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/* 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_decode_short_integer.c
ASN.1 DER, decode an integer, Tom St Denis
*/
#ifdef LTC_DER
/**
Read a short integer
@param in The DER encoded data
@param inlen Size of data
@param num [out] The integer to decode
@return CRYPT_OK if successful
*/
int der_decode_short_integer(const unsigned char *in, unsigned long inlen, unsigned long *num)
{
unsigned long len, x, y;
LTC_ARGCHK(num != NULL);
LTC_ARGCHK(in != NULL);
/* check length */
if (inlen < 2) {
return CRYPT_INVALID_PACKET;
}
/* check header */
x = 0;
if ((in[x++] & 0x1F) != 0x02) {
return CRYPT_INVALID_PACKET;
}
/* get the packet len */
len = in[x++];
if (x + len > inlen) {
return CRYPT_INVALID_PACKET;
}
/* read number */
y = 0;
while (len--) {
y = (y<<8) | (unsigned long)in[x++];
}
*num = y;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_decode_short_integer.c,v $ */
/* $Revision: 1.7 $ */
/* $Date: 2006/12/28 01:27:24 $ */
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