quiz/rxp.c

   1 /*-
   2  * Copyright (c) 1991 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Jim R. Oldroyd at The Instruction Set.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #ifndef lint
  38 static char sccsid[] = "@(#)rxp.c       5.1 (Berkeley) 11/10/91";
  39 #endif /* not lint */
  40
  41 /*
  42  * regular expression parser
  43  *
  44  * external functions and return values are:
  45  * rxp_compile(s)
  46  *      TRUE    success
  47  *      FALSE   parse failure; error message will be in char rxperr[]
  48  * metas are:
  49  *      {...}   optional pattern, equialent to [...|]
  50  *      |       alternate pattern
  51  *      [...]   pattern delimiters
  52  *
  53  * rxp_match(s)
  54  *      TRUE    string s matches compiled pattern
  55  *      FALSE   match failure or regexp error
  56  *
  57  * rxp_expand()
  58  *      char *  reverse-engineered regular expression string
  59  *      NULL    regexp error
  60  */
  61
  62 #include <stdio.h>
  63 #include <ctype.h>
  64 #include "quiz.h"
  65                                         /* regexp tokens,       arg */
  66 #define LIT     (-1)                    /* literal character,   char */
  67 #define SOT     (-2)                    /* start text anchor,   - */
  68 #define EOT     (-3)                    /* end text anchor,     - */
  69 #define GRP_S   (-4)                    /* start alternate grp, ptr_to_end */
  70 #define GRP_E   (-5)                    /* end group,           - */
  71 #define ALT_S   (-6)                    /* alternate starts,    ptr_to_next */
  72 #define ALT_E   (-7)                    /* alternate ends,      - */
  73 #define END     (-8)                    /* end of regexp,       - */
  74
  75 typedef short Rxp_t;                    /* type for regexp tokens */
  76
  77 static Rxp_t rxpbuf[RXP_LINE_SZ];       /* compiled regular expression buffer */
  78 char rxperr[128];                       /* parser error message */
  79
  80 int      rxp__compile __P((char *, int));
  81 char    *rxp__expand __P((int));
  82 int      rxp__match __P((char *, int, Rxp_t *, Rxp_t *, char *));
  83
  84 int
  85 rxp_compile(s)
  86         register char * s;
  87 {
  88         return (rxp__compile(s, TRUE));
  89 }
  90
  91 static int
  92 rxp__compile(s, first)
  93         register char *s;
  94         int first;
  95 {
  96         static Rxp_t *rp;
  97         static char *sp;
  98         Rxp_t *grp_ptr;
  99         Rxp_t *alt_ptr;
 100         int esc, err;
 101
 102         esc = 0;
 103         if (first) {
 104                 rp = rxpbuf;
 105                 sp = s;
 106                 *rp++ = SOT;    /* auto-anchor: pat is really ^pat$ */
 107                 *rp++ = GRP_S;  /* auto-group: ^pat$ is really ^[pat]$ */
 108                 *rp++ = 0;
 109         }
 110         *rp++ = ALT_S;
 111         alt_ptr = rp;
 112         *rp++ = 0;
 113         for (; *sp; ++sp) {
 114                 if (rp - rxpbuf >= RXP_LINE_SZ - 4) {
 115                         (void)snprintf(rxperr, sizeof(rxperr),
 116                             "regular expression too long %s", s);
 117                         return (FALSE);
 118                 }
 119                 if (*sp == ':' && !esc)
 120                         break;
 121                 if (esc) {
 122                         *rp++ = LIT;
 123                         *rp++ = *sp;
 124                         esc = 0;
 125                 }
 126                 else switch (*sp) {
 127                 case '\\':
 128                         esc = 1;
 129                         break;
 130                 case '{':
 131                 case '[':
 132                         *rp++ = GRP_S;
 133                         grp_ptr = rp;
 134                         *rp++ = 0;
 135                         sp++;
 136                         if ((err = rxp__compile(s, FALSE)) != TRUE)
 137                                 return (err);
 138                         *rp++ = GRP_E;
 139                         *grp_ptr = rp - rxpbuf;
 140                         break;
 141                 case '}':
 142                 case ']':
 143                 case '|':
 144                         *rp++ = ALT_E;
 145                         *alt_ptr = rp - rxpbuf;
 146                         if (*sp != ']') {
 147                                 *rp++ = ALT_S;
 148                                 alt_ptr = rp;
 149                                 *rp++ = 0;
 150                         }
 151                         if (*sp != '|') {
 152                                 if (*sp != ']') {
 153                                         *rp++ = ALT_E;
 154                                         *alt_ptr = rp - rxpbuf;
 155                                 }
 156                                 if (first) {
 157                                         (void)snprintf(rxperr, sizeof(rxperr),
 158                                             "unmatched alternator in regexp %s",
