1 files changed, 153 insertions, 0 deletions
diff --git a/lib/savewd.h b/lib/savewd.h
new file mode 100644
index 0000000..80cd280
--- /dev/null
+++ b/lib/savewd.h
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+/* Save and restore the working directory, possibly using a subprocess.
+
+   Copyright (C) 2006, 2009-2022 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 Paul Eggert.  */
+
+#ifndef SAVEWD_H
+# define SAVEWD_H 1
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+#ifndef _GL_INLINE_HEADER_BEGIN
+ #error "Please include config.h first."
+#endif
+_GL_INLINE_HEADER_BEGIN
+#ifndef SAVEWD_INLINE
+# define SAVEWD_INLINE _GL_INLINE
+#endif
+
+/* 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.  */
+SAVEWD_INLINE void
+savewd_init (struct savewd *wd)
+{
+  wd->state = INITIAL_STATE;
+}
+
+
+/* Options for savewd_chdir.  Can be ORed together.  */
+enum
+  {
+    /* Do not follow symbolic links, if supported.  */
+    SAVEWD_CHDIR_NOFOLLOW = 1,
+
+    /* Do not chdir if the directory is readable; simply succeed
+       without invoking chdir if the directory was opened.  */
+    SAVEWD_CHDIR_SKIP_READABLE = 2
+  };
+
+/* 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.  */
+SAVEWD_INLINE int _GL_ATTRIBUTE_PURE
+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);
+
+_GL_INLINE_HEADER_END
+
+#endif