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, 17 insertions, 0 deletions

diff --git a/src/character.c b/src/character.c
index cf460540725..1c6020ee468 100644
--- a/src/character.c
+++ b/src/character.c
@@ -1050,9 +1050,26 @@ blankp (int c)
   return XINT (category) == UNICODE_CATEGORY_Zs; /* separator, space */
 }
 
+signed char HEXDIGIT_CONST hexdigit[UCHAR_MAX + 1] =
+  {
+#if HEXDIGIT_IS_CONST
+    [0 ... UCHAR_MAX] = -1,
+#endif
+    ['0'] = 0, ['1'] = 1, ['2'] = 2, ['3'] = 3, ['4'] = 4,
+    ['5'] = 5, ['6'] = 6, ['7'] = 7, ['8'] = 8, ['9'] = 9,
+    ['A'] = 10, ['B'] = 11, ['C'] = 12, ['D'] = 13, ['E'] = 14, ['F'] = 15,
+    ['a'] = 10, ['b'] = 11, ['c'] = 12, ['d'] = 13, ['e'] = 14, ['f'] = 15
+  };
+
 void
 syms_of_character (void)
 {
+#if !HEXDIGIT_IS_CONST
+  /* Set the non-hex digit values to -1.  */
+  for (int i = 0; i <= UCHAR_MAX; i++)
+    hexdigit[i] -= i != '0' && !hexdigit[i];
+#endif
+
   DEFSYM (Qcharacterp, "characterp");
   DEFSYM (Qauto_fill_chars, "auto-fill-chars");