apropos_db.c

   1 /*      $Id: apropos_db.c,v 1.28 2011/12/25 14:58:39 schwarze Exp $ */
   2 /*
   3  * Copyright (c) 2011 Kristaps Dzonsons <kristaps@bsd.lv>
   4  * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18 #ifdef HAVE_CONFIG_H
  19 #include "config.h"
  20 #endif
  21
  22 #include <assert.h>
  23 #include <fcntl.h>
  24 #include <regex.h>
  25 #include <stdarg.h>
  26 #include <stdint.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30
  31 #if defined(__linux__)
  32 # include <endian.h>
  33 # include <db_185.h>
  34 #elif defined(__APPLE__)
  35 # include <libkern/OSByteOrder.h>
  36 # include <db.h>
  37 #else
  38 # include <db.h>
  39 #endif
  40
  41 #include "mandocdb.h"
  42 #include "apropos_db.h"
  43 #include "mandoc.h"
  44
  45 struct  rec {
  46         struct res       res; /* resulting record info */
  47         /*
  48          * Maintain a binary tree for checking the uniqueness of `rec'
  49          * when adding elements to the results array.
  50          * Since the results array is dynamic, use offset in the array
  51          * instead of a pointer to the structure.
  52          */
  53         int              lhs;
  54         int              rhs;
  55         int              matched; /* expression is true */
  56         int             *matches; /* partial truth evaluations */
  57 };
  58
  59 struct  expr {
  60         int              regex; /* is regex? */
  61         int              index; /* index in match array */
  62         uint64_t         mask; /* type-mask */
  63         int              and; /* is rhs of logical AND? */
  64         char            *v; /* search value */
  65         regex_t          re; /* compiled re, if regex */
  66         struct expr     *next; /* next in sequence */
  67         struct expr     *subexpr;
  68 };
  69
  70 struct  type {
  71         uint64_t         mask;
  72         const char      *name;
  73 };
  74
  75 struct  rectree {
  76         struct rec      *node; /* record array for dir tree */
  77         int              len; /* length of record array */
  78 };
  79
  80 static  const struct type types[] = {
  81         { TYPE_An, "An" },
  82         { TYPE_Ar, "Ar" },
  83         { TYPE_At, "At" },
  84         { TYPE_Bsx, "Bsx" },
  85         { TYPE_Bx, "Bx" },
  86         { TYPE_Cd, "Cd" },
  87         { TYPE_Cm, "Cm" },
  88         { TYPE_Dv, "Dv" },
  89         { TYPE_Dx, "Dx" },
  90         { TYPE_Em, "Em" },
  91         { TYPE_Er, "Er" },
  92         { TYPE_Ev, "Ev" },
  93         { TYPE_Fa, "Fa" },
  94         { TYPE_Fl, "Fl" },
  95         { TYPE_Fn, "Fn" },
  96         { TYPE_Fn, "Fo" },
  97         { TYPE_Ft, "Ft" },
  98         { TYPE_Fx, "Fx" },
  99         { TYPE_Ic, "Ic" },
 100         { TYPE_In, "In" },
 101         { TYPE_Lb, "Lb" },
 102         { TYPE_Li, "Li" },
 103         { TYPE_Lk, "Lk" },
 104         { TYPE_Ms, "Ms" },
 105         { TYPE_Mt, "Mt" },
 106         { TYPE_Nd, "Nd" },
 107         { TYPE_Nm, "Nm" },
 108         { TYPE_Nx, "Nx" },
 109         { TYPE_Ox, "Ox" },
 110         { TYPE_Pa, "Pa" },
 111         { TYPE_Rs, "Rs" },
 112         { TYPE_Sh, "Sh" },
 113         { TYPE_Ss, "Ss" },
 114         { TYPE_St, "St" },
 115         { TYPE_Sy, "Sy" },
 116         { TYPE_Tn, "Tn" },
 117         { TYPE_Va, "Va" },
 118         { TYPE_Va, "Vt" },
 119         { TYPE_Xr, "Xr" },
 120         { UINT64_MAX, "any" },
 121         { 0, NULL }
 122 };
 123
 124 static  DB      *btree_open(void);
 125 static  int      btree_read(const DBT *, const DBT *,
 126                         const struct mchars *,
 127                         uint64_t *, recno_t *, char **);
 128 static  int      expreval(const struct expr *, int *);
 129 static  void     exprexec(const struct expr *,
 130                         const char *, uint64_t, struct rec *);
 131 static  int      exprmark(const struct expr *,
 132                         const char *, uint64_t, int *);
 133 static  struct expr *exprexpr(int, char *[], int *, int *, size_t *);
 134 static  struct expr *exprterm(char *, int);
 135 static  DB      *index_open(void);
 136 static  int      index_read(const DBT *, const DBT *, int,
 137                         const struct mchars *, struct rec *);
 138 static  void     norm_string(const char *,
 139                         const struct mchars *, char **);
 140 static  size_t   norm_utf8(unsigned int, char[7]);
 141 static  void     recfree(struct rec *);
 142 static  int      single_search(struct rectree *, const struct opts *,
 143                         const struct expr *, size_t terms,
 144                         struct mchars *, int);
 145
 146 /*
 147  * Open the keyword mandoc-db database.
