utf8.h: Save a branch in a macro

By adding a mask, we can save a branch.  The two expressions match the
exact same code points.

diff --git a/utf8.h b/utf8.h
index 2de54a7..e312d87 100644 (file)
--- a/utf8.h
+++ b/utf8.h
@@ -164,7 +164,7 @@ Perl's extended UTF-8 means we can have start bytes up to FF.
 
 #define UNI_IS_INVARIANT(c)            (((UV)c) <  0x80)
 #define UTF8_IS_START(c)               (((U8)c) >= 0xc2)
-#define UTF8_IS_CONTINUATION(c)                (((U8)c) >= 0x80 && (((U8)c) <= 0xbf))
+#define UTF8_IS_CONTINUATION(c)                ((((U8)c) & 0xC0) == 0x80)
 #define UTF8_IS_CONTINUED(c)           (((U8)c) &  0x80)
 
 /* Masking with 0xfe allows low bit to be 0 or 1; thus this matches 0xc[23] */