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getcwd.c
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getcwd.c
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/*
* Copyright (c) 1989, 1991, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jan-Simon Pendry.
*
* 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 8.5 (Berkeley) 2/7/95";
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static char *getcwd_physical __P((char *, size_t));
#define ISDOT(dp) \
(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
char *
getcwd(pt, size)
char *pt;
size_t size;
{
char *pwd;
size_t pwdlen;
dev_t dev;
ino_t ino;
struct stat s;
/* Check $PWD -- if it's right, it's fast. */
if ((pwd = getenv("PWD")) != NULL && pwd[0] == '/' && !stat(pwd, &s)) {
dev = s.st_dev;
ino = s.st_ino;
if (!stat(".", &s) && dev == s.st_dev && ino == s.st_ino) {
pwdlen = strlen(pwd);
if (size != 0) {
if (pwdlen + 1 > size) {
errno = ERANGE;
return (NULL);
}
} else if ((pt = malloc(pwdlen + 1)) == NULL)
return (NULL);
memmove(pt, pwd, pwdlen);
pt[pwdlen] = '\0';
return (pt);
}
}
return (getcwd_physical(pt, size));
}
/*
* char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
*
* Find the real name of path, by removing all ".", ".." and symlink
* components. Returns (resolved) on success, or (NULL) on failure,
* in which case the path which caused trouble is left in (resolved).
*/
char *
realpath(path, resolved)
const char *path;
char *resolved;
{
struct stat sb;
int fd, n, rootd, serrno;
char *p, *q, wbuf[MAXPATHLEN];
/* Save the starting point. */
if ((fd = open(".", O_RDONLY)) < 0) {
(void)strcpy(resolved, ".");
return (NULL);
}
/*
* Find the dirname and basename from the path to be resolved.
* Change directory to the dirname component.
* lstat the basename part.
* if it is a symlink, read in the value and loop.
* if it is a directory, then change to that directory.
* get the current directory name and append the basename.
*/
(void)strncpy(resolved, path, MAXPATHLEN - 1);
resolved[MAXPATHLEN - 1] = '\0';
loop:
q = strrchr(resolved, '/');
if (q != NULL) {
p = q + 1;
if (q == resolved)
q = "/";
else {
do {
--q;
} while (q > resolved && *q == '/');
q[1] = '\0';
q = resolved;
}
if (chdir(q) < 0)
goto err1;
} else
p = resolved;
/* Deal with the last component. */
if (lstat(p, &sb) == 0) {
if (S_ISLNK(sb.st_mode)) {
n = readlink(p, resolved, MAXPATHLEN);
if (n < 0)
goto err1;
resolved[n] = '\0';
goto loop;
}
if (S_ISDIR(sb.st_mode)) {
if (chdir(p) < 0)
goto err1;
p = "";
}
}
/*
* Save the last component name and get the full pathname of
* the current directory.
*/
(void)strcpy(wbuf, p);
/*
* Call the inernal internal version of getcwd which
* does a physical search rather than using the $PWD short-cut
*/
if (getcwd_physical(resolved, MAXPATHLEN) == 0)
goto err1;
/*
* Join the two strings together, ensuring that the right thing
* happens if the last component is empty, or the dirname is root.
*/
if (resolved[0] == '/' && resolved[1] == '\0')
rootd = 1;
else
rootd = 0;
if (*wbuf) {
if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
errno = ENAMETOOLONG;
goto err1;
}
if (rootd == 0)
(void)strcat(resolved, "/");
(void)strcat(resolved, wbuf);
}
/* Go back to where we came from. */
if (fchdir(fd) < 0) {
serrno = errno;
goto err2;
}
/* It's okay if the close fails, what's an fd more or less? */
(void)close(fd);
return (resolved);
err1: serrno = errno;
(void)fchdir(fd);
err2: (void)close(fd);
errno = serrno;
return (NULL);
}
static char *
getcwd_physical(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 (NULL);
}
ept = pt + size;
} else {
if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
return (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 = malloc(upsize = 1024 - 4)) == NULL)
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 (lstat(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 = realloc(up, upsize *= 2)) == NULL)
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_fileno == ino)
break;
}
} else
for (;;) {
if (!(dp = readdir(dir)))
goto notfound;
if (ISDOT(dp))
continue;
bcopy(dp->d_name, bup, dp->d_namlen + 1);
/* Save the first error for later. */
if (lstat(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 <= dp->d_namlen + (first ? 1 : 2)) {
size_t len, off;
if (!ptsize) {
errno = ERANGE;
goto err;
}
off = bpt - pt;
len = ept - bpt;
if ((pt = realloc(pt, ptsize *= 2)) == NULL)
goto err;
bpt = pt + off;
ept = pt + ptsize;
(void)bcopy(bpt, ept - len, len);
bpt = ept - len;
}
if (!first)
*--bpt = '/';
bpt -= dp->d_namlen;
bcopy(dp->d_name, bpt, dp->d_namlen);
(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 (NULL);
}