quiz/rxp.c

   1 /*      $NetBSD: rxp.c,v 1.7 1999/09/08 21:17:56 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. 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 #include <sys/cdefs.h>
  41 #ifndef lint
  42 #if 0
  43 static char sccsid[] = "@(#)rxp.c       8.1 (Berkeley) 5/31/93";
  44 #else
  45 __RCSID("$NetBSD: rxp.c,v 1.7 1999/09/08 21:17:56 jsm Exp $");
  46 #endif
  47 #endif /* not lint */
  48
  49 /*
  50  * regular expression parser
  51  *
  52  * external functions and return values are:
  53  * rxp_compile(s)
  54  *      TRUE    success
  55  *      FALSE   parse failure; error message will be in char rxperr[]
  56  * metas are:
  57  *      {...}   optional pattern, equialent to [...|]
  58  *      |       alternate pattern
  59  *      [...]   pattern delimiters
  60  *
  61  * rxp_match(s)
  62  *      TRUE    string s matches compiled pattern
  63  *      FALSE   match failure or regexp error
  64  *
  65  * rxp_expand()
  66  *      char *  reverse-engineered regular expression string
  67  *      NULL    regexp error
  68  */
  69
  70 #include <stdio.h>
  71 #include <ctype.h>
  72 #include "quiz.h"
  73                                         /* regexp tokens,       arg */
  74 #define LIT     (-1)                    /* literal character,   char */
  75 #define SOT     (-2)                    /* start text anchor,   - */
  76 #define EOT     (-3)                    /* end text anchor,     - */
  77 #define GRP_S   (-4)                    /* start alternate grp, ptr_to_end */
  78 #define GRP_E   (-5)                    /* end group,           - */
  79 #define ALT_S   (-6)                    /* alternate starts,    ptr_to_next */
  80 #define ALT_E   (-7)                    /* alternate ends,      - */
  81 #define END     (-8)                    /* end of regexp,       - */
  82
  83 typedef short Rxp_t;                    /* type for regexp tokens */
  84
  85 static Rxp_t rxpbuf[RXP_LINE_SZ];       /* compiled regular expression buffer */
  86 char rxperr[128];                       /* parser error message */
  87
  88 static int       rxp__compile __P((const char *, int));
  89 static char     *rxp__expand __P((int));
  90 static int       rxp__match __P((const char *, int, Rxp_t *, Rxp_t *, const char *));
  91
  92 int
  93 rxp_compile(s)
  94         const char *    s;
  95 {
  96         return (rxp__compile(s, TRUE));
  97 }
  98
  99 static int
 100 rxp__compile(s, first)
 101         const char *s;
 102         int first;
 103 {
 104         static Rxp_t *rp;
 105         static const char *sp;
 106         Rxp_t *grp_ptr;
 107         Rxp_t *alt_ptr;
 108         int esc, err;
 109
 110         esc = 0;
 111         if (first) {
 112                 rp = rxpbuf;
 113                 sp = s;
 114                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 115                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 116                 *rp++ = 0;
 117         }
 118         *rp++ = ALT_S;
 119         alt_ptr = rp;
 120         *rp++ = 0;
 121         for (; *sp; ++sp) {
 122                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 123                         (void)snprintf(rxperr, sizeof(rxperr),
 124                             "regular expression too long %s", s);
 125                         return (FALSE);
 126                 }
 127                 if (*sp == ':' && !esc)
 128                         break;
 129                 if (esc) {
 130                         *rp++ = LIT;
 131                         *rp++ = *sp;
 132                         esc = 0;
 133                 }
 134                 else switch (*sp) {
 135                 case '\\':
 136                         esc = 1;
 137                         break;
 138                 case '{':
 139                 case '[':
 140                         *rp++ = GRP_S;
 141                         grp_ptr = rp;
 142                         *rp++ = 0;
 143                         sp++;
 144                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 145                                 return (err);
 146                         *rp++ = GRP_E;
 147                         *grp_ptr = rp - rxpbuf;
 148                         break;
 149                 case '}':
 150                 case ']':
 151                 case '|':
 152                         *rp++ = ALT_E;
 153                         *alt_ptr = rp - rxpbuf;
 154                         if (*sp != ']') {
 155                                 *rp++ = ALT_S;
 156                                 alt_ptr = rp;
 157                                 *rp++ = 0;
 158                         }
 159                         if (*sp != '|') {
 160                                 if (*sp != ']') {
 161                                         *rp++ = ALT_E;
 162                                         *alt_ptr = rp - rxpbuf;
 163                                 }
 164                                 if (first) {
 165                                         (void)snprintf(rxperr, sizeof(rxperr),
 166                                             "unmatched alternator in regexp %s",
 167                                              s);