 148  */
 149 static DB *
 150 btree_open(void)
 151 {
 152         BTREEINFO        info;
 153         DB              *db;
 154
 155         memset(&info, 0, sizeof(BTREEINFO));
 156         info.flags = R_DUP;
 157
 158         db = dbopen(MANDOC_DB, O_RDONLY, 0, DB_BTREE, &info);
 159         if (NULL != db)
 160                 return(db);
 161
 162         return(NULL);
 163 }
 164
 165 /*
 166  * Read a keyword from the database and normalise it.
 167  * Return 0 if the database is insane, else 1.
 168  */
 169 static int
 170 btree_read(const DBT *k, const DBT *v, const struct mchars *mc,
 171                 uint64_t *mask, recno_t *rec, char **buf)
 172 {
 173         uint64_t         vbuf[2];
 174
 175         /* Are our sizes sane? */
 176         if (k->size < 2 || sizeof(vbuf) != v->size)
 177                 return(0);
 178
 179         /* Is our string nil-terminated? */
 180         if ('\0' != ((const char *)k->data)[(int)k->size - 1])
 181                 return(0);
 182
 183         norm_string((const char *)k->data, mc, buf);
 184         memcpy(vbuf, v->data, v->size);
 185         *mask = betoh64(vbuf[0]);
 186         *rec  = betoh64(vbuf[1]);
 187         return(1);
 188 }
 189
 190 /*
 191  * Take a Unicode codepoint and produce its UTF-8 encoding.
 192  * This isn't the best way to do this, but it works.
 193  * The magic numbers are from the UTF-8 packaging.
 194  * They're not as scary as they seem: read the UTF-8 spec for details.
 195  */
 196 static size_t
 197 norm_utf8(unsigned int cp, char out[7])
 198 {
 199         int              rc;
 200
 201         rc = 0;
 202
 203         if (cp <= 0x0000007F) {
 204                 rc = 1;
 205                 out[0] = (char)cp;
 206         } else if (cp <= 0x000007FF) {
 207                 rc = 2;
 208                 out[0] = (cp >> 6  & 31) | 192;
 209                 out[1] = (cp       & 63) | 128;
 210         } else if (cp <= 0x0000FFFF) {
 211                 rc = 3;
 212                 out[0] = (cp >> 12 & 15) | 224;
 213                 out[1] = (cp >> 6  & 63) | 128;
 214                 out[2] = (cp       & 63) | 128;
 215         } else if (cp <= 0x001FFFFF) {
 216                 rc = 4;
 217                 out[0] = (cp >> 18 & 7) | 240;
 218                 out[1] = (cp >> 12 & 63) | 128;
 219                 out[2] = (cp >> 6  & 63) | 128;
 220                 out[3] = (cp       & 63) | 128;
 221         } else if (cp <= 0x03FFFFFF) {
 222                 rc = 5;
 223                 out[0] = (cp >> 24 & 3) | 248;
 224                 out[1] = (cp >> 18 & 63) | 128;
 225                 out[2] = (cp >> 12 & 63) | 128;
 226                 out[3] = (cp >> 6  & 63) | 128;
 227                 out[4] = (cp       & 63) | 128;
 228         } else if (cp <= 0x7FFFFFFF) {
 229                 rc = 6;
 230                 out[0] = (cp >> 30 & 1) | 252;
 231                 out[1] = (cp >> 24 & 63) | 128;
 232                 out[2] = (cp >> 18 & 63) | 128;
 233                 out[3] = (cp >> 12 & 63) | 128;
 234                 out[4] = (cp >> 6  & 63) | 128;
 235                 out[5] = (cp       & 63) | 128;
 236         } else
 237                 return(0);
 238
 239         out[rc] = '\0';
 240         return((size_t)rc);
 241 }
 242
 243 /*
 244  * Normalise strings from the index and database.
