src/iu_helpers.c

/* Iu interface specific helper functions */

/* (C) 2015 by Harald Welte <laforge@gnumonks.org>
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include <stdint.h>
#include <string.h>

#include <osmocom/core/utils.h>

/* decode a BCD-string as used inside ASN.1 encoded Iu interface protocols */
int ranap_bcd_decode(char *out, size_t out_len, const uint8_t *in, size_t in_len)
{
	const uint8_t *ch;
	char *outch = out;

	for (ch = in; ch < in + in_len; ch++) {
		char c = osmo_bcd2char(*ch & 0xF);
		*outch++ = c;
		if (outch + 1 >= out + out_len)
			break;
		c = osmo_bcd2char(*ch >> 4);
		/* skip padding nibble at end */
		if (c == 'F')
			break;
		*outch++ = c;
	}
	*outch++ = '\0';
	return outch - out;
}

/* decode an IMSI as used inside ASN.1 encoded Iu interface protocols */
int ranap_imsi_encode(uint8_t *out, size_t out_len, const char *in)
{
	unsigned int len = strlen(in);
	unsigned int octlen;
	uint8_t odd = (len & 0x01) == 1;
	unsigned int off = 0;
	unsigned int i;

	octlen = len/2;
	if (odd)
		octlen++;

	for (i = 0; i < octlen; i++) {
		uint8_t lower, upper;

		lower = osmo_char2bcd(in[off++]) & 0x0f;
		if (odd && off == len)
			upper = 0x0f;
		else
			upper = osmo_char2bcd(in[off++]) & 0x0f;

		out[i] = (upper << 4) | lower;
	}
	return i;
}