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      1 /*	$OpenBSD: getcwd.c,v 1.14 2005/08/08 08:05:34 espie Exp */
      2 /*
      3  * Copyright (c) 1989, 1991, 1993
      4  *	The Regents of the University of California.  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  * 3. 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 /* OPENBSD ORIGINAL: lib/libc/gen/getcwd.c */
     32 
     33 #include "includes.h"
     34 
     35 #if !defined(HAVE_GETCWD)
     36 
     37 #include <sys/param.h>
     38 #include <sys/stat.h>
     39 #include <errno.h>
     40 #include <dirent.h>
     41 #include <sys/dir.h>
     42 #include <stdio.h>
     43 #include <stdlib.h>
     44 #include <string.h>
     45 #include "includes.h"
     46 
     47 #define	ISDOT(dp) \
     48 	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
     49 	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
     50 
     51 char *
     52 getcwd(char *pt, size_t size)
     53 {
     54 	struct dirent *dp;
     55 	DIR *dir = NULL;
     56 	dev_t dev;
     57 	ino_t ino;
     58 	int first;
     59 	char *bpt, *bup;
     60 	struct stat s;
     61 	dev_t root_dev;
     62 	ino_t root_ino;
     63 	size_t ptsize, upsize;
     64 	int save_errno;
     65 	char *ept, *eup, *up;
     66 
     67 	/*
     68 	 * If no buffer specified by the user, allocate one as necessary.
     69 	 * If a buffer is specified, the size has to be non-zero.  The path
     70 	 * is built from the end of the buffer backwards.
     71 	 */
     72 	if (pt) {
     73 		ptsize = 0;
     74 		if (!size) {
     75 			errno = EINVAL;
     76 			return (NULL);
     77 		}
     78 		ept = pt + size;
     79 	} else {
     80 		if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
     81 			return (NULL);
     82 		ept = pt + ptsize;
     83 	}
     84 	bpt = ept - 1;
     85 	*bpt = '\0';
     86 
     87 	/*
     88 	 * Allocate bytes for the string of "../"'s.
     89 	 * Should always be enough (it's 340 levels).  If it's not, allocate
     90 	 * as necessary.  Special * case the first stat, it's ".", not "..".
     91 	 */
     92 	if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
     93 		goto err;
     94 	eup = up + upsize;
     95 	bup = up;
     96 	up[0] = '.';
     97 	up[1] = '\0';
     98 
     99 	/* Save root values, so know when to stop. */
    100 	if (stat("/", &s))
    101 		goto err;
    102 	root_dev = s.st_dev;
    103 	root_ino = s.st_ino;
    104 
    105 	errno = 0;			/* XXX readdir has no error return. */
    106 
    107 	for (first = 1;; first = 0) {
    108 		/* Stat the current level. */
    109 		if (lstat(up, &s))
    110 			goto err;
    111 
    112 		/* Save current node values. */
    113 		ino = s.st_ino;
    114 		dev = s.st_dev;
    115 
    116 		/* Check for reaching root. */
    117 		if (root_dev == dev && root_ino == ino) {
    118 			*--bpt = '/';
    119 			/*
    120 			 * It's unclear that it's a requirement to copy the
    121 			 * path to the beginning of the buffer, but it's always
    122 			 * been that way and stuff would probably break.
    123 			 */
    124 			memmove(pt, bpt, ept - bpt);
    125 			free(up);
    126 			return (pt);
    127 		}
    128 
    129 		/*
    130 		 * Build pointer to the parent directory, allocating memory
    131 		 * as necessary.  Max length is 3 for "../", the largest
    132 		 * possible component name, plus a trailing NUL.
    133 		 */
    134 		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
    135 			char *nup;
    136 
    137 			if ((nup = realloc(up, upsize *= 2)) == NULL)
    138 				goto err;
    139 			bup = nup + (bup - up);
    140 			up = nup;
    141 			eup = up + upsize;
    142 		}
    143 		*bup++ = '.';
    144 		*bup++ = '.';
    145 		*bup = '\0';
    146 
    147 		/* Open and stat parent directory. */
    148 		if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
    149 			goto err;
    150 
    151 		/* Add trailing slash for next directory. */
    152 		*bup++ = '/';
    153 
    154 		/*
    155 		 * If it's a mount point, have to stat each element because
    156 		 * the inode number in the directory is for the entry in the
    157 		 * parent directory, not the inode number of the mounted file.
    158 		 */
    159 		save_errno = 0;
    160 		if (s.st_dev == dev) {
    161 			for (;;) {
    162 				if (!(dp = readdir(dir)))
    163 					goto notfound;
    164 				if (dp->d_fileno == ino)
    165 					break;
    166 			}
    167 		} else
    168 			for (;;) {
    169 				if (!(dp = readdir(dir)))
    170 					goto notfound;
    171 				if (ISDOT(dp))
    172 					continue;
    173 				memcpy(bup, dp->d_name, dp->d_namlen + 1);
    174 
    175 				/* Save the first error for later. */
    176 				if (lstat(up, &s)) {
    177 					if (!save_errno)
    178 						save_errno = errno;
    179 					errno = 0;
    180 					continue;
    181 				}
    182 				if (s.st_dev == dev && s.st_ino == ino)
    183 					break;
    184 			}
    185 
    186 		/*
    187 		 * Check for length of the current name, preceding slash,
    188 		 * leading slash.
    189 		 */
    190 		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
    191 			size_t len;
    192 			char *npt;
    193 
    194 			if (!ptsize) {
    195 				errno = ERANGE;
    196 				goto err;
    197 			}
    198 			len = ept - bpt;
    199 			if ((npt = realloc(pt, ptsize *= 2)) == NULL)
    200 				goto err;
    201 			bpt = npt + (bpt - pt);
    202 			pt = npt;
    203 			ept = pt + ptsize;
    204 			memmove(ept - len, bpt, len);
    205 			bpt = ept - len;
    206 		}
    207 		if (!first)
    208 			*--bpt = '/';
    209 		bpt -= dp->d_namlen;
    210 		memcpy(bpt, dp->d_name, dp->d_namlen);
    211 		(void)closedir(dir);
    212 
    213 		/* Truncate any file name. */
    214 		*bup = '\0';
    215 	}
    216 
    217 notfound:
    218 	/*
    219 	 * If readdir set errno, use it, not any saved error; otherwise,
    220 	 * didn't find the current directory in its parent directory, set
    221 	 * errno to ENOENT.
    222 	 */
    223 	if (!errno)
    224 		errno = save_errno ? save_errno : ENOENT;
    225 	/* FALLTHROUGH */
    226 err:
    227 	save_errno = errno;
    228 
    229 	if (ptsize)
    230 		free(pt);
    231 	free(up);
    232 	if (dir)
    233 		(void)closedir(dir);
    234 
    235 	errno = save_errno;
    236 
    237 	return (NULL);
    238 }
    239 
    240 #endif /* !defined(HAVE_GETCWD) */
    241