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bn_shift.c

/* crypto/bn/bn_shift.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * 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 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 AUTHOR 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.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"

int BN_lshift1(BIGNUM *r, const BIGNUM *a)
      {
      register BN_ULONG *ap,*rp,t,c;
      int i;

      bn_check_top(r);
      bn_check_top(a);

      if (r != a)
            {
            r->neg=a->neg;
            if (bn_wexpand(r,a->top+1) == NULL) return(0);
            r->top=a->top;
            }
      else
            {
            if (bn_wexpand(r,a->top+1) == NULL) return(0);
            }
      ap=a->d;
      rp=r->d;
      c=0;
      for (i=0; i<a->top; i++)
            {
            t= *(ap++);
            *(rp++)=((t<<1)|c)&BN_MASK2;
            c=(t & BN_TBIT)?1:0;
            }
      if (c)
            {
            *rp=1;
            r->top++;
            }
      bn_check_top(r);
      return(1);
      }

int BN_rshift1(BIGNUM *r, const BIGNUM *a)
      {
      BN_ULONG *ap,*rp,t,c;
      int i;

      bn_check_top(r);
      bn_check_top(a);

      if (BN_is_zero(a))
            {
            BN_zero(r);
            return(1);
            }
      if (a != r)
            {
            if (bn_wexpand(r,a->top) == NULL) return(0);
            r->top=a->top;
            r->neg=a->neg;
            }
      ap=a->d;
      rp=r->d;
      c=0;
      for (i=a->top-1; i>=0; i--)
            {
            t=ap[i];
            rp[i]=((t>>1)&BN_MASK2)|c;
            c=(t&1)?BN_TBIT:0;
            }
      bn_correct_top(r);
      bn_check_top(r);
      return(1);
      }

int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
      {
      int i,nw,lb,rb;
      BN_ULONG *t,*f;
      BN_ULONG l;

      bn_check_top(r);
      bn_check_top(a);

      r->neg=a->neg;
      nw=n/BN_BITS2;
      if (bn_wexpand(r,a->top+nw+1) == NULL) return(0);
      lb=n%BN_BITS2;
      rb=BN_BITS2-lb;
      f=a->d;
      t=r->d;
      t[a->top+nw]=0;
      if (lb == 0)
            for (i=a->top-1; i>=0; i--)
                  t[nw+i]=f[i];
      else
            for (i=a->top-1; i>=0; i--)
                  {
                  l=f[i];
                  t[nw+i+1]|=(l>>rb)&BN_MASK2;
                  t[nw+i]=(l<<lb)&BN_MASK2;
                  }
      memset(t,0,nw*sizeof(t[0]));
/*    for (i=0; i<nw; i++)
            t[i]=0;*/
      r->top=a->top+nw+1;
      bn_correct_top(r);
      bn_check_top(r);
      return(1);
      }

int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
      {
      int i,j,nw,lb,rb;
      BN_ULONG *t,*f;
      BN_ULONG l,tmp;

      bn_check_top(r);
      bn_check_top(a);

      nw=n/BN_BITS2;
      rb=n%BN_BITS2;
      lb=BN_BITS2-rb;
      if (nw >= a->top || a->top == 0)
            {
            BN_zero(r);
            return(1);
            }
      if (r != a)
            {
            r->neg=a->neg;
            if (bn_wexpand(r,a->top-nw+1) == NULL) return(0);
            }
      else
            {
            if (n == 0)
                  return 1; /* or the copying loop will go berserk */
            }

      f= &(a->d[nw]);
      t=r->d;
      j=a->top-nw;
      r->top=j;

      if (rb == 0)
            {
            for (i=j; i != 0; i--)
                  *(t++)= *(f++);
            }
      else
            {
            l= *(f++);
            for (i=j-1; i != 0; i--)
                  {
                  tmp =(l>>rb)&BN_MASK2;
                  l= *(f++);
                  *(t++) =(tmp|(l<<lb))&BN_MASK2;
                  }
            *(t++) =(l>>rb)&BN_MASK2;
            }
      bn_correct_top(r);
      bn_check_top(r);
      return(1);
      }

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