 245  * These strings are escaped as defined by mandoc_char(7) along with
 246  * other goop in mandoc.h (e.g., soft hyphens).
 247  * This function normalises these into a nice UTF-8 string.
 248  * Returns 0 if the database is fucked.
 249  */
 250 static void
 251 norm_string(const char *val, const struct mchars *mc, char **buf)
 252 {
 253         size_t            sz, bsz;
 254         char              utfbuf[7];
 255         const char       *seq, *cpp;
 256         int               len, u, pos;
 257         enum mandoc_esc   esc;
 258         static const char res[] = { '\\', '\t',
 259                                 ASCII_NBRSP, ASCII_HYPH, '\0' };
 260
 261         /* Pre-allocate by the length of the input */
 262
 263         bsz = strlen(val) + 1;
 264         *buf = mandoc_realloc(*buf, bsz);
 265         pos = 0;
 266
 267         while ('\0' != *val) {
 268                 /*
 269                  * Halt on the first escape sequence.
 270                  * This also halts on the end of string, in which case
 271                  * we just copy, fallthrough, and exit the loop.
 272                  */
 273                 if ((sz = strcspn(val, res)) > 0) {
 274                         memcpy(&(*buf)[pos], val, sz);
 275                         pos += (int)sz;
 276                         val += (int)sz;
 277                 }
 278
 279                 if (ASCII_HYPH == *val) {
 280                         (*buf)[pos++] = '-';
 281                         val++;
 282                         continue;
 283                 } else if ('\t' == *val || ASCII_NBRSP == *val) {
 284                         (*buf)[pos++] = ' ';
 285                         val++;
 286                         continue;
 287                 } else if ('\\' != *val)
 288                         break;
 289
 290                 /* Read past the slash. */
 291
 292                 val++;
 293                 u = 0;
 294
 295                 /*
 296                  * Parse the escape sequence and see if it's a
 297                  * predefined character or special character.
 298                  */
 299
 300                 esc = mandoc_escape(&val, &seq, &len);
 301                 if (ESCAPE_ERROR == esc)
 302                         break;
 303
 304                 /*
 305                  * XXX - this just does UTF-8, but we need to know
 306                  * beforehand whether we should do text substitution.
 307                  */
 308
 309                 switch (esc) {
 310                 case (ESCAPE_SPECIAL):
 311                         if (0 != (u = mchars_spec2cp(mc, seq, len)))
 312                                 break;
 313                         /* FALLTHROUGH */
 314                 default:
 315                         continue;
 316                 }
 317
 318                 /*
 319                  * If we have a Unicode codepoint, try to convert that
 320                  * to a UTF-8 byte string.
 321                  */
 322
 323                 cpp = utfbuf;
 324                 if (0 == (sz = norm_utf8(u, utfbuf)))
 325                         continue;
 326
 327                 /* Copy the rendered glyph into the stream. */
 328
 329                 sz = strlen(cpp);
 330                 bsz += sz;
 331
 332                 *buf = mandoc_realloc(*buf, bsz);
 333
 334                 memcpy(&(*buf)[pos], cpp, sz);
 335                 pos += (int)sz;
 336         }
 337
 338         (*buf)[pos] = '\0';
 339 }
 340
 341 /*
 342  * Open the filename-index mandoc-db database.
 343  * Returns NULL if opening failed.
 344  */
 345 static DB *
 346 index_open(void)
 347 {
 348         DB              *db;
 349
 350         db = dbopen(MANDOC_IDX, O_RDONLY, 0, DB_RECNO, NULL);
 351         if (NULL != db)
 352                 return(db);
 353
 354         return(NULL);
 355 }
 356
 357 /*
 358  * Safely unpack from an index file record into the structure.
 359  * Returns 1 if an entry was unpacked, 0 if the database is insane.
