/*
 * Here we implement our twts005_read_frame() function.
 */

#include <ctype.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include "tw5reader.h"

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

int twts005_read_frame(FILE *hexf, unsigned *lineno, uint8_t *frame,
			unsigned *lenp)
{
	char linebuf[81];
	char *cp, *np;
	uint8_t *dp;
	unsigned len;

	for (;;) {
		if (!fgets(linebuf, sizeof linebuf, hexf))
			return 0;
		(*lineno)++;
		if (!index(linebuf, '\n'))
			return -2;
		for (cp = linebuf; isspace(*cp); cp++)
			;
		if (*cp != '\0' && *cp != '#')
			break;
	}
	for (np = cp; *cp && !isspace(*cp); cp++)
		;
	if (*cp)
		*cp++ = '\0';
	while (isspace(*cp))
		cp++;
	if (*cp != '\0' && *cp != '#')
		return -1;
	if (!strcasecmp(np, "NULL")) {
		*lenp = 0;
		return 1;
	}

	dp = frame;
	len = 0;
	for (cp = np; *cp; cp += 2) {
		if (!isxdigit(cp[0]) || !isxdigit(cp[1]))
			return -1;
		*dp++ = (decode_hex_digit(cp[0]) << 4) |
			decode_hex_digit(cp[1]);
		len++;
	}
	*lenp = len;
	return 1;
}