hexval
*bin = hexval(*hex++) << 4;
*bin++ |= hexval(*hex++);
*binnum++ = 16 * hexval(hexnum[2 * i]) +
hexval(hexnum[2 * i + 1]);
static char hexval();
char *ep, hexval[3];
hexval[2] = 0;
hexval[0] = *src++;
hexval[1] = *src++;
ch = strtoul(hexval, &ep, 16);
d = hexval(*p);
extern unsigned int hexval(unsigned int c);
*p = hexval(key[i]) << 4 | hexval(key[i + 1]);
val = (val << 4) | hexval(*cp++);
goto hexval;
hexval: