contrib/bsdtar/tree.c

   1 /*-
   2  * Copyright (c) 2003-2004 Tim Kientzle
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer
  10  *    in this position and unchanged.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 /*-
  28  * This is a new directory-walking system that addresses a number
  29  * of problems I've had with fts(3).  In particular, it has no
  30  * pathname-length limits (other than the size of 'int'), handles
  31  * deep logical traversals, uses considerably less memory, and has
  32  * an opaque interface (easier to modify in the future).
  33  *
  34  * Internally, it keeps a single list of "tree_entry" items that
  35  * represent filesystem objects that require further attention.
  36  * Non-directories are not kept in memory: they are pulled from
  37  * readdir(), returned to the client, then freed as soon as possible.
  38  * Any directory entry to be traversed gets pushed onto the stack.
  39  *
  40  * There is surprisingly little information that needs to be kept for
  41  * each item on the stack.  Just the name, depth (represented here as the
  42  * string length of the parent directory's pathname), and some markers
  43  * indicating how to get back to the parent (via chdir("..") for a
  44  * regular dir or via fchdir(2) for a symlink).
  45  */
  46 #include "bsdtar_platform.h"
  47 __FBSDID("$FreeBSD: src/usr.bin/tar/tree.c,v 1.1 2005/04/24 05:53:37 kientzle Exp $");
  48
  49 #include <sys/stat.h>
  50 #include <dirent.h>
  51 #include <errno.h>
  52 #include <fcntl.h>
  53 #include <stdlib.h>
  54 #include <string.h>
  55 #include <unistd.h>
  56
  57 #include "tree.h"
  58
  59 /*
  60  * TODO:
  61  *    1) Loop checking.
  62  *    3) Arbitrary logical traversals by closing/reopening intermediate fds.
  63  */
  64
  65 struct tree_entry {
  66         struct tree_entry *next;
  67         struct tree_entry *parent;
  68         char *name;
  69         size_t dirname_length;
  70         dev_t dev;
  71         ino_t ino;
  72         int fd;
  73         int flags;
  74 };
  75
  76 /* Definitions for tree_entry.flags bitmap. */
  77 #define isDir 1 /* This entry is a regular directory. */
  78 #define isDirLink 2 /* This entry is a symbolic link to a directory. */
  79 #define needsPreVisit 4 /* This entry needs to be previsited. */
  80 #define needsPostVisit 8 /* This entry needs to be postvisited. */
  81
  82 /*
  83  * Local data for this package.
  84  */
  85 struct tree {
  86         struct tree_entry       *stack;
  87         struct tree_entry       *current;
  88         DIR     *d;
  89         int      initialDirFd;
  90         int      flags;
  91         int      visit_type;
  92         int      tree_errno; /* Error code from last failed operation. */
  93
  94         char    *buff;
  95         const char      *basename;
  96         size_t   buff_length;
  97         size_t   path_length;
  98         size_t   dirname_length;
  99
 100         int      depth;
 101         int      openCount;
 102         int      maxOpenCount;
 103
 104         struct stat     lst;
 105         struct stat     st;
 106 };
 107
 108 /* Definitions for tree.flags bitmap. */
 109 #define needsReturn 8  /* Marks first entry as not having been returned yet. */
 110 #define hasStat 16  /* The st entry is set. */
 111 #define hasLstat 32 /* The lst entry is set. */
 112
 113
 114 #ifdef HAVE_DIRENT_D_NAMLEN
 115 /* BSD extension; avoids need for a strlen() call. */
 116 #define D_NAMELEN(dp)   (dp)->d_namlen
 117 #else
 118 #define D_NAMELEN(dp)   (strlen((dp)->d_name))
 119 #endif
 120
 121 #if 0
 122 #include <stdio.h>
 123 void
 124 tree_dump(struct tree *t, FILE *out)
 125 {
 126         struct tree_entry *te;
 127
 128         fprintf(out, "\tdepth: %d\n", t->depth);
 129         fprintf(out, "\tbuff: %s\n", t->buff);
 130         fprintf(out, "\tpwd: "); fflush(stdout); system("pwd");
 131         fprintf(out, "\taccess: %s\n", t->basename);
 132         fprintf(out, "\tstack:\n");
 133         for(te = t->stack; te != NULL; te = te->next) {
 134                 fprintf(out, "\t\tte->name: %s%s%s\n", te->name,
 135                     te->flags & needsPreVisit ? "" : " *",
 136                     t->current == te ? " (current)" : "");
 137         }
 138 }
 139 #endif
 140
 141 /*
 142  * Add a directory path to the current stack.
