/* 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://libtomcrypt.org */#include "tomcrypt.h"/**  @file der_encode_short_integer.c  ASN.1 DER, encode an integer, Tom St Denis*/#ifdef LTC_DER/* Exports a positive integer as DER format (upto 32-bits in size) *//**  Store a mp_int integer  @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) {      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++] = 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++] = (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: 1.3 $ *//* $Date: 2005/05/23 01:27:03 $ */