 159                                              s);
 160                                         return (FALSE);
 161                                 }
 162                                 return (TRUE);
 163                         }
 164                         break;
 165                 default:
 166                         *rp++ = LIT;
 167                         *rp++ = *sp;
 168                         esc = 0;
 169                         break;
 170                 }
 171         }
 172         if (!first) {
 173                 (void)snprintf(rxperr, sizeof(rxperr),
 174                     "unmatched alternator in regexp %s", s);
 175                 return (FALSE);
 176         }
 177         *rp++ = ALT_E;
 178         *alt_ptr = rp - rxpbuf;
 179         *rp++ = GRP_E;
 180         *(rxpbuf + 2) = rp - rxpbuf;
 181         *rp++ = EOT;
 182         *rp = END;
 183         return (TRUE);
 184 }
 185
 186 /*
 187  * match string against compiled regular expression
 188  */
 189 int
 190 rxp_match(s)
 191         register char * s;
 192 {
 193         return (rxp__match(s, TRUE, NULL, NULL, NULL));
 194 }
 195
 196 static int
 197 rxp__match(s, first, j_succ, j_fail, sp_fail)
 198         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         char *sp_fail;          /* reset sp to here on failed match */
 203 {
 204         static Rxp_t *rp;
 205         static char *sp;
 206         register int ch;
 207         Rxp_t *grp_end;
 208         int err;
 209
 210         if (first) {
 211                 rp = rxpbuf;
 212                 sp = s;
 213         }
 214         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 215                 switch(*rp) {
 216                 case LIT:
 217                         rp++;
 218                         ch = isascii(*rp) && isupper(*rp) ? tolower(*rp) : *rp;
 219                         if (ch != *sp++) {
 220                                 rp = j_fail;
 221                                 sp = sp_fail;
 222                                 return (TRUE);
 223                         }
 224                         rp++;
 225                         break;
 226                 case SOT:
 227                         if (sp != s)
 228                                 return (FALSE);
 229                         rp++;
 230                         break;
 231                 case EOT:
 232                         if (*sp != 0)
 233                                 return (FALSE);
 234                         rp++;
 235                         break;
 236                 case GRP_S:
 237                         rp++;
 238                         grp_end = rxpbuf + *rp++;
 239                         break;
 240                 case ALT_S:
 241                         rp++;
 242                         if ((err = rxp__match(sp,
 243                             FALSE, grp_end, rxpbuf + *rp++, sp)) != TRUE)
 244                                 return (err);
 245                         break;
 246                 case ALT_E:
 247                         rp = j_succ;
 248                         return (TRUE);
 249                 case GRP_E:
 250                 default:
 251                         return (FALSE);
 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()
 261 {
 262         return (rxp__expand(TRUE));
 263 }
 264
 265 static char *
 266 rxp__expand(first)
 267         int first;
 268 {
 269         static char buf[RXP_LINE_SZ/2];
 270         static Rxp_t *rp;
 271         static char *bp;
 272         Rxp_t *grp_ptr;
 273         char *err;
 274
 275         if (first) {
 276                 rp = rxpbuf;
 277                 bp = buf;
 278         }
 279         while (rp < rxpbuf + RXP_LINE_SZ && *rp != END)
 280                 switch(*rp) {
 281                 case LIT:
 282                         rp++;
 283                         *bp++ = *rp++;
 284                         break;
 285                 case GRP_S:
 286                         rp++;
 287                         grp_ptr = rxpbuf + *rp;
 288                         rp++;
 289                         if ((err = rxp__expand(FALSE)) == NULL)
 290                                 return (err);
 291                         rp = grp_ptr;
 292                         break;
 293                 case ALT_E:
 294                         return (buf);
 295                 case ALT_S:
 296                         rp++;
 297                         /* FALLTHROUGH */
 298                 case SOT:
 299                 case EOT:
 300                 case GRP_E:
 301                         rp++;
 302                         break;
 303                 default:
 304                         return (NULL);
 305                 }
 306         if (first) {
 307                 if (*rp != END)
 308                         return (NULL);
 309                 *bp = '\0';
 310         }
 311         return (buf);
 312 }