 360  */
 361 static int
 362 index_read(const DBT *key, const DBT *val, int index,
 363                 const struct mchars *mc, struct rec *rec)
 364 {
 365         size_t           left;
 366         char            *np, *cp;
 367         char             type;
 368
 369 #define INDEX_BREAD(_dst) \
 370         do { \
 371                 if (NULL == (np = memchr(cp, '\0', left))) \
 372                         return(0); \
 373                 norm_string(cp, mc, &(_dst)); \
 374                 left -= (np - cp) + 1; \
 375                 cp = np + 1; \
 376         } while (/* CONSTCOND */ 0)
 377
 378         if (0 == (left = val->size))
 379                 return(0);
 380
 381         cp = val->data;
 382         assert(sizeof(recno_t) == key->size);
 383         memcpy(&rec->res.rec, key->data, key->size);
 384         rec->res.volume = index;
 385
 386         if ('d' == (type = *cp++))
 387                 rec->res.type = RESTYPE_MDOC;
 388         else if ('a' == type)
 389                 rec->res.type = RESTYPE_MAN;
 390         else if ('c' == type)
 391                 rec->res.type = RESTYPE_CAT;
 392         else
 393                 return(0);
 394
 395         left--;
 396         INDEX_BREAD(rec->res.file);
 397         INDEX_BREAD(rec->res.cat);
 398         INDEX_BREAD(rec->res.title);
 399         INDEX_BREAD(rec->res.arch);
 400         INDEX_BREAD(rec->res.desc);
 401         return(1);
 402 }
 403
 404 /*
 405  * Search mandocdb databases in paths for expression "expr".
 406  * Filter out by "opts".
 407  * Call "res" with the results, which may be zero.
 408  * Return 0 if there was a database error, else return 1.
 409  */
 410 int
 411 apropos_search(int pathsz, char **paths, const struct opts *opts,
 412                 const struct expr *expr, size_t terms, void *arg,
 413                 void (*res)(struct res *, size_t, void *))
 414 {
 415         struct rectree   tree;
 416         struct mchars   *mc;
 417         struct res      *ress;
 418         int              i, mlen, rc;
 419
 420         memset(&tree, 0, sizeof(struct rectree));
 421
 422         rc = 0;
 423         mc = mchars_alloc();
 424
 425         /*
 426          * Main loop.  Change into the directory containing manpage
 427          * databases.  Run our expession over each database in the set.
 428          */
 429
 430         for (i = 0; i < pathsz; i++) {
 431                 if (chdir(paths[i]))
 432                         continue;
 433                 if ( ! single_search(&tree, opts, expr, terms, mc, i))
 434                         goto out;
 435         }
 436
 437         /*
 438          * Count matching files, transfer to a "clean" array, then feed
 439          * them to the output handler.
 440          */
 441
 442         for (mlen = i = 0; i < tree.len; i++)
 443                 if (tree.node[i].matched)
 444                         mlen++;
 445
 446         ress = mandoc_malloc(mlen * sizeof(struct res));
 447
 448         for (mlen = i = 0; i < tree.len; i++)
 449                 if (tree.node[i].matched)
 450                         memcpy(&ress[mlen++], &tree.node[i].res,
 451                                         sizeof(struct res));
 452
 453         (*res)(ress, mlen, arg);
 454         free(ress);
 455
 456         rc = 1;
 457 out:
 458         for (i = 0; i < tree.len; i++)
 459                 recfree(&tree.node[i]);
 460
 461         free(tree.node);
 462         mchars_free(mc);
 463         return(rc);
 464 }
 465
 466 static int
 467 single_search(struct rectree *tree, const struct opts *opts,
 468                 const struct expr *expr, size_t terms,
 469                 struct mchars *mc, int vol)
 470 {
 471         int              root, leaf, ch;
 472         DBT              key, val;
 473         DB              *btree, *idx;
 474         char            *buf;
 475         struct rec      *rs;
 476         struct rec       r;
 477         uint64_t         mask;
 478         recno_t          rec;
 479
 480         root    = -1;
 481         leaf    = -1;
 482         btree   = NULL;
 483         idx     = NULL;
 484         buf     = NULL;
 485         rs      = tree->node;
 486
 487         memset(&r, 0, sizeof(struct rec));
 488
 489         if (NULL == (btree = btree_open()))
 490                 return(1);
 491
 492         if (NULL == (idx = index_open())) {
 493                 (*btree->close)(btree);
 494                 return(1);
 495         }
 496
 497         while (0 == (ch = (*btree->seq)(btree, &key, &val, R_NEXT))) {
 498                 if ( ! btree_read(&key, &val, mc, &mask, &rec, &buf))
 499                         break;
 500
 501                 /*
 502                  * See if this keyword record matches any of the
 503                  * expressions we have stored.