 143  */
 144 static void
 145 tree_push(struct tree *t, const char *path)
 146 {
 147         struct tree_entry *te;
 148
 149         te = malloc(sizeof(*te));
 150         memset(te, 0, sizeof(*te));
 151         te->next = t->stack;
 152         t->stack = te;
 153         te->fd = -1;
 154         te->name = strdup(path);
 155         te->flags = needsPreVisit | needsPostVisit;
 156         te->dirname_length = t->dirname_length;
 157 }
 158
 159 /*
 160  * Append a name to the current path.
 161  */
 162 static void
 163 tree_append(struct tree *t, const char *name, size_t name_length)
 164 {
 165         char *p;
 166
 167         if (t->buff != NULL)
 168                 t->buff[t->dirname_length] = '\0';
 169         /* Strip trailing '/' from name, unless entire name is "/". */
 170         while (name_length > 1 && name[name_length - 1] == '/')
 171                 name_length--;
 172
 173         /* Resize pathname buffer as needed. */
 174         while (name_length + 1 + t->dirname_length >= t->buff_length) {
 175                 t->buff_length *= 2;
 176                 if (t->buff_length < 1024)
 177                         t->buff_length = 1024;
 178                 t->buff = realloc(t->buff, t->buff_length);
 179         }
 180         p = t->buff + t->dirname_length;
 181         t->path_length = t->dirname_length + name_length;
 182         /* Add a separating '/' if it's needed. */
 183         if (t->dirname_length > 0 && p[-1] != '/') {
 184                 *p++ = '/';
 185                 t->path_length ++;
 186         }
 187         strncpy(p, name, name_length);
 188         p[name_length] = '\0';
 189         t->basename = p;
 190 }
 191
 192 /*
 193  * Open a directory tree for traversal.
 194  */
 195 struct tree *
 196 tree_open(const char *path)
 197 {
 198         struct tree *t;
 199
 200         t = malloc(sizeof(*t));
 201         memset(t, 0, sizeof(*t));
 202         tree_append(t, path, strlen(path));
 203         t->initialDirFd = open(".", O_RDONLY);
 204         /*
 205          * During most of the traversal, items are set up and then
 206          * returned immediately from tree_next().  That doesn't work
 207          * for the very first entry, so we set a flag for this special
 208          * case.
 209          */
 210         t->flags = needsReturn;
 211         return (t);
 212 }
 213
 214 /*
 215  * We've finished a directory; ascend back to the parent.
 216  */
 217 static void
 218 tree_ascend(struct tree *t)
 219 {
 220         struct tree_entry *te;
 221
 222         te = t->stack;
 223         t->depth--;
 224         if (te->flags & isDirLink) {
 225                 fchdir(te->fd);
 226                 close(te->fd);
 227                 t->openCount--;
 228         } else {
 229                 chdir("..");
 230         }
 231 }
 232
 233 /*
 234  * Pop the working stack.
 235  */
 236 static void
 237 tree_pop(struct tree *t)
 238 {
 239         struct tree_entry *te;
 240
 241         t->buff[t->dirname_length] = '\0';
 242         if (t->stack == t->current && t->current != NULL)
 243                 t->current = t->current->parent;
 244         te = t->stack;
 245         t->stack = te->next;
 246         t->dirname_length = te->dirname_length;
 247         t->basename = t->buff + t->dirname_length;
 248         /* Special case: starting dir doesn't skip leading '/'. */
 249         if (t->dirname_length > 0)
 250                 t->basename++;
 251         free(te->name);
 252         free(te);
 253 }
 254
 255 /*
 256  * Get the next item in the tree traversal.
