105 lines
3.1 KiB
C
105 lines
3.1 KiB
C
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/* Read the contents of a symbolic link.
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Copyright (C) 2003-2007, 2009-2022 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/stat.h>
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#if !HAVE_READLINK
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/* readlink() substitute for systems that don't have a readlink() function,
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such as DJGPP 2.03 and mingw32. */
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ssize_t
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readlink (char const *file, _GL_UNUSED char *buf,
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_GL_UNUSED size_t bufsize)
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{
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struct stat statbuf;
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/* In general we should use lstat() here, not stat(). But on platforms
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without symbolic links, lstat() - if it exists - would be equivalent to
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stat(), therefore we can use stat(). This saves us a configure check. */
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if (stat (file, &statbuf) >= 0)
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errno = EINVAL;
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return -1;
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}
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#else /* HAVE_READLINK */
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# undef readlink
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/* readlink() wrapper that uses correct types, for systems like cygwin
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1.5.x where readlink returns int, and which rejects trailing slash,
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for Solaris 9. */
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ssize_t
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rpl_readlink (char const *file, char *buf, size_t bufsize)
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{
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# if READLINK_TRAILING_SLASH_BUG
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size_t file_len = strlen (file);
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if (file_len && file[file_len - 1] == '/')
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{
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/* Even if FILE without the slash is a symlink to a directory,
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both lstat() and stat() must resolve the trailing slash to
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the directory rather than the symlink. We can therefore
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safely use stat() to distinguish between EINVAL and
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ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat(). */
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struct stat st;
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if (stat (file, &st) == 0 || errno == EOVERFLOW)
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errno = EINVAL;
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return -1;
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}
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# endif /* READLINK_TRAILING_SLASH_BUG */
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ssize_t r = readlink (file, buf, bufsize);
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# if READLINK_TRUNCATE_BUG
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if (r < 0 && errno == ERANGE)
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{
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/* Try again with a bigger buffer. This is just for test cases;
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real code invariably discards short reads. */
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char stackbuf[4032];
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r = readlink (file, stackbuf, sizeof stackbuf);
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if (r < 0)
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{
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if (errno == ERANGE)
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{
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/* Clear the buffer, which is good enough for real code.
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Thankfully, no test cases try short reads of enormous
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symlinks and what would be the point anyway? */
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r = bufsize;
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memset (buf, 0, r);
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}
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}
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else
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{
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if (bufsize < r)
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r = bufsize;
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memcpy (buf, stackbuf, r);
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}
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}
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# endif
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return r;
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}
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#endif /* HAVE_READLINK */
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