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