 504                  */
 505                 if ( ! exprmark(expr, buf, mask, NULL))
 506                         continue;
 507
 508                 /*
 509                  * O(log n) scan for prior records.  Since a record
 510                  * number is unbounded, this has decent performance over
 511                  * a complex hash function.
 512                  */
 513
 514                 for (leaf = root; leaf >= 0; )
 515                         if (rec > rs[leaf].res.rec &&
 516                                         rs[leaf].rhs >= 0)
 517                                 leaf = rs[leaf].rhs;
 518                         else if (rec < rs[leaf].res.rec &&
 519                                         rs[leaf].lhs >= 0)
 520                                 leaf = rs[leaf].lhs;
 521                         else
 522                                 break;
 523
 524                 /*
 525                  * If we find a record, see if it has already evaluated
 526                  * to true.  If it has, great, just keep going.  If not,
 527                  * try to evaluate it now and continue anyway.
 528                  */
 529
 530                 if (leaf >= 0 && rs[leaf].res.rec == rec) {
 531                         if (0 == rs[leaf].matched)
 532                                 exprexec(expr, buf, mask, &rs[leaf]);
 533                         continue;
 534                 }
 535
 536                 /*
 537                  * We have a new file to examine.
 538                  * Extract the manpage's metadata from the index
 539                  * database, then begin partial evaluation.
 540                  */
 541
 542                 key.data = &rec;
 543                 key.size = sizeof(recno_t);
 544
 545                 if (0 != (*idx->get)(idx, &key, &val, 0))
 546                         break;
 547
 548                 r.lhs = r.rhs = -1;
 549                 if ( ! index_read(&key, &val, vol, mc, &r))
 550                         break;
 551
 552                 /* XXX: this should be elsewhere, I guess? */
 553
 554                 if (opts->cat && strcasecmp(opts->cat, r.res.cat))
 555                         continue;
 556
 557                 if (opts->arch && *r.res.arch)
 558                         if (strcasecmp(opts->arch, r.res.arch))
 559                                 continue;
 560
 561                 tree->node = rs = mandoc_realloc
 562                         (rs, (tree->len + 1) * sizeof(struct rec));
 563
 564                 memcpy(&rs[tree->len], &r, sizeof(struct rec));
 565                 memset(&r, 0, sizeof(struct rec));
 566                 rs[tree->len].matches =
 567                         mandoc_calloc(terms, sizeof(int));
 568
 569                 exprexec(expr, buf, mask, &rs[tree->len]);
 570
 571                 /* Append to our tree. */
 572
 573                 if (leaf >= 0) {
 574                         if (rec > rs[leaf].res.rec)
 575                                 rs[leaf].rhs = tree->len;
 576                         else
 577                                 rs[leaf].lhs = tree->len;
 578                 } else
 579                         root = tree->len;
 580
 581                 tree->len++;
 582         }
 583
 584         (*btree->close)(btree);
 585         (*idx->close)(idx);
 586
 587         free(buf);
 588         recfree(&r);
 589         return(1 == ch);
 590 }
 591
 592 static void
 593 recfree(struct rec *rec)
 594 {
 595
 596         free(rec->res.file);
 597         free(rec->res.cat);
 598         free(rec->res.title);
 599         free(rec->res.arch);
 600         free(rec->res.desc);
 601
 602         free(rec->matches);
 603 }
 604
 605 /*
 606  * Compile a list of straight-up terms.
 607  * The arguments are re-written into ~[[:<:]]term[[:>:]], or "term"
 608  * surrounded by word boundaries, then pumped through exprterm().
 609  * Terms are case-insensitive.
 610  * This emulates whatis(1) behaviour.
