find/tree.c

   1 /* tree.c -- helper functions to build and evaluate the expression tree.
   2    Copyright (C) 1990, 91, 92, 93, 94, 2000, 2003, 2004 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  17    USA.
  18 */
  19
  20 #include "defs.h"
  21 #include "../gnulib/lib/xalloc.h"
  22
  23 #if ENABLE_NLS
  24 # include <libintl.h>
  25 # define _(Text) gettext (Text)
  26 #else
  27 # define _(Text) Text
  28 #endif
  29 #ifdef gettext_noop
  30 # define N_(String) gettext_noop (String)
  31 #else
  32 /* See locate.c for explanation as to why not use (String) */
  33 # define N_(String) String
  34 #endif
  35
  36 static struct predicate *scan_rest PARAMS((struct predicate **input,
  37                                        struct predicate *head,
  38                                        short int prev_prec));
  39 static void merge_pred PARAMS((struct predicate *beg_list, struct predicate *end_list, struct predicate **last_p));
  40 static struct predicate *set_new_parent PARAMS((struct predicate *curr, enum predicate_precedence high_prec, struct predicate **prevp));
  41
  42 /* Return a pointer to a tree that represents the
  43    expression prior to non-unary operator *INPUT.
  44    Set *INPUT to point at the next input predicate node.
  45
  46    Only accepts the following:
  47
  48    <primary>
  49    expression           [operators of higher precedence]
  50    <uni_op><primary>
  51    (arbitrary expression)
  52    <uni_op>(arbitrary expression)
  53
  54    In other words, you can not start out with a bi_op or close_paren.
  55
  56    If the following operator (if any) is of a higher precedence than
  57    PREV_PREC, the expression just nabbed is part of a following
  58    expression, which really is the expression that should be handed to
  59    our caller, so get_expr recurses. */
  60
  61 struct predicate *
  62 get_expr (struct predicate **input, short int prev_prec)
  63 {
  64   struct predicate *next = NULL;
  65
  66   if (*input == NULL)
  67     error (1, 0, _("invalid expression"));
  68
  69   switch ((*input)->p_type)
  70     {
  71     case NO_TYPE:
  72       error (1, 0, _("invalid expression"));
  73       break;
  74
  75     case BI_OP:
  76       error (1, 0, _("invalid expression; you have used a binary operator with nothing before it."));
  77       break;
  78
  79     case CLOSE_PAREN:
  80       error (1, 0, _("invalid expression; you have too many ')'"));
  81       break;
  82
  83     case PRIMARY_TYPE:
  84       next = *input;
  85       *input = (*input)->pred_next;
  86       break;
  87
  88     case UNI_OP:
  89       next = *input;
  90       *input = (*input)->pred_next;
  91       next->pred_right = get_expr (input, NEGATE_PREC);
  92       break;
  93
  94     case OPEN_PAREN:
  95       *input = (*input)->pred_next;
  96       next = get_expr (input, NO_PREC);
  97       if ((*input == NULL)
  98           || ((*input)->p_type != CLOSE_PAREN))
  99         error (1, 0, _("invalid expression; I was expecting to find a ')' somewhere but did not see one."));
 100       *input = (*input)->pred_next;     /* move over close */
 101       break;
 102
 103     default:
 104       error (1, 0, _("oops -- invalid expression type!"));
 105       break;
 106     }
 107
 108   /* We now have the first expression and are positioned to check
 109      out the next operator.  If NULL, all done.  Otherwise, if
 110      PREV_PREC < the current node precedence, we must continue;
 111      the expression we just nabbed is more tightly bound to the
 112      following expression than to the previous one. */
 113   if (*input == NULL)
 114     return (next);
 115   if ((int) (*input)->p_prec > (int) prev_prec)
 116     {
 117       next = scan_rest (input, next, prev_prec);
 118       if (next == NULL)
 119         error (1, 0, _("invalid expression"));
 120     }
 121   return (next);
 122 }
 123 \f
 124 /* Scan across the remainder of a predicate input list starting
 125    at *INPUT, building the rest of the expression tree to return.
