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/*

 * 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.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *      This product includes software developed by the University of

 *      California, Berkeley and its contributors.

 * 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/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;

  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);

      /* 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);

  free (up);

  return (char *) NULL;

}

#endif /* _REENT_ONLY */