1 files changed, 118 insertions, 0 deletions
diff --git a/lib/targetdir.c b/lib/targetdir.c
new file mode 100644
index 0000000..e593dd1
--- /dev/null
+++ b/lib/targetdir.c
@@ -0,0 +1,118 @@
+/* Target directory operands for coreutils
+
+   Copyright 2004-2023 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/>.  */
+
+#include <config.h>
+
+#define TARGETDIR_INLINE _GL_EXTERN_INLINE
+#include <targetdir.h>
+
+#include <attribute.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#ifdef O_PATH
+enum { O_PATHSEARCH = O_PATH };
+#else
+enum { O_PATHSEARCH = O_SEARCH };
+#endif
+
+/* Must F designate the working directory?  */
+
+ATTRIBUTE_PURE static bool
+must_be_working_directory (char const *f)
+{
+  /* Return true for ".", "./.", ".///./", etc.  */
+  while (*f++ == '.')
+    {
+      if (*f != '/')
+        return !*f;
+      while (*++f == '/')
+        continue;
+      if (!*f)
+        return true;
+    }
+  return false;
+}
+
+/* Return a file descriptor open to FILE, for use in openat.
+   As an optimization, return AT_FDCWD if FILE must be the working directory.
+   As a side effect, possibly set *ST to the file's status.
+   Fail and set errno if FILE is not a directory.
+   On failure return -2 if AT_FDCWD is -1, -1 otherwise.  */
+
+int
+target_directory_operand (char const *file, struct stat *st)
+{
+  if (must_be_working_directory (file))
+    return AT_FDCWD;
+
+  int fd = -1;
+  int try_to_open = 1;
+  int stat_result;
+
+  /* On old systems without O_DIRECTORY, like Solaris 10, check with
+     stat first lest we try to open a fifo for example and hang.  */
+  if (!O_DIRECTORY)
+    {
+      stat_result = stat (file, st);
+      if (stat_result == 0)
+        {
+          try_to_open = S_ISDIR (st->st_mode);
+          errno = ENOTDIR;
+        }
+      else
+        {
+          /* On EOVERFLOW failure, give up on checking, as there is no
+             easy way to check.  This should be rare.  */
+          try_to_open = errno == EOVERFLOW;
+        }
+    }
+
+  if (try_to_open)
+    {
+      fd = open (file, O_PATHSEARCH | O_DIRECTORY);
+
+      /* On platforms lacking O_PATH, using O_SEARCH | O_DIRECTORY to
+         open an overly-protected non-directory can fail with either
+         EACCES or ENOTDIR.  Prefer ENOTDIR as it makes for better
+         diagnostics.  */
+      if (O_PATHSEARCH == O_SEARCH && fd < 0 && errno == EACCES)
+        errno = (((O_DIRECTORY ? stat (file, st) : stat_result) == 0
+                  && !S_ISDIR (st->st_mode))
+                 ? ENOTDIR : EACCES);
+    }
+
+  if (!O_DIRECTORY && 0 <= fd)
+    {
+      /* On old systems like Solaris 10 double check type,
+         to ensure we've opened a directory.  */
+      int err;
+      if (fstat (fd, st) == 0
+          ? !S_ISDIR (st->st_mode) && (err = ENOTDIR, true)
+          : (err = errno) != EOVERFLOW)
+        {
+          close (fd);
+          errno = err;
+          fd = -1;
+        }
+    }
+
+  return fd - (AT_FDCWD == -1 && fd < 0);
+}