diff options
Diffstat (limited to 'lib/at-func.c')
| -rw-r--r-- | lib/at-func.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/lib/at-func.c b/lib/at-func.c new file mode 100644 index 0000000..13e3fb3 --- /dev/null +++ b/lib/at-func.c @@ -0,0 +1,146 @@ +/* Define at-style functions like fstatat, unlinkat, fchownat, etc. + Copyright (C) 2006, 2009-2023 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/>. */ + +/* written by Jim Meyering */ + +#include "filename.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */ + +#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD +# include <errno.h> +# ifndef ENOTSUP +# define ENOTSUP EINVAL +# endif +#else +# include "openat.h" +# include "openat-priv.h" +# include "save-cwd.h" +#endif + +#ifdef AT_FUNC_USE_F1_COND +# define CALL_FUNC(F) \ + (flag == AT_FUNC_USE_F1_COND \ + ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS) \ + : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS)) +# define VALIDATE_FLAG(F) \ + if (flag & ~AT_FUNC_USE_F1_COND) \ + { \ + errno = EINVAL; \ + return FUNC_FAIL; \ + } +#else +# define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS)) +# define VALIDATE_FLAG(F) /* empty */ +#endif + +#ifdef AT_FUNC_RESULT +# define FUNC_RESULT AT_FUNC_RESULT +#else +# define FUNC_RESULT int +#endif + +#ifdef AT_FUNC_FAIL +# define FUNC_FAIL AT_FUNC_FAIL +#else +# define FUNC_FAIL -1 +#endif + +/* Call AT_FUNC_F1 to operate on FILE, which is in the directory + open on descriptor FD. If AT_FUNC_USE_F1_COND is defined to a value, + AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag; + call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than + AT_FUNC_USE_F1_COND. Return int and fail with -1 unless AT_FUNC_RESULT + or AT_FUNC_FAIL are defined. If possible, do it without changing the + working directory. Otherwise, resort to using save_cwd/fchdir, + then AT_FUNC_F?/restore_cwd. If either the save_cwd or the restore_cwd + fails, then give a diagnostic and exit nonzero. */ +FUNC_RESULT +AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS) +{ + VALIDATE_FLAG (flag); + + if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file)) + return CALL_FUNC (file); + +#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD + errno = ENOTSUP; + return FUNC_FAIL; +#else + { + /* Be careful to choose names unlikely to conflict with + AT_FUNC_POST_FILE_PARAM_DECLS. */ + struct saved_cwd saved_cwd; + int saved_errno; + FUNC_RESULT err; + + { + char proc_buf[OPENAT_BUFFER_SIZE]; + char *proc_file = openat_proc_name (proc_buf, fd, file); + if (proc_file) + { + FUNC_RESULT proc_result = CALL_FUNC (proc_file); + int proc_errno = errno; + if (proc_file != proc_buf) + free (proc_file); + /* If the syscall succeeds, or if it fails with an unexpected + errno value, then return right away. Otherwise, fall through + and resort to using save_cwd/restore_cwd. */ + if (FUNC_FAIL != proc_result) + return proc_result; + if (! EXPECTED_ERRNO (proc_errno)) + { + errno = proc_errno; + return proc_result; + } + } + } + + if (save_cwd (&saved_cwd) != 0) + openat_save_fail (errno); + if (0 <= fd && fd == saved_cwd.desc) + { + /* If saving the working directory collides with the user's + requested fd, then the user's fd must have been closed to + begin with. */ + free_cwd (&saved_cwd); + errno = EBADF; + return FUNC_FAIL; + } + + if (fchdir (fd) != 0) + { + saved_errno = errno; + free_cwd (&saved_cwd); + errno = saved_errno; + return FUNC_FAIL; + } + + err = CALL_FUNC (file); + saved_errno = (err == FUNC_FAIL ? errno : 0); + + if (restore_cwd (&saved_cwd) != 0) + openat_restore_fail (errno); + + free_cwd (&saved_cwd); + + if (saved_errno) + errno = saved_errno; + return err; + } +#endif +} +#undef CALL_FUNC +#undef FUNC_RESULT +#undef FUNC_FAIL |