openbsc/src/libcommon/utils.c

/* OpenBSC kitchen sink */

/* (C) 2015 by sysmocom s.m.f.c GmbH <info@sysmocom.de>
 * 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 <openbsc/utils.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/bit64gen.h>

/* Wishful thinking to generate a constant time compare */
int constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count)
{
	int x = 0, i;

	for (i = 0; i < count; ++i)
		x |= exp[i] ^ rel[i];

	/* if x is zero, all data was identical */
	return x? 1 : 0;
}


uint64_t decode_big_endian(const uint8_t *data, size_t data_len)
{
	uint64_t value = 0;

	while (data_len > 0) {
		value = (value << 8) + *data;
		data += 1;
		data_len -= 1;
	}

	return value;
}

uint8_t *encode_big_endian(uint64_t value, size_t data_len)
{
	static uint8_t buf[sizeof(uint64_t)];
	OSMO_ASSERT(data_len <= ARRAY_SIZE(buf));
	osmo_store64be_ext(value, buf, data_len);
	return buf;
}