 126    Stop at the first close parenthesis or the end of the input list.
 127    Assumes that get_expr has been called to nab the first element
 128    of the expression tree.
 129
 130    *INPUT points to the current input predicate list element.
 131    It is updated as we move along the list to point to the
 132    terminating input element.
 133    HEAD points to the predicate element that was obtained
 134    by the call to get_expr.
 135    PREV_PREC is the precedence of the previous predicate element. */
 136
 137 static struct predicate *
 138 scan_rest (struct predicate **input,
 139            struct predicate *head,
 140            short int prev_prec)
 141 {
 142   struct predicate *tree;       /* The new tree we are building. */
 143
 144   if ((*input == NULL) || ((*input)->p_type == CLOSE_PAREN))
 145     return (NULL);
 146   tree = head;
 147   while ((*input != NULL) && ((int) (*input)->p_prec > (int) prev_prec))
 148     {
 149       switch ((*input)->p_type)
 150         {
 151         case NO_TYPE:
 152         case PRIMARY_TYPE:
 153         case UNI_OP:
 154         case OPEN_PAREN:
 155           /* I'm not sure how we get here, so it is not obvious what
 156            * sort of mistakes might give rise to this condition.
 157            */
 158           error (1, 0, _("invalid expression"));
 159           break;
 160
 161         case BI_OP:
 162           (*input)->pred_left = tree;
 163           tree = *input;
 164           *input = (*input)->pred_next;
 165           tree->pred_right = get_expr (input, tree->p_prec);
 166           break;
 167
 168         case CLOSE_PAREN:
 169           return tree;
 170
 171         default:
 172           error (1, 0,
 173                  _("oops -- invalid expression type (%d)!"),
 174                  (int)(*input)->p_type);
 175           break;
 176         }
 177     }
 178   return tree;
 179 }
 180 \f
 181 /* Optimize the ordering of the predicates in the tree.  Rearrange
 182    them to minimize work.  Strategies:
 183    * Evaluate predicates that don't need inode information first;
 184      the predicates are divided into 1 or more groups separated by
 185      predicates (if any) which have "side effects", such as printing.
 186      The grouping implements the partial ordering on predicates which
 187      those with side effects impose.
 188
 189    * Place -name, -iname, -path, -ipath, -regex and -iregex at the front
 190      of a group, with -name, -iname, -path and -ipath ahead of
 191      -regex and -iregex.  Predicates which are moved to the front
 192      of a group by definition do not have side effects.  Both
 193      -regex and -iregex both use pred_regex.
 194
 195      This routine "normalizes" the predicate tree by ensuring that
 196      all expression predicates have AND (or OR or COMMA) parent nodes
 197      which are linked along the left edge of the expression tree.
 198      This makes manipulation of subtrees easier.
 199
 200      EVAL_TREEP points to the root pointer of the predicate tree
 201      to be rearranged.  opt_expr may return a new root pointer there.
 202      Return true if the tree contains side effects, false if not. */
 203
 204 boolean
 205 opt_expr (struct predicate **eval_treep)
 206 {
 207   /* List of -name and -path predicates to move. */
 208   struct predicate *name_list = NULL;
 209   struct predicate *end_name_list = NULL;
 210   /* List of -regex predicates to move. */
 211   struct predicate *regex_list = NULL;
 212   struct predicate *end_regex_list = NULL;
 213   struct predicate *curr;
 214   struct predicate **prevp;     /* Address of `curr' node. */
 215   struct predicate **last_sidep; /* Last predicate with side effects. */
 216   PFB pred_func;
 217   enum predicate_type p_type;
 218   boolean has_side_effects = false; /* Return value. */
 219   enum predicate_precedence prev_prec, /* precedence of last BI_OP in branch */
 220                             biop_prec; /* topmost BI_OP precedence in branch */
 221
 222
 223   if (eval_treep == NULL || *eval_treep == NULL)
 224     return (false);
 225
 226   /* Set up to normalize tree as a left-linked list of ANDs or ORs.
