source: trunk/libs/newlib/src/newlib/libc/unix/getcwd.c @ 577

#ifndef _NO_GETCWD
/*
 * Copyright (c) 1989, 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)getcwd.c    5.11 (Berkeley) 2/24/91";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <reent.h>
#include <_syslist.h>

#define bcopy(a,b,c)    memmove (b,a,c)

#define ISDOT(dp) \
        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
           (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))

#ifndef _REENT_ONLY

char *
getcwd (pt, size)
     char *pt;
     size_t size;
{
  register struct dirent *dp;
  register DIR *dir = NULL;
  register dev_t dev;
  register ino_t ino;
  register int first;
  register char *bpt, *bup;
  struct stat s;
  dev_t root_dev;
  ino_t root_ino;
  size_t ptsize, upsize;
  int save_errno;
  char *ept, *eup, *up;

  /*
   * If no buffer specified by the user, allocate one as necessary.
   * If a buffer is specified, the size has to be non-zero.  The path
   * is built from the end of the buffer backwards.
   */

  if (pt)
    {
      ptsize = 0;
      if (!size)
        {
          errno = EINVAL;
          return (char *) NULL;
        }
      ept = pt + size;
    }
  else
    {
      if (!(pt = (char *) malloc (ptsize = 1024 - 4)))
        {
          return (char *) NULL;
        }
      ept = pt + ptsize;
    }
  bpt = ept - 1;
  *bpt = '\0';

  /*
   * Allocate bytes (1024 - malloc space) for the string of "../"'s.
   * Should always be enough (it's 340 levels).  If it's not, allocate
   * as necessary.  Special * case the first stat, it's ".", not "..".
   */

  if (!(up = (char *) malloc (upsize = 1024 - 4)))
    {
      goto err;
    }
  eup = up + MAXPATHLEN;
  bup = up;
  up[0] = '.';
  up[1] = '\0';

  /* Save root values, so know when to stop. */
  if (stat ("/", &s))
    goto err;
  root_dev = s.st_dev;
  root_ino = s.st_ino;

  errno = 0;                    /* XXX readdir has no error return. */

  for (first = 1;; first = 0)
    {
      /* Stat the current level. */
      if (stat (up, &s))
        goto err;

      /* Save current node values. */
      ino = s.st_ino;
      dev = s.st_dev;

      /* Check for reaching root. */
      if (root_dev == dev && root_ino == ino)
        {
          *--bpt = '/';
          /*
           * It's unclear that it's a requirement to copy the
           * path to the beginning of the buffer, but it's always
           * been that way and stuff would probably break.
           */
          (void) bcopy (bpt, pt, ept - bpt);
          free (up);
          return pt;
        }

      /*
       * Build pointer to the parent directory, allocating memory
       * as necessary.  Max length is 3 for "../", the largest
       * possible component name, plus a trailing NULL.
       */

      if (bup + 3 + MAXNAMLEN + 1 >= eup)
        {
          if (!(up = (char *) realloc (up, upsize *= 2)))
            {
              goto err;
            }
          bup = up;
          eup = up + upsize;
        }
      *bup++ = '.';
      *bup++ = '.';
      *bup = '\0';

      /* Open and stat parent directory. */
      if (!(dir = opendir (up)) || fstat (__dirfd (dir), &s))
        goto err;

      /* Add trailing slash for next directory. */
      *bup++ = '/';

      /*
       * If it's a mount point, have to stat each element because
       * the inode number in the directory is for the entry in the
       * parent directory, not the inode number of the mounted file.
       */

      save_errno = 0;
      if (s.st_dev == dev)
        {
          for (;;)
            {
              if (!(dp = readdir (dir)))
                goto notfound;
              if (dp->d_ino == ino)
                break;
            }
        }
      else
        for (;;)
          {
            if (!(dp = readdir (dir)))
              goto notfound;
            if (ISDOT (dp))
              continue;
            bcopy (dp->d_name, bup, strlen (dp->d_name) + 1);

            /* Save the first error for later. */
            if (stat (up, &s))
              {
                if (!save_errno)
                  save_errno = errno;
                errno = 0;
                continue;
              }
            if (s.st_dev == dev && s.st_ino == ino)
              break;
          }

      /*
       * Check for length of the current name, preceding slash,
       * leading slash.
       */

      if (bpt - pt <= strlen (dp->d_name) + (first ? 1 : 2))
        {
          size_t len, off;

          if (!ptsize)
            {
              errno = ERANGE;
              goto err;
            }
          off = bpt - pt;
          len = ept - bpt;
          if (!(pt = (char *) realloc (pt, ptsize *= 2)))
            {
              goto err;
            }
          bpt = pt + off;
          ept = pt + ptsize;
          (void) bcopy (bpt, ept - len, len);
          bpt = ept - len;
        }
      if (!first)
        *--bpt = '/';
      bpt -= strlen (dp->d_name);
      bcopy (dp->d_name, bpt, strlen (dp->d_name));
      (void) closedir (dir);
      dir = NULL;

      /* Truncate any file name. */
      *bup = '\0';
    }

notfound:
  /*
   * If readdir set errno, use it, not any saved error; otherwise,
   * didn't find the current directory in its parent directory, set
   * errno to ENOENT.
   */

  if (!errno)
    errno = save_errno ? save_errno : ENOENT;
  /* FALLTHROUGH */

err:
  if (ptsize)
    free (pt);
  if (dir)
    (void) closedir (dir);
  free (up);
  return (char *) NULL;
}

#endif /* _REENT_ONLY */
#endif /* !_NO_GETCWD  */