crypto/bn/bn_word.c

   1 /* crypto/bn/bn_word.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 BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
  64         {
  65 #ifndef BN_LLONG
  66         BN_ULONG ret=0;
  67 #else
  68         BN_ULLONG ret=0;
  69 #endif
  70         int i;
  71
  72         bn_check_top(a);
  73         w&=BN_MASK2;
  74         for (i=a->top-1; i>=0; i--)
  75                 {
  76 #ifndef BN_LLONG
  77                 ret=((ret<<BN_BITS4)|((a->d[i]>>BN_BITS4)&BN_MASK2l))%w;
  78                 ret=((ret<<BN_BITS4)|(a->d[i]&BN_MASK2l))%w;
  79 #else
  80                 ret=(BN_ULLONG)(((ret<<(BN_ULLONG)BN_BITS2)|a->d[i])%
  81                         (BN_ULLONG)w);
  82 #endif
  83                 }
  84         return((BN_ULONG)ret);
  85         }
  86
  87 BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
  88         {
  89         BN_ULONG ret = 0;
  90         int i, j;
  91
  92         bn_check_top(a);
  93         w &= BN_MASK2;
  94
  95         if (!w)
  96                 /* actually this an error (division by zero) */
  97                 return 0;
  98         if (a->top == 0)
  99                 return 0;
 100
 101         /* normalize input (so bn_div_words doesn't complain) */
 102         j = BN_BITS2 - BN_num_bits_word(w);
 103         w <<= j;
 104         if (!BN_lshift(a, a, j))
 105                 return 0;
 106
 107         for (i=a->top-1; i>=0; i--)
 108                 {
 109                 BN_ULONG l,d;
 110
 111                 l=a->d[i];
 112                 d=bn_div_words(ret,l,w);
 113                 ret=(l-((d*w)&BN_MASK2))&BN_MASK2;
 114                 a->d[i]=d;
 115                 }
 116         if ((a->top > 0) && (a->d[a->top-1] == 0))
 117                 a->top--;
 118         ret >>= j;
 119         bn_check_top(a);
 120         return(ret);
 121         }
 122
 123 int BN_add_word(BIGNUM *a, BN_ULONG w)
 124         {
 125         BN_ULONG l;
 126         int i;
 127
 128         bn_check_top(a);
 129         w &= BN_MASK2;
 130
 131         /* degenerate case: w is zero */
 132         if (!w) return 1;
 133         /* degenerate case: a is zero */
 134         if(BN_is_zero(a)) return BN_set_word(a, w);
 135         /* handle 'a' when negative */
 136         if (a->neg)
 137                 {
 138                 a->neg=0;
 139                 i=BN_sub_word(a,w);
 140                 if (!BN_is_zero(a))
 141                         a->neg=!(a->neg);
 142                 return(i);
 143                 }
 144         /* Only expand (and risk failing) if it's possibly necessary */
 145         if (((BN_ULONG)(a->d[a->top - 1] + 1) == 0) &&
 146                         (bn_wexpand(a,a->top+1) == NULL))
 147                 return(0);
 148         i=0;
 149         for (;;)
 150                 {
 151                 if (i >= a->top)
 152                         l=w;
 153                 else
 154                         l=(a->d[i]+w)&BN_MASK2;
 155                 a->d[i]=l;
 156                 if (w > l)
 157                         w=1;
 158                 else
 159                         break;
 160                 i++;
 161                 }
 162         if (i >= a->top)
 163                 a->top++;
 164         bn_check_top(a);
 165         return(1);
 166         }
 167
 168 int BN_sub_word(BIGNUM *a, BN_ULONG w)
 169         {
 170         int i;
 171
 172         bn_check_top(a);
 173         w &= BN_MASK2;
 174
 175         /* degenerate case: w is zero */
 176         if (!w) return 1;
 177         /* degenerate case: a is zero */
 178         if(BN_is_zero(a)) return BN_set_word(a,w);
 179         /* handle 'a' when negative */
 180         if (a->neg)
 181                 {
 182                 a->neg=0;
 183                 i=BN_add_word(a,w);
 184                 a->neg=1;
 185                 return(i);
 186                 }
 187
 188         if ((a->top == 1) && (a->d[0] < w))
 189                 {
 190                 a->d[0]=w-a->d[0];
 191                 a->neg=1;
 192                 return(1);
 193                 }
 194         i=0;
 195         for (;;)
 196                 {
 197                 if (a->d[i] >= w)
 198                         {
 199                         a->d[i]-=w;
 200                         break;
 201                         }
 202                 else
 203                         {
 204                         a->d[i]=(a->d[i]-w)&BN_MASK2;
 205                         i++;
 206                         w=1;
 207                         }
 208                 }
 209         if ((a->d[i] == 0) && (i == (a->top-1)))
 210                 a->top--;
 211         bn_check_top(a);
 212         return(1);
 213         }
 214
 215 int BN_mul_word(BIGNUM *a, BN_ULONG w)
 216         {
 217         BN_ULONG ll;
 218
 219         bn_check_top(a);
 220         w&=BN_MASK2;
 221         if (a->top)
 222                 {
 223                 if (w == 0)
 224                         BN_zero(a);
 225                 else
 226                         {
 227                         ll=bn_mul_words(a->d,a->d,a->top,w);
 228                         if (ll)
 229                                 {
 230                                 if (bn_wexpand(a,a->top+1) == NULL) return(0);
 231                                 a->d[a->top++]=ll;
 232                                 }
 233                         }
 234                 }
 235         bn_check_top(a);
 236         return(1);
 237         }
 238