crypto/bn/bn_shift.c

   1 /* crypto/bn/bn_shift.c */
   2 /* Copyright (C) 1995-1998 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(BIGNUM *r, const BIGNUM *a)
  64 {
  65     register BN_ULONG *ap, *rp, t, c;
  66     int i;
  67
  68     bn_check_top(r);
  69     bn_check_top(a);
  70
  71     if (r != a) {
  72         r->neg = a->neg;
  73         if (bn_wexpand(r, a->top + 1) == NULL)
  74             return (0);
  75         r->top = a->top;
  76     } else {
  77         if (bn_wexpand(r, a->top + 1) == NULL)
  78             return (0);
  79     }
  80     ap = a->d;
  81     rp = r->d;
  82     c = 0;
  83     for (i = 0; i < a->top; i++) {
  84         t = *(ap++);
  85         *(rp++) = ((t << 1) | c) & BN_MASK2;
  86         c = (t & BN_TBIT) ? 1 : 0;
  87     }
  88     if (c) {
  89         *rp = 1;
  90         r->top++;
  91     }
  92     bn_check_top(r);
  93     return (1);
  94 }
  95
  96 int BN_rshift1(BIGNUM *r, const BIGNUM *a)
  97 {
  98     BN_ULONG *ap, *rp, t, c;
  99     int i;
 100
 101     bn_check_top(r);
 102     bn_check_top(a);
 103
 104     if (BN_is_zero(a)) {
 105         BN_zero(r);
 106         return (1);
 107     }
 108     if (a != r) {
 109         if (bn_wexpand(r, a->top) == NULL)
 110             return (0);
 111         r->top = a->top;
 112         r->neg = a->neg;
 113     }
 114     ap = a->d;
 115     rp = r->d;
 116     c = 0;
 117     for (i = a->top - 1; i >= 0; i--) {
 118         t = ap[i];
 119         rp[i] = ((t >> 1) & BN_MASK2) | c;
 120         c = (t & 1) ? BN_TBIT : 0;
 121     }
 122     bn_correct_top(r);
 123     bn_check_top(r);
 124     return (1);
 125 }
 126
 127 int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
 128 {
 129     int i, nw, lb, rb;
 130     BN_ULONG *t, *f;
 131     BN_ULONG l;
 132
 133     bn_check_top(r);
 134     bn_check_top(a);
 135
 136     if (n < 0) {
 137         BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT);
 138         return 0;
 139     }
 140
 141     r->neg = a->neg;
 142     nw = n / BN_BITS2;
 143     if (bn_wexpand(r, a->top + nw + 1) == NULL)
 144         return (0);
 145     lb = n % BN_BITS2;
 146     rb = BN_BITS2 - lb;
 147     f = a->d;
 148     t = r->d;
 149     t[a->top + nw] = 0;
 150     if (lb == 0)
 151         for (i = a->top - 1; i >= 0; i--)
 152             t[nw + i] = f[i];
 153     else
 154         for (i = a->top - 1; i >= 0; i--) {
 155             l = f[i];
 156             t[nw + i + 1] |= (l >> rb) & BN_MASK2;
 157             t[nw + i] = (l << lb) & BN_MASK2;
 158         }
 159     memset(t, 0, nw * sizeof(t[0]));
 160     /*
 161      * for (i=0; i<nw; i++) t[i]=0;
 162      */
 163     r->top = a->top + nw + 1;
 164     bn_correct_top(r);
 165     bn_check_top(r);
 166     return (1);
 167 }
 168
 169 int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
 170 {
 171     int i, j, nw, lb, rb;
 172     BN_ULONG *t, *f;
 173     BN_ULONG l, tmp;
 174
 175     bn_check_top(r);
 176     bn_check_top(a);
 177
 178     if (n < 0) {
 179         BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT);
 180         return 0;
 181     }
 182
 183     nw = n / BN_BITS2;
 184     rb = n % BN_BITS2;
 185     lb = BN_BITS2 - rb;
 186     if (nw >= a->top || a->top == 0) {
 187         BN_zero(r);
 188         return (1);
 189     }
 190     if (r != a) {
 191         r->neg = a->neg;
 192         if (bn_wexpand(r, a->top - nw + 1) == NULL)
 193             return (0);
 194     } else {
 195         if (n == 0)
 196             return 1;           /* or the copying loop will go berserk */
 197     }
 198
 199     f = &(a->d[nw]);
 200     t = r->d;
 201     j = a->top - nw;
 202     r->top = j;
 203
 204     if (rb == 0) {
 205         for (i = j; i != 0; i--)
 206             *(t++) = *(f++);
 207     } else {
 208         l = *(f++);
 209         for (i = j - 1; i != 0; i--) {
 210             tmp = (l >> rb) & BN_MASK2;
 211             l = *(f++);
 212             *(t++) = (tmp | (l << lb)) & BN_MASK2;
 213         }
 214         *(t++) = (l >> rb) & BN_MASK2;
 215     }
 216     bn_correct_top(r);
 217     bn_check_top(r);
 218     return (1);
 219 }