crypto/bn/bn_shift.c

   1 /* crypto/bn/bn_shift.c */
   2 /* Copyright (C) 1995-1997 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 #include <stdio.h>
  60 #include "cryptlib.h"
  61 #include "bn_lcl.h"
  62
  63 int BN_lshift1(r, a)
  64 BIGNUM *r;
  65 BIGNUM *a;
  66         {
  67         register BN_ULONG *ap,*rp,t,c;
  68         int i;
  69
  70         if (r != a)
  71                 {
  72                 r->neg=a->neg;
  73                 if (bn_expand(r,(a->top+1)*BN_BITS2) == NULL) return(0);
  74                 r->top=a->top;
  75                 }
  76         else
  77                 {
  78                 if (bn_expand(r,(a->top+1)*BN_BITS2) == NULL) return(0);
  79                 }
  80         ap=a->d;
  81         rp=r->d;
  82         c=0;
  83         for (i=0; i<a->top; i++)
  84                 {
  85                 t= *(ap++);
  86                 *(rp++)=((t<<1)|c)&BN_MASK2;
  87                 c=(t & BN_TBIT)?1:0;
  88                 }
  89         if (c)
  90                 {
  91                 *rp=1;
  92                 r->top++;
  93                 }
  94         return(1);
  95         }
  96
  97 int BN_rshift1(r, a)
  98 BIGNUM *r;
  99 BIGNUM *a;
 100         {
 101         BN_ULONG *ap,*rp,t,c;
 102         int i;
 103
 104         if (BN_is_zero(a))
 105                 {
 106                 BN_zero(r);
 107                 return(1);
 108                 }
 109         if (a != r)
 110                 {
 111                 if (bn_expand(r,a->top*BN_BITS2) == NULL) return(0);
 112                 r->top=a->top;
 113                 r->neg=a->neg;
 114                 }
 115         ap=a->d;
 116         rp=r->d;
 117         c=0;
 118         for (i=a->top-1; i>=0; i--)
 119                 {
 120                 t=ap[i];
 121                 rp[i]=((t>>1)&BN_MASK2)|c;
 122                 c=(t&1)?BN_TBIT:0;
 123                 }
 124         bn_fix_top(r);
 125         return(1);
 126         }
 127
 128 int BN_lshift(r, a, n)
 129 BIGNUM *r;
 130 BIGNUM *a;
 131 int n;
 132         {
 133         int i,nw,lb,rb;
 134         BN_ULONG *t,*f;
 135         BN_ULONG l;
 136
 137         r->neg=a->neg;
 138         if (bn_expand(r,(a->top*BN_BITS2)+n) == NULL) return(0);
 139         nw=n/BN_BITS2;
 140         lb=n%BN_BITS2;
 141         rb=BN_BITS2-lb;
 142         f=a->d;
 143         t=r->d;
 144         t[a->top+nw]=0;
 145         if (lb == 0)
 146                 for (i=a->top-1; i>=0; i--)
 147                         t[nw+i]=f[i];
 148         else
 149                 for (i=a->top-1; i>=0; i--)
 150                         {
 151                         l=f[i];
 152                         t[nw+i+1]|=(l>>rb)&BN_MASK2;
 153                         t[nw+i]=(l<<lb)&BN_MASK2;
 154                         }
 155         memset(t,0,nw*sizeof(t[0]));
 156 /*      for (i=0; i<nw; i++)
 157                 t[i]=0;*/
 158         r->top=a->top+nw+1;
 159         bn_fix_top(r);
 160         return(1);
 161         }
 162
 163 int BN_rshift(r, a, n)
 164 BIGNUM *r;
 165 BIGNUM *a;
 166 int n;
 167         {
 168         int i,j,nw,lb,rb;
 169         BN_ULONG *t,*f;
 170         BN_ULONG l,tmp;
 171
 172         nw=n/BN_BITS2;
 173         rb=n%BN_BITS2;
 174         lb=BN_BITS2-rb;
 175         if (nw > a->top)
 176                 {
 177                 BN_zero(r);
 178                 return(1);
 179                 }
 180         if (r != a)
 181                 {
 182                 r->neg=a->neg;
 183                 if (bn_expand(r,(a->top-nw+1)*BN_BITS2) == NULL) return(0);
 184                 }
 185
 186         f= &(a->d[nw]);
 187         t=r->d;
 188         j=a->top-nw;
 189         r->top=j;
 190
 191         if (rb == 0)
 192                 {
 193                 for (i=j+1; i > 0; i--)
 194                         *(t++)= *(f++);
 195                 }
 196         else
 197                 {
 198                 l= *(f++);
 199                 for (i=1; i<j; i++)
 200                         {
 201                         tmp =(l>>rb)&BN_MASK2;
 202                         l= *(f++);
 203                         *(t++) =(tmp|(l<<lb))&BN_MASK2;
 204                         }
 205                 *(t++) =(l>>rb)&BN_MASK2;
 206                 }
 207         *t=0;
 208         bn_fix_top(r);
 209         return(1);
 210         }