 227      Set `curr' to the leftmost node, `prevp' to its address, and
 228      `pred_func' to the predicate type of its parent. */
 229   prevp = eval_treep;
 230   prev_prec = AND_PREC;
 231   curr = *prevp;
 232   while (curr->pred_left != NULL)
 233     {
 234       prevp = &curr->pred_left;
 235       prev_prec = curr->p_prec; /* must be a BI_OP */
 236       curr = curr->pred_left;
 237     }
 238
 239   /* Link in the appropriate BI_OP for the last expression, if needed. */
 240   if (curr->p_type != BI_OP)
 241     set_new_parent (curr, prev_prec, prevp);
 242
 243 #ifdef DEBUG
 244   /* Normalized tree. */
 245   fprintf (stderr, _("Normalized Eval Tree:\n"));
 246   print_tree (stderr, *eval_treep, 0);
 247 #endif
 248
 249   /* Rearrange the predicates. */
 250   prevp = eval_treep;
 251   biop_prec = NO_PREC; /* not COMMA_PREC */
 252   if ((*prevp) && (*prevp)->p_type == BI_OP)
 253     biop_prec = (*prevp)->p_prec;
 254   while ((curr = *prevp) != NULL)
 255     {
 256       /* If there is a BI_OP of different precedence from the first
 257          in the pred_left chain, create a new parent of the
 258          original precedence, link the new parent to the left of the
 259          previous and link CURR to the right of the new parent.
 260          This preserves the precedence of expressions in the tree
 261          in case we rearrange them. */
 262       if (curr->p_type == BI_OP)
 263         {
 264           if (curr->p_prec != biop_prec)
 265             curr = set_new_parent(curr, biop_prec, prevp);
 266         }
 267
 268       /* See which predicate type we have. */
 269       p_type = curr->pred_right->p_type;
 270       pred_func = curr->pred_right->pred_func;
 271
 272       switch (p_type)
 273         {
 274         case NO_TYPE:
 275         case PRIMARY_TYPE:
 276           /* Don't rearrange the arguments of the comma operator, it is
 277              not commutative.  */
 278           if (biop_prec == COMMA_PREC)
 279             break;
 280
 281           /* If it's one of our special primaries, move it to the
 282              front of the list for that primary. */
 283           if (pred_func == pred_name || pred_func == pred_path ||
 284               pred_func == pred_iname || pred_func == pred_ipath)
 285             {
 286               *prevp = curr->pred_left;
 287               curr->pred_left = name_list;
 288               name_list = curr;
 289
 290               if (end_name_list == NULL)
 291                 end_name_list = curr;
 292
 293               continue;
 294             }
 295
 296           if (pred_func == pred_regex)
 297             {
 298               *prevp = curr->pred_left;
 299               curr->pred_left = regex_list;
 300               regex_list = curr;
 301
 302               if (end_regex_list == NULL)
 303                 end_regex_list = curr;
 304
 305               continue;
 306             }
 307
 308           break;
 309
 310         case UNI_OP:
 311           /* For NOT, check the expression trees below the NOT. */
 312           curr->pred_right->side_effects
 313             = opt_expr (&curr->pred_right->pred_right);
 314           break;
 315
 316         case BI_OP:
 317           /* For nested AND or OR, recurse (AND/OR form layers on the left of
 318              the tree), and continue scanning this level of AND or OR. */
 319           curr->pred_right->side_effects = opt_expr (&curr->pred_right);
 320           break;
 321
 322           /* At this point, get_expr and scan_rest have already removed
 323              all of the user's parentheses. */
 324
 325         default:
 326           error (1, 0, _("oops -- invalid expression type!"));
 327           break;
 328         }
 329
 330       if (curr->pred_right->side_effects == true)
 331         {
 332           last_sidep = prevp;
 333
 334           /* Incorporate lists and reset list pointers for this group.  */
 335           if (name_list != NULL)
 336             {