 257  */
 258 int
 259 tree_next(struct tree *t)
 260 {
 261         struct dirent *de = NULL;
 262
 263         /* Handle the startup case by returning the initial entry. */
 264         if (t->flags & needsReturn) {
 265                 t->flags &= ~needsReturn;
 266                 return (t->visit_type = TREE_REGULAR);
 267         }
 268
 269         while (t->stack != NULL) {
 270                 /* If there's an open dir, get the next entry from there. */
 271                 while (t->d != NULL) {
 272                         de = readdir(t->d);
 273                         if (de == NULL) {
 274                                 closedir(t->d);
 275                                 t->d = NULL;
 276                         } else if (de->d_name[0] == '.'
 277                             && de->d_name[1] == '\0') {
 278                                 /* Skip '.' */
 279                         } else if (de->d_name[0] == '.'
 280                             && de->d_name[1] == '.'
 281                             && de->d_name[2] == '\0') {
 282                                 /* Skip '..' */
 283                         } else {
 284                                 /*
 285                                  * Append the path to the current path
 286                                  * and return it.
 287                                  */
 288                                 tree_append(t, de->d_name, D_NAMELEN(de));
 289                                 t->flags &= ~hasLstat;
 290                                 t->flags &= ~hasStat;
 291                                 return (t->visit_type = TREE_REGULAR);
 292                         }
 293                 }
 294
 295                 /* If the current dir needs to be visited, set it up. */
 296                 if (t->stack->flags & needsPreVisit) {
 297                         t->current = t->stack;
 298                         tree_append(t, t->stack->name, strlen(t->stack->name));
 299                         t->stack->flags &= ~needsPreVisit;
 300                         /* If it is a link, set up fd for the ascent. */
 301                         if (t->stack->flags & isDirLink) {
 302                                 t->stack->fd = open(".", O_RDONLY);
 303                                 t->openCount++;
 304                                 if (t->openCount > t->maxOpenCount)
 305                                         t->maxOpenCount = t->openCount;
 306                         }
 307                         t->dirname_length = t->path_length;
 308                         if (chdir(t->stack->name) != 0) {
 309                                 /* chdir() failed; return error */
 310                                 tree_pop(t);
 311                                 t->tree_errno = errno;
 312                                 return (t->visit_type = TREE_ERROR);
 313                         }
 314                         t->d = opendir(".");
 315                         if (t->d == NULL) {
 316                                 tree_pop(t);
 317                                 t->tree_errno = errno;
 318                                 return (t->visit_type = TREE_ERROR);
 319                         }
 320                         t->depth++;
 321                         t->flags &= ~hasLstat;
 322                         t->flags &= ~hasStat;
 323                         t->basename = ".";
 324                         return (t->visit_type = TREE_POSTDESCENT);
 325                 }
 326
 327                 /* We've done everything necessary for the top stack entry. */
 328                 if (t->stack->flags & needsPostVisit) {
 329                         tree_ascend(t);
 330                         tree_pop(t);
 331                         t->flags &= ~hasLstat;
 332                         t->flags &= ~hasStat;
 333                         return (t->visit_type = TREE_POSTASCENT);
 334                 }
 335         }
 336         return (t->visit_type = 0);
 337 }
 338
 339 /*
 340  * Return error code.
 341  */
 342 int
 343 tree_errno(struct tree *t)
 344 {
 345         return (t->tree_errno);
 346 }
 347
 348 /*
 349  * Called by the client to mark the directory just returned from
 350  * tree_next() as needing to be visited.
 351  */
 352 void
 353 tree_descend(struct tree *t)
 354 {
 355         if (t->visit_type != TREE_REGULAR)
 356                 return;
 357
 358         if (tree_current_is_physical_dir(t)) {
 359                 tree_push(t, t->basename);
 360                 t->stack->flags |= isDir;
 361         } else if (tree_current_is_dir(t)) {
 362                 tree_push(t, t->basename);
 363                 t->stack->flags |= isDirLink;
 364         }
 365 }
 366
 367 /*
 368  * Get the stat() data for the entry just returned from tree_next().
 369  */
 370 const struct stat *
 371 tree_current_stat(struct tree *t)
 372 {
 373         if (!(t->flags & hasStat)) {
 374                 if (stat(t->basename, &t->st) != 0)
 375                         return NULL;
 376                 t->flags |= hasStat;
 377         }
 378         return (&t->st);
 379 }
 380
 381 /*
 382  * Get the lstat() data for the entry just returned from tree_next().
