1 files changed, 141 insertions, 0 deletions
diff --git a/lib/mkancesdirs.c b/lib/mkancesdirs.c
new file mode 100644
index 0000000..14646f4
--- /dev/null
+++ b/lib/mkancesdirs.c
@@ -0,0 +1,141 @@
+/* Make a file's ancestor directories.
+
+   Copyright (C) 2006, 2009-2020 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.  */
+
+#include <config.h>
+
+#include "mkancesdirs.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <errno.h>
+#include <unistd.h>
+
+#include "dirname.h"
+#include "savewd.h"
+
+/* Ensure that the ancestor directories of FILE exist, using an
+   algorithm that should work even if two processes execute this
+   function in parallel.  Modify FILE as necessary to access the
+   ancestor directories, but restore FILE to an equivalent value
+   if successful.
+
+   WD points to the working directory, using the conventions of
+   savewd.
+
+   Create any ancestor directories that don't already exist, by
+   invoking MAKE_DIR (FILE, COMPONENT, MAKE_DIR_ARG).  This function
+   should return 0 if successful, -1 (setting errno) otherwise.  If
+   COMPONENT is relative, it is relative to the temporary working
+   directory, which may differ from *WD.
+
+   Ordinarily MAKE_DIR is executed with the working directory changed
+   to reflect the already-made prefix, and mkancesdirs returns with
+   the working directory changed a prefix of FILE.  However, if the
+   initial working directory cannot be saved in a file descriptor,
+   MAKE_DIR is invoked in a subprocess and this function returns in
+   both the parent and child process, so the caller should not assume
+   any changed state survives other than the EXITMAX component of WD,
+   and the caller should take care that the parent does not attempt to
+   do the work that the child is doing.
+
+   If successful and if this process can go ahead and create FILE,
+   return the length of the prefix of FILE that has already been made.
+   If successful so far but a child process is doing the actual work,
+   return -2.  If unsuccessful, return -1 and set errno.  */
+
+ptrdiff_t
+mkancesdirs (char *file, struct savewd *wd,
+             int (*make_dir) (char const *, char const *, void *),
+             void *make_dir_arg)
+{
+  /* Address of the previous directory separator that follows an
+     ordinary byte in a file name in the left-to-right scan, or NULL
+     if no such separator precedes the current location P.  */
+  char *sep = NULL;
+
+  /* Address of the leftmost file name component that has not yet
+     been processed.  */
+  char *component = file;
+
+  char *p = file + FILE_SYSTEM_PREFIX_LEN (file);
+  char c;
+  bool made_dir = false;
+
+  /* Scan forward through FILE, creating and chdiring into directories
+     along the way.  Try MAKE_DIR before chdir, so that the procedure
+     works even when two or more processes are executing it in
+     parallel.  Isolate each file name component by having COMPONENT
+     point to its start and SEP point just after its end.  */
+
+  while ((c = *p++))
+    if (ISSLASH (*p))
+      {
+        if (! ISSLASH (c))
+          sep = p;
+      }
+    else if (ISSLASH (c) && *p && sep)
+      {
+        /* Don't bother to make or test for "." since it does not
+           affect the algorithm.  */
+        if (! (sep - component == 1 && component[0] == '.'))
+          {
+            int make_dir_errno = 0;
+            int savewd_chdir_options = 0;
+            int chdir_result;
+
+            /* Temporarily modify FILE to isolate this file name
+               component.  */
+            *sep = '\0';
+
+            /* Invoke MAKE_DIR on this component, except don't bother
+               with ".." since it must exist if its "parent" does.  */
+            if (sep - component == 2
+                && component[0] == '.' && component[1] == '.')
+              made_dir = false;
+            else if (make_dir (file, component, make_dir_arg) < 0)
+              make_dir_errno = errno;
+            else
+              made_dir = true;
+
+            if (made_dir)
+              savewd_chdir_options |= SAVEWD_CHDIR_NOFOLLOW;
+
+            chdir_result =
+              savewd_chdir (wd, component, savewd_chdir_options, NULL);
+
+            /* Undo the temporary modification to FILE, unless there
+               was a failure.  */
+            if (chdir_result != -1)
+              *sep = '/';
+
+            if (chdir_result != 0)
+              {
+                if (make_dir_errno != 0 && errno == ENOENT)
+                  errno = make_dir_errno;
+                return chdir_result;
+              }
+          }
+
+        component = p;
+      }
+
+  return component - file;
+}