| /* Read the contents of a symbolic link. | |
| Copyright (C) 2003-2007, 2009-2023 Free Software Foundation, Inc. | |
| This file is free software: you can redistribute it and/or modify | |
| it under the terms of the GNU Lesser General Public License as | |
| published by the Free Software Foundation; either version 2.1 of the | |
| License, or (at your option) any later version. | |
| This file 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 Lesser General Public License for more details. | |
| You should have received a copy of the GNU Lesser General Public License | |
| along with this program. If not, see <https://www.gnu.org/licenses/>. */ | |
| /* Specification. */ | |
| /* readlink() substitute for systems that don't have a readlink() function, | |
| such as DJGPP 2.03 and mingw32. */ | |
| ssize_t | |
| readlink (char const *file, _GL_UNUSED char *buf, | |
| _GL_UNUSED size_t bufsize) | |
| { | |
| 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 (file, &statbuf) >= 0) | |
| errno = EINVAL; | |
| return -1; | |
| } | |
| /* 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 (char const *file, char *buf, size_t bufsize) | |
| { | |
| size_t file_len = strlen (file); | |
| if (file_len && file[file_len - 1] == '/') | |
| { | |
| /* Even if FILE 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 (file, &st) == 0 || errno == EOVERFLOW) | |
| errno = EINVAL; | |
| return -1; | |
| } | |
| ssize_t r = readlink (file, buf, bufsize); | |
| if (r < 0 && errno == ERANGE) | |
| { | |
| /* Try again with a bigger buffer. This is just for test cases; | |
| real code invariably discards short reads. */ | |
| char stackbuf[4032]; | |
| r = readlink (file, stackbuf, sizeof stackbuf); | |
| if (r < 0) | |
| { | |
| if (errno == ERANGE) | |
| { | |
| /* Clear the buffer, which is good enough for real code. | |
| Thankfully, no test cases try short reads of enormous | |
| symlinks and what would be the point anyway? */ | |
| r = bufsize; | |
| memset (buf, 0, r); | |
| } | |
| } | |
| else | |
| { | |
| if (bufsize < r) | |
| r = bufsize; | |
| memcpy (buf, stackbuf, r); | |
| } | |
| } | |
| return r; | |
| } | |