[PATCH] ftw.c: Check for "." and ".." branchlessly

[James Tirta Halim <tirtajames45@gmail.com>]

---
 io/ftw.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/io/ftw.c b/io/ftw.c
index a72c7d5171..742369a2d2 100644
--- a/io/ftw.c
+++ b/io/ftw.c
@@ -66,6 +66,7 @@ char *alloca ();
 #include <unistd.h>
 #include <not-cancel.h>
 #include <sys/param.h>
+#include <endian.h>
 #ifdef _LIBC
 # include <include/sys/stat.h>
 #else
@@ -388,6 +389,25 @@ open_dir_stream (int *dfdp, struct ftw_data *data, struct dir_data *dirp)
 }
 
 
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#  define SH <<
+#else
+#  define SH >>
+#endif
+
+static int
+is_relative (const char *fname)
+{
+	typedef uint16_t w2 __attribute__ ((__may_alias__));
+	typedef uint32_t w4 __attribute__ ((__may_alias__));
+	const uint16_t n1 = '.' | '\0' SH 8;
+	const uint32_t n2 = '.' | '.' SH 8 | '\0' SH 16;
+	return (*(w2 *)fname == n1) | ((*(w4 *)fname | '\0' SH 24) == n2);
+}
+
+#undef SH
+
+
 static int
 process_entry (struct ftw_data *data, struct dir_data *dir, const char *name,
 	       size_t namlen, int d_type)
@@ -397,9 +417,8 @@ process_entry (struct ftw_data *data, struct dir_data *dir, const char *name,
   int flag = 0;
   size_t new_buflen;
 
-  if (name[0] == '.' && (name[1] == '\0'
-			 || (name[1] == '.' && name[2] == '\0')))
-    /* Don't process the "." and ".." entries.  */
+  /* Don't process the "." and ".." entries.  */
+  if (is_relative(name))
     return 0;
 
   new_buflen = data->ftw.base + namlen + 2;
-- 
2.42.0