#include <sys/types.h>
#include <ctype.h>
#include <stdio.h>

static
decode_hex_digit(c)
{
	if (isdigit(c))
		return c - '0';
	else if (islower(c))
		return c - 'a' + 10;
	else
		return c - 'A' + 10;
}

parse_hex_input(inbuf, outbuf)
	char *inbuf;
	u_char *outbuf;
{
	char *cp;
	unsigned count;

	count = 0;
	for (cp = inbuf; ; ) {
		while (isspace(*cp))
			cp++;
		if (!*cp)
			break;
		if (!isxdigit(cp[0]) || !isxdigit(cp[1])) {
			printf("error: invalid hex APDU input\n");
			return(-1);
		}
		if (count >= 260) {
			printf("error: command APDU is too long\n");
			return(-1);
		}
		outbuf[count++] = (decode_hex_digit(cp[0]) << 4) |
				  decode_hex_digit(cp[1]);
		cp += 2;
	}
	return count;
}