 611  */
 612 struct expr *
 613 termcomp(int argc, char *argv[], size_t *tt)
 614 {
 615         char            *buf;
 616         int              pos;
 617         struct expr     *e, *next;
 618         size_t           sz;
 619
 620         buf = NULL;
 621         e = NULL;
 622         *tt = 0;
 623
 624         for (pos = argc - 1; pos >= 0; pos--) {
 625                 sz = strlen(argv[pos]) + 18;
 626                 buf = mandoc_realloc(buf, sz);
 627                 strlcpy(buf, "Nm~[[:<:]]", sz);
 628                 strlcat(buf, argv[pos], sz);
 629                 strlcat(buf, "[[:>:]]", sz);
 630                 if (NULL == (next = exprterm(buf, 0))) {
 631                         free(buf);
 632                         exprfree(e);
 633                         return(NULL);
 634                 }
 635                 next->next = e;
 636                 e = next;
 637                 (*tt)++;
 638         }
 639
 640         free(buf);
 641         return(e);
 642 }
 643
 644 /*
 645  * Compile a sequence of logical expressions.
 646  * See apropos.1 for a grammar of this sequence.
 647  */
 648 struct expr *
 649 exprcomp(int argc, char *argv[], size_t *tt)
 650 {
 651         int              pos, lvl;
 652         struct expr     *e;
 653
 654         pos = lvl = 0;
 655         *tt = 0;
 656
 657         e = exprexpr(argc, argv, &pos, &lvl, tt);
 658
 659         if (0 == lvl && pos >= argc)
 660                 return(e);
 661
 662         exprfree(e);
 663         return(NULL);
 664 }
 665
 666 /*
 667  * Compile an array of tokens into an expression.
 668  * An informal expression grammar is defined in apropos(1).
 669  * Return NULL if we fail doing so.  All memory will be cleaned up.
 670  * Return the root of the expression sequence if alright.
 671  */
 672 static struct expr *
 673 exprexpr(int argc, char *argv[], int *pos, int *lvl, size_t *tt)
 674 {
 675         struct expr     *e, *first, *next;
 676         int              log;
 677
 678         first = next = NULL;
 679
 680         for ( ; *pos < argc; (*pos)++) {
 681                 e = next;
 682
 683                 /*
 684                  * Close out a subexpression.
 685                  */
 686
 687                 if (NULL != e && 0 == strcmp(")", argv[*pos])) {
 688                         if (--(*lvl) < 0)
 689                                 goto err;
 690                         break;
 691                 }
 692
 693                 /*
 694                  * Small note: if we're just starting, don't let "-a"
 695                  * and "-o" be considered logical operators: they're
 696                  * just tokens unless pairwise joining, in which case we
 697                  * record their existence (or assume "OR").
 698                  */
 699                 log = 0;
 700
 701                 if (NULL != e && 0 == strcmp("-a", argv[*pos]))
 702                         log = 1;
 703                 else if (NULL != e && 0 == strcmp("-o", argv[*pos]))
 704                         log = 2;
 705
 706                 if (log > 0 && ++(*pos) >= argc)
 707                         goto err;
 708
 709                 /*
 710                  * Now we parse the term part.  This can begin with
 711                  * "-i", in which case the expression is case
 712                  * insensitive.
 713                  */
 714
 715                 if (0 == strcmp("(", argv[*pos])) {
 716                         ++(*pos);
 717                         ++(*lvl);
 718                         next = mandoc_calloc(1, sizeof(struct expr));
 719                         next->subexpr = exprexpr(argc, argv, pos, lvl, tt);
 720                         if (NULL == next->subexpr) {
 721                                 free(next);
 722                                 next = NULL;
 723                         }
 724                 } else if (0 == strcmp("-i", argv[*pos])) {
 725                         if (++(*pos) >= argc)
 726                                 goto err;
 727                         next = exprterm(argv[*pos], 0);
 728                 } else
 729                         next = exprterm(argv[*pos], 1);
 730
 731                 if (NULL == next)
 732                         goto err;
 733
 734                 next->and = log == 1;
 735                 next->index = (int)(*tt)++;
 736
 737                 /* Append to our chain of expressions. */
 738
 739                 if (NULL == first) {
 740                         assert(NULL == e);
 741                         first = next;
 742                 } else {
 743                         assert(NULL != e);
 744                         e->next = next;
 745                 }
 746         }
 747
 748         return(first);
 749 err:
 750         exprfree(first);
 751         return(NULL);
 752 }
 753
 754 /*
 755  * Parse a terminal expression with the grammar as defined in
 756  * apropos(1).
 757  * Return NULL if we fail the parse.
 758  */
 759 static struct expr *
 760 exprterm(char *buf, int cs)
 761 {
 762         struct expr      e;
 763         struct expr     *p;
 764         char            *key;
 765         int              i;
 766
 767         memset(&e, 0, sizeof(struct expr));
 768
 769         /* Choose regex or substring match. */
 770
 771         if (NULL == (e.v = strpbrk(buf, "=~"))) {
 772                 e.regex = 0;
 773                 e.v = buf;
 774         } else {
 775                 e.regex = '~' == *e.v;
 776                 *e.v++ = '\0';
 777         }
 778
 779         /* Determine the record types to search for. */
 780
 781         e.mask = 0;
 782         if (buf < e.v) {
 783                 while (NULL != (key = strsep(&buf, ","))) {
 784                         i = 0;
 785                         while (types[i].mask &&
 786                                         strcmp(types[i].name, key))
 787                                 i++;
 788                         e.mask |= types[i].mask;
 789                 }
 790         }
 791         if (0 == e.mask)
 792                 e.mask = TYPE_Nm | TYPE_Nd;
 793
 794         if (e.regex) {
 795                 i = REG_EXTENDED | REG_NOSUB | (cs ? 0 : REG_ICASE);
 796                 if (regcomp(&e.re, e.v, i))
 797                         return(NULL);
 798         }
 799
 800         e.v = mandoc_strdup(e.v);
 801
 802         p = mandoc_calloc(1, sizeof(struct expr));
 803         memcpy(p, &e, sizeof(struct expr));
 804         return(p);
 805 }
 806
 807 void
 808 exprfree(struct expr *p)
 809 {
 810         struct expr     *pp;
 811
 812         while (NULL != p) {
 813                 if (p->subexpr)
 814                         exprfree(p->subexpr);
 815                 if (p->regex)
 816                         regfree(&p->re);
 817                 free(p->v);
 818                 pp = p->next;
 819                 free(p);
 820                 p = pp;
 821         }
 822 }
 823
 824 static int
 825 exprmark(const struct expr *p, const char *cp,
 826                 uint64_t mask, int *ms)
 827 {
 828
 829         for ( ; p; p = p->next) {
 830                 if (p->subexpr) {
 831                         if (exprmark(p->subexpr, cp, mask, ms))
 832                                 return(1);
 833                         continue;
 834                 } else if ( ! (mask & p->mask))
 835                         continue;
 836
 837                 if (p->regex) {
 838                         if (regexec(&p->re, cp, 0, NULL, 0))
 839                                 continue;
 840                 } else if (NULL == strcasestr(cp, p->v))
 841                         continue;
 842
 843                 if (NULL == ms)
 844                         return(1);
 845                 else
 846                         ms[p->index] = 1;
 847         }
 848
 849         return(0);
 850 }
 851
 852 static int
 853 expreval(const struct expr *p, int *ms)
 854 {
 855         int              match;
 856
 857         /*
 858          * AND has precedence over OR.  Analysis is left-right, though
 859          * it doesn't matter because there are no side-effects.
 860          * Thus, step through pairwise ANDs and accumulate their Boolean
 861          * evaluation.  If we encounter a single true AND collection or
 862          * standalone term, the whole expression is true (by definition
 863          * of OR).
 864          */
 865
 866         for (match = 0; p && ! match; p = p->next) {
 867                 /* Evaluate a subexpression, if applicable. */
 868                 if (p->subexpr && ! ms[p->index])
 869                         ms[p->index] = expreval(p->subexpr, ms);
 870
 871                 match = ms[p->index];
 872                 for ( ; p->next && p->next->and; p = p->next) {
 873                         /* Evaluate a subexpression, if applicable. */
 874                         if (p->next->subexpr && ! ms[p->next->index])
 875                                 ms[p->next->index] =
 876                                         expreval(p->next->subexpr, ms);
 877                         match = match && ms[p->next->index];
 878                 }
 879         }
 880
 881         return(match);
 882 }
 883
 884 /*
 885  * First, update the array of terms for which this expression evaluates
 886  * to true.
 887  * Second, logically evaluate all terms over the updated array of truth
 888  * values.
 889  * If this evaluates to true, mark the expression as satisfied.
 890  */
 891 static void
 892 exprexec(const struct expr *e, const char *cp,
 893                 uint64_t mask, struct rec *r)
 894 {
 895
 896         assert(0 == r->matched);
 897         exprmark(e, cp, mask, r->matches);
 898         r->matched = expreval(e, r->matches);
 899 }