1 files changed, 104 insertions, 0 deletions
diff --git a/lib/readlink.c b/lib/readlink.c
new file mode 100644
index 0000000..531913e
--- /dev/null
+++ b/lib/readlink.c
@@ -0,0 +1,104 @@
+/* Read the contents of a symbolic link.
+   Copyright (C) 2003-2007, 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/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <errno.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#if !HAVE_READLINK
+
+/* readlink() substitute for systems that don't have a readlink() function,
+   such as DJGPP 2.03 and mingw32.  */
+
+ssize_t
+readlink (char const *file, char *buf _GL_UNUSED,
+          size_t bufsize _GL_UNUSED)
+{
+  struct stat statbuf;
+
+  /* In general we should use lstat() here, not stat().  But on platforms
+     without symbolic links, lstat() - if it exists - would be equivalent to
+     stat(), therefore we can use stat().  This saves us a configure check.  */
+  if (stat (file, &statbuf) >= 0)
+    errno = EINVAL;
+  return -1;
+}
+
+#else /* HAVE_READLINK */
+
+# undef readlink
+
+/* readlink() wrapper that uses correct types, for systems like cygwin
+   1.5.x where readlink returns int, and which rejects trailing slash,
+   for Solaris 9.  */
+
+ssize_t
+rpl_readlink (char const *file, char *buf, size_t bufsize)
+{
+# if READLINK_TRAILING_SLASH_BUG
+  size_t file_len = strlen (file);
+  if (file_len && file[file_len - 1] == '/')
+    {
+      /* Even if FILE without the slash is a symlink to a directory,
+         both lstat() and stat() must resolve the trailing slash to
+         the directory rather than the symlink.  We can therefore
+         safely use stat() to distinguish between EINVAL and
+         ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat().  */
+      struct stat st;
+      if (stat (file, &st) == 0 || errno == EOVERFLOW)
+        errno = EINVAL;
+      return -1;
+    }
+# endif /* READLINK_TRAILING_SLASH_BUG */
+
+  ssize_t r = readlink (file, buf, bufsize);
+
+# if READLINK_TRUNCATE_BUG
+  if (r < 0 && errno == ERANGE)
+    {
+      /* Try again with a bigger buffer.  This is just for test cases;
+         real code invariably discards short reads.  */
+      char stackbuf[4032];
+      r = readlink (file, stackbuf, sizeof stackbuf);
+      if (r < 0)
+        {
+          if (errno == ERANGE)
+            {
+              /* Clear the buffer, which is good enough for real code.
+                 Thankfully, no test cases try short reads of enormous
+                 symlinks and what would be the point anyway?  */
+              r = bufsize;
+              memset (buf, 0, r);
+            }
+        }
+      else
+        {
+          if (bufsize < r)
+            r = bufsize;
+          memcpy (buf, stackbuf, r);
+        }
+    }
+# endif
+
+  return r;
+}
+
+#endif /* HAVE_READLINK */