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