newlib/libc/unix/getcwd.c

   1 #ifndef _NO_GETCWD
   2 /*
   3  * Copyright (c) 1989, 1991 The Regents of the University of California.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  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  * 4. Neither the name of the University nor the names of its contributors
  15  *    may be used to endorse or promote products derived from this software
  16  *    without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  */
  30
  31 #if defined(LIBC_SCCS) && !defined(lint)
  32 static char sccsid[] = "@(#)getcwd.c    5.11 (Berkeley) 2/24/91";
  33 #endif /* LIBC_SCCS and not lint */
  34
  35 #include <sys/param.h>
  36 #include <sys/stat.h>
  37 #include <errno.h>
  38 #include <dirent.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #include <reent.h>
  44 #include <_syslist.h>
  45
  46 #define bcopy(a,b,c)    memmove (b,a,c)
  47
  48 #define ISDOT(dp) \
  49         (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
  50            (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
  51
  52 #ifndef _REENT_ONLY
  53
  54 char *
  55 getcwd (pt, size)
  56      char *pt;
  57      size_t size;
  58 {
  59   register struct dirent *dp;
  60   register DIR *dir = NULL;
  61   register dev_t dev;
  62   register ino_t ino;
  63   register int first;
  64   register char *bpt, *bup;
  65   struct stat s;
  66   dev_t root_dev;
  67   ino_t root_ino;
  68   size_t ptsize, upsize;
  69   int save_errno;
  70   char *ept, *eup, *up;
  71
  72   /*
  73    * If no buffer specified by the user, allocate one as necessary.
  74    * If a buffer is specified, the size has to be non-zero.  The path
  75    * is built from the end of the buffer backwards.
  76    */
  77
  78   if (pt)
  79     {
  80       ptsize = 0;
  81       if (!size)
  82         {
  83           errno = EINVAL;
  84           return (char *) NULL;
  85         }
  86       ept = pt + size;
  87     }
  88   else
  89     {
  90       if (!(pt = (char *) malloc (ptsize = 1024 - 4)))
  91         {
  92           return (char *) NULL;
  93         }
  94       ept = pt + ptsize;
  95     }
  96   bpt = ept - 1;
  97   *bpt = '\0';
  98
  99   /*
 100    * Allocate bytes (1024 - malloc space) for the string of "../"'s.
 101    * Should always be enough (it's 340 levels).  If it's not, allocate
 102    * as necessary.  Special * case the first stat, it's ".", not "..".
 103    */
 104
 105   if (!(up = (char *) malloc (upsize = 1024 - 4)))
 106     {
 107       goto err;
 108     }
 109   eup = up + MAXPATHLEN;
 110   bup = up;
 111   up[0] = '.';
 112   up[1] = '\0';
 113
 114   /* Save root values, so know when to stop. */
 115   if (stat ("/", &s))
 116     goto err;
 117   root_dev = s.st_dev;
 118   root_ino = s.st_ino;
 119
 120   errno = 0;                    /* XXX readdir has no error return. */
 121
 122   for (first = 1;; first = 0)
 123     {
 124       /* Stat the current level. */
 125       if (stat (up, &s))
 126         goto err;
 127
 128       /* Save current node values. */
 129       ino = s.st_ino;
 130       dev = s.st_dev;
 131
 132       /* Check for reaching root. */
 133       if (root_dev == dev && root_ino == ino)
 134         {
 135           *--bpt = '/';
 136           /*
 137            * It's unclear that it's a requirement to copy the
 138            * path to the beginning of the buffer, but it's always
 139            * been that way and stuff would probably break.
 140            */
 141           (void) bcopy (bpt, pt, ept - bpt);
 142           free (up);
 143           return pt;
 144         }
 145
 146       /*
 147        * Build pointer to the parent directory, allocating memory
 148        * as necessary.  Max length is 3 for "../", the largest
 149        * possible component name, plus a trailing NULL.
 150        */
 151
 152       if (bup + 3 + MAXNAMLEN + 1 >= eup)
 153         {
 154           if (!(up = (char *) realloc (up, upsize *= 2)))
 155             {
 156               goto err;
 157             }
 158           bup = up;
 159           eup = up + upsize;
 160         }
 161       *bup++ = '.';
 162       *bup++ = '.';
 163       *bup = '\0';
 164
 165       /* Open and stat parent directory. */
 166       if (!(dir = opendir (up)) || fstat (__dirfd (dir), &s))
 167         goto err;
 168
 169       /* Add trailing slash for next directory. */
 170       *bup++ = '/';
 171
 172       /*
 173        * If it's a mount point, have to stat each element because
 174        * the inode number in the directory is for the entry in the
 175        * parent directory, not the inode number of the mounted file.
 176        */
 177
 178       save_errno = 0;
 179       if (s.st_dev == dev)
 180         {
 181           for (;;)
 182             {
 183               if (!(dp = readdir (dir)))
 184                 goto notfound;
 185               if (dp->d_ino == ino)
 186                 break;
 187             }
 188         }
 189       else
 190         for (;;)
 191           {
 192             if (!(dp = readdir (dir)))
 193               goto notfound;
 194             if (ISDOT (dp))
 195               continue;
 196             bcopy (dp->d_name, bup, strlen (dp->d_name) + 1);
 197
 198             /* Save the first error for later. */
 199             if (stat (up, &s))
 200               {
 201                 if (!save_errno)
 202                   save_errno = errno;
 203                 errno = 0;
 204                 continue;
 205               }
 206             if (s.st_dev == dev && s.st_ino == ino)
 207               break;
 208           }
 209
 210       /*
 211        * Check for length of the current name, preceding slash,
 212        * leading slash.
 213        */
 214
 215       if (bpt - pt <= strlen (dp->d_name) + (first ? 1 : 2))
 216         {
 217           size_t len, off;
 218
 219           if (!ptsize)
 220             {
 221               errno = ERANGE;
 222               goto err;
 223             }
 224           off = bpt - pt;
 225           len = ept - bpt;
 226           if (!(pt = (char *) realloc (pt, ptsize *= 2)))
 227             {
 228               goto err;
 229             }
 230           bpt = pt + off;
 231           ept = pt + ptsize;
 232           (void) bcopy (bpt, ept - len, len);
 233           bpt = ept - len;
 234         }
 235       if (!first)
 236         *--bpt = '/';
 237       bpt -= strlen (dp->d_name);
 238       bcopy (dp->d_name, bpt, strlen (dp->d_name));
 239       (void) closedir (dir);
 240       dir = NULL;
 241
 242       /* Truncate any file name. */
 243       *bup = '\0';
 244     }
 245
 246 notfound:
 247   /*
 248    * If readdir set errno, use it, not any saved error; otherwise,
 249    * didn't find the current directory in its parent directory, set
 250    * errno to ENOENT.
 251    */
 252
 253   if (!errno)
 254     errno = save_errno ? save_errno : ENOENT;
 255   /* FALLTHROUGH */
 256
 257 err:
 258   if (ptsize)
 259     free (pt);
 260   if (dir)
 261     (void) closedir (dir);
 262   free (up);
 263   return (char *) NULL;
 264 }
 265
 266 #endif /* _REENT_ONLY */
 267 #endif /* !_NO_GETCWD  */