asn1enc.c

/*
 * Copyright (c) 2018 Thomas Pornin <[email protected]>
 *
 * Permission is hereby granted, free of charge, to any person obtaining 
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "inner.h"

/* see inner.h */
br_asn1_uint
br_asn1_uint_prepare(const void *xdata, size_t xlen)
{
	const unsigned char *x;
	br_asn1_uint t;

	x = xdata;
	while (xlen > 0 && *x == 0) {
		x ++;
		xlen --;
	}
	t.data = x;
	t.len = xlen;
	t.asn1len = xlen;
	if (xlen == 0 || x[0] >= 0x80) {
		t.asn1len ++;
	}
	return t;
}

/* see inner.h */
size_t
br_asn1_encode_length(void *dest, size_t len)
{
	unsigned char *buf;
	size_t z;
	int i, j;

	buf = dest;
	if (len < 0x80) {
		if (buf != NULL) {
			*buf = len;
		}
		return 1;
	}
	i = 0;
	for (z = len; z != 0; z >>= 8) {
		i ++;
	}
	if (buf != NULL) {
		*buf ++ = 0x80 + i;
		for (j = i - 1; j >= 0; j --) {
			*buf ++ = len >> (j << 3);
		}
	}
	return i + 1;
}

/* see inner.h */
size_t
br_asn1_encode_uint(void *dest, br_asn1_uint pp)
{
	unsigned char *buf;
	size_t lenlen;

	if (dest == NULL) {
		return 1 + br_asn1_encode_length(NULL, pp.asn1len) + pp.asn1len;
	}
	buf = dest;
	*buf ++ = 0x02;
	lenlen = br_asn1_encode_length(buf, pp.asn1len);
	buf += lenlen;
	*buf = 0x00;
	memcpy(buf + pp.asn1len - pp.len, pp.data, pp.len);
	return 1 + lenlen + pp.asn1len;
}