #define GRP_S   (-4)                    /* start alternate grp, ptr_to_end */
  77 #define GRP_E   (-5)                    /* end group,           - */
  78 #define ALT_S   (-6)                    /* alternate starts,    ptr_to_next */
  79 #define ALT_E   (-7)                    /* alternate ends,      - */
  80 #define END     (-8)                    /* end of regexp,       - */
  81
  82 typedef short Rxp_t;                    /* type for regexp tokens */
  83
  84 static Rxp_t rxpbuf[RXP_LINE_SZ];       /* compiled regular expression buffer */
  85 char rxperr[128];                       /* parser error message */
  86
  87 static int       rxp__compile __P((char *, int));
  88 static char     *rxp__expand __P((int));
  89 static int       rxp__match __P((char *, int, Rxp_t *, Rxp_t *, char *));
  90
  91 int
  92 rxp_compile(s)
  93         register char * s;
  94 {
  95         return (rxp__compile(s, TRUE));
  96 }
  97
  98 static int
  99 rxp__compile(s, first)
 100         register char *s;
 101         int first;
 102 {
 103         static Rxp_t *rp;
 104         static char *sp;
 105         Rxp_t *grp_ptr;
 106         Rxp_t *alt_ptr;
 107         int esc, err;
 108
 109         esc = 0;
 110         if (first) {
 111                 rp = rxpbuf;
 112                 sp = s;
 113                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 114                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 115                 *rp++ = 0;
 116         }
 117         *rp++ = ALT_S;
 118         alt_ptr = rp;
 119         *rp++ = 0;
 120         for (; *sp; ++sp) {
 121                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 122                         (void)snprintf(rxperr, sizeof(rxperr),
 123                             "regular expression too long %s", s);
 124                         return (FALSE);
 125                 }
 126                 if (*sp == ':' && !esc)
 127                         break;
 128                 if (esc) {
 129                         *rp++ = LIT;
 130                         *rp++ = *sp;
 131                         esc = 0;
 132                 }
 133                 else switch (*sp) {
 134                 case '\\':
 135                         esc = 1;
 136                         break;
 137                 case '{':
 138                 case '[':
 139                         *rp++ = GRP_S;
 140                         grp_ptr = rp;
 141                         *rp++ = 0;
 142                         sp++;
 143                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 144                                 return (err);
 145                         *rp++ = GRP_E;
 146                         *grp_ptr = rp - rxpbuf;
 147                         break;
 148                 case '}':
 149                 case ']':
 150                 case '|':
 151                         *rp++ = ALT_E;
 152                         *alt_ptr = rp - rxpbuf;
 153                         if (*sp != ']') {
 154                                 *rp++ = ALT_S;
 155                                 alt_ptr = rp;
 156                                 *rp++ = 0;
 157                         }
 158                         if (*sp != '|') {
 159                                 if (*sp != ']') {
 160                                         *rp++ = ALT_E;
 161                                         *alt_ptr = rp - rxpbuf;
 162                                 }
 163                                 if (first) {
 164                                         (void)snprintf(rxperr, sizeof(rxperr),
 165                                             "unmatched alternator in regexp %s",
 166                                              s);
 167                                         return (FALSE);
 168                                 }
 169                                 return (TRUE);
 170                         }
 171                         break;
 172                 default:
 173                         *rp++ = LIT;
 174                         *rp++ = *sp;
 175                         esc = 0;
 176                         break;
 177                 }
 178         }
 179         if (!first) {
 180                 (void)snprintf(rxperr, sizeof(rxperr),
 181                     "unmatched alternator in regexp %s", s);
 182                 return (FALSE);
 183         }
 184         *rp++ = ALT_E;
 185         *alt_ptr = rp - rxpbuf;
 186         *rp++ = GRP_E;
 187         *(rxpbuf + 2) = rp - rxpbuf;
 188         *rp++ = EOT;
 189         *rp = END;
 190         return (TRUE);
 191 }
 192
 193 /*
 194  * match string against compiled regular expression
 195  */
 196 int
 197 rxp_match(s)
 198         register char * s;
 199 {
 200         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 201 }
 202
 203 static int
 204 rxp__match(s, first, j_succ, j_fail, sp_fail)
 205         char *s;
 206         int first;
 207         Rxp_t *j_succ;          /* jump here on successful alt match */
 208         Rxp_t *j_fail;          /* jump here on failed match */
 209         char *sp_fail;          /* reset sp to here on failed match */
 210 {
 211         static Rxp_t *rp;
 212         static char *sp;
 213         register int ch;
 214         Rxp_t *grp_end;
 215         int err;
 216
 217         if (first) {
 218                 rp = rxpbuf;
 219                 sp = s;
 220         }
 221         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 222                 switch(*rp) {
 223                 case LIT:
 224                         rp++;
 225                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 226                         if (ch != *sp++) {
 227                                 rp = j_fail;
 228                                 sp = sp_fail;
 229                                 return (TRUE);
 230                         }
 231                         rp++;
 232                         break;
 233                 case SOT:
 234                         if (sp != s)
 235                                 return (FALSE);
 236                         rp++;
 237                         break;
 238                 case EOT:
 239                         if (*sp != 0)
 240                                 return (FALSE);
 241                         rp++;
 242                         break;
 243                 case GRP_S:
 244                         rp++;
 245                         grp_end = rxpbuf + *rp++;
 246                         break;
 247                 case ALT_S:
 248                         rp++;
 249                         if ((err = rxp__match(sp,
 250                             FALSE, grp_end, rxpbuf + *rp++, sp)) != TRUE)
 251                                 return (err);
 252                         break;
 253                 case ALT_E:
 254                         rp = j_succ;
 255                         return (TRUE);
 256                 case GRP_E:
 257                 default:
 258                         return (FALSE);
 259                 }
 260         return (*rp != END ? FALSE : TRUE);
 261 }
 262
 263 /*
 264  * Reverse engineer the regular expression, by picking first of all alternates.
 265  */
 266 char *
 267 rxp_expand()
 268 {
 269         return (rxp__expand(TRUE));
 270 }
 271
 272 static char *
 273 rxp__expand(first)
 274         int first;
 275 {
 276         static char buf[RXP_LINE_SZ/2];
 277         static Rxp_t *rp;
 278         static char *bp;
 279         Rxp_t *grp_ptr;
 280         char *err;
 281
 282         if (first) {
 283                 rp = rxpbuf;
 284                 bp = buf;
 285         }
 286         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 287                 switch(*rp) {
 288                 case LIT:
 289                         rp++;
 290                         *bp++ = *rp++;
 291                         break;
 292                 case GRP_S:
 293                         rp++;
 294                         grp_ptr = rxpbuf + *rp;
 295                         rp++;
 296                         if ((err = rxp__expand(FALSE)) == NULL)
 297                                 return (err);
 298                         rp = grp_ptr;
 299                         break;
 300                 case ALT_E:
 301                         return (buf);
 302                 case ALT_S:
 303                         rp++;
 304                         /* FALLTHROUGH */
 305                 case SOT:
 306                 case EOT:
 307                 case GRP_E:
 308                         rp++;
 309                         break;
 310                 default:
 311                         return (NULL);
 312                 }
 313         if (first) {
 314                 if (*rp != END)
 315                         return (NULL);
 316                 *bp = '\0';
 317         }
 318         return (buf);
 319 }