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/*
* Copyright (c) 2001-2007, Tom St Denis
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
#include "tomcrypt.h"
/**
@file der_encode_short_integer.c
ASN.1 DER, encode an integer, Tom St Denis
*/
#ifdef LTC_DER
/**
Store a short integer in the range (0,2^32-1)
@param num The integer to encode
@param out [out] The destination for the DER encoded integers
@param outlen [in/out] The max size and resulting size of the DER encoded integers
@return CRYPT_OK if successful
*/
int der_encode_short_integer(unsigned long num, unsigned char *out, unsigned long *outlen)
{
unsigned long len, x, y, z;
int err;
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
/* force to 32 bits */
num &= 0xFFFFFFFFUL;
/* find out how big this will be */
if ((err = der_length_short_integer(num, &len)) != CRYPT_OK) {
return err;
}
if (*outlen < len) {
*outlen = len;
return CRYPT_BUFFER_OVERFLOW;
}
/* get len of output */
z = 0;
y = num;
while (y) {
++z;
y >>= 8;
}
/* handle zero */
if (z == 0) {
z = 1;
}
/* see if msb is set */
z += (num&(1UL<<((z<<3) - 1))) ? 1 : 0;
/* adjust the number so the msB is non-zero */
for (x = 0; (z <= 4) && (x < (4 - z)); x++) {
num <<= 8;
}
/* store header */
x = 0;
out[x++] = 0x02;
out[x++] = (unsigned char)z;
/* if 31st bit is set output a leading zero and decrement count */
if (z == 5) {
out[x++] = 0;
--z;
}
/* store values */
for (y = 0; y < z; y++) {
out[x++] = (unsigned char)((num >> 24) & 0xFF);
num <<= 8;
}
/* we good */
*outlen = x;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c,v $ */
/* $Revision: 1.8 $ */
/* $Date: 2006/12/28 01:27:24 $ */
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