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emacs/lib/readlink.c

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/* Stub for readlink().
Copyright (C) 2003-2007, 2009-2017 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#if !HAVE_READLINK
/* readlink() substitute for systems that don't have a readlink() function,
such as DJGPP 2.03 and mingw32. */
ssize_t
readlink (const char *name, char *buf _GL_UNUSED,
size_t bufsize _GL_UNUSED)
{
struct stat statbuf;
/* In general we should use lstat() here, not stat(). But on platforms
without symbolic links, lstat() - if it exists - would be equivalent to
stat(), therefore we can use stat(). This saves us a configure check. */
if (stat (name, &statbuf) >= 0)
errno = EINVAL;
return -1;
}
#else /* HAVE_READLINK */
# undef readlink
/* readlink() wrapper that uses correct types, for systems like cygwin
1.5.x where readlink returns int, and which rejects trailing slash,
for Solaris 9. */
ssize_t
rpl_readlink (const char *name, char *buf, size_t bufsize)
{
# if READLINK_TRAILING_SLASH_BUG
size_t len = strlen (name);
if (len && name[len - 1] == '/')
{
/* Even if name without the slash is a symlink to a directory,
both lstat() and stat() must resolve the trailing slash to
the directory rather than the symlink. We can therefore
safely use stat() to distinguish between EINVAL and
ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat(). */
struct stat st;
if (stat (name, &st) == 0)
errno = EINVAL;
return -1;
}
# endif /* READLINK_TRAILING_SLASH_BUG */
return readlink (name, buf, bufsize);
}
#endif /* HAVE_READLINK */