Initial version.

1 files changed, 132 insertions, 0 deletions

diff --git a/lib/mkancesdirs.c b/lib/mkancesdirs.c
new file mode 100644
index 000000000..473774236
--- /dev/null
+++ b/lib/mkancesdirs.c
@@ -0,0 +1,132 @@
+/* Make a file's ancestor directories.
+
+   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.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "mkancesdirs.h"
+
+#include <errno.h>
+#include <sys/stat.h>
+
+#include "dirname.h"
+#include "stat-macros.h"
+
+/* Return 0 if FILE is a directory, otherwise -1 (setting errno).  */
+
+static int
+test_dir (char const *file)
+{
+  struct stat st;
+  if (stat (file, &st) == 0)
+    {
+      if (S_ISDIR (st.st_mode))
+	return 0;
+      errno = ENOTDIR;
+    }
+  return -1;
+}
+
+/* Ensure that the ancestor directories of FILE exist, using an
+   algorithm that should work even if two processes execute this
+   function in parallel.  Temporarily modify FILE by storing '\0'
+   bytes into it, to access the ancestor directories.
+
+   Create any ancestor directories that don't already exist, by
+   invoking MAKE_DIR (ANCESTOR, MAKE_DIR_ARG).  This function should
+   return zero if successful, -1 (setting errno) otherwise.
+
+   If successful, return 0 with FILE set back to its original value;
+   otherwise, return -1 (setting errno), storing a '\0' into *FILE so
+   that it names the ancestor directory that had problems.  */
+
+int
+mkancesdirs (char *file,
+	     int (*make_dir) (char const *, void *),
+	     void *make_dir_arg)
+{
+  /* This algorithm is O(N**2) but in typical practice the fancier
+     O(N) algorithms are slower.  */
+
+  /* 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;
+
+  char const *prefix_end = file + FILE_SYSTEM_PREFIX_LEN (file);
+  char *p;
+  char c;
+
+  /* Search backward through FILE using mkdir to create the
+     furthest-away ancestor that is needed.  This loop isn't needed
+     for correctness, but typically ancestors already exist so this
+     loop speeds things up a bit.
+
+     This loop runs a bit faster if errno initially contains an error
+     number corresponding to a failed access to FILE.  However, things
+     work correctly regardless of errno's initial value.  */
+
+  for (p = last_component (file); prefix_end < p; p--)
+    if (ISSLASH (*p) && ! ISSLASH (p[-1]))
+      {
+	*p = '\0';
+
+	if (errno == ENOENT && make_dir (file, make_dir_arg) == 0)
+	  {
+	    *p = '/';
+	    break;
+	  }
+
+	if (errno != ENOENT)
+	  {
+	    if (test_dir (file) == 0)
+	      {
+		*p = '/';
+		break;
+	      }
+	    if (errno != ENOENT)
+	      return -1;
+	  }
+
+	*p = '/';
+      }
+
+  /* Scan forward through FILE, creating directories along the way.
+     Try mkdir before stat, so that the procedure works even when two
+     or more processes are executing it in parallel.  */
+
+  while ((c = *p++))
+    if (ISSLASH (*p))
+      {
+	if (! ISSLASH (c))
+	  sep = p;
+      }
+    else if (ISSLASH (c) && *p && sep)
+      {
+	*sep = '\0';
+	if (make_dir (file, make_dir_arg) != 0 && test_dir (file) != 0)
+	  return -1;
+	*sep = '/';
+      }
+
+
+  return 0;
+}