define a constant used by both url.c and hex.c

src/hex.c

@@ -46,12 +46,12 @@ const char hex_alphabet[][16] = {
  * into 55 bytes (cacheline friendly).
  */
 const uint8_t nibble[] = {
-	   0,    1,    2,    3,    4,    5,    6,    7,    8,    9,
-	   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 10,   11,   12,
-	   13,   14,   15,   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-	   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-	   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,   10,
-	   11,   12,   13,   14,   15
+	   0,   1,   2,   3,   4,   5,   6,   7,   8,   9,
+	   ILL, ILL, ILL, ILL, ILL, ILL, ILL, 10,  11,  12,
+	   13,  14,  15,  ILL, ILL, ILL, ILL, ILL, ILL, ILL,
+	   ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
+	   ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL, 10,
+	   11,  12,  13,  14,  15
 };
 
 size_t

src/hex.h

@@ -28,6 +28,8 @@
 
 #include <stdint.h>
 
+#define ILL (0xff)
+
 /* These are defined in hex.c */
 
 extern const char hex_alphabet[][16];

src/url.c

@@ -148,7 +148,7 @@ url_decode(const enum encoding dec, char *restrict const buf,
 				break;
 			case PERCENT:
 				if (isoutofrange(*s)
-				    || (nib = nibble[*s - '0']) == 0xff) {
+				    || (nib = nibble[*s - '0']) == ILL) {
 					errno = EINVAL;
 					return -1;
 				}
@@ -160,7 +160,7 @@ url_decode(const enum encoding dec, char *restrict const buf,
 					return -1;
 				}
 				if (isoutofrange(*s)
-				    || (nib2 = nibble[*s - '0']) == 0xff) {
+				    || (nib2 = nibble[*s - '0']) == ILL) {
 					errno = EINVAL;
 					return -1;
 				}