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 "internal/cryptlib.h"
  60 #include "bn_lcl.h"
  61
  62 BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
  63 {
  64 #ifndef BN_LLONG
  65     BN_ULONG ret = 0;
  66 #else
  67     BN_ULLONG ret = 0;
  68 #endif
  69     int i;
  70
  71     if (w == 0)
  72         return (BN_ULONG)-1;
  73
  74     bn_check_top(a);
  75     w &= BN_MASK2;
  76     for (i = a->top - 1; i >= 0; i--) {
  77 #ifndef BN_LLONG
  78         ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;
  79         ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
  80 #else
  81         ret = (BN_ULLONG) (((ret << (BN_ULLONG) BN_BITS2) | a->d[i]) %
  82                            (BN_ULLONG) w);
  83 #endif
  84     }
  85     return ((BN_ULONG)ret);
  86 }
  87
  88 BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
  89 {
  90     BN_ULONG ret = 0;
  91     int i, j;
  92
  93     bn_check_top(a);
  94     w &= BN_MASK2;
  95
  96     if (!w)
  97         /* actually this an error (division by zero) */
  98         return (BN_ULONG)-1;
  99     if (a->top == 0)
 100         return 0;
 101
 102     /* normalize input (so bn_div_words doesn't complain) */
 103     j = BN_BITS2 - BN_num_bits_word(w);
 104     w <<= j;
 105     if (!BN_lshift(a, a, j))
 106         return (BN_ULONG)-1;
 107
 108     for (i = a->top - 1; i >= 0; i--) {
 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)
 133         return 1;
 134     /* degenerate case: a is zero */
 135     if (BN_is_zero(a))
 136         return BN_set_word(a, w);
 137     /* handle 'a' when negative */
 138     if (a->neg) {
 139         a->neg = 0;
 140         i = BN_sub_word(a, w);
 141         if (!BN_is_zero(a))
 142             a->neg = !(a->neg);
 143         return (i);
 144     }
 145     for (i = 0; w != 0 && i < a->top; i++) {
 146         a->d[i] = l = (a->d[i] + w) & BN_MASK2;
 147         w = (w > l) ? 1 : 0;
 148     }
 149     if (w && i == a->top) {
 150         if (bn_wexpand(a, a->top + 1) == NULL)
 151             return 0;
 152         a->top++;
 153         a->d[i] = w;
 154     }
 155     bn_check_top(a);
 156     return (1);
 157 }
 158
 159 int BN_sub_word(BIGNUM *a, BN_ULONG w)
 160 {
 161     int i;
 162
 163     bn_check_top(a);
 164     w &= BN_MASK2;
 165
 166     /* degenerate case: w is zero */
 167     if (!w)
 168         return 1;
 169     /* degenerate case: a is zero */
 170     if (BN_is_zero(a)) {
 171         i = BN_set_word(a, w);
 172         if (i != 0)
 173             BN_set_negative(a, 1);
 174         return i;
 175     }
 176     /* handle 'a' when negative */
 177     if (a->neg) {
 178         a->neg = 0;
 179         i = BN_add_word(a, w);
 180         a->neg = 1;
 181         return (i);
 182     }
 183
 184     if ((a->top == 1) && (a->d[0] < w)) {
 185         a->d[0] = w - a->d[0];
 186         a->neg = 1;
 187         return (1);
 188     }
 189     i = 0;
 190     for (;;) {
 191         if (a->d[i] >= w) {
 192             a->d[i] -= w;
 193             break;
 194         } else {
 195             a->d[i] = (a->d[i] - w) & BN_MASK2;
 196             i++;
 197             w = 1;
 198         }
 199     }
 200     if ((a->d[i] == 0) && (i == (a->top - 1)))
 201         a->top--;
 202     bn_check_top(a);
 203     return (1);
 204 }
 205
 206 int BN_mul_word(BIGNUM *a, BN_ULONG w)
 207 {
 208     BN_ULONG ll;
 209
 210     bn_check_top(a);
 211     w &= BN_MASK2;
 212     if (a->top) {
 213         if (w == 0)
 214             BN_zero(a);
 215         else {
 216             ll = bn_mul_words(a->d, a->d, a->top, w);
 217             if (ll) {
 218                 if (bn_wexpand(a, a->top + 1) == NULL)
 219                     return (0);
 220                 a->d[a->top++] = ll;
 221             }
 222         }
 223     }
 224     bn_check_top(a);
 225     return (1);
 226 }