[PATCH][RFC] Avoid table lookup in isascii, isxdigit.

[OndÅej BÃlka <neleai at seznam dot cz>]

Hi, I looked to ctype and thougth if it is possible to decrease table
size to 512 bytes. I did not succeed but made following three
optimizations.

1. In isdigit use & instead &&. Gcc contains bug that optimizes first
but not second case.
2. Refactor isdigit macro
3. Write isxdigit and isascii.

Following code is enclosed in

#ifndef _ISOMAC
# if !defined __NO_CTYPE && !defined NOT_IN_libc

Is there reason why we cannot also transform user code in this way?

---
 include/ctype.h |   23 ++++++++++++++++++++---
 1 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/include/ctype.h b/include/ctype.h
index 6a18039..7f9e928 100644
--- a/include/ctype.h
+++ b/include/ctype.h
@@ -56,11 +56,28 @@ __ctype_tolower_loc (void)
 /* The spec says that isdigit must only match the decimal digits.  We
    can check this without a memory access.  */
 #  undef isdigit
-#  define isdigit(c) ({ int __c = (c); __c >= '0' && __c <= '9'; })
+#  define isdigit(c) ({ int __c = (c); (__c >= '0') & (__c <= '9'); })
 #  undef isdigit_l
-#  define isdigit_l(c, l) ({ int __c = (c); __c >= '0' && __c <= '9'; })
+#  define isdigit_l(c, l) isdigit(c)
 #  undef __isdigit_l
-#  define __isdigit_l(c, l) ({ int __c = (c); __c >= '0' && __c <= '9'; })
+#  define __isdigit_l(c, l) isdigit(c)
+
+/* The spec says that isxdigit must only match the hexadecimal digits.  We
+   can check this without a memory access.  */
+#  undef isxdigit
+#  define isxdigit(c) ({ int __c = (c); ((__c >= '0') & (__c <= '9')) || ((__c >= 'a') & (__c <= 'f')) || ((__c >= 'A') & (__c <= 'F')); })
+#  undef isxdigit_l
+#  define isxdigit_l(c, l) isxdigit(c)
+#  undef __isxdigit_l
+#  define __isxdigit_l(c, l) isxdigit(c)
+
+#  undef isascii
+#  define isascii(c) ({ int __c = (c); (__c & 128 == 0); })
+#  undef isascii_l
+#  define isascii_l(c, l) isascii(c)
+#  undef __isascii_l
+#  define __isascii_l(c, l) isascii(c)
+
 # endif
 #endif
 
-- 
1.7.4.4