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Diffstat (limited to 'lib/savewd.h')
| -rw-r--r-- | lib/savewd.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/lib/savewd.h b/lib/savewd.h new file mode 100644 index 0000000..880b8f1 --- /dev/null +++ b/lib/savewd.h @@ -0,0 +1,149 @@ +/* Save and restore the working directory, possibly using a subprocess. + + Copyright (C) 2006 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 2, 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, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* Written by Paul Eggert. */ + +#ifndef SAVEWD_H +# define SAVEWD_H 1 + +#include <stdbool.h> +#include <sys/types.h> + +/* A saved working directory. The member names and constants defined + by this structure are private to the savewd module. */ +struct savewd +{ + /* The state of this object. */ + enum + { + /* This object has been created but does not yet represent + the working directory. */ + INITIAL_STATE, + + /* val.fd is the original working directory's file descriptor. + It is still the working directory. */ + FD_STATE, + + /* Like FD_STATE, but the working directory has changed, so + restoring it will require a fchdir. */ + FD_POST_CHDIR_STATE, + + /* Fork and let the subprocess do the work. val.child is 0 in a + child, negative in a childless parent, and the child process + ID in a parent with a child. */ + FORKING_STATE, + + /* A serious problem argues against further efforts. val.errnum + contains the error number (e.g., EIO). */ + ERROR_STATE, + + /* savewd_finish has been called, so the application no longer + cares whether the working directory is saved, and there is no + more work to do. */ + FINAL_STATE + } state; + + /* The object's value. */ + union + { + int fd; + int errnum; + pid_t child; + } val; +}; + +/* Initialize a saved working directory object. */ +static inline void +savewd_init (struct savewd *wd) +{ + wd->state = INITIAL_STATE; +} + + +/* Options for savewd_chdir. */ +enum + { + /* Do not follow symbolic links, if supported. */ + SAVEWD_CHDIR_NOFOLLOW = 1, + + /* The directory should be readable, so fail if it happens to be + discovered that the directory is not readable. (Unreadable + directories are not necessarily diagnosed, though.) */ + SAVEWD_CHDIR_READABLE = 2, + + /* Do not chdir if the directory is readable; simply succeed + without invoking chdir if the directory was opened. */ + SAVEWD_CHDIR_SKIP_READABLE = 4 + }; + +/* Change the directory, and if successful, record into *WD the fact + that the process chdired into DIR. A process using this module + should use savewd_chdir rather than chdir or fchdir. Obey the + options specified in OPTIONS. + + If OPEN_RESULT is not null, store into OPEN_RESULT[0] a file + descriptor that accesses DIR if a file descriptor is successfully + obtained. Store -1 otherwise, setting OPEN_RESULT[1] to the error + number. Store through OPEN_RESULT regardless of whether the chdir + is successful. However, when -2 is returned, the contents of + OPEN_RESULT are indeterminate since the file descriptor is closed + in the parent. + + Return -2 if a subprocess was spun off to do the real work, -1 + (setting errno) if unsuccessful, 0 if successful. */ +int savewd_chdir (struct savewd *wd, char const *dir, int options, + int open_result[2]); + +/* Restore the working directory from *WD. STATUS indicates the exit + status corresponding to the work done since the last save; this is + used when the caller is in a subprocess. Return 0 if successful, + -1 (setting errno) on our failure, a positive subprocess exit + status if the working directory was restored in the parent but the + subprocess failed. */ +int savewd_restore (struct savewd *wd, int status); + +/* Return WD's error number, or 0 if WD is not in an error state. */ +static inline int +savewd_errno (struct savewd const *wd) +{ + return (wd->state == ERROR_STATE ? wd->val.errnum : 0); +} + +/* Deallocate any resources associated with WD. A program that chdirs + should restore before finishing. */ +void savewd_finish (struct savewd *wd); + +/* Process N_FILES file names, FILE[0] through FILE[N_FILES - 1]. + For each file name F, call ACT (F, WD, OPTIONS); ACT should invoke + savewd_chdir as needed, and should return an exit status. WD + represents the working directory; it may be in an error state when + ACT is called. + + Save and restore the working directory as needed by the file name + vector; assume that ACT does not require access to any relative + file names other than its first argument, and that it is OK if the + working directory is changed when this function returns. Some + actions may be applied in a subprocess. + + Return the maximum exit status that any call to ACT returned, or + EXIT_SUCCESS (i.e., 0) if no calls were made. */ +int savewd_process_files (int n_files, char **file, + int (*act) (char *, struct savewd *, void *), + void *options); + +#endif |