 168                                         return (FALSE);
 169                                 }
 170                                 return (TRUE);
 171                         }
 172                         break;
 173                 default:
 174                         *rp++ = LIT;
 175                         *rp++ = *sp;
 176                         esc = 0;
 177                         break;
 178                 }
 179         }
 180         if (!first) {
 181                 (void)snprintf(rxperr, sizeof(rxperr),
 182                     "unmatched alternator in regexp %s", s);
 183                 return (FALSE);
 184         }
 185         *rp++ = ALT_E;
 186         *alt_ptr = rp - rxpbuf;
 187         *rp++ = GRP_E;
 188         *(rxpbuf + 2) = rp - rxpbuf;
 189         *rp++ = EOT;
 190         *rp = END;
 191         return (TRUE);
 192 }
 193
 194 /*
 195  * match string against compiled regular expression
 196  */
 197 int
 198 rxp_match(s)
 199         const char *    s;
 200 {
 201         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 202 }
 203
 204 static int
 205 rxp__match(s, first, j_succ, j_fail, sp_fail)
 206         const char *s;
 207         int first;
 208         Rxp_t *j_succ;          /* jump here on successful alt match */
 209         Rxp_t *j_fail;          /* jump here on failed match */
 210         const char *sp_fail;            /* reset sp to here on failed match */
 211 {
 212         static Rxp_t *rp;
 213         static const char *sp;
 214         int ch;
 215         Rxp_t *grp_end = NULL;
 216         int err;
 217
 218         if (first) {
 219                 rp = rxpbuf;
 220                 sp = s;
 221         }
 222         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 223                 switch(*rp) {
 224                 case LIT:
 225                         rp++;
 226                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 227                         if (ch != *sp++) {
 228                                 rp = j_fail;
 229                                 sp = sp_fail;
 230                                 return (TRUE);
 231                         }
 232                         rp++;
 233                         break;
 234                 case SOT:
 235                         if (sp != s)
 236                                 return (FALSE);
 237                         rp++;
 238                         break;
 239                 case EOT:
 240                         if (*sp != 0)
 241                                 return (FALSE);
 242                         rp++;
 243                         break;
 244                 case GRP_S:
 245                         rp++;
 246                         grp_end = rxpbuf + *rp++;
 247                         break;
 248                 case ALT_S:
 249                         rp++;
 250                         if ((err = rxp__match(sp,
 251                             FALSE, grp_end, rxpbuf + *rp++, sp)) != TRUE)
 252                                 return (err);
 253                         break;
 254                 case ALT_E:
 255                         rp = j_succ;
 256                         return (TRUE);
 257                 case GRP_E:
 258                 default:
 259                         return (FALSE);
 260                 }
 261         return (*rp != END ? FALSE : TRUE);
 262 }
 263
 264 /*
 265  * Reverse engineer the regular expression, by picking first of all alternates.
 266  */
 267 char *
 268 rxp_expand()
 269 {
 270         return (rxp__expand(TRUE));
 271 }
 272
 273 static char *
 274 rxp__expand(first)
 275         int first;
 276 {
 277         static char buf[RXP_LINE_SZ/2];
 278         static Rxp_t *rp;
 279         static char *bp;
 280         Rxp_t *grp_ptr;
 281         char *err;
 282
 283         if (first) {
 284                 rp = rxpbuf;
 285                 bp = buf;
 286         }
 287         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 288                 switch(*rp) {
 289                 case LIT:
 290                         rp++;
 291                         *bp++ = *rp++;
 292                         break;
 293                 case GRP_S:
 294                         rp++;
 295                         grp_ptr = rxpbuf + *rp;
 296                         rp++;
 297                         if ((err = rxp__expand(FALSE)) == NULL)
 298                                 return (err);
 299                         rp = grp_ptr;
 300                         break;
 301                 case ALT_E:
 302                         return (buf);
 303                 case ALT_S:
 304                         rp++;
 305                         /* FALLTHROUGH */
 306                 case SOT:
 307                 case EOT:
 308                 case GRP_E:
 309                         rp++;
 310                         break;
 311                 default:
 312                         return (NULL);
 313                 }
 314         if (first) {
 315                 if (*rp != END)
 316                         return (NULL);
 317                 *bp = '\0';
 318         }
 319         return (buf);
 320 }