 337               merge_pred (name_list, end_name_list, last_sidep);
 338               name_list = end_name_list = NULL;
 339             }
 340
 341           if (regex_list != NULL)
 342             {
 343               merge_pred (regex_list, end_regex_list, last_sidep);
 344               regex_list = end_regex_list = NULL;
 345             }
 346
 347           has_side_effects = true;
 348         }
 349
 350       prevp = &curr->pred_left;
 351     }
 352
 353   /* Do final list merges. */
 354   last_sidep = prevp;
 355   if (name_list != NULL)
 356     merge_pred (name_list, end_name_list, last_sidep);
 357   if (regex_list != NULL)
 358     merge_pred (regex_list, end_regex_list, last_sidep);
 359
 360   return (has_side_effects);
 361 }
 362
 363 /* Link in a new parent BI_OP node for CURR, at *PREVP, with precedence
 364    HIGH_PREC. */
 365
 366 static struct predicate *
 367 set_new_parent (struct predicate *curr, enum predicate_precedence high_prec, struct predicate **prevp)
 368 {
 369   struct predicate *new_parent;
 370
 371   new_parent = (struct predicate *) xmalloc (sizeof (struct predicate));
 372   new_parent->p_type = BI_OP;
 373   new_parent->p_prec = high_prec;
 374   new_parent->need_stat = false;
 375
 376   switch (high_prec)
 377     {
 378     case COMMA_PREC:
 379       new_parent->pred_func = pred_comma;
 380       break;
 381     case OR_PREC:
 382       new_parent->pred_func = pred_or;
 383       break;
 384     case AND_PREC:
 385       new_parent->pred_func = pred_and;
 386       break;
 387     default:
 388       ;                         /* empty */
 389     }
 390
 391   new_parent->side_effects = false;
 392   new_parent->no_default_print = false;
 393   new_parent->args.str = NULL;
 394   new_parent->pred_next = NULL;
 395
 396   /* Link in new_parent.
 397      Pushes rest of left branch down 1 level to new_parent->pred_right. */
 398   new_parent->pred_left = NULL;
 399   new_parent->pred_right = curr;
 400   *prevp = new_parent;
 401
 402 #ifdef  DEBUG
 403   new_parent->p_name = (char *) find_pred_name (new_parent->pred_func);
 404 #endif /* DEBUG */
 405
 406   return (new_parent);
 407 }
 408
 409 /* Merge the predicate list that starts at BEG_LIST and ends at END_LIST
 410    into the tree at LAST_P. */
 411
 412 static void
 413 merge_pred (struct predicate *beg_list, struct predicate *end_list, struct predicate **last_p)
 414 {
 415   end_list->pred_left = *last_p;
 416   *last_p = beg_list;
 417 }
 418 \f
 419 /* Find the first node in expression tree TREE that requires
 420    a stat call and mark the operator above it as needing a stat
 421    before calling the node.   Since the expression precedences
 422    are represented in the tree, some preds that need stat may not
 423    get executed (because the expression value is determined earlier.)
 424    So every expression needing stat must be marked as such, not just
 425    the earliest, to be sure to obtain the stat.  This still guarantees
 426    that a stat is made as late as possible.  Return true if the top node
 427    in TREE requires a stat, false if not. */
 428
 429 boolean
 430 mark_stat (struct predicate *tree)
 431 {
 432   /* The tree is executed in-order, so walk this way (apologies to Aerosmith)
 433      to find the first predicate for which the stat is needed. */
 434   switch (tree->p_type)
 435     {
 436     case NO_TYPE:
 437     case PRIMARY_TYPE:
 438       return tree->need_stat;
 439
 440     case UNI_OP:
 441       if (mark_stat (tree->pred_right))
 442         tree->need_stat = true;
 443       return (false);
 444
 445     case BI_OP:
 446       /* ANDs and ORs are linked along ->left ending in NULL. */
 447       if (tree->pred_left != NULL)
 448         mark_stat (tree->pred_left);
 449
 450       if (mark_stat (tree->pred_right))
 451         tree->need_stat = true;
 452
 453       return (false);
 454
 455     default:
 456       error (1, 0, _("oops -- invalid expression type!"));
 457       return (false);
 458     }
 459 }