1 files changed, 101 insertions, 0 deletions
diff --git a/lib/symlinkat.c b/lib/symlinkat.c
new file mode 100644
index 0000000..1346da8
--- /dev/null
+++ b/lib/symlinkat.c
@@ -0,0 +1,101 @@
+/* Create a symlink relative to an open directory.
+   Copyright (C) 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 Eric Blake */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+
+#if HAVE_SYMLINKAT
+# undef symlinkat
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <string.h>
+
+/* Create a symlink, but reject trailing slash.  */
+int
+rpl_symlinkat (char const *contents, int fd, char const *name)
+{
+  size_t len = strlen (name);
+  if (len && name[len - 1] == '/')
+    {
+      struct stat st;
+      if (fstatat (fd, name, &st, AT_SYMLINK_NOFOLLOW) == 0
+          || errno == EOVERFLOW)
+        errno = EEXIST;
+      return -1;
+    }
+  return symlinkat (contents, fd, name);
+}
+
+#elif !HAVE_SYMLINK
+/* Mingw lacks symlink, and it is more efficient to provide a trivial
+   wrapper than to go through at-func.c to call rpl_symlink.  */
+
+int
+symlinkat (_GL_UNUSED char const *path1, _GL_UNUSED int fd,
+           _GL_UNUSED char const *path2)
+{
+  errno = ENOSYS;
+  return -1;
+}
+
+#else /* HAVE_SYMLINK */
+
+/* Our openat helper functions expect the directory parameter first,
+   not second.  These shims make life easier.  */
+
+/* Like symlink, but with arguments reversed.  */
+static int
+symlink_reversed (char const *file, char const *contents)
+{
+  return symlink (contents, file);
+}
+
+/* Like symlinkat, but with arguments reversed.  */
+
+static int
+symlinkat_reversed (int fd, char const *file, char const *contents);
+
+# define AT_FUNC_NAME symlinkat_reversed
+# define AT_FUNC_F1 symlink_reversed
+# define AT_FUNC_POST_FILE_PARAM_DECLS , char const *contents
+# define AT_FUNC_POST_FILE_ARGS        , contents
+# include "at-func.c"
+# undef AT_FUNC_NAME
+# undef AT_FUNC_F1
+# undef AT_FUNC_POST_FILE_PARAM_DECLS
+# undef AT_FUNC_POST_FILE_ARGS
+
+/* Create a symlink FILE, in the directory open on descriptor FD,
+   holding CONTENTS.  If possible, do it without changing the
+   working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then symlink/restore_cwd.  If either the save_cwd or the restore_cwd
+   fails, then give a diagnostic and exit nonzero.  */
+
+int
+symlinkat (char const *contents, int fd, char const *file)
+{
+  return symlinkat_reversed (fd, file, contents);
+}
+
+#endif /* HAVE_SYMLINK */