Convert hex digits more systematically

This makes the code a bit smaller and presumably faster, as
it substitutes a single lookup for conditional jumps.
* src/character.c (hexdigit): New constant.
(syms_of_character) [HEXDIGIT_IS_CONST]: Initialize it.
* src/character.h (HEXDIGIT_CONST, HEXDIGIT_IS_CONST): New macros.
(hexdigit): New decl.
(char_hexdigit): New inline function.
* src/charset.c: Do not include c-ctype.h.
* src/charset.c (read_hex):
* src/editfns.c (styled_format):
* src/image.c (xbm_scan):
* src/lread.c (read_escape):
* src/regex.c (ISXDIGIT) [emacs]:
Use char_hexdigit insted of doing it by hand.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/character.h b/src/character.h
index 62d252e91ba..b073a0dd1e4 100644
--- a/src/character.h
+++ b/src/character.h
@@ -700,6 +700,24 @@ char_table_translate (Lisp_Object obj, int ch)
   return CHARACTERP (obj) ? XINT (obj) : ch;
 }
 
+#if defined __GNUC__ && !defined __STRICT_ANSI__
+# define HEXDIGIT_CONST const
+# define HEXDIGIT_IS_CONST true
+#else
+# define HEXDIGIT_CONST
+# define HEXDIGIT_IS_CONST false
+#endif
+extern signed char HEXDIGIT_CONST hexdigit[];
+
+/* If C is a hexadecimal digit ('0'-'9', 'a'-'f', 'A'-'F'), return its
+   value (0-15).  Otherwise return -1.  */
+
+INLINE int
+char_hexdigit (int c)
+{
+  return 0 <= c && c <= UCHAR_MAX ? hexdigit[c] : -1;
+}
+
 INLINE_HEADER_END
 
 #endif /* EMACS_CHARACTER_H */