 383  */
 384 const struct stat *
 385 tree_current_lstat(struct tree *t)
 386 {
 387         if (!(t->flags & hasLstat)) {
 388                 if (lstat(t->basename, &t->lst) != 0)
 389                         return NULL;
 390                 t->flags |= hasLstat;
 391         }
 392         return (&t->lst);
 393 }
 394
 395 /*
 396  * Test whether current entry is a dir or dir link.
 397  */
 398 int
 399 tree_current_is_dir(struct tree *t)
 400 {
 401         /* If we've already pulled stat(), just use that. */
 402         if (t->flags & hasStat)
 403                 return (S_ISDIR(tree_current_stat(t)->st_mode));
 404
 405         /* If we've already pulled lstat(), we may be able to use that. */
 406         if (t->flags & hasLstat) {
 407                 /* If lstat() says it's a dir, it must be a dir. */
 408                 if (S_ISDIR(tree_current_lstat(t)->st_mode))
 409                         return 1;
 410                 /* If it's not a dir and not a link, we're done. */
 411                 if (!S_ISLNK(tree_current_lstat(t)->st_mode))
 412                         return 0;
 413                 /*
 414                  * If the above two tests fail, then it's a link, but
 415                  * we don't know whether it's a link to a dir or a
 416                  * non-dir.
 417                  */
 418         }
 419
 420         /* TODO: Use a more efficient mechanism when available. */
 421         return (S_ISDIR(tree_current_stat(t)->st_mode));
 422 }
 423
 424 /*
 425  * Test whether current entry is a physical directory.
 426  */
 427 int
 428 tree_current_is_physical_dir(struct tree *t)
 429 {
 430         /* If we've already pulled lstat(), just use that. */
 431         if (t->flags & hasLstat)
 432                 return (S_ISDIR(tree_current_lstat(t)->st_mode));
 433
 434         /* TODO: Use a more efficient mechanism when available. */
 435         return (S_ISDIR(tree_current_lstat(t)->st_mode));
 436 }
 437
 438 /*
 439  * Test whether current entry is a symbolic link.
 440  */
 441 int
 442 tree_current_is_physical_link(struct tree *t)
 443 {
 444         /* If we've already pulled lstat(), just use that. */
 445         if (t->flags & hasLstat)
 446                 return (S_ISLNK(tree_current_lstat(t)->st_mode));
 447
 448         /* TODO: Use a more efficient mechanism when available. */
 449         return (S_ISLNK(tree_current_lstat(t)->st_mode));
 450 }
 451
 452 /*
 453  * Return the access path for the entry just returned from tree_next().
 454  */
 455 const char *
 456 tree_current_access_path(struct tree *t)
 457 {
 458         return (t->basename);
 459 }
 460
 461 /*
 462  * Return the full path for the entry just returned from tree_next().
 463  */
 464 const char *
 465 tree_current_path(struct tree *t)
 466 {
 467         return (t->buff);
 468 }
 469
 470 /*
 471  * Return the length of the path for the entry just returned from tree_next().
 472  */
 473 size_t
 474 tree_current_pathlen(struct tree *t)
 475 {
 476         return (t->path_length);
 477 }
 478
 479 /*
 480  * Return the nesting depth of the entry just returned from tree_next().
 481  */
 482 int
 483 tree_current_depth(struct tree *t)
 484 {
 485         return (t->depth);
 486 }
 487
 488 /*
 489  * Terminate the traversal and release any resources.
 490  */
 491 void
 492 tree_close(struct tree *t)
 493 {
 494         /* Release anything remaining in the stack. */
 495         while (t->stack != NULL)
 496                 tree_pop(t);
 497         if (t->buff)
 498                 free(t->buff);
 499         /* chdir() back to where we started. */
 500         if (t->initialDirFd >= 0) {
 501                 fchdir(t->initialDirFd);
 502                 close(t->initialDirFd);
 503                 t->initialDirFd = -1;
 504         }
 505         free(t);
 506 }